Fix optional and sided mod filtering properly

Now always asks the user before proceeding past the point where optional mods could be selected and configured
When updating files, the hash is checked so an update isn't redownloaded if it already exists
Added DevMain file for running in a dev environment

.gitignore

@@ -1,9 +1,9 @@
 
-# Created by https://www.gitignore.io/api/java,gradle,intellij
-# Edit at https://www.gitignore.io/?templates=java,gradle,intellij
+# Created by https://www.toptal.com/developers/gitignore/api/java,gradle,intellij+all
+# Edit at https://www.toptal.com/developers/gitignore?templates=java,gradle,intellij+all
 
-### Intellij ###
-# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio and WebStorm
+### Intellij+all ###
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
 # Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
 
 # User-specific stuff
@@ -33,6 +33,9 @@
 # When using Gradle or Maven with auto-import, you should exclude module files,
 # since they will be recreated, and may cause churn.  Uncomment if using
 # auto-import.
+# .idea/artifacts
+# .idea/compiler.xml
+# .idea/jarRepositories.xml
 # .idea/modules.xml
 # .idea/*.iml
 # .idea/modules
@@ -72,13 +75,18 @@ fabric.properties
 # Android studio 3.1+ serialized cache file
 .idea/caches/build_file_checksums.ser
 
-### Intellij Patch ###
-# Comment Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-215987721
+### Intellij+all Patch ###
+# Ignores the whole .idea folder and all .iml files
+# See https://github.com/joeblau/gitignore.io/issues/186 and https://github.com/joeblau/gitignore.io/issues/360
 
-# *.iml
-# modules.xml
-# .idea/misc.xml
-# *.ipr
+.idea/
+
+# Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-249601023
+
+*.iml
+modules.xml
+.idea/misc.xml
+*.ipr
 
 # Sonarlint plugin
 .idea/sonarlint
@@ -127,4 +135,4 @@ gradle-app.setting
 ### Gradle Patch ###
 **/build/
 
-# End of https://www.gitignore.io/api/java,gradle,intellij
+# End of https://www.toptal.com/developers/gitignore/api/java,gradle,intellij+all

.idea/inspectionProfiles/Project_Default.xml

@@ -1,36 +0,0 @@
-<component name="InspectionProjectProfileManager">
-  <profile version="1.0">
-    <option name="myName" value="Project Default" />
-    <inspection_tool class="JavaDoc" enabled="true" level="WARNING" enabled_by_default="true">
-      <option name="TOP_LEVEL_CLASS_OPTIONS">
-        <value>
-          <option name="ACCESS_JAVADOC_REQUIRED_FOR" value="none" />
-          <option name="REQUIRED_TAGS" value="" />
-        </value>
-      </option>
-      <option name="INNER_CLASS_OPTIONS">
-        <value>
-          <option name="ACCESS_JAVADOC_REQUIRED_FOR" value="none" />
-          <option name="REQUIRED_TAGS" value="" />
-        </value>
-      </option>
-      <option name="METHOD_OPTIONS">
-        <value>
-          <option name="ACCESS_JAVADOC_REQUIRED_FOR" value="none" />
-          <option name="REQUIRED_TAGS" value="@return@param@throws or @exception" />
-        </value>
-      </option>
-      <option name="FIELD_OPTIONS">
-        <value>
-          <option name="ACCESS_JAVADOC_REQUIRED_FOR" value="none" />
-          <option name="REQUIRED_TAGS" value="" />
-        </value>
-      </option>
-      <option name="IGNORE_DEPRECATED" value="false" />
-      <option name="IGNORE_JAVADOC_PERIOD" value="true" />
-      <option name="IGNORE_DUPLICATED_THROWS" value="false" />
-      <option name="IGNORE_POINT_TO_ITSELF" value="false" />
-      <option name="myAdditionalJavadocTags" value="wbp.parser.entryPoint" />
-    </inspection_tool>
-  </profile>
-</component>

.idea/misc.xml

@@ -1,10 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="EntryPointsManager">
-    <list size="1">
-      <item index="0" class="java.lang.String" itemvalue="com.google.gson.annotations.SerializedName" />
-    </list>
-  </component>
-  <component name="ExternalStorageConfigurationManager" enabled="true" />
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="false" project-jdk-name="11" project-jdk-type="JavaSDK" />
-</project>

.idea/vcs.xml

@@ -1,6 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="VcsDirectoryMappings">
-    <mapping directory="" vcs="Git" />
-  </component>
-</project>

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2019
+Copyright (c) 2021 comp500
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -1,2 +1,2 @@
 # packwiz-installer
-An installer for launching packwiz modpacks with MultiMC.
+An installer for launching packwiz modpacks with MultiMC. You'll need [the bootstrapper](https://github.com/comp500/packwiz-installer-bootstrap/releases) to actually use this.

build.gradle

@@ -1,72 +0,0 @@
-plugins {
-    id 'java'
-    id 'application'
-    id 'com.github.johnrengelman.shadow' version '5.0.0'
-    id 'com.palantir.git-version' version '0.11.0'
-    id 'com.github.breadmoirai.github-release' version '2.2.9'
-}
-
-sourceCompatibility = 1.8
-
-dependencies {
-	implementation 'commons-cli:commons-cli:1.4'
-	implementation 'com.moandjiezana.toml:toml4j:0.7.2'
-    // TODO: Implement tests
-    //testImplementation 'junit:junit:4.12'
-    implementation 'com.google.code.gson:gson:2.8.1'
-    implementation 'com.squareup.okio:okio:2.2.2'
-}
-
-repositories {
-    jcenter()
-}
-
-mainClassName = 'link.infra.packwiz.installer.RequiresBootstrap'
-version gitVersion()
-
-jar {
-    manifest {
-        attributes(
-            'Main-Class': 'link.infra.packwiz.installer.RequiresBootstrap',
-            'Implementation-Version': project.version
-        )
-    }
-}
-
-// Commons CLI and Minimal JSON are already included in packwiz-installer-bootstrap
-shadowJar {
-   dependencies {
-       exclude(dependency('commons-cli:commons-cli:1.4'))
-       exclude(dependency('com.eclipsesource.minimal-json:minimal-json:0.9.5'))
-   }
-}
-
-// Used for vscode launch.json
-task copyJar(type: Copy) {
-    from shadowJar
-    rename "packwiz-installer-(.*)\\.jar", "packwiz-installer.jar"
-    into "build/libs/"
-}
-
-build.dependsOn copyJar
-
-if (project.hasProperty("github.token")) {
-    githubRelease {
-        // IntelliJ u ok?
-        //noinspection GroovyAssignabilityCheck
-        owner "comp500"
-        //noinspection GroovyAssignabilityCheck
-        repo "packwiz-installer"
-        //noinspection GroovyAssignabilityCheck
-        tagName "${project.version}"
-        //noinspection GroovyAssignabilityCheck
-        releaseName "Release ${project.version}"
-        //noinspection GroovyAssignabilityCheck
-        draft true
-        //noinspection GroovyAssignabilityCheck
-        token findProperty("github.token") ?: ""
-        releaseAssets = [jar.destinationDirectory.file("packwiz-installer.jar").get()]
-    }
-
-    tasks.githubRelease.dependsOn(build)
-}

build.gradle.kts

@@ -0,0 +1,169 @@
+buildscript {
+	repositories {
+		mavenCentral()
+	}
+	dependencies {
+		classpath("com.guardsquare:proguard-gradle:7.1.0") {
+			exclude("com.android.tools.build")
+		}
+	}
+}
+
+plugins {
+	java
+	application
+	id("com.github.johnrengelman.shadow") version "7.1.2"
+	id("com.palantir.git-version") version "0.13.0"
+	id("com.github.breadmoirai.github-release") version "2.2.12"
+	kotlin("jvm") version "1.6.10"
+	id("com.github.jk1.dependency-license-report") version "2.0"
+	`maven-publish`
+}
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("commons-cli:commons-cli:1.5.0")
+	implementation("com.moandjiezana.toml:toml4j:0.7.2")
+	implementation("com.google.code.gson:gson:2.8.9")
+	implementation("com.squareup.okio:okio:3.0.0")
+	implementation(kotlin("stdlib-jdk8"))
+	implementation("com.squareup.okhttp3:okhttp:4.9.3")
+	implementation("com.michael-bull.kotlin-result:kotlin-result:1.1.14")
+}
+
+application {
+	mainClassName = "link.infra.packwiz.installer.RequiresBootstrap"
+}
+
+val gitVersion: groovy.lang.Closure<*> by extra
+version = gitVersion()
+
+tasks.jar {
+	manifest {
+		attributes["Main-Class"] = "link.infra.packwiz.installer.RequiresBootstrap"
+		attributes["Implementation-Version"] = project.version
+	}
+}
+
+licenseReport {
+	renderers = arrayOf<com.github.jk1.license.render.ReportRenderer>(
+		com.github.jk1.license.render.InventoryMarkdownReportRenderer("licenses.md", "packwiz-installer")
+	)
+	filters = arrayOf<com.github.jk1.license.filter.DependencyFilter>(com.github.jk1.license.filter.LicenseBundleNormalizer())
+}
+
+tasks.shadowJar {
+	exclude("**/*.kotlin_metadata")
+	exclude("**/*.kotlin_builtins")
+	exclude("META-INF/maven/**/*")
+	exclude("META-INF/proguard/**/*")
+
+	// Relocate Commons CLI, so that it doesn't clash with old packwiz-installer-bootstrap (that shades it)
+	relocate("org.apache.commons.cli", "link.infra.packwiz.installer.deps.commons-cli")
+
+	// from Commons CLI
+	exclude("META-INF/LICENSE.txt")
+	exclude("META-INF/NOTICE.txt")
+}
+
+tasks.register<proguard.gradle.ProGuardTask>("shrinkJar") {
+	injars(tasks.shadowJar)
+	outjars("build/libs/" + tasks.shadowJar.get().outputs.files.first().name.removeSuffix(".jar") + "-shrink.jar")
+	if (System.getProperty("java.version").startsWith("1.")) {
+		libraryjars("${System.getProperty("java.home")}/lib/rt.jar")
+		libraryjars("${System.getProperty("java.home")}/lib/jce.jar")
+	} else {
+		// Use jmods for Java 9+
+		val mods = listOf("java.base", "java.logging", "java.desktop", "java.sql")
+		for (mod in mods) {
+			libraryjars(mapOf(
+				"jarfilter" to "!**.jar",
+				"filter" to "!module-info.class"
+			), "${System.getProperty("java.home")}/jmods/$mod.jmod")
+		}
+	}
+
+	keep("class link.infra.packwiz.installer.** { *; }")
+	dontoptimize()
+	dontobfuscate()
+
+	// Used by Okio and OkHttp
+	dontwarn("org.codehaus.mojo.animal_sniffer.*")
+	dontwarn("okhttp3.internal.platform.**")
+	dontwarn("org.conscrypt.**")
+	dontwarn("org.bouncycastle.**")
+	dontwarn("org.openjsse.**")
+}
+
+// Used for vscode launch.json
+tasks.register<Copy>("copyJar") {
+	from(tasks.named("shrinkJar"))
+	rename("packwiz-installer-(.*)\\.jar", "packwiz-installer.jar")
+	into("build/libs/")
+}
+
+tasks.build {
+	dependsOn("copyJar")
+}
+
+if (project.hasProperty("github.token")) {
+	githubRelease {
+		owner("comp500")
+		repo("packwiz-installer")
+		tagName("${project.version}")
+		releaseName("Release ${project.version}")
+		draft(true)
+		token(findProperty("github.token") as String? ?: "")
+		releaseAssets(tasks.jar.get().destinationDirectory.file("packwiz-installer.jar").get())
+	}
+
+	tasks.githubRelease {
+		dependsOn(tasks.build)
+	}
+}
+
+tasks.compileKotlin {
+	kotlinOptions {
+		jvmTarget = "1.8"
+		freeCompilerArgs = listOf("-Xjvm-default=enable", "-Xallow-result-return-type", "-Xopt-in=kotlin.io.path.ExperimentalPathApi")
+	}
+}
+tasks.compileTestKotlin {
+	kotlinOptions {
+		jvmTarget = "1.8"
+		freeCompilerArgs = listOf("-Xjvm-default=enable", "-Xallow-result-return-type", "-Xopt-in=kotlin.io.path.ExperimentalPathApi")
+	}
+}
+
+if (project.hasProperty("bunnycdn.token")) {
+	publishing {
+		publications {
+			create<MavenPublication>("maven") {
+				groupId = "link.infra.packwiz"
+				artifactId = "packwiz-installer"
+
+				from(components["java"])
+			}
+		}
+		repositories {
+			maven {
+				url = uri("https://storage.bunnycdn.com/comp-maven")
+				credentials(HttpHeaderCredentials::class) {
+					name = "AccessKey"
+					value = findProperty("bunnycdn.token") as String?
+				}
+				authentication {
+					create<HttpHeaderAuthentication>("header")
+				}
+			}
+		}
+	}
+}
+

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.3.3-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

src/main/java/link/infra/packwiz/installer/DownloadTask.java

@@ -1,245 +0,0 @@
-package link.infra.packwiz.installer;
-
-import link.infra.packwiz.installer.metadata.IndexFile;
-import link.infra.packwiz.installer.metadata.ManifestFile;
-import link.infra.packwiz.installer.metadata.SpaceSafeURI;
-import link.infra.packwiz.installer.metadata.hash.GeneralHashingSource;
-import link.infra.packwiz.installer.metadata.hash.Hash;
-import link.infra.packwiz.installer.metadata.hash.HashUtils;
-import link.infra.packwiz.installer.ui.IExceptionDetails;
-import link.infra.packwiz.installer.ui.IOptionDetails;
-import okio.Buffer;
-import okio.Okio;
-import okio.Source;
-
-import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
-import java.nio.file.StandardCopyOption;
-import java.util.ArrayList;
-import java.util.List;
-
-class DownloadTask implements IOptionDetails, IExceptionDetails {
-	final IndexFile.File metadata;
-	ManifestFile.File cachedFile = null;
-	private Exception failure = null;
-	private boolean alreadyUpToDate = false;
-	private boolean metadataRequired = true;
-	private boolean invalidated = false;
-	// If file is new or isOptional changed to true, the option needs to be presented again
-	private boolean newOptional = true;
-	private final UpdateManager.Options.Side downloadSide;
-
-	private DownloadTask(IndexFile.File metadata, String defaultFormat, UpdateManager.Options.Side downloadSide) {
-		this.metadata = metadata;
-		if (metadata.hashFormat == null || metadata.hashFormat.length() == 0) {
-			metadata.hashFormat = defaultFormat;
-		}
-		this.downloadSide = downloadSide;
-	}
-
-	void invalidate() {
-		invalidated = true;
-		alreadyUpToDate = false;
-	}
-
-	void updateFromCache(ManifestFile.File cachedFile) {
-		if (failure != null) return;
-		if (cachedFile == null) {
-			this.cachedFile = new ManifestFile.File();
-			return;
-		}
-
-		this.cachedFile = cachedFile;
-
-		if (!invalidated) {
-			Hash currHash;
-			try {
-				currHash = HashUtils.getHash(metadata.hashFormat, metadata.hash);
-			} catch (Exception e) {
-				failure = e;
-				return;
-			}
-			if (currHash != null && currHash.equals(cachedFile.hash)) {
-				// Already up to date
-				alreadyUpToDate = true;
-				metadataRequired = false;
-			}
-		}
-		if (cachedFile.isOptional) {
-			// Because option selection dialog might set this task to true/false, metadata is always needed to download
-			// the file, and to show the description and name
-			metadataRequired = true;
-		}
-	}
-
-	void downloadMetadata(IndexFile parentIndexFile, SpaceSafeURI indexUri) {
-		if (failure != null) return;
-		if (metadataRequired) {
-			try {
-				metadata.downloadMeta(parentIndexFile, indexUri);
-			} catch (Exception e) {
-				failure = e;
-				return;
-			}
-			if (metadata.linkedFile != null) {
-				if (metadata.linkedFile.option != null) {
-					if (metadata.linkedFile.option.optional) {
-						if (cachedFile.isOptional) {
-							// isOptional didn't change
-							newOptional = false;
-						} else {
-							// isOptional false -> true, set option to it's default value
-							// TODO: preserve previous option value, somehow??
-							cachedFile.optionValue = this.metadata.linkedFile.option.defaultValue;
-						}
-					}
-				}
-				cachedFile.isOptional = isOptional();
-				cachedFile.onlyOtherSide = !correctSide();
-			}
-		}
-	}
-
-	void download(String packFolder, SpaceSafeURI indexUri) {
-		if (failure != null) return;
-
-		// Ensure it is removed
-		if (!cachedFile.optionValue || !correctSide()) {
-			if (cachedFile.cachedLocation == null) return;
-			try {
-				Files.deleteIfExists(Paths.get(packFolder, cachedFile.cachedLocation));
-			} catch (IOException e) {
-				// TODO: how much of a problem is this? use log4j/other log library to show warning?
-				e.printStackTrace();
-			}
-			cachedFile.cachedLocation = null;
-			return;
-		}
-
-		if (alreadyUpToDate) return;
-
-		Path destPath = Paths.get(packFolder, metadata.getDestURI().toString());
-
-		// Don't update files marked with preserve if they already exist on disk
-		if (metadata.preserve) {
-			if (Files.exists(destPath)) {
-				return;
-			}
-		}
-
-		try {
-			Hash hash;
-			String fileHashFormat;
-			if (metadata.linkedFile != null) {
-				hash = metadata.linkedFile.getHash();
-				fileHashFormat = metadata.linkedFile.download.hashFormat;
-			} else {
-				hash = metadata.getHash();
-				fileHashFormat = metadata.hashFormat;
-			}
-
-			Source src = metadata.getSource(indexUri);
-			GeneralHashingSource fileSource = HashUtils.getHasher(fileHashFormat).getHashingSource(src);
-			Buffer data = new Buffer();
-			Okio.buffer(fileSource).readAll(data);
-
-			if (fileSource.hashIsEqual(hash)) {
-				Files.createDirectories(destPath.getParent());
-				Files.copy(data.inputStream(), destPath, StandardCopyOption.REPLACE_EXISTING);
-			} else {
-				// TODO: no more SYSOUT!!!!!!!!!
-				System.out.println("Invalid hash for " + metadata.getDestURI().toString());
-				System.out.println("Calculated: " + fileSource.getHash());
-				System.out.println("Expected:   " + hash);
-				failure = new Exception("Hash invalid!");
-			}
-
-			if (cachedFile.cachedLocation != null && !destPath.equals(Paths.get(packFolder, cachedFile.cachedLocation))) {
-				// Delete old file if location changes
-				Files.delete(Paths.get(packFolder, cachedFile.cachedLocation));
-			}
-		} catch (Exception e) {
-			failure = e;
-		}
-		if (failure == null) {
-			if (cachedFile == null) {
-				cachedFile = new ManifestFile.File();
-			}
-			// Update the manifest file
-			try {
-				cachedFile.hash = metadata.getHash();
-			} catch (Exception e) {
-				failure = e;
-				return;
-			}
-			cachedFile.isOptional = isOptional();
-			cachedFile.cachedLocation = metadata.getDestURI().toString();
-			if (metadata.linkedFile != null) {
-				try {
-					cachedFile.linkedFileHash = metadata.linkedFile.getHash();
-				} catch (Exception e) {
-					failure = e;
-				}
-			}
-		}
-	}
-
-	public Exception getException() {
-		return failure;
-	}
-
-	boolean isOptional() {
-		if (metadata.linkedFile != null) {
-			return metadata.linkedFile.isOptional();
-		}
-		return false;
-	}
-
-	boolean isNewOptional() {
-		return isOptional() && this.newOptional;
-	}
-
-	boolean correctSide() {
-		if (metadata.linkedFile != null) {
-			return metadata.linkedFile.side.hasSide(downloadSide);
-		}
-		return true;
-	}
-
-	public String getName() {
-		return metadata.getName();
-	}
-
-	@Override
-	public boolean getOptionValue() {
-		return cachedFile.optionValue;
-	}
-
-	@Override
-	public String getOptionDescription() {
-		if (metadata.linkedFile != null) {
-			return metadata.linkedFile.option.description;
-		}
-		return null;
-	}
-
-	public void setOptionValue(boolean value) {
-		if (value && !cachedFile.optionValue) {
-			// Ensure that an update is done if it changes from false to true, or from true to false
-			alreadyUpToDate = false;
-		}
-		cachedFile.optionValue = value;
-	}
-
-	static List<DownloadTask> createTasksFromIndex(IndexFile index, String defaultFormat, UpdateManager.Options.Side downloadSide) {
-		ArrayList<DownloadTask> tasks = new ArrayList<>();
-		for (IndexFile.File file : index.files) {
-			tasks.add(new DownloadTask(file, defaultFormat, downloadSide));
-		}
-		return tasks;
-	}
-
-
-}

src/main/java/link/infra/packwiz/installer/Main.java

@@ -1,148 +0,0 @@
-package link.infra.packwiz.installer;
-
-import link.infra.packwiz.installer.metadata.SpaceSafeURI;
-import link.infra.packwiz.installer.ui.CLIHandler;
-import link.infra.packwiz.installer.ui.IUserInterface;
-import link.infra.packwiz.installer.ui.InputStateHandler;
-import link.infra.packwiz.installer.ui.InstallWindow;
-import org.apache.commons.cli.*;
-
-import javax.swing.*;
-import java.awt.*;
-import java.net.URISyntaxException;
-
-@SuppressWarnings("unused")
-public class Main {
-
-	// Actual main() is in RequiresBootstrap!
-	@SuppressWarnings("unused")
-	public Main(String[] args) {
-		// Big overarching try/catch just in case everything breaks
-		try {
-			this.startup(args);
-		} catch (Exception e) {
-			e.printStackTrace();
-			EventQueue.invokeLater(() -> {
-				JOptionPane.showMessageDialog(null,
-						"A fatal error occurred: \n" + e.getClass().getCanonicalName() + ": " + e.getMessage(),
-						"packwiz-installer", JOptionPane.ERROR_MESSAGE);
-				System.exit(1);
-			});
-			// In case the eventqueue is broken, exit after 1 minute
-			try {
-				Thread.sleep(60 * 1000);
-			} catch (InterruptedException e1) {
-				// Good, it was already called?
-				return;
-			}
-			System.exit(1);
-		}
-	}
-
-	private void startup(String[] args) {
-		Options options = new Options();
-		addNonBootstrapOptions(options);
-		addBootstrapOptions(options);
-
-		CommandLineParser parser = new DefaultParser();
-		CommandLine cmd = null;
-		try {
-			cmd = parser.parse(options, args);
-		} catch (ParseException e) {
-			e.printStackTrace();
-			try {
-				UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-			} catch (Exception e1) {
-				// Ignore the exceptions, just continue using the ugly L&F
-			}
-			JOptionPane.showMessageDialog(null, e.getMessage(), "packwiz-installer", JOptionPane.ERROR_MESSAGE);
-			System.exit(1);
-		}
-
-		IUserInterface ui;
-		// if "headless", GUI creation will fail anyway!
-		if (cmd.hasOption("no-gui") || GraphicsEnvironment.isHeadless()) {
-			ui = new CLIHandler();
-		} else {
-			ui = new InstallWindow();
-		}
-
-		String[] unparsedArgs = cmd.getArgs();
-		if (unparsedArgs.length > 1) {
-			ui.handleExceptionAndExit(new RuntimeException("Too many arguments specified!"));
-			return;
-		} else if (unparsedArgs.length < 1) {
-			ui.handleExceptionAndExit(new RuntimeException("URI to install from must be specified!"));
-			return;
-		}
-
-		String title = cmd.getOptionValue("title");
-		if (title != null) {
-			ui.setTitle(title);
-		}
-
-		InputStateHandler inputStateHandler = new InputStateHandler();
-		ui.show(inputStateHandler);
-
-		UpdateManager.Options uOptions = new UpdateManager.Options();
-
-		String side = cmd.getOptionValue("side");
-		if (side != null) {
-			uOptions.side = UpdateManager.Options.Side.from(side);
-		}
-
-		String packFolder = cmd.getOptionValue("pack-folder");
-		if (packFolder != null) {
-			uOptions.packFolder = packFolder;
-		}
-
-		String metaFile = cmd.getOptionValue("meta-file");
-		if (metaFile != null) {
-			uOptions.manifestFile = metaFile;
-		}
-
-		try {
-			uOptions.downloadURI = new SpaceSafeURI(unparsedArgs[0]);
-		} catch (URISyntaxException e) {
-			// TODO: better error message?
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-
-		// Start update process!
-		// TODO: start in SwingWorker?
-		try {
-			ui.executeManager(() -> {
-				try {
-					new UpdateManager(uOptions, ui, inputStateHandler);
-				} catch (Exception e) {
-					// TODO: better error message?
-					ui.handleExceptionAndExit(e);
-				}
-			});
-		} catch (Exception e) {
-			// TODO: better error message?
-			ui.handleExceptionAndExit(e);
-		}
-	}
-
-	// Called by packwiz-installer-bootstrap to set up the help command
-	@SuppressWarnings("WeakerAccess")
-	public static void addNonBootstrapOptions(Options options) {
-		options.addOption("s", "side", true, "Side to install mods from (client/server, defaults to client)");
-		options.addOption(null, "title", true, "Title of the installer window");
-		options.addOption(null, "pack-folder", true, "Folder to install the pack to (defaults to the JAR directory)");
-		options.addOption(null, "meta-file", true, "JSON file to store pack metadata, relative to the pack folder (defaults to packwiz.json)");
-	}
-	
-	// TODO: link these somehow so they're only defined once?
-	private static void addBootstrapOptions(Options options) {
-		options.addOption(null, "bootstrap-update-url", true, "Github API URL for checking for updates");
-		options.addOption(null, "bootstrap-update-token", true, "Github API Access Token, for private repositories");
-		options.addOption(null, "bootstrap-no-update", false, "Don't update packwiz-installer");
-		options.addOption(null, "bootstrap-main-jar", true, "Location of the packwiz-installer JAR file");
-		options.addOption("g", "no-gui", false, "Don't display a GUI to show update progress");
-		options.addOption("h", "help", false, "Display this message"); // Implemented in packwiz-installer-bootstrap!
-	}
-	
-}

src/main/java/link/infra/packwiz/installer/RequiresBootstrap.java

@@ -8,8 +8,6 @@ public class RequiresBootstrap {
 	public static void main(String[] args) {
 		// Very small CLI implementation, because Commons CLI complains on unexpected
 		// options
-		// Also so that Commons CLI can be excluded from the shaded JAR, as it is
-		// included in the bootstrap
 		if (Arrays.stream(args).map(str -> {
 			if (str == null) return "";
 			if (str.startsWith("--")) {

src/main/java/link/infra/packwiz/installer/UpdateManager.java

@@ -1,500 +0,0 @@
-package link.infra.packwiz.installer;
-
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
-import com.google.gson.JsonIOException;
-import com.google.gson.JsonSyntaxException;
-import com.google.gson.annotations.SerializedName;
-import com.moandjiezana.toml.Toml;
-import link.infra.packwiz.installer.metadata.IndexFile;
-import link.infra.packwiz.installer.metadata.ManifestFile;
-import link.infra.packwiz.installer.metadata.PackFile;
-import link.infra.packwiz.installer.metadata.SpaceSafeURI;
-import link.infra.packwiz.installer.metadata.hash.GeneralHashingSource;
-import link.infra.packwiz.installer.metadata.hash.Hash;
-import link.infra.packwiz.installer.metadata.hash.HashUtils;
-import link.infra.packwiz.installer.request.HandlerManager;
-import link.infra.packwiz.installer.ui.IExceptionDetails;
-import link.infra.packwiz.installer.ui.IUserInterface;
-import link.infra.packwiz.installer.ui.InputStateHandler;
-import link.infra.packwiz.installer.ui.InstallProgress;
-import okio.Okio;
-import okio.Source;
-
-import java.io.*;
-import java.nio.file.Files;
-import java.nio.file.Paths;
-import java.util.*;
-import java.util.concurrent.*;
-import java.util.stream.Collectors;
-
-public class UpdateManager {
-
-	private final Options opts;
-	public final IUserInterface ui;
-	private boolean cancelled;
-	private boolean cancelledStartGame = false;
-	private InputStateHandler stateHandler;
-	private boolean errorsOccurred = false;
-
-	public static class Options {
-		SpaceSafeURI downloadURI = null;
-		String manifestFile = "packwiz.json"; // TODO: make configurable
-		String packFolder = ".";
-		Side side = Side.CLIENT;
-
-		public enum Side {
-			@SerializedName("client")
-			CLIENT("client"),
-			@SerializedName("server")
-			SERVER("server"),
-			@SerializedName("both")
-			BOTH("both", new Side[] { CLIENT, SERVER });
-
-			private final String sideName;
-			private final Side[] depSides;
-
-			Side(String sideName) {
-				this.sideName = sideName.toLowerCase();
-				this.depSides = null;
-			}
-
-			Side(String sideName, Side[] depSides) {
-				this.sideName = sideName.toLowerCase();
-				this.depSides = depSides;
-			}
-
-			@Override
-			public String toString() {
-				return this.sideName;
-			}
-
-			public boolean hasSide(Side tSide) {
-				if (this.equals(tSide)) {
-					return true;
-				}
-				if (this.depSides != null) {
-					for (Side depSide : this.depSides) {
-						if (depSide.equals(tSide)) {
-							return true;
-						}
-					}
-				}
-				return false;
-			}
-
-			public static Side from(String name) {
-				String lowerName = name.toLowerCase();
-				for (Side side : Side.values()) {
-					if (side.sideName.equals(lowerName)) {
-						return side;
-					}
-				}
-				return null;
-			}
-		}
-	}
-
-	UpdateManager(Options opts, IUserInterface ui, InputStateHandler inputStateHandler) {
-		this.opts = opts;
-		this.ui = ui;
-		this.stateHandler = inputStateHandler;
-		this.start();
-	}
-
-	private void start() {
-		this.checkOptions();
-
-		ui.submitProgress(new InstallProgress("Loading manifest file..."));
-		Gson gson = new GsonBuilder().registerTypeAdapter(Hash.class, new Hash.TypeHandler()).create();
-		ManifestFile manifest;
-		try {
-			manifest = gson.fromJson(new FileReader(Paths.get(opts.packFolder, opts.manifestFile).toString()),
-					ManifestFile.class);
-		} catch (FileNotFoundException e) {
-			manifest = new ManifestFile();
-		} catch (JsonSyntaxException | JsonIOException e) {
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-
-		if (stateHandler.getCancelButton()) {
-			showCancellationDialog();
-			handleCancellation();
-		}
-
-		ui.submitProgress(new InstallProgress("Loading pack file..."));
-		GeneralHashingSource packFileSource;
-		try {
-			Source src = HandlerManager.getFileSource(opts.downloadURI);
-			packFileSource = HashUtils.getHasher("sha256").getHashingSource(src);
-		} catch (Exception e) {
-			// TODO: still launch the game if updating doesn't work?
-			// TODO: ask user if they want to launch the game, exit(1) if they don't
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-		PackFile pf;
-		try {
-			pf = new Toml().read(Okio.buffer(packFileSource).inputStream()).to(PackFile.class);
-		} catch (IllegalStateException e) {
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-
-		if (stateHandler.getCancelButton()) {
-			showCancellationDialog();
-			handleCancellation();
-		}
-
-		ui.submitProgress(new InstallProgress("Checking local files..."));
-
-		// Invalidation checking must be done here, as it must happen before pack/index hashes are checked
-		List<SpaceSafeURI> invalidatedUris = new ArrayList<>();
-		if (manifest.cachedFiles != null) {
-			for (Map.Entry<SpaceSafeURI, ManifestFile.File> entry : manifest.cachedFiles.entrySet()) {
-				// ignore onlyOtherSide files
-				if (entry.getValue().onlyOtherSide) {
-					continue;
-				}
-				boolean invalid = false;
-				// if isn't optional, or is optional but optionValue == true
-				if (!entry.getValue().isOptional || entry.getValue().optionValue) {
-					if (entry.getValue().cachedLocation != null) {
-						if (!Files.exists(Paths.get(opts.packFolder, entry.getValue().cachedLocation))) {
-							invalid = true;
-						}
-					} else {
-						// if cachedLocation == null, should probably be installed!!
-						invalid = true;
-					}
-				}
-				if (invalid) {
-					SpaceSafeURI fileUri = entry.getKey();
-					System.out.println("File " + fileUri.toString() + " invalidated, marked for redownloading");
-					invalidatedUris.add(fileUri);
-				}
-			}
-		}
-
-		if (manifest.packFileHash != null && packFileSource.hashIsEqual(manifest.packFileHash) && invalidatedUris.isEmpty()) {
-			System.out.println("Modpack is already up to date!");
-			// todo: --force?
-			if (!stateHandler.getOptionsButton()) {
-				return;
-			}
-		}
-
-		System.out.println("Modpack name: " + pf.name);
-
-		if (stateHandler.getCancelButton()) {
-			showCancellationDialog();
-			handleCancellation();
-		}
-
-		try {
-			// This is badly written, I'll probably heavily refactor it at some point
-			processIndex(HandlerManager.getNewLoc(opts.downloadURI, pf.index.file),
-					HashUtils.getHash(pf.index.hashFormat, pf.index.hash), pf.index.hashFormat, manifest, invalidatedUris);
-		} catch (Exception e1) {
-			ui.handleExceptionAndExit(e1);
-		}
-
-		handleCancellation();
-
-		// TODO: update MMC params, java args etc
-
-		// If there were errors, don't write the manifest/index hashes, to ensure they are rechecked later
-		if (errorsOccurred) {
-			manifest.indexFileHash = null;
-			manifest.packFileHash = null;
-		} else {
-			manifest.packFileHash = packFileSource.getHash();
-		}
-
-		manifest.cachedSide = opts.side;
-		try (Writer writer = new FileWriter(Paths.get(opts.packFolder, opts.manifestFile).toString())) {
-			gson.toJson(manifest, writer);
-		} catch (IOException e) {
-			// TODO: add message?
-			ui.handleException(e);
-		}
-
-	}
-
-	private void checkOptions() {
-		// TODO: implement
-	}
-
-	private void processIndex(SpaceSafeURI indexUri, Hash indexHash, String hashFormat, ManifestFile manifest, List<SpaceSafeURI> invalidatedUris) {
-		if (manifest.indexFileHash != null && manifest.indexFileHash.equals(indexHash) && invalidatedUris.isEmpty()) {
-			System.out.println("Modpack files are already up to date!");
-			if (!stateHandler.getOptionsButton()) {
-				return;
-			}
-		}
-		manifest.indexFileHash = indexHash;
-
-		GeneralHashingSource indexFileSource;
-		try {
-			Source src = HandlerManager.getFileSource(indexUri);
-			indexFileSource = HashUtils.getHasher(hashFormat).getHashingSource(src);
-		} catch (Exception e) {
-			// TODO: still launch the game if updating doesn't work?
-			// TODO: ask user if they want to launch the game, exit(1) if they don't
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-		IndexFile indexFile;
-		try {
-			indexFile = new Toml().read(Okio.buffer(indexFileSource).inputStream()).to(IndexFile.class);
-		} catch (IllegalStateException e) {
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-
-		if (!indexFileSource.hashIsEqual(indexHash)) {
-			// TODO: throw exception
-			System.out.println("I was meant to put an error message here but I'll do that later");
-			return;
-		}
-
-		if (stateHandler.getCancelButton()) {
-			showCancellationDialog();
-			return;
-		}
-
-		if (manifest.cachedFiles == null) {
-			manifest.cachedFiles = new HashMap<>();
-		}
-
-		ui.submitProgress(new InstallProgress("Checking local files..."));
-		Iterator<Map.Entry<SpaceSafeURI, ManifestFile.File>> it = manifest.cachedFiles.entrySet().iterator();
-		while (it.hasNext()) {
-			Map.Entry<SpaceSafeURI, ManifestFile.File> entry = it.next();
-			if (entry.getValue().cachedLocation != null) {
-				boolean alreadyDeleted = false;
-				// Delete if option value has been set to false
-				if (entry.getValue().isOptional && !entry.getValue().optionValue) {
-					try {
-						Files.deleteIfExists(Paths.get(opts.packFolder, entry.getValue().cachedLocation));
-					} catch (IOException e) {
-						// TODO: should this be shown to the user in some way?
-						e.printStackTrace();
-					}
-					// Set to null, as it doesn't exist anymore
-					entry.getValue().cachedLocation = null;
-					alreadyDeleted = true;
-				}
-				if (indexFile.files.stream().noneMatch(f -> f.file.equals(entry.getKey()))) {
-					// File has been removed from the index
-					if (!alreadyDeleted) {
-						try {
-							Files.deleteIfExists(Paths.get(opts.packFolder, entry.getValue().cachedLocation));
-						} catch (IOException e) {
-							// TODO: should this be shown to the user in some way?
-							e.printStackTrace();
-						}
-					}
-					it.remove();
-				}
-			}
-		}
-
-		if (stateHandler.getCancelButton()) {
-			showCancellationDialog();
-			return;
-		}
-		ui.submitProgress(new InstallProgress("Comparing new files..."));
-
-		// TODO: progress bar?
-		if (indexFile.files == null || indexFile.files.size() == 0) {
-			System.out.println("Warning: Index is empty!");
-			indexFile.files = new ArrayList<>();
-		}
-		List<DownloadTask> tasks = DownloadTask.createTasksFromIndex(indexFile, indexFile.hashFormat, opts.side);
-		// If the side changes, invalidate EVERYTHING just in case
-		// Might not be needed, but done just to be safe
-		boolean invalidateAll = !opts.side.equals(manifest.cachedSide);
-		if (invalidateAll) {
-			System.out.println("Side changed, invalidating all mods");
-		}
-		tasks.forEach(f -> {
-			// TODO: should linkedfile be checked as well? should this be done in the download section?
-			if (invalidateAll) {
-				f.invalidate();
-			} else if (invalidatedUris.contains(f.metadata.file)) {
-				f.invalidate();
-			}
-			ManifestFile.File file = manifest.cachedFiles.get(f.metadata.file);
-			if (file != null) {
-				// Ensure the file can be reverted later if necessary - the DownloadTask modifies the file so if it fails we need the old version back
-				file.backup();
-			}
-			// If it is null, the DownloadTask will make a new empty cachedFile
-			f.updateFromCache(file);
-		});
-
-		if (stateHandler.getCancelButton()) {
-			showCancellationDialog();
-			return;
-		}
-
-		// Let's hope downloadMetadata is a pure function!!!
-		tasks.parallelStream().forEach(f -> f.downloadMetadata(indexFile, indexUri));
-
-		List<IExceptionDetails> failedTasks = tasks.stream().filter(t -> t.getException() != null).collect(Collectors.toList());
-		if (!failedTasks.isEmpty()) {
-			errorsOccurred = true;
-			IExceptionDetails.ExceptionListResult exceptionListResult;
-			try {
-				exceptionListResult = ui.showExceptions(failedTasks, tasks.size(), true).get();
-			} catch (InterruptedException | ExecutionException e) {
-				// Interrupted means cancelled???
-				ui.handleExceptionAndExit(e);
-				return;
-			}
-			switch (exceptionListResult) {
-				case CONTINUE:
-					break;
-				case CANCEL:
-					cancelled = true;
-					return;
-				case IGNORE:
-					cancelledStartGame = true;
-					return;
-			}
-		}
-
-		if (stateHandler.getCancelButton()) {
-			showCancellationDialog();
-			return;
-		}
-
-		List<DownloadTask> nonFailedFirstTasks = tasks.stream().filter(t -> t.getException() == null).collect(Collectors.toList());
-		List<DownloadTask> optionTasks = nonFailedFirstTasks.stream().filter(DownloadTask::correctSide).filter(DownloadTask::isOptional).collect(Collectors.toList());
-		// If options changed, present all options again
-		if (stateHandler.getOptionsButton() || optionTasks.stream().anyMatch(DownloadTask::isNewOptional)) {
-			// new ArrayList is requires so it's an IOptionDetails rather than a DownloadTask list
-			Future<Boolean> cancelledResult = ui.showOptions(new ArrayList<>(optionTasks));
-			try {
-				if (cancelledResult.get()) {
-					cancelled = true;
-					// TODO: Should the UI be closed somehow??
-					return;
-				}
-			} catch (InterruptedException | ExecutionException e) {
-				// Interrupted means cancelled???
-				ui.handleExceptionAndExit(e);
-			}
-		}
-		ui.disableOptionsButton();
-
-		// TODO: different thread pool type?
-		ExecutorService threadPool = Executors.newFixedThreadPool(10);
-		CompletionService<DownloadTask> completionService = new ExecutorCompletionService<>(threadPool);
-
-		tasks.forEach(t -> completionService.submit(() -> {
-			t.download(opts.packFolder, indexUri);
-			return t;
-		}));
-
-		for (int i = 0; i < tasks.size(); i++) {
-			DownloadTask task;
-			try {
-				task = completionService.take().get();
-			} catch (InterruptedException | ExecutionException e) {
-				ui.handleException(e);
-				task = null;
-			}
-			// Update manifest - If there were no errors cachedFile has already been modified in place (good old pass by reference)
-			if (task != null) {
-				if (task.getException() != null) {
-					ManifestFile.File file = task.cachedFile.getRevert();
-					if (file != null) {
-						manifest.cachedFiles.putIfAbsent(task.metadata.file, file);
-					}
-				} else {
-					// idiot, if it wasn't there in the first place it won't magically appear there
-					manifest.cachedFiles.putIfAbsent(task.metadata.file, task.cachedFile);
-				}
-			}
-
-			String progress;
-			if (task != null) {
-				if (task.getException() != null) {
-					progress = "Failed to download " + task.metadata.getName() + ": " + task.getException().getMessage();
-					task.getException().printStackTrace();
-				} else {
-					// TODO: should this be revised for tasks that didn't actually download it?
-					progress = "Downloaded " + task.metadata.getName();
-				}
-			} else {
-				progress = "Failed to download, unknown reason";
-			}
-			ui.submitProgress(new InstallProgress(progress, i + 1, tasks.size()));
-
-			if (stateHandler.getCancelButton()) {
-				// Stop all tasks, don't launch the game (it's in an invalid state!)
-				threadPool.shutdown();
-				cancelled = true;
-				return;
-			}
-		}
-
-		// Shut down the thread pool when the update is done
-		threadPool.shutdown();
-
-		List<IExceptionDetails> failedTasks2ElectricBoogaloo = nonFailedFirstTasks.stream().filter(t -> t.getException() != null).collect(Collectors.toList());
-		if (!failedTasks2ElectricBoogaloo.isEmpty()) {
-			errorsOccurred = true;
-			IExceptionDetails.ExceptionListResult exceptionListResult;
-			try {
-				exceptionListResult = ui.showExceptions(failedTasks2ElectricBoogaloo, tasks.size(), false).get();
-			} catch (InterruptedException | ExecutionException e) {
-				// Interrupted means cancelled???
-				ui.handleExceptionAndExit(e);
-				return;
-			}
-			switch (exceptionListResult) {
-				case CONTINUE:
-					break;
-				case CANCEL:
-					cancelled = true;
-					return;
-				case IGNORE:
-					cancelledStartGame = true;
-			}
-		}
-	}
-
-	private void showCancellationDialog() {
-		IExceptionDetails.ExceptionListResult exceptionListResult;
-		try {
-			exceptionListResult = ui.showCancellationDialog().get();
-		} catch (InterruptedException | ExecutionException e) {
-			// Interrupted means cancelled???
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-		switch (exceptionListResult) {
-			case CONTINUE:
-				throw new RuntimeException("Continuation not allowed here!");
-			case CANCEL:
-				cancelled = true;
-				return;
-			case IGNORE:
-				cancelledStartGame = true;
-		}
-	}
-
-	private void handleCancellation() {
-		if (cancelled) {
-			System.out.println("Update cancelled by user!");
-			System.exit(1);
-		} else if (cancelledStartGame) {
-			System.out.println("Update cancelled by user! Continuing to start game...");
-			System.exit(0);
-		}
-	}
-}

src/main/java/link/infra/packwiz/installer/metadata/EfficientBooleanAdapter.java

@@ -1,29 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import com.google.gson.TypeAdapter;
-import com.google.gson.stream.JsonReader;
-import com.google.gson.stream.JsonToken;
-import com.google.gson.stream.JsonWriter;
-
-import java.io.IOException;
-
-public class EfficientBooleanAdapter extends TypeAdapter<Boolean> {
-
-	@Override
-	public void write(JsonWriter out, Boolean value) throws IOException {
-		if (value == null || !value) {
-			out.nullValue();
-			return;
-		}
-		out.value(true);
-	}
-
-	@Override
-	public Boolean read(JsonReader in) throws IOException {
-		if (in.peek() == JsonToken.NULL) {
-			in.nextNull();
-			return false;
-		}
-		return in.nextBoolean();
-	}
-}

src/main/java/link/infra/packwiz/installer/metadata/IndexFile.java

@@ -1,105 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import com.google.gson.annotations.SerializedName;
-import com.moandjiezana.toml.Toml;
-import link.infra.packwiz.installer.metadata.hash.GeneralHashingSource;
-import link.infra.packwiz.installer.metadata.hash.Hash;
-import link.infra.packwiz.installer.metadata.hash.HashUtils;
-import link.infra.packwiz.installer.request.HandlerManager;
-import okio.Okio;
-import okio.Source;
-
-import java.nio.file.Paths;
-import java.util.List;
-
-public class IndexFile {
-	@SerializedName("hash-format")
-	public String hashFormat;
-	public List<File> files;
-	
-	public static class File {
-		public SpaceSafeURI file;
-		@SerializedName("hash-format")
-		public String hashFormat;
-		public String hash;
-		public SpaceSafeURI alias;
-		public boolean metafile;
-		public boolean preserve;
-
-		public transient ModFile linkedFile;
-		public transient SpaceSafeURI linkedFileURI;
-
-		public void downloadMeta(IndexFile parentIndexFile, SpaceSafeURI indexUri) throws Exception {
-			if (!metafile) {
-				return;
-			}
-			if (hashFormat == null || hashFormat.length() == 0) {
-				hashFormat = parentIndexFile.hashFormat;
-			}
-			Hash fileHash = HashUtils.getHash(hashFormat, hash);
-			linkedFileURI = HandlerManager.getNewLoc(indexUri, file);
-			Source src = HandlerManager.getFileSource(linkedFileURI);
-			GeneralHashingSource fileStream = HashUtils.getHasher(hashFormat).getHashingSource(src);
-
-			linkedFile = new Toml().read(Okio.buffer(fileStream).inputStream()).to(ModFile.class);
-			if (!fileStream.hashIsEqual(fileHash)) {
-				throw new Exception("Invalid mod file hash");
-			}
-		}
-
-		public Source getSource(SpaceSafeURI indexUri) throws Exception {
-			if (metafile) {
-				if (linkedFile == null) {
-					throw new Exception("Linked file doesn't exist!");
-				}
-				return linkedFile.getSource(linkedFileURI);
-			} else {
-				SpaceSafeURI newLoc = HandlerManager.getNewLoc(indexUri, file);
-				if (newLoc == null) {
-					throw new Exception("Index file URI is invalid");
-				}
-				return HandlerManager.getFileSource(newLoc);
-			}
-		}
-
-		public Hash getHash() throws Exception {
-			if (hash == null) {
-				// TODO: should these be more specific exceptions (e.g. IndexFileException?!)
-				throw new Exception("Index file doesn't have a hash");
-			}
-			if (hashFormat == null) {
-				throw new Exception("Index file doesn't have a hash format");
-			}
-			return HashUtils.getHash(hashFormat, hash);
-		}
-
-		public String getName() {
-			if (metafile) {
-				if (linkedFile != null) {
-					if (linkedFile.name != null) {
-						return linkedFile.name;
-					} else if (linkedFile.filename != null) {
-						return linkedFile.filename;
-					}
-				}
-			}
-			if (file != null) {
-				return Paths.get(file.getPath()).getFileName().toString();
-			}
-			// TODO: throw some kind of exception?
-			return "Invalid file";
-		}
-
-		public SpaceSafeURI getDestURI() {
-			if (alias != null) {
-				return alias;
-			}
-			if (metafile && linkedFile != null) {
-				// TODO: URIs are bad
-				return file.resolve(linkedFile.filename);
-			} else {
-				return file;
-			}
-		}
-	}
-}

src/main/java/link/infra/packwiz/installer/metadata/ManifestFile.java

@@ -1,45 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import com.google.gson.annotations.JsonAdapter;
-import link.infra.packwiz.installer.UpdateManager;
-import link.infra.packwiz.installer.metadata.hash.Hash;
-
-import java.util.Map;
-
-public class ManifestFile {
-	public Hash packFileHash = null;
-	public Hash indexFileHash = null;
-	public Map<SpaceSafeURI, File> cachedFiles;
-	// If the side changes, EVERYTHING invalidates. FUN!!!
-	public UpdateManager.Options.Side cachedSide = UpdateManager.Options.Side.CLIENT;
-
-	public static class File {
-		private transient File revert;
-
-		public Hash hash = null;
-		public Hash linkedFileHash = null;
-		public String cachedLocation = null;
-
-		@JsonAdapter(EfficientBooleanAdapter.class)
-		public boolean isOptional = false;
-		public boolean optionValue = true;
-
-		@JsonAdapter(EfficientBooleanAdapter.class)
-		public boolean onlyOtherSide = false;
-
-		// When an error occurs, the state needs to be reverted. To do this, I have a crude revert system.
-		public void backup() {
-			revert = new File();
-			revert.hash = hash;
-			revert.linkedFileHash = linkedFileHash;
-			revert.cachedLocation = cachedLocation;
-			revert.isOptional = isOptional;
-			revert.optionValue = optionValue;
-			revert.onlyOtherSide = onlyOtherSide;
-		}
-
-		public File getRevert() {
-			return revert;
-		}
-	}
-}

src/main/java/link/infra/packwiz/installer/metadata/ModFile.java

@@ -1,70 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import com.google.gson.annotations.SerializedName;
-import link.infra.packwiz.installer.UpdateManager.Options.Side;
-import link.infra.packwiz.installer.metadata.hash.Hash;
-import link.infra.packwiz.installer.metadata.hash.HashUtils;
-import link.infra.packwiz.installer.request.HandlerManager;
-import okio.Source;
-
-import java.util.Map;
-
-public class ModFile {
-	public String name;
-	public String filename;
-	public Side side;
-
-	public Download download;
-	public static class Download {
-		public SpaceSafeURI url;
-		@SerializedName("hash-format")
-		public String hashFormat;
-		public String hash;
-	}
-
-	public Map<String, Object> update;
-
-	public Option option;
-	public static class Option {
-		public boolean optional;
-		public String description;
-		@SerializedName("default")
-		public boolean defaultValue;
-	}
-
-	public Source getSource(SpaceSafeURI baseLoc) throws Exception {
-		if (download == null) {
-			throw new Exception("Metadata file doesn't have download");
-		}
-		if (download.url == null) {
-			throw new Exception("Metadata file doesn't have a download URI");
-		}
-		SpaceSafeURI newLoc = HandlerManager.getNewLoc(baseLoc, download.url);
-		if (newLoc == null) {
-			throw new Exception("Metadata file URI is invalid");
-		}
-		
-		return HandlerManager.getFileSource(newLoc);
-	}
-
-	public Hash getHash() throws Exception {
-		if (download == null) {
-			throw new Exception("Metadata file doesn't have download");
-		}
-		if (download.hash == null) {
-			throw new Exception("Metadata file doesn't have a hash");
-		}
-		if (download.hashFormat == null) {
-			throw new Exception("Metadata file doesn't have a hash format");
-		}
-		return HashUtils.getHash(download.hashFormat, download.hash);
-	}
-
-	public boolean isOptional() {
-		if (option != null) {
-			return option.optional;
-		}
-		return false;
-	}
-
-}

src/main/java/link/infra/packwiz/installer/metadata/PackFile.java

@@ -1,21 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import com.google.gson.annotations.SerializedName;
-
-import java.util.Map;
-
-public class PackFile {
-	public String name;
-
-	public IndexFileLoc index;
-	public static class IndexFileLoc {
-		public SpaceSafeURI file;
-		@SerializedName("hash-format")
-		public String hashFormat;
-		public String hash;
-	}
-
-	public Map<String, String> versions;
-	public Map<String, Object> client;
-	public Map<String, Object> server;
-}

src/main/java/link/infra/packwiz/installer/metadata/SpaceSafeURI.java

@@ -1,88 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import com.google.gson.annotations.JsonAdapter;
-
-import java.io.Serializable;
-import java.net.MalformedURLException;
-import java.net.URI;
-import java.net.URISyntaxException;
-import java.net.URL;
-
-// The world's worst URI wrapper
-@JsonAdapter(SpaceSafeURIParser.class)
-public class SpaceSafeURI implements Comparable<SpaceSafeURI>, Serializable {
-	private final URI u;
-
-	public SpaceSafeURI(String str) throws URISyntaxException {
-		u = new URI(str.replace(" ", "%20"));
-	}
-
-	public SpaceSafeURI(URI uri) {
-		this.u = uri;
-	}
-
-	public SpaceSafeURI(String scheme, String authority, String path, String query, String fragment) throws URISyntaxException {
-		// TODO: do all components need to be replaced?
-		scheme = scheme.replace(" ", "%20");
-		authority = authority.replace(" ", "%20");
-		path = path.replace(" ", "%20");
-		query = query.replace(" ", "%20");
-		fragment = fragment.replace(" ", "%20");
-		u = new URI(scheme, authority, path, query, fragment);
-	}
-
-	public String getPath() {
-		return u.getPath().replace("%20", " ");
-	}
-
-	public String toString() {
-		return u.toString().replace("%20", " ");
-	}
-
-	@SuppressWarnings("WeakerAccess")
-	public SpaceSafeURI resolve(String path) {
-		return new SpaceSafeURI(u.resolve(path.replace(" ", "%20")));
-	}
-
-	public SpaceSafeURI resolve(SpaceSafeURI loc) {
-		return new SpaceSafeURI(u.resolve(loc.u));
-	}
-
-	public SpaceSafeURI relativize(SpaceSafeURI loc) {
-		return new SpaceSafeURI(u.relativize(loc.u));
-	}
-
-	@Override
-	public boolean equals(Object obj) {
-		if (obj instanceof SpaceSafeURI) {
-			return u.equals(((SpaceSafeURI) obj).u);
-		}
-		return false;
-	}
-
-	@Override
-	public int hashCode() {
-		return u.hashCode();
-	}
-
-	@Override
-	public int compareTo(SpaceSafeURI uri) {
-		return u.compareTo(uri.u);
-	}
-
-	public String getScheme() {
-		return u.getScheme();
-	}
-
-	public String getAuthority() {
-		return u.getAuthority();
-	}
-
-	public String getHost() {
-		return u.getHost();
-	}
-
-	public URL toURL() throws MalformedURLException {
-		return u.toURL();
-	}
-}

src/main/java/link/infra/packwiz/installer/metadata/SpaceSafeURIParser.java

@@ -1,29 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import com.google.gson.JsonDeserializationContext;
-import com.google.gson.JsonDeserializer;
-import com.google.gson.JsonElement;
-import com.google.gson.JsonParseException;
-
-import java.lang.reflect.Type;
-import java.net.URISyntaxException;
-
-/**
- * This class encodes spaces before parsing the URI, so the URI can actually be
- * parsed.
- */
-class SpaceSafeURIParser implements JsonDeserializer<SpaceSafeURI> {
-
-	@Override
-	public SpaceSafeURI deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
-			throws JsonParseException {
-		try {
-			return new SpaceSafeURI(json.getAsString());
-		} catch (URISyntaxException e) {
-			throw new JsonParseException("Failed to parse URI", e);
-		}
-	}
-
-	// TODO: replace this with a better solution?
-
-}

src/main/java/link/infra/packwiz/installer/metadata/hash/GeneralHashingSource.java

@@ -1,18 +0,0 @@
-package link.infra.packwiz.installer.metadata.hash;
-
-import okio.ForwardingSource;
-import okio.Source;
-
-public abstract class GeneralHashingSource extends ForwardingSource {
-
-	public GeneralHashingSource(Source delegate) {
-		super(delegate);
-	}
-
-	public abstract Hash getHash();
-
-	public boolean hashIsEqual(Object compareTo) {
-		return compareTo.equals(getHash());
-	}
-
-}

src/main/java/link/infra/packwiz/installer/metadata/hash/Hash.java

@@ -1,48 +0,0 @@
-package link.infra.packwiz.installer.metadata.hash;
-
-import java.lang.reflect.Type;
-
-import com.google.gson.JsonDeserializationContext;
-import com.google.gson.JsonDeserializer;
-import com.google.gson.JsonElement;
-import com.google.gson.JsonObject;
-import com.google.gson.JsonParseException;
-import com.google.gson.JsonPrimitive;
-import com.google.gson.JsonSerializationContext;
-import com.google.gson.JsonSerializer;
-
-public abstract class Hash {
-	protected abstract String getStringValue();
-
-	protected abstract String getType();
-
-	public static class TypeHandler implements JsonDeserializer<Hash>, JsonSerializer<Hash> {
-
-		@Override
-		public JsonElement serialize(Hash src, Type typeOfSrc, JsonSerializationContext context) {
-			JsonObject out = new JsonObject();
-			out.add("type", new JsonPrimitive(src.getType()));
-			out.add("value", new JsonPrimitive(src.getStringValue()));
-			return out;
-		}
-
-		@Override
-		public Hash deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
-				throws JsonParseException {
-			JsonObject obj = json.getAsJsonObject();
-			String type, value;
-			try {
-				type = obj.get("type").getAsString();
-				value = obj.get("value").getAsString();
-			} catch (NullPointerException e) {
-				throw new JsonParseException("Invalid hash JSON data");
-			}
-			try {
-				return HashUtils.getHash(type, value);
-			} catch (Exception e) {
-				throw new JsonParseException("Failed to create hash object", e);
-			}
-		}
-
-	}
-}

src/main/java/link/infra/packwiz/installer/metadata/hash/HashUtils.java

@@ -1,29 +0,0 @@
-package link.infra.packwiz.installer.metadata.hash;
-
-import java.util.HashMap;
-import java.util.Map;
-
-public class HashUtils {
-	private static final Map<String, IHasher> hashTypeConversion = new HashMap<String, IHasher>();
-	static {
-		hashTypeConversion.put("sha256", new HashingSourceHasher("sha256"));
-		hashTypeConversion.put("murmur2", new Murmur2Hasher());
-	}
-
-	public static IHasher getHasher(String type) throws Exception {
-		IHasher hasher = hashTypeConversion.get(type);
-		if (hasher == null) {
-			throw new Exception("Hash type not supported: " + type);
-		}
-		return hasher;
-	}
-
-	public static Hash getHash(String type, String value) throws Exception {
-		if (hashTypeConversion.containsKey(type)) {
-			return hashTypeConversion.get(type).getHash(value);
-		}
-
-		throw new Exception("Hash type not supported: " + type);
-	}
-
-}

src/main/java/link/infra/packwiz/installer/metadata/hash/HashingSourceHasher.java

@@ -1,89 +0,0 @@
-package link.infra.packwiz.installer.metadata.hash;
-
-import okio.HashingSource;
-import okio.Source;
-
-public class HashingSourceHasher implements IHasher {
-	private String type;
-
-	HashingSourceHasher(String type) {
-		this.type = type;
-	}
-
-	// i love naming things
-	private class HashingSourceGeneralHashingSource extends GeneralHashingSource {
-		HashingSource delegateHashing;
-		HashingSourceHash value;
-
-		HashingSourceGeneralHashingSource(HashingSource delegate) {
-			super(delegate);
-			delegateHashing = delegate;
-		}
-
-		@Override
-		public Hash getHash() {
-			if (value == null) {
-				value = new HashingSourceHash(delegateHashing.hash().hex());
-			}
-			return value;
-		}
-
-	}
-
-	// this some funky inner class stuff
-	// each of these classes is specific to the instance of the HasherHashingSource
-	// therefore HashingSourceHashes from different parent instances will be not instanceof each other
-	private class HashingSourceHash extends Hash {
-		String value;
-		private HashingSourceHash(String value) {
-			this.value = value;
-		}
-
-		@Override
-		public boolean equals(Object obj) {
-			if (!(obj instanceof HashingSourceHash)) {
-				return false;
-			}
-			HashingSourceHash objHash = (HashingSourceHash) obj;
-			if (value != null) {
-				return value.equalsIgnoreCase(objHash.value);
-			} else {
-				return objHash.value == null;
-			}
-		}
-
-		@Override
-		public String toString() {
-			return type + ": " + value;
-		}
-
-		@Override
-		protected String getStringValue() {
-			return value;
-		}
-
-		@Override
-		protected String getType() {
-			return type;
-		}
-	}
-
-	@Override
-	public GeneralHashingSource getHashingSource(Source delegate) {
-		switch (type) {
-			case "md5":
-				return new HashingSourceGeneralHashingSource(HashingSource.md5(delegate));
-			case "sha256":
-				return new HashingSourceGeneralHashingSource(HashingSource.sha256(delegate));
-			case "sha512":
-				return new HashingSourceGeneralHashingSource(HashingSource.sha512(delegate));
-		}
-		throw new RuntimeException("Invalid hash type provided");
-	}
-
-	@Override
-	public Hash getHash(String value) {
-		return new HashingSourceHash(value);
-	}
-	
-}

src/main/java/link/infra/packwiz/installer/metadata/hash/IHasher.java

@@ -1,8 +0,0 @@
-package link.infra.packwiz.installer.metadata.hash;
-
-import okio.Source;
-
-public interface IHasher {
-	public GeneralHashingSource getHashingSource(Source delegate);
-	public Hash getHash(String value);
-}

src/main/java/link/infra/packwiz/installer/metadata/hash/Murmur2Hasher.java

@@ -1,103 +0,0 @@
-package link.infra.packwiz.installer.metadata.hash;
-
-import okio.Buffer;
-import okio.Source;
-
-import java.io.IOException;
-
-public class Murmur2Hasher implements IHasher {
-	private class Murmur2GeneralHashingSource extends GeneralHashingSource {
-		Murmur2Hash value;
-		Buffer internalBuffer = new Buffer();
-		Buffer tempBuffer = new Buffer();
-		Source delegate;
-
-		public Murmur2GeneralHashingSource(Source delegate) {
-			super(delegate);
-			this.delegate = delegate;
-		}
-
-		@Override
-		public long read(Buffer sink, long byteCount) throws IOException {
-			long out = delegate.read(tempBuffer, byteCount);
-			if (out > -1) {
-				sink.write(tempBuffer.clone(), out);
-				internalBuffer.write(tempBuffer, out);
-			}
-			return out;
-		}
-
-		@Override
-		public Hash getHash() {
-			if (value == null) {
-				byte[] data = computeNormalizedArray(internalBuffer.readByteArray());
-				value = new Murmur2Hash(Murmur2Lib.hash32(data, data.length, 1));
-			}
-			return value;
-		}
-
-		// Credit to https://github.com/modmuss50/CAV2/blob/master/murmur.go
-		private byte[] computeNormalizedArray(byte[] input) {
-			byte[] output = new byte[input.length];
-			int num = 0;
-			for (byte b : input) {
-				if (!(b == 9 || b == 10 || b == 13 || b == 32)) {
-					output[num] = b;
-					num++;
-				}
-			}
-			byte[] outputTrimmed = new byte[num];
-			System.arraycopy(output, 0, outputTrimmed, 0, num);
-			return outputTrimmed;
-		}
-
-	}
-
-	private static class Murmur2Hash extends Hash {
-		int value;
-		private Murmur2Hash(String value) {
-			// Parsing as long then casting to int converts values gt int max value but lt uint max value
-			// into negatives. I presume this is how the murmur2 code handles this.
-			this.value = (int)Long.parseLong(value);
-		}
-
-		private Murmur2Hash(int value) {
-			this.value = value;
-		}
-
-		@Override
-		public boolean equals(Object obj) {
-			if (!(obj instanceof Murmur2Hash)) {
-				return false;
-			}
-			Murmur2Hash objHash = (Murmur2Hash) obj;
-			return value == objHash.value;
-		}
-
-		@Override
-		public String toString() {
-			return "murmur2: " + value;
-		}
-
-		@Override
-		protected String getStringValue() {
-			return Integer.toString(value);
-		}
-
-		@Override
-		protected String getType() {
-			return "murmur2";
-		}
-	}
-
-	@Override
-	public GeneralHashingSource getHashingSource(Source delegate) {
-		return new Murmur2GeneralHashingSource(delegate);
-	}
-
-	@Override
-	public Hash getHash(String value) {
-		return new Murmur2Hash(value);
-	}
-	
-}

src/main/java/link/infra/packwiz/installer/metadata/hash/Murmur2Lib.java

@@ -74,13 +74,13 @@ public class Murmur2Lib {
     int left = length - len_m;
     if (left != 0) {
       if (left >= 3) {
-        h ^= (int) data[length - 3] << 16;
+        h ^= (int) data[length - (left - 2)] << 16;
       }
       if (left >= 2) {
-        h ^= (int) data[length - 2] << 8;
+        h ^= (int) data[length - (left - 1)] << 8;
       }
       if (left >= 1) {
-        h ^= (int) data[length - 1];
+        h ^= data[length - left];
       }
 
       h *= M_32;
@@ -152,7 +152,7 @@ public class Murmur2Lib {
       case 2:
         h ^= (long) (data[tailStart + 1] & 0xff) << 8;
       case 1:
-        h ^= (long) (data[tailStart] & 0xff);
+        h ^= data[tailStart] & 0xff;
         h *= M_64;
     }
 

src/main/java/link/infra/packwiz/installer/request/HandlerManager.java

@@ -1,59 +0,0 @@
-package link.infra.packwiz.installer.request;
-
-import link.infra.packwiz.installer.metadata.SpaceSafeURI;
-import link.infra.packwiz.installer.request.handlers.RequestHandlerGithub;
-import link.infra.packwiz.installer.request.handlers.RequestHandlerHTTP;
-import okio.Source;
-
-import java.util.ArrayList;
-import java.util.List;
-
-public abstract class HandlerManager {
-	
-	private static List<IRequestHandler> handlers = new ArrayList<>();
-	
-	static {
-		handlers.add(new RequestHandlerGithub());
-		handlers.add(new RequestHandlerHTTP());
-	}
-	
-	public static SpaceSafeURI getNewLoc(SpaceSafeURI base, SpaceSafeURI loc) {
-		if (loc == null) return null;
-		if (base != null) {
-			loc = base.resolve(loc);
-		}
-		
-		for (IRequestHandler handler : handlers) {
-			if (handler.matchesHandler(loc)) {
-				return handler.getNewLoc(loc);
-			}
-		}
-		return loc;
-	}
-	
-	// TODO: What if files are read multiple times??
-	// Zip handler discards once read, requesting multiple times on other handlers would cause multiple downloads
-	// Caching system? Copy from already downloaded files?
-
-	public static Source getFileSource(SpaceSafeURI loc) throws Exception {
-		for (IRequestHandler handler : handlers) {
-			if (handler.matchesHandler(loc)) {
-				Source src = handler.getFileSource(loc);
-				if (src == null) {
-					throw new Exception("Couldn't find URI: " + loc.toString());
-				} else {
-					return src;
-				}
-			}
-		}
-		// TODO: specialised exception classes??
-		throw new Exception("No handler available for URI: " + loc.toString());
-	}
-	
-	// github toml resolution
-	// e.g. https://github.com/comp500/Demagnetize -> demagnetize.toml
-	// https://github.com/comp500/Demagnetize/blob/master/demagnetize.toml
-	
-	// To handle "progress", just count tasks, rather than individual progress
-	// It'll look bad, especially for zip-based things, but it should work fine
-}

src/main/java/link/infra/packwiz/installer/request/handlers/RequestHandlerGithub.java

@@ -1,90 +0,0 @@
-package link.infra.packwiz.installer.request.handlers;
-
-import link.infra.packwiz.installer.metadata.SpaceSafeURI;
-
-import java.util.HashMap;
-import java.util.Map;
-import java.util.concurrent.locks.ReentrantReadWriteLock;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
-public class RequestHandlerGithub extends RequestHandlerZip {
-	
-	public RequestHandlerGithub() {
-		super(true);
-	}
-
-	@Override
-	public SpaceSafeURI getNewLoc(SpaceSafeURI loc) {
-		return loc;
-	}
-	
-	// TODO: is caching really needed, if HTTPURLConnection follows redirects correctly?
-	private Map<String, SpaceSafeURI> zipUriMap = new HashMap<>();
-	private final ReentrantReadWriteLock zipUriLock = new ReentrantReadWriteLock();
-	private static Pattern repoMatcherPattern = Pattern.compile("/([\\w.-]+/[\\w.-]+).*");
-	
-	private String getRepoName(SpaceSafeURI loc) {
-		Matcher matcher = repoMatcherPattern.matcher(loc.getPath());
-		if (matcher.matches()) {
-			return matcher.group(1);
-		} else {
-			return null;
-		}
-	}
-
-	@Override
-	protected SpaceSafeURI getZipUri(SpaceSafeURI loc) throws Exception {
-		String repoName = getRepoName(loc);
-		String branchName = getBranch(loc);
-		zipUriLock.readLock().lock();
-		SpaceSafeURI zipUri = zipUriMap.get(repoName + "/" + branchName);
-		zipUriLock.readLock().unlock();
-		if (zipUri != null) {
-			return zipUri;
-		}
-		
-		zipUri = new SpaceSafeURI("https://api.github.com/repos/" + repoName + "/zipball/" + branchName);
-		
-		zipUriLock.writeLock().lock();
-		// If another thread sets the value concurrently, use the value of the
-		// thread that first acquired the lock.
-		SpaceSafeURI zipUriInserted = zipUriMap.putIfAbsent(repoName + "/" + branchName, zipUri);
-		if (zipUriInserted != null) {
-			zipUri = zipUriInserted;
-		}
-		zipUriLock.writeLock().unlock();
-		return zipUri;
-	}
-	
-	private static Pattern branchMatcherPattern = Pattern.compile("/[\\w.-]+/[\\w.-]+/blob/([\\w.-]+).*");
-	
-	private String getBranch(SpaceSafeURI loc) {
-		Matcher matcher = branchMatcherPattern.matcher(loc.getPath());
-		if (matcher.matches()) {
-			return matcher.group(1);
-		} else {
-			return null;
-		}
-	}
-
-	@Override
-	protected SpaceSafeURI getLocationInZip(SpaceSafeURI loc) throws Exception {
-		String path = "/" + getRepoName(loc) + "/blob/" + getBranch(loc);
-		return new SpaceSafeURI(loc.getScheme(), loc.getAuthority(), path, null, null).relativize(loc);
-	}
-
-	@Override
-	public boolean matchesHandler(SpaceSafeURI loc) {
-		String scheme = loc.getScheme();
-		if (!("http".equals(scheme) || "https".equals(scheme))) {
-			return false;
-		}
-		if (!"github.com".equals(loc.getHost())) {
-			return false;
-		}
-		// TODO: sanity checks, support for more github urls
-		return true;
-	}
-
-}

src/main/java/link/infra/packwiz/installer/request/handlers/RequestHandlerHTTP.java

@@ -1,29 +0,0 @@
-package link.infra.packwiz.installer.request.handlers;
-
-import link.infra.packwiz.installer.metadata.SpaceSafeURI;
-import link.infra.packwiz.installer.request.IRequestHandler;
-import okio.Okio;
-import okio.Source;
-
-import java.net.URLConnection;
-
-public class RequestHandlerHTTP implements IRequestHandler {
-
-	@Override
-	public boolean matchesHandler(SpaceSafeURI loc) {
-		String scheme = loc.getScheme();
-		return "http".equals(scheme) || "https".equals(scheme);
-	}
-
-	@Override
-	public Source getFileSource(SpaceSafeURI loc) throws Exception {
-		URLConnection conn = loc.toURL().openConnection();
-		// TODO: when do we send specific headers??? should there be a way to signal this?
-		// github *sometimes* requires it, sometimes not!
-		//conn.addRequestProperty("Accept", "application/octet-stream");
-		// 30 second read timeout
-		conn.setReadTimeout(30 * 1000);
-		return Okio.source(conn.getInputStream());
-	}
-
-}

src/main/java/link/infra/packwiz/installer/request/handlers/RequestHandlerZip.java

@@ -1,169 +0,0 @@
-package link.infra.packwiz.installer.request.handlers;
-
-import link.infra.packwiz.installer.metadata.SpaceSafeURI;
-import okio.Buffer;
-import okio.BufferedSource;
-import okio.Okio;
-import okio.Source;
-
-import java.io.IOException;
-import java.net.URISyntaxException;
-import java.util.HashMap;
-import java.util.Map;
-import java.util.concurrent.locks.ReentrantLock;
-import java.util.concurrent.locks.ReentrantReadWriteLock;
-import java.util.function.Predicate;
-import java.util.zip.ZipEntry;
-import java.util.zip.ZipInputStream;
-
-public abstract class RequestHandlerZip extends RequestHandlerHTTP {
-	
-	private final boolean modeHasFolder;
-	
-	public RequestHandlerZip(boolean modeHasFolder) {
-		this.modeHasFolder = modeHasFolder;
-	}
-	
-	private String removeFolder(String name) {
-		if (modeHasFolder) {
-			return name.substring(name.indexOf("/")+1);
-		} else {
-			return name;
-		}
-	}
-	
-	private class ZipReader {
-		
-		private final ZipInputStream zis;
-		private final Map<SpaceSafeURI, Buffer> readFiles = new HashMap<>();
-		// Write lock implies access to ZipInputStream - only 1 thread must read at a time!
-		final ReentrantLock filesLock = new ReentrantLock();
-		private ZipEntry entry;
-
-		private final BufferedSource zipSource;
-
-		ZipReader(Source zip) {
-			zis = new ZipInputStream(Okio.buffer(zip).inputStream());
-			zipSource = Okio.buffer(Okio.source(zis));
-		}
-		
-		// File lock must be obtained before calling this function
-		private Buffer readCurrFile() throws IOException {
-			Buffer fileBuffer = new Buffer();
-			zipSource.readFully(fileBuffer, entry.getSize());
-			return fileBuffer;
-		}
-		
-		// File lock must be obtained before calling this function
-		private Buffer findFile(SpaceSafeURI loc) throws IOException, URISyntaxException {
-			while (true) {
-				entry = zis.getNextEntry();
-				if (entry == null) {
-					return null;
-				}
-				Buffer data = readCurrFile();
-				SpaceSafeURI fileLoc = new SpaceSafeURI(removeFolder(entry.getName()));
-				if (loc.equals(fileLoc)) {
-					return data;
-				} else {
-					readFiles.put(fileLoc, data);
-				}
-			}
-		}
-		
-		Source getFileSource(SpaceSafeURI loc) throws Exception {
-			filesLock.lock();
-			// Assume files are only read once, allow GC by removing
-			Buffer file = readFiles.remove(loc);
-			if (file != null) {
-				filesLock.unlock();
-				return file;
-			}
-			
-			file = findFile(loc);
-			filesLock.unlock();
-			return file;
-		}
-
-		SpaceSafeURI findInZip(Predicate<SpaceSafeURI> matches) throws Exception {
-			filesLock.lock();
-			for (SpaceSafeURI file : readFiles.keySet()) {
-				if (matches.test(file)) {
-					filesLock.unlock();
-					return file;
-				}
-			}
-			
-			while (true) {
-				entry = zis.getNextEntry();
-				if (entry == null) {
-					filesLock.unlock();
-					return null;
-				}
-				Buffer data = readCurrFile();
-				SpaceSafeURI fileLoc = new SpaceSafeURI(removeFolder(entry.getName()));
-				readFiles.put(fileLoc, data);
-				if (matches.test(fileLoc)) {
-					filesLock.unlock();
-					return fileLoc;
-				}
-			}
-		}
-		
-	}
-	
-	private final Map<SpaceSafeURI, ZipReader> cache = new HashMap<>();
-	private final ReentrantReadWriteLock cacheLock = new ReentrantReadWriteLock();
-	
-	protected abstract SpaceSafeURI getZipUri(SpaceSafeURI loc) throws Exception;
-	
-	protected abstract SpaceSafeURI getLocationInZip(SpaceSafeURI loc) throws Exception;
-	
-	@Override
-	public abstract boolean matchesHandler(SpaceSafeURI loc);
-
-	@Override
-	public Source getFileSource(SpaceSafeURI loc) throws Exception {
-		SpaceSafeURI zipUri = getZipUri(loc);
-		cacheLock.readLock().lock();
-		ZipReader zr = cache.get(zipUri);
-		cacheLock.readLock().unlock();
-		if (zr == null) {
-			cacheLock.writeLock().lock();
-			// Recheck, because unlocking read lock allows another thread to modify it
-			zr = cache.get(zipUri);
-			if (zr == null) {
-				Source src = super.getFileSource(zipUri);
-				if (src == null) {
-					cacheLock.writeLock().unlock();
-					return null;
-				}
-				zr = new ZipReader(src);
-				cache.put(zipUri, zr);
-			}
-			cacheLock.writeLock().unlock();
-		}
-		
-		return zr.getFileSource(getLocationInZip(loc));
-	}
-	
-	protected SpaceSafeURI findInZip(SpaceSafeURI loc, Predicate<SpaceSafeURI> matches) throws Exception {
-		SpaceSafeURI zipUri = getZipUri(loc);
-		cacheLock.readLock().lock();
-		ZipReader zr = cache.get(zipUri);
-		cacheLock.readLock().unlock();
-		if (zr == null) {
-			cacheLock.writeLock().lock();
-			// Recheck, because unlocking read lock allows another thread to modify it
-			zr = cache.get(zipUri);
-			if (zr == null) {
-				zr = new ZipReader(super.getFileSource(zipUri));
-				cache.put(zipUri, zr);
-			}
-			cacheLock.writeLock().unlock();
-		}
-		
-		return zr.findInZip(matches);
-	}
-
-}

src/main/java/link/infra/packwiz/installer/ui/CLIHandler.java

@@ -1,55 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-import java.util.List;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.Future;
-
-public class CLIHandler implements IUserInterface {
-
-	@Override
-	public void handleException(Exception e) {
-		e.printStackTrace();
-	}
-
-	@Override
-	public void show(InputStateHandler h) {}
-
-	@Override
-	public void submitProgress(InstallProgress progress) {
-		StringBuilder sb = new StringBuilder();
-		if (progress.hasProgress) {
-			sb.append('(');
-			sb.append(progress.progress);
-			sb.append('/');
-			sb.append(progress.progressTotal);
-			sb.append(") ");
-		}
-		sb.append(progress.message);
-		System.out.println(sb.toString());
-	}
-
-	@Override
-	public void executeManager(Runnable task) {
-		task.run();
-		System.out.println("Finished successfully!");
-	}
-
-	@Override
-	public Future<Boolean> showOptions(List<IOptionDetails> options) {
-		for (IOptionDetails opt : options) {
-			opt.setOptionValue(true);
-			System.out.println("Warning: accepting option " + opt.getName() + " as option choosing is not implemented in the CLI");
-		}
-		CompletableFuture<Boolean> future = new CompletableFuture<>();
-		future.complete(false); // Can't be cancelled!
-		return future;
-	}
-
-	@Override
-	public Future<IExceptionDetails.ExceptionListResult> showExceptions(List<IExceptionDetails> opts, int numTotal, boolean allowsIgnore) {
-		CompletableFuture<IExceptionDetails.ExceptionListResult> future = new CompletableFuture<>();
-		future.complete(IExceptionDetails.ExceptionListResult.CANCEL);
-		return future;
-	}
-
-}

src/main/java/link/infra/packwiz/installer/ui/ExceptionListWindow.java

@@ -1,183 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-import link.infra.packwiz.installer.ui.IExceptionDetails.ExceptionListResult;
-
-import javax.swing.*;
-import javax.swing.border.EmptyBorder;
-import java.awt.*;
-import java.awt.event.WindowAdapter;
-import java.awt.event.WindowEvent;
-import java.io.IOException;
-import java.io.PrintWriter;
-import java.io.StringWriter;
-import java.net.URI;
-import java.net.URISyntaxException;
-import java.util.List;
-import java.util.concurrent.CompletableFuture;
-
-class ExceptionListWindow extends JDialog {
-
-	private static final long serialVersionUID = 1L;
-	private final JTextArea lblExceptionStacktrace;
-
-	/**
-	 * Create the dialog.
-	 */
-	ExceptionListWindow(List<IExceptionDetails> eList, CompletableFuture<ExceptionListResult> future, int numTotal, boolean allowsIgnore, JFrame parentWindow) {
-		super(parentWindow, "Failed file downloads", true);
-
-		setBounds(100, 100, 540, 340);
-		setLocationRelativeTo(parentWindow);
-		getContentPane().setLayout(new BorderLayout());
-		{
-			JPanel errorPanel = new JPanel();
-			getContentPane().add(errorPanel, BorderLayout.NORTH);
-			{
-				JLabel lblWarning = new JLabel("One or more errors were encountered while installing the modpack!");
-				lblWarning.setIcon(UIManager.getIcon("OptionPane.warningIcon"));
-				errorPanel.add(lblWarning);
-			}
-		}
-		JPanel contentPanel = new JPanel();
-		contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
-		getContentPane().add(contentPanel, BorderLayout.CENTER);
-		contentPanel.setLayout(new BorderLayout(0, 0));
-		{
-			JSplitPane splitPane = new JSplitPane();
-			splitPane.setResizeWeight(0.3);
-			contentPanel.add(splitPane);
-			{
-				lblExceptionStacktrace = new JTextArea("Select a file");
-				lblExceptionStacktrace.setBackground(UIManager.getColor("List.background"));
-				lblExceptionStacktrace.setOpaque(true);
-				lblExceptionStacktrace.setWrapStyleWord(true);
-				lblExceptionStacktrace.setLineWrap(true);
-				lblExceptionStacktrace.setEditable(false);
-				lblExceptionStacktrace.setFocusable(true);
-				lblExceptionStacktrace.setFont(UIManager.getFont("Label.font"));
-				lblExceptionStacktrace.setBorder(new EmptyBorder(5, 5, 5, 5));
-				JScrollPane scrollPane = new JScrollPane(lblExceptionStacktrace);
-				scrollPane.setBorder(new EmptyBorder(0, 0, 0, 0));
-				splitPane.setRightComponent(scrollPane);
-			}
-			{
-				JList<String> list = new JList<>();
-				list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
-				list.setBorder(new EmptyBorder(5, 5, 5, 5));
-				ExceptionListModel listModel = new ExceptionListModel(eList);
-				list.setModel(listModel);
-				list.addListSelectionListener(e -> {
-					int i = list.getSelectedIndex();
-					if (i > -1) {
-						StringWriter sw = new StringWriter();
-						listModel.getExceptionAt(i).printStackTrace(new PrintWriter(sw));
-						lblExceptionStacktrace.setText(sw.toString());
-						// Scroll to the top
-						lblExceptionStacktrace.setCaretPosition(0);
-					} else {
-						lblExceptionStacktrace.setText("Select a file");
-					}
-				});
-				JScrollPane scrollPane = new JScrollPane(list);
-				scrollPane.setBorder(new EmptyBorder(0, 0, 0, 0));
-				splitPane.setLeftComponent(scrollPane);
-			}
-		}
-		{
-			JPanel buttonPane = new JPanel();
-			getContentPane().add(buttonPane, BorderLayout.SOUTH);
-			buttonPane.setLayout(new BorderLayout(0, 0));
-			{
-				JPanel rightButtons = new JPanel();
-				buttonPane.add(rightButtons, BorderLayout.EAST);
-				{
-					JButton btnContinue = new JButton("Continue");
-					btnContinue.setToolTipText("Attempt to continue installing, excluding the failed downloads");
-					btnContinue.addActionListener(e -> {
-						future.complete(ExceptionListResult.CONTINUE);
-						ExceptionListWindow.this.dispose();
-					});
-					rightButtons.add(btnContinue);
-				}
-				{
-					JButton btnCancelLaunch = new JButton("Cancel launch");
-					btnCancelLaunch.setToolTipText("Stop launching the game");
-					btnCancelLaunch.addActionListener(e -> {
-						future.complete(ExceptionListResult.CANCEL);
-						ExceptionListWindow.this.dispose();
-					});
-					rightButtons.add(btnCancelLaunch);
-				}
-				{
-					JButton btnIgnoreUpdate = new JButton("Ignore update");
-					btnIgnoreUpdate.setEnabled(allowsIgnore);
-					btnIgnoreUpdate.setToolTipText("Start the game without attempting to update");
-					btnIgnoreUpdate.addActionListener(e -> {
-						future.complete(ExceptionListResult.IGNORE);
-						ExceptionListWindow.this.dispose();
-					});
-					rightButtons.add(btnIgnoreUpdate);
-					{
-						JLabel lblErrored = new JLabel(eList.size() + "/" + numTotal + " errored");
-						lblErrored.setHorizontalAlignment(SwingConstants.CENTER);
-						buttonPane.add(lblErrored, BorderLayout.CENTER);
-					}
-					{
-						JPanel leftButtons = new JPanel();
-						buttonPane.add(leftButtons, BorderLayout.WEST);
-						{
-							JButton btnReportIssue = new JButton("Report issue");
-							boolean supported = Desktop.isDesktopSupported() && Desktop.getDesktop().isSupported(Desktop.Action.BROWSE);
-							btnReportIssue.setEnabled(supported);
-							if (supported) {
-								btnReportIssue.addActionListener(e -> {
-									try {
-										Desktop.getDesktop().browse(new URI("https://github.com/comp500/packwiz-installer/issues/new"));
-									} catch (IOException | URISyntaxException e1) {
-										// lol the button just won't work i guess
-									}
-								});
-							}
-							leftButtons.add(btnReportIssue);
-						}
-					}
-				}
-			}
-		}
-		addWindowListener(new WindowAdapter() {
-			@Override
-			public void windowClosing(WindowEvent e) {
-				future.complete(ExceptionListResult.CANCEL);
-			}
-
-			@Override
-			public void windowClosed(WindowEvent e) {
-				// Just in case closing didn't get triggered - if something else called dispose() the
-				// future will have already completed
-				future.complete(ExceptionListResult.CANCEL);
-			}
-		});
-	}
-
-	private static class ExceptionListModel extends AbstractListModel<String> {
-		private static final long serialVersionUID = 1L;
-		private final List<IExceptionDetails> details;
-
-		ExceptionListModel(List<IExceptionDetails> details) {
-			this.details = details;
-		}
-
-		public int getSize() {
-			return details.size();
-		}
-
-		public String getElementAt(int index) {
-			return details.get(index).getName();
-		}
-
-		Exception getExceptionAt(int index) {
-			return details.get(index).getException();
-		}
-	}
-
-}

src/main/java/link/infra/packwiz/installer/ui/IExceptionDetails.java

@@ -1,10 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-public interface IExceptionDetails {
-	Exception getException();
-	String getName();
-
-	enum ExceptionListResult {
-		CONTINUE, CANCEL, IGNORE
-	}
-}

src/main/java/link/infra/packwiz/installer/ui/IOptionDetails.java

@@ -1,8 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-public interface IOptionDetails {
-	String getName();
-	boolean getOptionValue();
-	String getOptionDescription();
-	void setOptionValue(boolean value);
-}

src/main/java/link/infra/packwiz/installer/ui/IUserInterface.java

@@ -1,38 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-import java.util.List;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.Future;
-
-public interface IUserInterface {
-	
-	void show(InputStateHandler handler);
-
-	void handleException(Exception e);
-
-	default void handleExceptionAndExit(Exception e) {
-		handleException(e);
-		System.exit(1);
-	}
-
-	default void setTitle(String title) {}
-
-	void submitProgress(InstallProgress progress);
-
-	void executeManager(Runnable task);
-
-	// Return true if the installation was cancelled!
-	Future<Boolean> showOptions(List<IOptionDetails> option);
-
-	Future<IExceptionDetails.ExceptionListResult> showExceptions(List<IExceptionDetails> opts, int numTotal, boolean allowsIgnore);
-
-	default void disableOptionsButton() {}
-
-	// Should not return CONTINUE
-	default Future<IExceptionDetails.ExceptionListResult> showCancellationDialog() {
-		CompletableFuture<IExceptionDetails.ExceptionListResult> future = new CompletableFuture<>();
-		future.complete(IExceptionDetails.ExceptionListResult.CANCEL);
-		return future;
-	}
-	
-}

src/main/java/link/infra/packwiz/installer/ui/InputStateHandler.java

@@ -1,22 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-public class InputStateHandler {
-	private boolean optionsButtonPressed = false;
-	private boolean cancelButtonPressed = false;
-
-	synchronized void pressCancelButton() {
-		this.cancelButtonPressed = true;
-	}
-
-	synchronized void pressOptionsButton() {
-		this.optionsButtonPressed = true;
-	}
-
-	public synchronized boolean getCancelButton() {
-		return cancelButtonPressed;
-	}
-
-	public synchronized boolean getOptionsButton() {
-		return optionsButtonPressed;
-	}
-}

src/main/java/link/infra/packwiz/installer/ui/InstallProgress.java

@@ -1,22 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-public class InstallProgress {
-	public final String message;
-	public final boolean hasProgress;
-	public final int progress;
-	public final int progressTotal;
-
-	public InstallProgress(String message) {
-		this.message = message;
-		hasProgress = false;
-		progress = 0;
-		progressTotal = 0;
-	}
-
-	public InstallProgress(String message, int progress, int progressTotal) {
-		this.message = message;
-		hasProgress = true;
-		this.progress = progress;
-		this.progressTotal = progressTotal;
-	}
-}

src/main/java/link/infra/packwiz/installer/ui/InstallWindow.java

@@ -1,228 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-import javax.swing.*;
-import javax.swing.border.EmptyBorder;
-import java.awt.*;
-import java.util.List;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.Future;
-import java.util.concurrent.atomic.AtomicBoolean;
-
-public class InstallWindow implements IUserInterface {
-
-	private JFrame frmPackwizlauncher;
-	private JLabel lblProgresslabel;
-	private JProgressBar progressBar;
-	private InputStateHandler inputStateHandler;
-
-	private String title = "Updating modpack...";
-	private SwingWorkerButWithPublicPublish<Void, InstallProgress> worker;
-	private AtomicBoolean aboutToCrash = new AtomicBoolean();
-	private JButton btnOptions;
-
-	@Override
-	public void show(InputStateHandler handler) {
-		this.inputStateHandler = handler;
-		EventQueue.invokeLater(() -> {
-			try {
-				UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-				initialize();
-				frmPackwizlauncher.setVisible(true);
-			} catch (Exception e) {
-				e.printStackTrace();
-			}
-		});
-	}
-
-	/**
-	 * Initialize the contents of the frame.
-	 * @wbp.parser.entryPoint
-	 */
-	private void initialize() {
-		frmPackwizlauncher = new JFrame();
-		frmPackwizlauncher.setTitle(title);
-		frmPackwizlauncher.setBounds(100, 100, 493, 95);
-		frmPackwizlauncher.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
-		frmPackwizlauncher.setLocationRelativeTo(null);
-
-		JPanel panel = new JPanel();
-		panel.setBorder(new EmptyBorder(10, 10, 10, 10));
-		frmPackwizlauncher.getContentPane().add(panel, BorderLayout.CENTER);
-		panel.setLayout(new BorderLayout(0, 0));
-
-		progressBar = new JProgressBar();
-		progressBar.setIndeterminate(true);
-		panel.add(progressBar, BorderLayout.CENTER);
-
-		lblProgresslabel = new JLabel("Loading...");
-		panel.add(lblProgresslabel, BorderLayout.SOUTH);
-
-		JPanel panel_1 = new JPanel();
-		panel_1.setBorder(new EmptyBorder(0, 5, 0, 5));
-		frmPackwizlauncher.getContentPane().add(panel_1, BorderLayout.EAST);
-		GridBagLayout gbl_panel_1 = new GridBagLayout();
-		panel_1.setLayout(gbl_panel_1);
-
-		btnOptions = new JButton("Optional mods...");
-		btnOptions.addActionListener(e -> {
-			btnOptions.setText("Loading...");
-			btnOptions.setEnabled(false);
-			inputStateHandler.pressOptionsButton();
-		});
-		btnOptions.setAlignmentX(Component.CENTER_ALIGNMENT);
-		GridBagConstraints gbc_btnOptions = new GridBagConstraints();
-		gbc_btnOptions.gridx = 0;
-		gbc_btnOptions.gridy = 0;
-		panel_1.add(btnOptions, gbc_btnOptions);
-
-		JButton btnCancel = new JButton("Cancel");
-		btnCancel.addActionListener(e -> {
-			btnCancel.setEnabled(false);
-			inputStateHandler.pressCancelButton();
-		});
-		btnCancel.setAlignmentX(Component.CENTER_ALIGNMENT);
-		GridBagConstraints gbc_btnCancel = new GridBagConstraints();
-		gbc_btnCancel.gridx = 0;
-		gbc_btnCancel.gridy = 1;
-		panel_1.add(btnCancel, gbc_btnCancel);
-	}
-
-	@Override
-	public void handleException(Exception e) {
-		e.printStackTrace();
-		EventQueue.invokeLater(() -> {
-			JOptionPane.showMessageDialog(null, "An error occurred: \n" + e.getClass().getCanonicalName() + ": " + e.getMessage(), title, JOptionPane.ERROR_MESSAGE);
-		});
-	}
-
-	@Override
-	public void handleExceptionAndExit(Exception e) {
-		e.printStackTrace();
-		// Used to prevent the done() handler of SwingWorker executing if the invokeLater hasn't happened yet
-		aboutToCrash.set(true);
-		EventQueue.invokeLater(() -> {
-			JOptionPane.showMessageDialog(null, "A fatal error occurred: \n" + e.getClass().getCanonicalName() + ": " + e.getMessage(), title, JOptionPane.ERROR_MESSAGE);
-			System.exit(1);
-		});
-		// Pause forever, so it blocks while we wait for System.exit to take effect
-		try {
-			Thread.currentThread().join();
-		} catch (InterruptedException ex) {
-			// no u
-		}
-	}
-
-	@Override
-	public void setTitle(String title) {
-		this.title = title;
-		if (frmPackwizlauncher != null) {
-			EventQueue.invokeLater(() -> frmPackwizlauncher.setTitle(title));
-		}
-	}
-
-	@Override
-	public void submitProgress(InstallProgress progress) {
-		StringBuilder sb = new StringBuilder();
-		if (progress.hasProgress) {
-			sb.append('(');
-			sb.append(progress.progress);
-			sb.append('/');
-			sb.append(progress.progressTotal);
-			sb.append(") ");
-		}
-		sb.append(progress.message);
-		// TODO: better logging library?
-		System.out.println(sb.toString());
-		if (worker != null) {
-			worker.publishPublic(progress);
-		}
-	}
-
-	@Override
-	public void executeManager(Runnable task) {
-		EventQueue.invokeLater(() -> {
-			worker = new SwingWorkerButWithPublicPublish<Void, InstallProgress>() {
-
-				@Override
-				protected Void doInBackground() {
-					task.run();
-					return null;
-				}
-
-				@Override
-				protected void process(List<InstallProgress> chunks) {
-					// Only process last chunk
-					if (chunks.size() > 0) {
-						InstallProgress prog = chunks.get(chunks.size() - 1);
-						if (prog.hasProgress) {
-							progressBar.setIndeterminate(false);
-							progressBar.setValue(prog.progress);
-							progressBar.setMaximum(prog.progressTotal);
-						} else {
-							progressBar.setIndeterminate(true);
-							progressBar.setValue(0);
-						}
-						lblProgresslabel.setText(prog.message);
-					}
-				}
-
-				@Override
-				protected void done() {
-					if (aboutToCrash.get()) {
-						return;
-					}
-					// TODO: a better way to do this?
-					frmPackwizlauncher.dispose();
-					System.out.println("Finished successfully!");
-					System.exit(0);
-				}
-
-			};
-			worker.execute();
-		});
-	}
-
-	@Override
-	public Future<Boolean> showOptions(List<IOptionDetails> opts) {
-		CompletableFuture<Boolean> future = new CompletableFuture<>();
-		EventQueue.invokeLater(() -> {
-			OptionsSelectWindow dialog = new OptionsSelectWindow(opts, future, frmPackwizlauncher);
-			dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
-			dialog.setVisible(true);
-		});
-		return future;
-	}
-
-	@Override
-	public Future<IExceptionDetails.ExceptionListResult> showExceptions(List<IExceptionDetails> opts, int numTotal, boolean allowsIgnore) {
-		CompletableFuture<IExceptionDetails.ExceptionListResult> future = new CompletableFuture<>();
-		EventQueue.invokeLater(() -> {
-			ExceptionListWindow dialog = new ExceptionListWindow(opts, future, numTotal, allowsIgnore, frmPackwizlauncher);
-			dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
-			dialog.setVisible(true);
-		});
-		return future;
-	}
-
-	@Override
-	public void disableOptionsButton() {
-		if (btnOptions != null) {
-			btnOptions.setText("Optional mods...");
-			btnOptions.setEnabled(false);
-		}
-	}
-
-	@Override
-	public Future<IExceptionDetails.ExceptionListResult> showCancellationDialog() {
-		CompletableFuture<IExceptionDetails.ExceptionListResult> future = new CompletableFuture<>();
-		EventQueue.invokeLater(() -> {
-			Object[] buttons = {"Quit", "Ignore"};
-			int result = JOptionPane.showOptionDialog(frmPackwizlauncher,
-					"The installation was cancelled. Would you like to quit the game, or ignore the update and start the game?",
-					"Cancelled installation",
-					JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, buttons, buttons[0]);
-			future.complete(result == 0 ? IExceptionDetails.ExceptionListResult.CANCEL : IExceptionDetails.ExceptionListResult.IGNORE);
-		});
-		return future;
-	}
-}

src/main/java/link/infra/packwiz/installer/ui/OptionTempHandler.java

@@ -1,33 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-// Serves as a proxy for IOptionDetails, so that setOptionValue isn't called until OK is clicked
-class OptionTempHandler implements IOptionDetails {
-	private final IOptionDetails opt;
-	private boolean tempValue;
-
-	OptionTempHandler(IOptionDetails opt) {
-		this.opt = opt;
-		tempValue = opt.getOptionValue();
-	}
-
-	public String getName() {
-		return opt.getName();
-	}
-
-	public String getOptionDescription() {
-		return opt.getOptionDescription();
-	}
-
-	public boolean getOptionValue() {
-		return tempValue;
-	}
-
-	public void setOptionValue(boolean value) {
-		tempValue = value;
-	}
-
-	void finalise() {
-		opt.setOptionValue(tempValue);
-	}
-
-}

src/main/java/link/infra/packwiz/installer/ui/OptionsSelectWindow.java

@@ -1,205 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-import javax.swing.*;
-import javax.swing.border.EmptyBorder;
-import javax.swing.event.ListSelectionEvent;
-import javax.swing.event.ListSelectionListener;
-import javax.swing.event.TableModelListener;
-import javax.swing.table.TableModel;
-import java.awt.*;
-import java.awt.event.ActionEvent;
-import java.awt.event.ActionListener;
-import java.awt.event.WindowAdapter;
-import java.awt.event.WindowEvent;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.CompletableFuture;
-
-public class OptionsSelectWindow extends JDialog implements ActionListener {
-
-	private static final long serialVersionUID = 1L;
-	private final JTextArea lblOptionDescription;
-	private final OptionTableModel tableModel;
-	private final CompletableFuture<Boolean> future;
-
-	/**
-	 * Create the dialog.
-	 */
-	OptionsSelectWindow(List<IOptionDetails> optList, CompletableFuture<Boolean> future, JFrame parentWindow) {
-		super(parentWindow, "Select optional mods...", true);
-
-		tableModel = new OptionTableModel(optList);
-		this.future = future;
-
-		setBounds(100, 100, 450, 300);
-		setLocationRelativeTo(parentWindow);
-		getContentPane().setLayout(new BorderLayout());
-		JPanel contentPanel = new JPanel();
-		contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
-		getContentPane().add(contentPanel, BorderLayout.CENTER);
-		contentPanel.setLayout(new BorderLayout(0, 0));
-		{
-			JSplitPane splitPane = new JSplitPane();
-			splitPane.setResizeWeight(0.5);
-			contentPanel.add(splitPane);
-			{
-				JTable table = new JTable();
-				table.setShowVerticalLines(false);
-				table.setShowHorizontalLines(false);
-				table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
-				table.setShowGrid(false);
-				table.setModel(tableModel);
-				table.getColumnModel().getColumn(0).setResizable(false);
-				table.getColumnModel().getColumn(0).setPreferredWidth(15);
-				table.getColumnModel().getColumn(0).setMaxWidth(15);
-				table.getColumnModel().getColumn(1).setResizable(false);
-				table.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
-					@Override
-					public void valueChanged(ListSelectionEvent e) {
-						int i = table.getSelectedRow();
-						if (i > -1) {
-							lblOptionDescription.setText(tableModel.getDescription(i));
-						} else {
-							lblOptionDescription.setText("Select an option...");
-						}
-					}
-				});
-				table.setTableHeader(null);
-				JScrollPane scrollPane = new JScrollPane(table);
-				scrollPane.getViewport().setBackground(UIManager.getColor("List.background"));
-				scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
-				scrollPane.setBorder(new EmptyBorder(0, 0, 0, 0));
-				splitPane.setLeftComponent(scrollPane);
-			}
-			{
-				lblOptionDescription = new JTextArea("Select an option...");
-				lblOptionDescription.setBackground(UIManager.getColor("List.background"));
-				lblOptionDescription.setOpaque(true);
-				lblOptionDescription.setWrapStyleWord(true);
-				lblOptionDescription.setLineWrap(true);
-				lblOptionDescription.setEditable(false);
-				lblOptionDescription.setFocusable(false);
-				lblOptionDescription.setFont(UIManager.getFont("Label.font"));
-				lblOptionDescription.setBorder(new EmptyBorder(10, 10, 10, 10));
-				JScrollPane scrollPane = new JScrollPane(lblOptionDescription);
-				scrollPane.setBorder(new EmptyBorder(0, 0, 0, 0));
-				splitPane.setRightComponent(scrollPane);
-			}
-		}
-		{
-			JPanel buttonPane = new JPanel();
-			buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
-			getContentPane().add(buttonPane, BorderLayout.SOUTH);
-			{
-				JButton okButton = new JButton("OK");
-				okButton.setActionCommand("OK");
-				okButton.addActionListener(this);
-				buttonPane.add(okButton);
-				getRootPane().setDefaultButton(okButton);
-			}
-			{
-				JButton cancelButton = new JButton("Cancel");
-				cancelButton.setActionCommand("Cancel");
-				cancelButton.addActionListener(this);
-				buttonPane.add(cancelButton);
-			}
-		}
-		addWindowListener(new WindowAdapter() {
-			@Override
-			public void windowClosing(WindowEvent e) {
-				future.complete(true);
-			}
-
-			@Override
-			public void windowClosed(WindowEvent e) {
-				// Just in case closing didn't get triggered - if something else called dispose() the
-				// future will have already completed
-				future.complete(true);
-			}
-		});
-	}
-
-	private static class OptionTableModel implements TableModel {
-		private List<OptionTempHandler> opts = new ArrayList<>();
-
-		OptionTableModel(List<IOptionDetails> givenOpts) {
-			for (IOptionDetails opt : givenOpts) {
-				opts.add(new OptionTempHandler(opt));
-			}
-		}
-
-		@Override
-		public int getRowCount() {
-			return opts.size();
-		}
-
-		@Override
-		public int getColumnCount() {
-			return 2;
-		}
-
-		private final String[] columnNames = {"Enabled", "Mod name"};
-		private final Class<?>[] columnTypes = {Boolean.class, String.class};
-		private final boolean[] columnEditables = {true, false};
-
-		@Override
-		public String getColumnName(int columnIndex) {
-			return columnNames[columnIndex];
-		}
-
-		@Override
-		public Class<?> getColumnClass(int columnIndex) {
-			return columnTypes[columnIndex];
-		}
-
-		@Override
-		public boolean isCellEditable(int rowIndex, int columnIndex) {
-			return columnEditables[columnIndex];
-		}
-
-		@Override
-		public Object getValueAt(int rowIndex, int columnIndex) {
-			OptionTempHandler opt = opts.get(rowIndex);
-			return columnIndex == 0 ? opt.getOptionValue() : opt.getName();
-		}
-
-		@Override
-		public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
-			if (columnIndex == 0) {
-				OptionTempHandler opt = opts.get(rowIndex);
-				opt.setOptionValue((boolean) aValue);
-			}
-		}
-
-		// Noop, the table model doesn't change!
-		@Override
-		public void addTableModelListener(TableModelListener l) {}
-
-		@Override
-		public void removeTableModelListener(TableModelListener l) {}
-
-		String getDescription(int rowIndex) {
-			return opts.get(rowIndex).getOptionDescription();
-		}
-
-		void finalise() {
-			for (OptionTempHandler opt : opts) {
-				opt.finalise();
-			}
-		}
-
-	}
-
-	@Override
-	public void actionPerformed(ActionEvent e) {
-		if (e.getActionCommand().equals("OK")) {
-			tableModel.finalise();
-			future.complete(false);
-			dispose();
-		} else if (e.getActionCommand().equals("Cancel")) {
-			future.complete(true);
-			dispose();
-		}
-	}
-
-}

src/main/java/link/infra/packwiz/installer/ui/SwingWorkerButWithPublicPublish.java

@@ -1,13 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-import javax.swing.SwingWorker;
-
-// Q: AAA WHAT HAVE YOU DONE THIS IS DISGUSTING
-// A: it just makes things easier, so i can easily have one interface for CLI/GUI
-//    if someone has a better way to do this please PR it
-public abstract class SwingWorkerButWithPublicPublish<T,V> extends SwingWorker<T,V> {
-	@SafeVarargs
-	public final void publishPublic(V... chunks) {
-		publish(chunks);
-	}
-}

src/main/kotlin/link/infra/packwiz/installer/DevMain.kt

@@ -0,0 +1,5 @@
+package link.infra.packwiz.installer
+
+fun main(args: Array<String>) {
+	Main(args)
+}

src/main/kotlin/link/infra/packwiz/installer/DownloadTask.kt

@@ -0,0 +1,305 @@
+package link.infra.packwiz.installer
+
+import link.infra.packwiz.installer.metadata.IndexFile
+import link.infra.packwiz.installer.metadata.ManifestFile
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashUtils.getHash
+import link.infra.packwiz.installer.metadata.hash.HashUtils.getHasher
+import link.infra.packwiz.installer.target.Side
+import link.infra.packwiz.installer.ui.data.ExceptionDetails
+import link.infra.packwiz.installer.ui.data.IOptionDetails
+import link.infra.packwiz.installer.util.Log
+import okio.*
+import okio.Path.Companion.toOkioPath
+import java.io.IOException
+import java.nio.file.Files
+import java.nio.file.Paths
+import java.nio.file.StandardCopyOption
+import java.util.*
+import kotlin.io.use
+
+internal class DownloadTask private constructor(val metadata: IndexFile.File, defaultFormat: String, private val downloadSide: Side) : IOptionDetails {
+	var cachedFile: ManifestFile.File? = null
+
+	private var err: Exception? = null
+	val exceptionDetails get() = err?.let { e -> ExceptionDetails(name, e) }
+
+	fun failed() = err != null
+
+	var alreadyUpToDate = false
+	private var metadataRequired = true
+	private var invalidated = false
+	// If file is new or isOptional changed to true, the option needs to be presented again
+	private var newOptional = true
+
+	val isOptional get() = metadata.linkedFile?.isOptional ?: false
+
+	fun isNewOptional() = isOptional && newOptional
+
+	fun correctSide() = metadata.linkedFile?.side?.hasSide(downloadSide) ?: true
+
+	override val name get() = metadata.name
+
+	// Ensure that an update is done if it changes from false to true, or from true to false
+	override var optionValue: Boolean
+		get() = cachedFile?.optionValue ?: true
+		set(value) {
+			if (value && !optionValue) { // Ensure that an update is done if it changes from false to true, or from true to false
+				alreadyUpToDate = false
+			}
+			cachedFile?.optionValue = value
+		}
+
+	override val optionDescription get() = metadata.linkedFile?.option?.description ?: ""
+
+	init {
+		if (metadata.hashFormat?.isEmpty() != false) {
+			metadata.hashFormat = defaultFormat
+		}
+	}
+
+	fun invalidate() {
+		invalidated = true
+		alreadyUpToDate = false
+	}
+
+	fun updateFromCache(cachedFile: ManifestFile.File?) {
+		if (err != null) return
+
+		if (cachedFile == null) {
+			this.cachedFile = ManifestFile.File()
+			return
+		}
+		this.cachedFile = cachedFile
+		if (!invalidated) {
+			val currHash = try {
+				getHash(metadata.hashFormat!!, metadata.hash!!)
+			} catch (e: Exception) {
+				err = e
+				return
+			}
+			if (currHash == cachedFile.hash) { // Already up to date
+				alreadyUpToDate = true
+				metadataRequired = false
+			}
+		}
+		if (cachedFile.isOptional) {
+			// Because option selection dialog might set this task to true/false, metadata is always needed to download
+			// the file, and to show the description and name
+			metadataRequired = true
+		}
+	}
+
+	fun downloadMetadata(parentIndexFile: IndexFile, indexUri: SpaceSafeURI) {
+		if (err != null) return
+
+		if (metadataRequired) {
+			try {
+				// Retrieve the linked metadata file
+				metadata.downloadMeta(parentIndexFile, indexUri)
+			} catch (e: Exception) {
+				err = e
+				return
+			}
+			cachedFile?.let { cachedFile ->
+				val linkedFile = metadata.linkedFile
+				if (linkedFile != null) {
+					linkedFile.option?.let { opt ->
+						if (opt.optional) {
+							if (cachedFile.isOptional) {
+								// isOptional didn't change
+								newOptional = false
+							} else {
+								// isOptional false -> true, set option to it's default value
+								// TODO: preserve previous option value, somehow??
+								cachedFile.optionValue = opt.defaultValue
+							}
+						}
+					}
+					cachedFile.isOptional = isOptional
+					cachedFile.onlyOtherSide = !correctSide()
+				}
+			}
+		}
+	}
+
+	/**
+	 * Check if the file in the destination location is already valid
+	 * Must be done after metadata retrieval
+	 */
+	fun validateExistingFile(packFolder: String) {
+		if (!alreadyUpToDate) {
+			try {
+				// TODO: only do this for files that didn't exist before or have been modified since last full update?
+				val destPath = Paths.get(packFolder, metadata.destURI.toString())
+				FileSystem.SYSTEM.source(destPath.toOkioPath()).buffer().use { src ->
+					val hash: Hash
+					val fileHashFormat: String
+					val linkedFile = metadata.linkedFile
+
+					if (linkedFile != null) {
+						hash = linkedFile.hash
+						fileHashFormat = linkedFile.download!!.hashFormat!!
+					} else {
+						hash = metadata.getHashObj()
+						fileHashFormat = metadata.hashFormat!!
+					}
+
+					val fileSource = getHasher(fileHashFormat).getHashingSource(src)
+					fileSource.buffer().readAll(blackholeSink())
+					if (fileSource.hashIsEqual(hash)) {
+						alreadyUpToDate = true
+
+						// Update the manifest file
+						cachedFile = (cachedFile ?: ManifestFile.File()).also {
+							try {
+								it.hash = metadata.getHashObj()
+							} catch (e: Exception) {
+								err = e
+								return
+							}
+							it.isOptional = isOptional
+							it.cachedLocation = metadata.destURI.toString()
+							metadata.linkedFile?.let { linked ->
+								try {
+									it.linkedFileHash = linked.hash
+								} catch (e: Exception) {
+									err = e
+								}
+							}
+						}
+					}
+				}
+			} catch (e: IOException) {
+				// Ignore exceptions; if the file doesn't exist we'll be downloading it
+			}
+		}
+	}
+
+	fun download(packFolder: String, indexUri: SpaceSafeURI) {
+		if (err != null) return
+
+		// Exclude wrong-side and optional false files
+		cachedFile?.let {
+			if ((it.isOptional && !it.optionValue) || !correctSide()) {
+				if (it.cachedLocation != null) {
+					// Ensure wrong-side or optional false files are removed
+					try {
+						Files.deleteIfExists(Paths.get(packFolder, it.cachedLocation))
+					} catch (e: IOException) {
+						Log.warn("Failed to delete file", e)
+					}
+				}
+				it.cachedLocation = null
+				return
+			}
+		}
+		if (alreadyUpToDate) return
+
+		val destPath = Paths.get(packFolder, metadata.destURI.toString())
+
+		// Don't update files marked with preserve if they already exist on disk
+		if (metadata.preserve) {
+			if (destPath.toFile().exists()) {
+				return
+			}
+		}
+
+		// TODO: if already exists and has correct hash, ignore?
+		// TODO: add .disabled support?
+
+		try {
+			val hash: Hash
+			val fileHashFormat: String
+			val linkedFile = metadata.linkedFile
+
+			if (linkedFile != null) {
+				hash = linkedFile.hash
+				fileHashFormat = linkedFile.download!!.hashFormat!!
+			} else {
+				hash = metadata.getHashObj()
+				fileHashFormat = metadata.hashFormat!!
+			}
+
+			val src = metadata.getSource(indexUri)
+			val fileSource = getHasher(fileHashFormat).getHashingSource(src)
+			val data = Buffer()
+
+			// Read all the data into a buffer (very inefficient for large files! but allows rollback if hash check fails)
+			// TODO: should we instead rename the existing file, then stream straight to the file and rollback from the renamed file?
+			fileSource.buffer().use {
+				it.readAll(data)
+			}
+
+			if (fileSource.hashIsEqual(hash)) {
+				// isDirectory follows symlinks, but createDirectories doesn't
+				try {
+					Files.createDirectories(destPath.parent)
+				} catch (e: java.nio.file.FileAlreadyExistsException) {
+					if (!Files.isDirectory(destPath.parent)) {
+						throw e
+					}
+				}
+				Files.copy(data.inputStream(), destPath, StandardCopyOption.REPLACE_EXISTING)
+				data.clear()
+			} else {
+				// TODO: move println to something visible in the error window
+				println("Invalid hash for " + metadata.destURI.toString())
+				println("Calculated: " + fileSource.hash)
+				println("Expected:   $hash")
+				// Attempt to get the SHA256 hash
+				val sha256 = HashingSink.sha256(blackholeSink())
+				data.readAll(sha256)
+				println("SHA256 hash value: " + sha256.hash)
+				err = Exception("Hash invalid!")
+				data.clear()
+				return
+			}
+			cachedFile?.cachedLocation?.let {
+				if (destPath != Paths.get(packFolder, it)) {
+					// Delete old file if location changes
+					try {
+						Files.delete(Paths.get(packFolder, cachedFile!!.cachedLocation))
+					} catch (e: IOException) {
+						// Continue, as it was probably already deleted?
+						// TODO: log it
+					}
+				}
+			}
+		} catch (e: Exception) {
+			err = e
+			return
+		}
+
+		// Update the manifest file
+		cachedFile = (cachedFile ?: ManifestFile.File()).also {
+			try {
+				it.hash = metadata.getHashObj()
+			} catch (e: Exception) {
+				err = e
+				return
+			}
+			it.isOptional = isOptional
+			it.cachedLocation = metadata.destURI.toString()
+			metadata.linkedFile?.let { linked ->
+				try {
+					it.linkedFileHash = linked.hash
+				} catch (e: Exception) {
+					err = e
+				}
+			}
+		}
+	}
+
+	companion object {
+		@JvmStatic
+		fun createTasksFromIndex(index: IndexFile, defaultFormat: String, downloadSide: Side): MutableList<DownloadTask> {
+			val tasks = ArrayList<DownloadTask>()
+			for (file in Objects.requireNonNull(index.files)) {
+				tasks.add(DownloadTask(file, defaultFormat, downloadSide))
+			}
+			return tasks
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/Main.kt

@@ -0,0 +1,132 @@
+@file:JvmName("Main")
+
+package link.infra.packwiz.installer
+
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import link.infra.packwiz.installer.target.Side
+import link.infra.packwiz.installer.ui.cli.CLIHandler
+import link.infra.packwiz.installer.ui.gui.GUIHandler
+import link.infra.packwiz.installer.util.Log
+import org.apache.commons.cli.DefaultParser
+import org.apache.commons.cli.Options
+import org.apache.commons.cli.ParseException
+import java.awt.EventQueue
+import java.awt.GraphicsEnvironment
+import java.net.URISyntaxException
+import javax.swing.JOptionPane
+import javax.swing.UIManager
+import kotlin.system.exitProcess
+
+@Suppress("unused")
+class Main(args: Array<String>) {
+	// Don't attempt to start a GUI if we are headless
+	private var guiEnabled = !GraphicsEnvironment.isHeadless()
+
+	private fun startup(args: Array<String>) {
+		val options = Options()
+		addNonBootstrapOptions(options)
+		addBootstrapOptions(options)
+
+		val parser = DefaultParser()
+		val cmd = try {
+			parser.parse(options, args)
+		} catch (e: ParseException) {
+			Log.fatal("Failed to parse command line arguments", e)
+			if (guiEnabled) {
+				EventQueue.invokeAndWait {
+					try {
+						UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName())
+					} catch (ignored: Exception) {
+						// Ignore the exceptions, just continue using the ugly L&F
+					}
+					JOptionPane.showMessageDialog(null, "Failed to parse command line arguments: $e",
+						"packwiz-installer", JOptionPane.ERROR_MESSAGE)
+				}
+			}
+			exitProcess(1)
+		}
+
+		if (guiEnabled && cmd.hasOption("no-gui")) {
+			guiEnabled = false
+		}
+
+		val ui = if (guiEnabled) GUIHandler() else CLIHandler()
+
+		val unparsedArgs = cmd.args
+		if (unparsedArgs.size > 1) {
+			ui.showErrorAndExit("Too many arguments specified!")
+		} else if (unparsedArgs.isEmpty()) {
+			ui.showErrorAndExit("pack.toml URI to install from must be specified!")
+		}
+
+		val title = cmd.getOptionValue("title")
+		if (title != null) {
+			ui.title = title
+		}
+
+		ui.show()
+
+		val uOptions = try {
+			UpdateManager.Options.construct(
+				downloadURI = SpaceSafeURI(unparsedArgs[0]),
+				side = cmd.getOptionValue("side")?.let((Side)::from),
+				packFolder = cmd.getOptionValue("pack-folder"),
+				manifestFile = cmd.getOptionValue("meta-file")
+			)
+		} catch (e: URISyntaxException) {
+			ui.showErrorAndExit("Failed to read pack.toml URI", e)
+		}
+
+		// Start update process!
+		try {
+			UpdateManager(uOptions, ui)
+		} catch (e: Exception) {
+			ui.showErrorAndExit("Update process failed", e)
+		}
+		println("Finished successfully!")
+		ui.dispose()
+	}
+
+	companion object {
+		// Called by packwiz-installer-bootstrap to set up the help command
+		@JvmStatic
+		fun addNonBootstrapOptions(options: Options) {
+			options.addOption("s", "side", true, "Side to install mods from (client/server, defaults to client)")
+			options.addOption(null, "title", true, "Title of the installer window")
+			options.addOption(null, "pack-folder", true, "Folder to install the pack to (defaults to the JAR directory)")
+			options.addOption(null, "meta-file", true, "JSON file to store pack metadata, relative to the pack folder (defaults to packwiz.json)")
+		}
+
+		// TODO: link these somehow so they're only defined once?
+		@JvmStatic
+		private fun addBootstrapOptions(options: Options) {
+			options.addOption(null, "bootstrap-update-url", true, "Github API URL for checking for updates")
+			options.addOption(null, "bootstrap-update-token", true, "Github API Access Token, for private repositories")
+			options.addOption(null, "bootstrap-no-update", false, "Don't update packwiz-installer")
+			options.addOption(null, "bootstrap-main-jar", true, "Location of the packwiz-installer JAR file")
+			options.addOption("g", "no-gui", false, "Don't display a GUI to show update progress")
+			options.addOption("h", "help", false, "Display this message") // Implemented in packwiz-installer-bootstrap!
+		}
+	}
+
+	// Actual main() is in RequiresBootstrap!
+	init {
+		// Big overarching try/catch just in case everything breaks
+		try {
+			startup(args)
+		} catch (e: Exception) {
+			Log.fatal("Error from main", e)
+			if (guiEnabled) {
+				EventQueue.invokeLater {
+					JOptionPane.showMessageDialog(null,
+						"A fatal error occurred: \n$e",
+						"packwiz-installer", JOptionPane.ERROR_MESSAGE)
+					exitProcess(1)
+				}
+				// In case the EventQueue is broken, exit after 1 minute
+				Thread.sleep(60 * 1000.toLong())
+			}
+			exitProcess(1)
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/UpdateManager.kt

@@ -0,0 +1,469 @@
+package link.infra.packwiz.installer
+
+import com.google.gson.GsonBuilder
+import com.google.gson.JsonIOException
+import com.google.gson.JsonSyntaxException
+import com.moandjiezana.toml.Toml
+import link.infra.packwiz.installer.DownloadTask.Companion.createTasksFromIndex
+import link.infra.packwiz.installer.metadata.IndexFile
+import link.infra.packwiz.installer.metadata.ManifestFile
+import link.infra.packwiz.installer.metadata.PackFile
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import link.infra.packwiz.installer.metadata.curseforge.resolveCfMetadata
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashUtils.getHash
+import link.infra.packwiz.installer.metadata.hash.HashUtils.getHasher
+import link.infra.packwiz.installer.request.HandlerManager.getFileSource
+import link.infra.packwiz.installer.request.HandlerManager.getNewLoc
+import link.infra.packwiz.installer.target.Side
+import link.infra.packwiz.installer.ui.IUserInterface
+import link.infra.packwiz.installer.ui.IUserInterface.CancellationResult
+import link.infra.packwiz.installer.ui.IUserInterface.ExceptionListResult
+import link.infra.packwiz.installer.ui.data.InstallProgress
+import link.infra.packwiz.installer.util.Log
+import link.infra.packwiz.installer.util.ifletOrErr
+import okio.buffer
+import java.io.*
+import java.nio.file.Files
+import java.nio.file.Paths
+import java.util.concurrent.CompletionService
+import java.util.concurrent.ExecutionException
+import java.util.concurrent.ExecutorCompletionService
+import java.util.concurrent.Executors
+import kotlin.system.exitProcess
+
+class UpdateManager internal constructor(private val opts: Options, val ui: IUserInterface) {
+	private var cancelled = false
+	private var cancelledStartGame = false
+	private var errorsOccurred = false
+
+	init {
+		start()
+	}
+
+	data class Options(
+		val downloadURI: SpaceSafeURI,
+		val manifestFile: String,
+		val packFolder: String,
+		val side: Side
+	) {
+		// Horrible workaround for default params not working cleanly with nullable values
+		companion object {
+			fun construct(downloadURI: SpaceSafeURI, manifestFile: String?, packFolder: String?, side: Side?) =
+				Options(downloadURI, manifestFile ?: "packwiz.json", packFolder ?: ".", side ?: Side.CLIENT)
+		}
+
+	}
+
+	private fun start() {
+		checkOptions()
+
+		ui.submitProgress(InstallProgress("Loading manifest file..."))
+		val gson = GsonBuilder().registerTypeAdapter(Hash::class.java, Hash.TypeHandler()).create()
+		val manifest = try {
+			gson.fromJson(FileReader(Paths.get(opts.packFolder, opts.manifestFile).toString()),
+					ManifestFile::class.java)
+		} catch (e: FileNotFoundException) {
+			ui.firstInstall = true
+			ManifestFile()
+		} catch (e: JsonSyntaxException) {
+			ui.showErrorAndExit("Invalid local manifest file, try deleting ${opts.manifestFile}", e)
+		} catch (e: JsonIOException) {
+			ui.showErrorAndExit("Failed to read local manifest file, try deleting ${opts.manifestFile}", e)
+		}
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			handleCancellation()
+		}
+
+		ui.submitProgress(InstallProgress("Loading pack file..."))
+		val packFileSource = try {
+			val src = getFileSource(opts.downloadURI)
+			getHasher("sha256").getHashingSource(src)
+		} catch (e: Exception) {
+			ui.showErrorAndExit("Failed to download pack.toml", e)
+		}
+		val pf = packFileSource.buffer().use {
+			try {
+				Toml().read(InputStreamReader(it.inputStream(), "UTF-8")).to(PackFile::class.java)
+			} catch (e: IllegalStateException) {
+				ui.showErrorAndExit("Failed to parse pack.toml", e)
+			}
+		}
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			handleCancellation()
+		}
+
+		ui.submitProgress(InstallProgress("Checking local files..."))
+
+		// Invalidation checking must be done here, as it must happen before pack/index hashes are checked
+		val invalidatedUris: MutableList<SpaceSafeURI> = ArrayList()
+		for ((fileUri, file) in manifest.cachedFiles) {
+			// ignore onlyOtherSide files
+			if (file.onlyOtherSide) {
+				continue
+			}
+
+			var invalid = false
+			// if isn't optional, or is optional but optionValue == true
+			if (!file.isOptional || file.optionValue) {
+				if (file.cachedLocation != null) {
+					if (!Paths.get(opts.packFolder, file.cachedLocation).toFile().exists()) {
+						invalid = true
+					}
+				} else {
+					// if cachedLocation == null, should probably be installed!!
+					invalid = true
+				}
+			}
+			if (invalid) {
+				Log.info("File $fileUri invalidated, marked for redownloading")
+				invalidatedUris.add(fileUri)
+			}
+		}
+
+		if (manifest.packFileHash?.let { packFileSource.hashIsEqual(it) } == true && invalidatedUris.isEmpty()) {
+			// todo: --force?
+			ui.submitProgress(InstallProgress("Modpack is already up to date!", 1, 1))
+			if (manifest.cachedFiles.any { it.value.isOptional }) {
+				ui.awaitOptionalButton(false)
+			}
+			if (!ui.optionsButtonPressed) {
+				return
+			}
+		}
+
+		Log.info("Modpack name: ${pf.name}")
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			handleCancellation()
+		}
+		try {
+			// TODO: switch to OkHttp for better redirect handling
+			ui.ifletOrErr(pf.index, "No index file found, or the pack file is empty; note that Java doesn't automatically follow redirects from HTTP to HTTPS (and may cause this error)") { index ->
+				ui.ifletOrErr(index.hashFormat, index.hash, "Pack has no hash or hashFormat for index") { hashFormat, hash ->
+					ui.ifletOrErr(getNewLoc(opts.downloadURI, index.file), "Pack has invalid index file: " + index.file) { newLoc ->
+						processIndex(
+							newLoc,
+							getHash(hashFormat, hash),
+							hashFormat,
+							manifest,
+							invalidatedUris
+						)
+					}
+				}
+			}
+		} catch (e1: Exception) {
+			ui.showErrorAndExit("Failed to process index file", e1)
+		}
+
+		handleCancellation()
+
+		// TODO: update MMC params, java args etc
+
+		// If there were errors, don't write the manifest/index hashes, to ensure they are rechecked later
+		if (errorsOccurred) {
+			manifest.indexFileHash = null
+			manifest.packFileHash = null
+		} else {
+			manifest.packFileHash = packFileSource.hash
+		}
+
+		manifest.cachedSide = opts.side
+		try {
+			FileWriter(Paths.get(opts.packFolder, opts.manifestFile).toString()).use { writer -> gson.toJson(manifest, writer) }
+		} catch (e: IOException) {
+			ui.showErrorAndExit("Failed to save local manifest file", e)
+		}
+	}
+
+	private fun checkOptions() {
+		// TODO: implement
+	}
+
+	private fun processIndex(indexUri: SpaceSafeURI, indexHash: Hash, hashFormat: String, manifest: ManifestFile, invalidatedUris: List<SpaceSafeURI>) {
+		if (manifest.indexFileHash == indexHash && invalidatedUris.isEmpty()) {
+			ui.submitProgress(InstallProgress("Modpack files are already up to date!", 1, 1))
+			if (manifest.cachedFiles.any { it.value.isOptional }) {
+				ui.awaitOptionalButton(false)
+			}
+			if (!ui.optionsButtonPressed) {
+				return
+			}
+			if (ui.cancelButtonPressed) {
+				showCancellationDialog()
+				return
+			}
+		}
+		manifest.indexFileHash = indexHash
+
+		val indexFileSource = try {
+			val src = getFileSource(indexUri)
+			getHasher(hashFormat).getHashingSource(src)
+		} catch (e: Exception) {
+			ui.showErrorAndExit("Failed to download index file", e)
+		}
+
+		val indexFile = try {
+			Toml().read(InputStreamReader(indexFileSource.buffer().inputStream(), "UTF-8")).to(IndexFile::class.java)
+		} catch (e: IllegalStateException) {
+			ui.showErrorAndExit("Failed to parse index file", e)
+		}
+		if (!indexFileSource.hashIsEqual(indexHash)) {
+			ui.showErrorAndExit("Your index file hash is invalid! The pack developer should packwiz refresh on the pack again")
+		}
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			return
+		}
+
+		ui.submitProgress(InstallProgress("Checking local files..."))
+		// TODO: use kotlin filtering/FP rather than an iterator?
+		val it: MutableIterator<Map.Entry<SpaceSafeURI, ManifestFile.File>> = manifest.cachedFiles.entries.iterator()
+		while (it.hasNext()) {
+			val (uri, file) = it.next()
+			if (file.cachedLocation != null) {
+				var alreadyDeleted = false
+				// Delete if option value has been set to false
+				if (file.isOptional && !file.optionValue) {
+					try {
+						Files.deleteIfExists(Paths.get(opts.packFolder, file.cachedLocation))
+					} catch (e: IOException) {
+						Log.warn("Failed to delete optional disabled file", e)
+					}
+					// Set to null, as it doesn't exist anymore
+					file.cachedLocation = null
+					alreadyDeleted = true
+				}
+				if (indexFile.files.none { it.file == uri }) { // File has been removed from the index
+					if (!alreadyDeleted) {
+						try {
+							Files.deleteIfExists(Paths.get(opts.packFolder, file.cachedLocation))
+						} catch (e: IOException) {
+							Log.warn("Failed to delete file removed from index", e)
+						}
+					}
+					it.remove()
+				}
+			}
+		}
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			return
+		}
+		ui.submitProgress(InstallProgress("Comparing new files..."))
+
+		// TODO: progress bar?
+		if (indexFile.files.isEmpty()) {
+			Log.warn("Index is empty!")
+		}
+		val tasks = createTasksFromIndex(indexFile, indexFile.hashFormat, opts.side)
+		// If the side changes, invalidate EVERYTHING just in case
+		// Might not be needed, but done just to be safe
+		val invalidateAll = opts.side != manifest.cachedSide
+		if (invalidateAll) {
+			Log.info("Side changed, invalidating all mods")
+		}
+		tasks.forEach{ f ->
+			// TODO: should linkedfile be checked as well? should this be done in the download section?
+			if (invalidateAll) {
+				f.invalidate()
+			} else if (invalidatedUris.contains(f.metadata.file)) {
+				f.invalidate()
+			}
+			val file = manifest.cachedFiles[f.metadata.file]
+			// Ensure the file can be reverted later if necessary - the DownloadTask modifies the file so if it fails we need the old version back
+			file?.backup()
+			// If it is null, the DownloadTask will make a new empty cachedFile
+			f.updateFromCache(file)
+		}
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			return
+		}
+
+		// Let's hope downloadMetadata is a pure function!!!
+		tasks.parallelStream().forEach { f -> f.downloadMetadata(indexFile, indexUri) }
+
+		val failedTaskDetails = tasks.asSequence().map(DownloadTask::exceptionDetails).filterNotNull().toList()
+		if (failedTaskDetails.isNotEmpty()) {
+			errorsOccurred = true
+			when (ui.showExceptions(failedTaskDetails, tasks.size, true)) {
+				ExceptionListResult.CONTINUE -> {}
+				ExceptionListResult.CANCEL -> {
+					cancelled = true
+					return
+				}
+				ExceptionListResult.IGNORE -> {
+					cancelledStartGame = true
+					return
+				}
+			}
+		}
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			return
+		}
+
+		// TODO: task failed function?
+		tasks.removeAll { it.failed() }
+		val optionTasks = tasks.filter(DownloadTask::correctSide).filter(DownloadTask::isOptional).toList()
+		val optionsChanged = optionTasks.any(DownloadTask::isNewOptional)
+		if (optionTasks.isNotEmpty() && !optionsChanged) {
+			if (!ui.optionsButtonPressed) {
+				// TODO: this is so ugly
+				ui.submitProgress(InstallProgress("Reconfigure optional mods?", 0,1))
+				ui.awaitOptionalButton(true)
+				if (ui.cancelButtonPressed) {
+					showCancellationDialog()
+					return
+				}
+			}
+		}
+		// If options changed, present all options again
+		if (ui.optionsButtonPressed || optionsChanged) {
+			// new ArrayList is required so it's an IOptionDetails rather than a DownloadTask list
+			if (ui.showOptions(ArrayList(optionTasks))) {
+				cancelled = true
+				handleCancellation()
+			}
+		}
+		// TODO: keep this enabled? then apply changes after download process?
+		ui.disableOptionsButton(optionTasks.isNotEmpty())
+
+		while (true) {
+			when (validateAndResolve(tasks)) {
+				ResolveResult.RETRY -> {}
+				ResolveResult.QUIT -> return
+				ResolveResult.SUCCESS -> break
+			}
+		}
+
+		// TODO: different thread pool type?
+		val threadPool = Executors.newFixedThreadPool(10)
+		val completionService: CompletionService<DownloadTask> = ExecutorCompletionService(threadPool)
+		tasks.forEach { t ->
+			completionService.submit {
+				t.download(opts.packFolder, indexUri)
+				t
+			}
+		}
+		for (i in tasks.indices) {
+			val task: DownloadTask = try {
+				completionService.take().get()
+			} catch (e: InterruptedException) {
+				ui.showErrorAndExit("Interrupted when consuming download tasks", e)
+			} catch (e: ExecutionException) {
+				ui.showErrorAndExit("Failed to execute download task", e)
+			}
+			// Update manifest - If there were no errors cachedFile has already been modified in place (good old pass by reference)
+			task.cachedFile?.let { file ->
+				if (task.failed()) {
+					val oldFile = file.revert
+					if (oldFile != null) {
+						task.metadata.file?.let { uri -> manifest.cachedFiles.putIfAbsent(uri, oldFile) }
+					} else { null }
+				} else {
+					task.metadata.file?.let { uri -> manifest.cachedFiles.putIfAbsent(uri, file) }
+				}
+			}
+
+			val exDetails = task.exceptionDetails
+			val progress = if (exDetails != null) {
+				"Failed to download ${exDetails.name}: ${exDetails.exception.message}"
+			} else {
+				"Downloaded ${task.name}"
+			}
+			ui.submitProgress(InstallProgress(progress, i + 1, tasks.size))
+
+			if (ui.cancelButtonPressed) { // Stop all tasks, don't launch the game (it's in an invalid state!)
+				threadPool.shutdown()
+				cancelled = true
+				return
+			}
+		}
+
+		// Shut down the thread pool when the update is done
+		threadPool.shutdown()
+
+		val failedTasks2ElectricBoogaloo = tasks.asSequence().map(DownloadTask::exceptionDetails).filterNotNull().toList()
+		if (failedTasks2ElectricBoogaloo.isNotEmpty()) {
+			errorsOccurred = true
+			when (ui.showExceptions(failedTasks2ElectricBoogaloo, tasks.size, false)) {
+				ExceptionListResult.CONTINUE -> {}
+				ExceptionListResult.CANCEL -> cancelled = true
+				ExceptionListResult.IGNORE -> cancelledStartGame = true
+			}
+		}
+	}
+
+	enum class ResolveResult {
+		RETRY,
+		QUIT,
+		SUCCESS;
+	}
+
+	private fun validateAndResolve(nonFailedFirstTasks: List<DownloadTask>): ResolveResult {
+		ui.submitProgress(InstallProgress("Validating existing files..."))
+
+		// Validate existing files
+		for (downloadTask in nonFailedFirstTasks.filter(DownloadTask::correctSide)) {
+			downloadTask.validateExistingFile(opts.packFolder)
+		}
+
+		// Resolve CurseForge metadata
+		val cfFiles = nonFailedFirstTasks.asSequence().filter { !it.alreadyUpToDate }
+			.filter(DownloadTask::correctSide)
+			.map { it.metadata }
+			.filter { it.linkedFile != null }
+			.filter { it.linkedFile?.download?.mode == "metadata:curseforge" }.toList()
+		if (cfFiles.isNotEmpty()) {
+			ui.submitProgress(InstallProgress("Resolving CurseForge metadata..."))
+			val resolveFailures = resolveCfMetadata(cfFiles)
+			if (resolveFailures.isNotEmpty()) {
+				errorsOccurred = true
+				return when (ui.showExceptions(resolveFailures, cfFiles.size, true)) {
+					ExceptionListResult.CONTINUE -> {
+						ResolveResult.RETRY
+					}
+					ExceptionListResult.CANCEL -> {
+						cancelled = true
+						ResolveResult.QUIT
+					}
+					ExceptionListResult.IGNORE -> {
+						cancelledStartGame = true
+						ResolveResult.QUIT
+					}
+				}
+			}
+		}
+		return ResolveResult.SUCCESS
+	}
+
+	private fun showCancellationDialog() {
+		when (ui.showCancellationDialog()) {
+			CancellationResult.QUIT -> cancelled = true
+			CancellationResult.CONTINUE -> cancelledStartGame = true
+		}
+	}
+
+	// TODO: move to UI?
+	private fun handleCancellation() {
+		if (cancelled) {
+			println("Update cancelled by user!")
+			exitProcess(1)
+		} else if (cancelledStartGame) {
+			println("Update cancelled by user! Continuing to start game...")
+			exitProcess(0)
+		}
+	}
+
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/EfficientBooleanAdapter.kt

@@ -0,0 +1,27 @@
+package link.infra.packwiz.installer.metadata
+
+import com.google.gson.TypeAdapter
+import com.google.gson.stream.JsonReader
+import com.google.gson.stream.JsonToken
+import com.google.gson.stream.JsonWriter
+import java.io.IOException
+
+class EfficientBooleanAdapter : TypeAdapter<Boolean?>() {
+	@Throws(IOException::class)
+	override fun write(out: JsonWriter, value: Boolean?) {
+		if (value == null || !value) {
+			out.nullValue()
+			return
+		}
+		out.value(true)
+	}
+
+	@Throws(IOException::class)
+	override fun read(reader: JsonReader): Boolean? {
+		if (reader.peek() == JsonToken.NULL) {
+			reader.nextNull()
+			return false
+		}
+		return reader.nextBoolean()
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/IndexFile.kt

@@ -0,0 +1,100 @@
+package link.infra.packwiz.installer.metadata
+
+import com.google.gson.annotations.SerializedName
+import com.moandjiezana.toml.Toml
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashUtils.getHash
+import link.infra.packwiz.installer.metadata.hash.HashUtils.getHasher
+import link.infra.packwiz.installer.request.HandlerManager.getFileSource
+import link.infra.packwiz.installer.request.HandlerManager.getNewLoc
+import okio.Source
+import okio.buffer
+import java.io.InputStreamReader
+import java.nio.file.Paths
+
+class IndexFile {
+	@SerializedName("hash-format")
+	var hashFormat: String = "sha-256"
+	var files: MutableList<File> = ArrayList()
+
+	class File {
+		var file: SpaceSafeURI? = null
+		@SerializedName("hash-format")
+		var hashFormat: String? = null
+		var hash: String? = null
+		var alias: SpaceSafeURI? = null
+		var metafile = false
+		var preserve = false
+
+		@Transient
+		var linkedFile: ModFile? = null
+		@Transient
+		var linkedFileURI: SpaceSafeURI? = null
+
+		@Throws(Exception::class)
+		fun downloadMeta(parentIndexFile: IndexFile, indexUri: SpaceSafeURI?) {
+			if (!metafile) {
+				return
+			}
+			if (hashFormat?.length ?: 0 == 0) {
+				hashFormat = parentIndexFile.hashFormat
+			}
+			// TODO: throw a proper exception instead of allowing NPE?
+			val fileHash = getHash(hashFormat!!, hash!!)
+			linkedFileURI = getNewLoc(indexUri, file)
+			val src = getFileSource(linkedFileURI!!)
+			val fileStream = getHasher(hashFormat!!).getHashingSource(src)
+			linkedFile = Toml().read(InputStreamReader(fileStream.buffer().inputStream(), "UTF-8")).to(ModFile::class.java)
+			if (!fileStream.hashIsEqual(fileHash)) {
+				throw Exception("Invalid mod file hash")
+			}
+		}
+
+		@Throws(Exception::class)
+		fun getSource(indexUri: SpaceSafeURI?): Source {
+			return if (metafile) {
+				if (linkedFile == null) {
+					throw Exception("Linked file doesn't exist!")
+				}
+				linkedFile!!.getSource(linkedFileURI)
+			} else {
+				val newLoc = getNewLoc(indexUri, file) ?: throw Exception("Index file URI is invalid")
+				getFileSource(newLoc)
+			}
+		}
+
+		@Throws(Exception::class)
+		fun getHashObj(): Hash {
+			if (hash == null) { // TODO: should these be more specific exceptions (e.g. IndexFileException?!)
+				throw Exception("Index file doesn't have a hash")
+			}
+			if (hashFormat == null) {
+				throw Exception("Index file doesn't have a hash format")
+			}
+			return getHash(hashFormat!!, hash!!)
+		}
+
+		// TODO: throw some kind of exception?
+		val name: String
+			get() {
+				if (metafile) {
+					return linkedFile?.name ?: linkedFile?.filename ?:
+					file?.run { Paths.get(path ?: return "Invalid file").fileName.toString() } ?: "Invalid file"
+				}
+				return file?.run { Paths.get(path ?: return "Invalid file").fileName.toString() } ?: "Invalid file"
+			}
+
+		// TODO: URIs are bad
+		val destURI: SpaceSafeURI?
+			get() {
+				if (alias != null) {
+					return alias
+				}
+				return if (metafile && linkedFile != null) {
+					linkedFile?.filename?.let { file?.resolve(it) }
+				} else {
+					file
+				}
+			}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/ManifestFile.kt

@@ -0,0 +1,44 @@
+package link.infra.packwiz.installer.metadata
+
+import com.google.gson.annotations.JsonAdapter
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.target.Side
+
+class ManifestFile {
+	var packFileHash: Hash? = null
+	var indexFileHash: Hash? = null
+	var cachedFiles: MutableMap<SpaceSafeURI, File> = HashMap()
+	// If the side changes, EVERYTHING invalidates. FUN!!!
+	var cachedSide = Side.CLIENT
+
+	// TODO: switch to Kotlin-friendly JSON/TOML libs?
+	class File {
+		@Transient
+		var revert: File? = null
+			private set
+
+		var hash: Hash? = null
+		var linkedFileHash: Hash? = null
+		var cachedLocation: String? = null
+
+		@JsonAdapter(EfficientBooleanAdapter::class)
+		var isOptional = false
+		var optionValue = true
+
+		@JsonAdapter(EfficientBooleanAdapter::class)
+		var onlyOtherSide = false
+
+		// When an error occurs, the state needs to be reverted. To do this, I have a crude revert system.
+		fun backup() {
+			revert = File().also {
+				it.hash = hash
+				it.linkedFileHash = linkedFileHash
+				it.cachedLocation = cachedLocation
+				it.isOptional = isOptional
+				it.optionValue = optionValue
+				it.onlyOtherSide = onlyOtherSide
+			}
+		}
+
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/ModFile.kt

@@ -0,0 +1,74 @@
+package link.infra.packwiz.installer.metadata
+
+import com.google.gson.annotations.JsonAdapter
+import com.google.gson.annotations.SerializedName
+import link.infra.packwiz.installer.metadata.curseforge.UpdateData
+import link.infra.packwiz.installer.metadata.curseforge.UpdateDeserializer
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashUtils.getHash
+import link.infra.packwiz.installer.request.HandlerManager.getFileSource
+import link.infra.packwiz.installer.request.HandlerManager.getNewLoc
+import link.infra.packwiz.installer.target.Side
+import okio.Source
+
+class ModFile {
+	var name: String? = null
+	var filename: String? = null
+	var side: Side? = null
+	var download: Download? = null
+
+	class Download {
+		var url: SpaceSafeURI? = null
+		@SerializedName("hash-format")
+		var hashFormat: String? = null
+		var hash: String? = null
+		var mode: String? = null
+	}
+
+	@JsonAdapter(UpdateDeserializer::class)
+	var update: Map<String, UpdateData>? = null
+	var option: Option? = null
+
+	@Transient
+	val resolvedUpdateData = mutableMapOf<String, SpaceSafeURI>()
+
+	class Option {
+		var optional = false
+		var description: String? = null
+		@SerializedName("default")
+		var defaultValue = false
+	}
+
+	@Throws(Exception::class)
+	fun getSource(baseLoc: SpaceSafeURI?): Source {
+		download?.let {
+			if (it.mode == null || it.mode == "" || it.mode == "url") {
+				if (it.url == null) {
+					throw Exception("Metadata file doesn't have a download URI")
+				}
+				val newLoc = getNewLoc(baseLoc, it.url) ?: throw Exception("Metadata file URI is invalid")
+				return getFileSource(newLoc)
+			} else if (it.mode == "metadata:curseforge") {
+				if (!resolvedUpdateData.contains("curseforge")) {
+					throw Exception("Metadata file specifies CurseForge mode, but is missing metadata")
+				}
+				return getFileSource(resolvedUpdateData["curseforge"]!!)
+			} else {
+				throw Exception("Unsupported download mode " + it.mode)
+			}
+		} ?: throw Exception("Metadata file doesn't have download")
+	}
+
+	@get:Throws(Exception::class)
+	val hash: Hash
+		get() {
+			download?.let {
+				return getHash(
+						it.hashFormat ?: throw Exception("Metadata file doesn't have a hash format"),
+						it.hash ?: throw Exception("Metadata file doesn't have a hash")
+				)
+			} ?: throw Exception("Metadata file doesn't have download")
+		}
+
+	val isOptional: Boolean get() = option?.optional ?: false
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/PackFile.kt

@@ -0,0 +1,17 @@
+package link.infra.packwiz.installer.metadata
+
+import com.google.gson.annotations.SerializedName
+
+class PackFile {
+	var name: String? = null
+	var index: IndexFileLoc? = null
+
+	class IndexFileLoc {
+		var file: SpaceSafeURI? = null
+		@SerializedName("hash-format")
+		var hashFormat: String? = null
+		var hash: String? = null
+	}
+
+	var versions: Map<String, String>? = null
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/SpaceSafeURI.kt

@@ -0,0 +1,61 @@
+package link.infra.packwiz.installer.metadata
+
+import com.google.gson.annotations.JsonAdapter
+import java.io.Serializable
+import java.net.MalformedURLException
+import java.net.URI
+import java.net.URISyntaxException
+import java.net.URL
+
+// The world's worst URI wrapper
+@JsonAdapter(SpaceSafeURIParser::class)
+class SpaceSafeURI : Comparable<SpaceSafeURI>, Serializable {
+	private val u: URI
+
+	@Throws(URISyntaxException::class)
+	constructor(str: String) {
+		u = URI(str.replace(" ", "%20"))
+	}
+
+	constructor(uri: URI) {
+		u = uri
+	}
+
+	@Throws(URISyntaxException::class)
+	constructor(scheme: String?, authority: String?, path: String?, query: String?, fragment: String?) { // TODO: do all components need to be replaced?
+		u = URI(
+				scheme?.replace(" ", "%20"),
+				authority?.replace(" ", "%20"),
+				path?.replace(" ", "%20"),
+				query?.replace(" ", "%20"),
+				fragment?.replace(" ", "%20")
+		)
+	}
+
+	val path: String? get() = u.path?.replace("%20", " ")
+
+	override fun toString(): String = u.toString().replace("%20", " ")
+
+	fun resolve(path: String): SpaceSafeURI = SpaceSafeURI(u.resolve(path.replace(" ", "%20")))
+
+	fun resolve(loc: SpaceSafeURI): SpaceSafeURI = SpaceSafeURI(u.resolve(loc.u))
+
+	fun relativize(loc: SpaceSafeURI): SpaceSafeURI = SpaceSafeURI(u.relativize(loc.u))
+
+	override fun equals(other: Any?): Boolean {
+		return if (other is SpaceSafeURI) {
+			u == other.u
+		} else false
+	}
+
+	override fun hashCode() = u.hashCode()
+
+	override fun compareTo(other: SpaceSafeURI): Int = u.compareTo(other.u)
+
+	val scheme: String? get() = u.scheme
+	val authority: String? get() = u.authority
+	val host: String? get() = u.host
+
+	@Throws(MalformedURLException::class)
+	fun toURL(): URL = u.toURL()
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/SpaceSafeURIParser.kt

@@ -0,0 +1,25 @@
+package link.infra.packwiz.installer.metadata
+
+import com.google.gson.JsonDeserializationContext
+import com.google.gson.JsonDeserializer
+import com.google.gson.JsonElement
+import com.google.gson.JsonParseException
+import java.lang.reflect.Type
+import java.net.URISyntaxException
+
+/**
+ * This class encodes spaces before parsing the URI, so the URI can actually be
+ * parsed.
+ */
+internal class SpaceSafeURIParser : JsonDeserializer<SpaceSafeURI> {
+	@Throws(JsonParseException::class)
+	override fun deserialize(json: JsonElement, typeOfT: Type, context: JsonDeserializationContext): SpaceSafeURI {
+		return try {
+			SpaceSafeURI(json.asString)
+		} catch (e: URISyntaxException) {
+			throw JsonParseException("Failed to parse URI", e)
+		}
+	}
+
+	// TODO: replace this with a better solution?
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/curseforge/CurseForgeSourcer.kt

@@ -0,0 +1,132 @@
+package link.infra.packwiz.installer.metadata.curseforge
+
+import com.google.gson.Gson
+import com.google.gson.JsonIOException
+import com.google.gson.JsonSyntaxException
+import link.infra.packwiz.installer.metadata.IndexFile
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import link.infra.packwiz.installer.target.ClientHolder
+import link.infra.packwiz.installer.ui.data.ExceptionDetails
+import okhttp3.MediaType.Companion.toMediaType
+import okhttp3.Request
+import okhttp3.RequestBody.Companion.toRequestBody
+import okhttp3.internal.closeQuietly
+import okio.ByteString.Companion.decodeBase64
+import java.nio.charset.StandardCharsets
+
+private class GetFilesRequest(val fileIds: List<Int>)
+private class GetModsRequest(val modIds: List<Int>)
+
+private class GetFilesResponse {
+	class CfFile {
+		var id = 0
+		var modId = 0
+		var downloadUrl: SpaceSafeURI? = null
+	}
+	val data = mutableListOf<CfFile>()
+}
+
+private class GetModsResponse {
+	class CfMod {
+		var id = 0
+		var name = ""
+		var links: CfLinks? = null
+	}
+	class CfLinks {
+		var websiteUrl = ""
+	}
+	val data = mutableListOf<CfMod>()
+}
+
+private const val APIServer = "api.curseforge.com"
+// If you fork/derive from packwiz, I request that you obtain your own API key.
+private val APIKey = "JDJhJDEwJHNBWVhqblU1N0EzSmpzcmJYM3JVdk92UWk2NHBLS3BnQ2VpbGc1TUM1UGNKL0RYTmlGWWxh".decodeBase64()!!
+	.string(StandardCharsets.UTF_8)
+
+private val clientHolder = ClientHolder()
+
+// TODO: switch to PackwizPath stuff and OkHttp in old code
+
+@Throws(JsonSyntaxException::class, JsonIOException::class)
+fun resolveCfMetadata(mods: List<IndexFile.File>): List<ExceptionDetails> {
+	val failures = mutableListOf<ExceptionDetails>()
+	val fileIdMap = mutableMapOf<Int, IndexFile.File>()
+
+	for (mod in mods) {
+		if (mod.linkedFile!!.update == null) {
+			failures.add(ExceptionDetails(mod.linkedFile!!.name ?: mod.linkedFile!!.filename!!, Exception("Failed to resolve CurseForge metadata: no update section")))
+			continue
+		}
+		if (!mod.linkedFile!!.update!!.contains("curseforge")) {
+			failures.add(ExceptionDetails(mod.linkedFile!!.name ?: mod.linkedFile!!.filename!!, Exception("Failed to resolve CurseForge metadata: no CurseForge update section")))
+			continue
+		}
+		fileIdMap[(mod.linkedFile!!.update!!["curseforge"] as CurseForgeUpdateData).fileId] = mod
+	}
+
+	val reqData = GetFilesRequest(fileIdMap.keys.toList())
+	val req = Request.Builder()
+		.url("https://${APIServer}/v1/mods/files")
+		.header("Accept", "application/json")
+		.header("User-Agent", "packwiz-installer")
+		.header("X-API-Key", APIKey)
+		.post(Gson().toJson(reqData, GetFilesRequest::class.java).toRequestBody("application/json".toMediaType()))
+		.build()
+	val res = clientHolder.okHttpClient.newCall(req).execute()
+	if (!res.isSuccessful || res.body == null) {
+		res.closeQuietly()
+		failures.add(ExceptionDetails("Other", Exception("Failed to resolve CurseForge metadata for file data: error code ${res.code}")))
+		return failures
+	}
+
+	val resData = Gson().fromJson(res.body!!.charStream(), GetFilesResponse::class.java)
+	res.closeQuietly()
+
+	val manualDownloadMods = mutableMapOf<Int, Pair<IndexFile.File, Int>>()
+	for (file in resData.data) {
+		if (!fileIdMap.contains(file.id)) {
+			failures.add(ExceptionDetails(file.id.toString(),
+				Exception("Failed to find file from result: ID ${file.id}, Project ID ${file.modId}")))
+			continue
+		}
+		if (file.downloadUrl == null) {
+			manualDownloadMods[file.modId] = Pair(fileIdMap[file.id]!!, file.id)
+			continue
+		}
+		fileIdMap[file.id]!!.linkedFile!!.resolvedUpdateData["curseforge"] = file.downloadUrl!!
+	}
+
+	if (manualDownloadMods.isNotEmpty()) {
+		val reqModsData = GetModsRequest(manualDownloadMods.keys.toList())
+		val reqMods = Request.Builder()
+			.url("https://${APIServer}/v1/mods")
+			.header("Accept", "application/json")
+			.header("User-Agent", "packwiz-installer")
+			.header("X-API-Key", APIKey)
+			.post(Gson().toJson(reqModsData, GetModsRequest::class.java).toRequestBody("application/json".toMediaType()))
+			.build()
+		val resMods = clientHolder.okHttpClient.newCall(reqMods).execute()
+		if (!resMods.isSuccessful || resMods.body == null) {
+			resMods.closeQuietly()
+			failures.add(ExceptionDetails("Other", Exception("Failed to resolve CurseForge metadata for mod data: error code ${resMods.code}")))
+			return failures
+		}
+
+		val resModsData = Gson().fromJson(resMods.body!!.charStream(), GetModsResponse::class.java)
+		resMods.closeQuietly()
+
+		for (mod in resModsData.data) {
+			if (!manualDownloadMods.contains(mod.id)) {
+				failures.add(ExceptionDetails(mod.name,
+					Exception("Failed to find project from result: ID ${mod.id}")))
+				continue
+			}
+
+			val modFile = manualDownloadMods[mod.id]!!
+			failures.add(ExceptionDetails(mod.name, Exception("This mod is excluded from the CurseForge API and must be downloaded manually.\n" +
+				"Please go to ${mod.links?.websiteUrl}/files/${modFile.second} and save this file to ${modFile.first.destURI}")))
+		}
+	}
+
+	return failures
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/curseforge/CurseForgeUpdateData.kt

@@ -0,0 +1,10 @@
+package link.infra.packwiz.installer.metadata.curseforge
+
+import com.google.gson.annotations.SerializedName
+
+class CurseForgeUpdateData: UpdateData {
+	@SerializedName("file-id")
+	var fileId = 0
+	@SerializedName("project-id")
+	var projectId = 0
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/curseforge/UpdateData.kt

@@ -0,0 +1,3 @@
+package link.infra.packwiz.installer.metadata.curseforge
+
+interface UpdateData

src/main/kotlin/link/infra/packwiz/installer/metadata/curseforge/UpdateDeserializer.kt

@@ -0,0 +1,22 @@
+package link.infra.packwiz.installer.metadata.curseforge
+
+import com.google.gson.JsonDeserializationContext
+import com.google.gson.JsonDeserializer
+import com.google.gson.JsonElement
+import java.lang.reflect.Type
+
+class UpdateDeserializer: JsonDeserializer<Map<String, UpdateData>> {
+	override fun deserialize(
+		json: JsonElement?,
+		typeOfT: Type?,
+		context: JsonDeserializationContext?
+	): Map<String, UpdateData> {
+		val out = mutableMapOf<String, UpdateData>()
+		for ((k, v) in json!!.asJsonObject.entrySet()) {
+			if (k == "curseforge") {
+				out[k] = context!!.deserialize(v, CurseForgeUpdateData::class.java)
+			}
+		}
+		return out
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/hash/GeneralHashingSource.kt

@@ -0,0 +1,10 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import okio.ForwardingSource
+import okio.Source
+
+abstract class GeneralHashingSource(delegate: Source) : ForwardingSource(delegate) {
+	abstract val hash: Hash
+
+	fun hashIsEqual(compareTo: Any) = compareTo == hash
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Hash.kt

@@ -0,0 +1,34 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import com.google.gson.*
+import java.lang.reflect.Type
+
+abstract class Hash {
+	protected abstract val stringValue: String
+	protected abstract val type: String
+
+	class TypeHandler : JsonDeserializer<Hash>, JsonSerializer<Hash> {
+		override fun serialize(src: Hash, typeOfSrc: Type, context: JsonSerializationContext): JsonElement = JsonObject().apply {
+			add("type", JsonPrimitive(src.type))
+			add("value", JsonPrimitive(src.stringValue))
+		}
+
+		@Throws(JsonParseException::class)
+		override fun deserialize(json: JsonElement, typeOfT: Type, context: JsonDeserializationContext): Hash {
+			val obj = json.asJsonObject
+			val type: String
+			val value: String
+			try {
+				type = obj["type"].asString
+				value = obj["value"].asString
+			} catch (e: NullPointerException) {
+				throw JsonParseException("Invalid hash JSON data")
+			}
+			return try {
+				HashUtils.getHash(type, value)
+			} catch (e: Exception) {
+				throw JsonParseException("Failed to create hash object", e)
+			}
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/hash/HashUtils.kt

@@ -0,0 +1,22 @@
+package link.infra.packwiz.installer.metadata.hash
+
+object HashUtils {
+	private val hashTypeConversion: Map<String, IHasher> = mapOf(
+			"sha256" to HashingSourceHasher("sha256"),
+			"sha512" to HashingSourceHasher("sha512"),
+			"murmur2" to Murmur2Hasher(),
+			"sha1" to HashingSourceHasher("sha1")
+	)
+
+	@JvmStatic
+	@Throws(Exception::class)
+	fun getHasher(type: String): IHasher {
+		return hashTypeConversion[type] ?: throw Exception("Hash type not supported: $type")
+	}
+
+	@JvmStatic
+	@Throws(Exception::class)
+	fun getHash(type: String, value: String): Hash {
+		return hashTypeConversion[type]?.getHash(value) ?: throw Exception("Hash type not supported: $type")
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/hash/HashingSourceHasher.kt

@@ -0,0 +1,46 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import okio.HashingSource
+import okio.Source
+
+class HashingSourceHasher internal constructor(private val type: String) : IHasher {
+	// i love naming things
+	private inner class HashingSourceGeneralHashingSource(val delegateHashing: HashingSource) : GeneralHashingSource(delegateHashing) {
+		override val hash: Hash by lazy(LazyThreadSafetyMode.NONE) {
+			HashingSourceHash(delegateHashing.hash.hex())
+		}
+	}
+
+	// this some funky inner class stuff
+	// each of these classes is specific to the instance of the HasherHashingSource
+	// therefore HashingSourceHashes from different parent instances will be not instanceof each other
+	private inner class HashingSourceHash(val value: String) : Hash() {
+		override val stringValue get() = value
+
+		override fun equals(other: Any?): Boolean {
+			if (other !is HashingSourceHash) {
+				return false
+			}
+			return stringValue.equals(other.stringValue, ignoreCase = true)
+		}
+
+		override fun toString(): String = "$type: $stringValue"
+		override fun hashCode(): Int = value.hashCode()
+
+		override val type: String get() = this@HashingSourceHasher.type
+	}
+
+	override fun getHashingSource(delegate: Source): GeneralHashingSource {
+		when (type) {
+			"md5" -> return HashingSourceGeneralHashingSource(HashingSource.md5(delegate))
+			"sha256" -> return HashingSourceGeneralHashingSource(HashingSource.sha256(delegate))
+			"sha512" -> return HashingSourceGeneralHashingSource(HashingSource.sha512(delegate))
+			"sha1" -> return HashingSourceGeneralHashingSource(HashingSource.sha1(delegate))
+		}
+		throw RuntimeException("Invalid hash type provided")
+	}
+
+	override fun getHash(value: String): Hash {
+		return HashingSourceHash(value)
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/hash/IHasher.kt

@@ -0,0 +1,8 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import okio.Source
+
+interface IHasher {
+	fun getHashingSource(delegate: Source): GeneralHashingSource
+	fun getHash(value: String): Hash
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Murmur2Hasher.kt

@@ -0,0 +1,91 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import okio.Buffer
+import okio.Source
+import java.io.IOException
+
+class Murmur2Hasher : IHasher {
+	private inner class Murmur2GeneralHashingSource(delegate: Source) : GeneralHashingSource(delegate) {
+		val internalBuffer = Buffer()
+		val tempBuffer = Buffer()
+
+		override val hash: Hash by lazy(LazyThreadSafetyMode.NONE) {
+			val data = internalBuffer.readByteArray()
+			Murmur2Hash(Murmur2Lib.hash32(data, data.size, 1))
+		}
+
+		@Throws(IOException::class)
+		override fun read(sink: Buffer, byteCount: Long): Long {
+			val out = delegate.read(tempBuffer, byteCount)
+			if (out > -1) {
+				sink.write(tempBuffer.clone(), out)
+				computeNormalizedBufferFaster(tempBuffer, internalBuffer)
+			}
+			return out
+		}
+
+		// Credit to https://github.com/modmuss50/CAV2/blob/master/murmur.go
+//		private fun computeNormalizedArray(input: ByteArray): ByteArray {
+//			val output = ByteArray(input.size)
+//			var index = 0
+//			for (b in input) {
+//				when (b) {
+//					9.toByte(), 10.toByte(), 13.toByte(), 32.toByte() -> {}
+//					else -> {
+//						output[index] = b
+//						index++
+//					}
+//				}
+//			}
+//			val outputTrimmed = ByteArray(index)
+//			System.arraycopy(output, 0, outputTrimmed, 0, index)
+//			return outputTrimmed
+//		}
+
+		private fun computeNormalizedBufferFaster(input: Buffer, output: Buffer) {
+			var index = 0
+			val arr = input.readByteArray()
+			for (b in arr) {
+				when (b) {
+					9.toByte(), 10.toByte(), 13.toByte(), 32.toByte() -> {}
+					else -> {
+						arr[index] = b
+						index++
+					}
+				}
+			}
+			output.write(arr, 0, index)
+		}
+
+	}
+
+	private class Murmur2Hash : Hash {
+		val value: Int
+
+		constructor(value: String) {
+			// Parsing as long then casting to int converts values gt int max value but lt uint max value
+			// into negatives. I presume this is how the murmur2 code handles this.
+			this.value = value.toLong().toInt()
+		}
+
+		constructor(value: Int) {
+			this.value = value
+		}
+
+		override val stringValue get() = value.toString()
+		override val type get() = "murmur2"
+
+		override fun equals(other: Any?): Boolean {
+			if (other !is Murmur2Hash) {
+				return false
+			}
+			return value == other.value
+		}
+
+		override fun toString(): String = "murmur2: $value"
+		override fun hashCode(): Int = value
+	}
+
+	override fun getHashingSource(delegate: Source): GeneralHashingSource = Murmur2GeneralHashingSource(delegate)
+	override fun getHash(value: String): Hash = Murmur2Hash(value)
+}

src/main/kotlin/link/infra/packwiz/installer/request/HandlerManager.kt

@@ -0,0 +1,52 @@
+package link.infra.packwiz.installer.request
+
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import link.infra.packwiz.installer.request.handlers.RequestHandlerFile
+import link.infra.packwiz.installer.request.handlers.RequestHandlerGithub
+import link.infra.packwiz.installer.request.handlers.RequestHandlerHTTP
+import okio.Source
+
+object HandlerManager {
+
+	private val handlers: List<IRequestHandler> = listOf(
+			RequestHandlerGithub(),
+			RequestHandlerHTTP(),
+			RequestHandlerFile()
+	)
+
+	 // TODO: get rid of nullable stuff here
+	@JvmStatic
+	fun getNewLoc(base: SpaceSafeURI?, loc: SpaceSafeURI?): SpaceSafeURI? {
+		if (loc == null) {
+			return null
+		}
+		val dest = base?.run { resolve(loc) } ?: loc
+		for (handler in handlers) with (handler) {
+			if (matchesHandler(dest)) {
+				return getNewLoc(dest)
+			}
+		}
+		return dest
+	}
+
+	// TODO: What if files are read multiple times??
+	// Zip handler discards once read, requesting multiple times on other handlers would cause multiple downloads
+	// Caching system? Copy from already downloaded files?
+
+	// TODO: change to use something more idiomatic than exceptions?
+
+	@JvmStatic
+	@Throws(Exception::class)
+	fun getFileSource(loc: SpaceSafeURI): Source {
+		for (handler in handlers) {
+			if (handler.matchesHandler(loc)) {
+				return handler.getFileSource(loc) ?: throw Exception("Couldn't find URI: $loc")
+			}
+		}
+		throw Exception("No handler available for URI: $loc")
+	}
+
+	// TODO: github toml resolution?
+	// e.g. https://github.com/comp500/Demagnetize -> demagnetize.toml
+	// https://github.com/comp500/Demagnetize/blob/master/demagnetize.toml
+}

src/main/kotlin/link/infra/packwiz/installer/request/IRequestHandler.kt

@@ -1,19 +1,18 @@
-package link.infra.packwiz.installer.request;
+package link.infra.packwiz.installer.request
 
-import link.infra.packwiz.installer.metadata.SpaceSafeURI;
-import okio.Source;
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import okio.Source
 
 /**
  * IRequestHandler handles requests for locations specified in modpack metadata.
  */
-public interface IRequestHandler {
-	
-	boolean matchesHandler(SpaceSafeURI loc);
-	
-	default SpaceSafeURI getNewLoc(SpaceSafeURI loc) {
-		return loc;
+interface IRequestHandler {
+	fun matchesHandler(loc: SpaceSafeURI): Boolean
+
+	fun getNewLoc(loc: SpaceSafeURI): SpaceSafeURI {
+		return loc
 	}
-	
+
 	/**
 	 * Gets the Source for a location. Must be threadsafe.
 	 * It is assumed that each location is read only once for the duration of an IRequestHandler.
@@ -21,6 +20,5 @@ public interface IRequestHandler {
 	 * @return The Source containing the data of the file
 	 * @throws Exception Exception if it failed to download a file!!!
 	 */
-	Source getFileSource(SpaceSafeURI loc) throws Exception;
-
-}
+	fun getFileSource(loc: SpaceSafeURI): Source?
+}

src/main/kotlin/link/infra/packwiz/installer/request/RequestExceptions.kt

@@ -0,0 +1,70 @@
+package link.infra.packwiz.installer.request
+
+import okhttp3.Response
+import okio.IOException
+
+sealed class RequestException: Exception {
+	constructor(message: String, cause: Throwable) : super(message, cause)
+	constructor(message: String) : super(message)
+
+	/**
+	 * Internal errors that should not be shown to the user when the code is correct
+	 */
+	sealed class Internal: RequestException {
+		constructor(message: String, cause: Throwable) : super(message, cause)
+		constructor(message: String) : super(message)
+
+		class UnsinkableBase: Internal("Base associated with this path is not a SinkableBase")
+
+		sealed class HTTP: Internal {
+			constructor(message: String, cause: Throwable) : super(message, cause)
+			constructor(message: String) : super(message)
+
+			class NoResponseBody: HTTP("HTTP response in onResponse must have a response body")
+			class RequestFailed(cause: IOException): HTTP("HTTP request failed; may have been cancelled", cause)
+			class IllegalState(cause: IllegalStateException): HTTP("Internal fatal HTTP request error", cause)
+		}
+	}
+
+	/**
+	 * Errors indicating that the request is malformed
+	 */
+	sealed class Validation: RequestException {
+		constructor(message: String, cause: Throwable) : super(message, cause)
+		constructor(message: String) : super(message)
+
+		// TODO: move out of RequestException?
+		class PathContainsNUL(path: String): Validation("Invalid path; contains NUL bytes: ${path.replace("\u0000", "")}")
+		class PathContainsVolumeLetter(path: String): Validation("Invalid path; contains volume letter: $path")
+	}
+
+	/**
+	 * Errors relating to the response from the server
+	 */
+	sealed class Response: RequestException {
+		constructor(message: String, cause: Throwable) : super(message, cause)
+		constructor(message: String) : super(message)
+
+		// TODO: fancier way of displaying this?
+		sealed class HTTP: Response {
+			val response: okhttp3.Response
+
+			constructor(response: okhttp3.Response, message: String, cause: Throwable) : super(message, cause) {
+				this.response = response
+			}
+			constructor(response: okhttp3.Response, message: String) : super(message) {
+				this.response = response
+			}
+
+			class ErrorCode(res: okhttp3.Response): HTTP(res, "Non-successful error code from HTTP request: ${res.code}")
+		}
+
+		sealed class File: RequestException {
+			constructor(message: String, cause: Throwable) : super(message, cause)
+			constructor(message: String) : super(message)
+
+			class FileNotFound(file: String): File("File path not found: $file")
+			class Other(cause: Throwable): File("Failed to read file", cause)
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/request/handlers/RequestHandlerFile.kt

@@ -0,0 +1,18 @@
+package link.infra.packwiz.installer.request.handlers
+
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import link.infra.packwiz.installer.request.IRequestHandler
+import okio.Source
+import okio.source
+import java.nio.file.Paths
+
+open class RequestHandlerFile : IRequestHandler {
+	override fun matchesHandler(loc: SpaceSafeURI): Boolean {
+		return "file" == loc.scheme
+	}
+
+	override fun getFileSource(loc: SpaceSafeURI): Source? {
+		val path = Paths.get(loc.toURL().toURI())
+		return path.source()
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/request/handlers/RequestHandlerGithub.kt

@@ -0,0 +1,70 @@
+package link.infra.packwiz.installer.request.handlers
+
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import java.util.concurrent.locks.ReentrantReadWriteLock
+import java.util.regex.Pattern
+import kotlin.concurrent.read
+import kotlin.concurrent.write
+
+class RequestHandlerGithub : RequestHandlerZip(true) {
+	override fun getNewLoc(loc: SpaceSafeURI): SpaceSafeURI {
+		return loc
+	}
+
+	companion object {
+		private val repoMatcherPattern = Pattern.compile("/([\\w.-]+/[\\w.-]+).*")
+		private val branchMatcherPattern = Pattern.compile("/[\\w.-]+/[\\w.-]+/blob/([\\w.-]+).*")
+	}
+
+	// TODO: is caching really needed, if HTTPURLConnection follows redirects correctly?
+	private val zipUriMap: MutableMap<String, SpaceSafeURI> = HashMap()
+	private val zipUriLock = ReentrantReadWriteLock()
+	private fun getRepoName(loc: SpaceSafeURI): String? {
+		val matcher = repoMatcherPattern.matcher(loc.path ?: return null)
+		return if (matcher.matches()) {
+			matcher.group(1)
+		} else {
+			null
+		}
+	}
+
+	override fun getZipUri(loc: SpaceSafeURI): SpaceSafeURI {
+		val repoName = getRepoName(loc)
+		val branchName = getBranch(loc)
+
+		zipUriLock.read {
+			zipUriMap["$repoName/$branchName"]
+		}?.let { return it }
+
+		var zipUri = SpaceSafeURI("https://api.github.com/repos/$repoName/zipball/$branchName")
+		zipUriLock.write {
+			// If another thread sets the value concurrently, use the existing value from the
+			// thread that first acquired the lock.
+			zipUri = zipUriMap.putIfAbsent("$repoName/$branchName", zipUri) ?: zipUri
+		}
+		return zipUri
+	}
+
+	private fun getBranch(loc: SpaceSafeURI): String? {
+		val matcher = branchMatcherPattern.matcher(loc.path ?: return null)
+		return if (matcher.matches()) {
+			matcher.group(1)
+		} else {
+			null
+		}
+	}
+
+	override fun getLocationInZip(loc: SpaceSafeURI): SpaceSafeURI {
+		val path = "/" + getRepoName(loc) + "/blob/" + getBranch(loc)
+		return SpaceSafeURI(loc.scheme, loc.authority, path, null, null).relativize(loc)
+	}
+
+	override fun matchesHandler(loc: SpaceSafeURI): Boolean {
+		val scheme = loc.scheme
+		if (!("http" == scheme || "https" == scheme)) {
+			return false
+		}
+		// TODO: more match testing?
+		return "github.com" == loc.host && branchMatcherPattern.matcher(loc.path ?: return false).matches()
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/request/handlers/RequestHandlerHTTP.kt

@@ -0,0 +1,29 @@
+package link.infra.packwiz.installer.request.handlers
+
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import link.infra.packwiz.installer.request.IRequestHandler
+import okio.Source
+import okio.source
+import java.net.HttpURLConnection
+
+open class RequestHandlerHTTP : IRequestHandler {
+	override fun matchesHandler(loc: SpaceSafeURI): Boolean {
+		val scheme = loc.scheme
+		return "http" == scheme || "https" == scheme
+	}
+
+	override fun getFileSource(loc: SpaceSafeURI): Source? {
+		val conn = loc.toURL().openConnection() as HttpURLConnection
+		// TODO: when do we send specific headers??? should there be a way to signal this?
+		conn.addRequestProperty("Accept", "application/octet-stream")
+		// TODO: include version?
+		conn.addRequestProperty("User-Agent", "packwiz-installer")
+
+		conn.apply {
+			// 30 second read timeout
+			readTimeout = 30 * 1000
+			requestMethod = "GET"
+		}
+		return conn.inputStream.source()
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/request/handlers/RequestHandlerZip.kt

@@ -0,0 +1,123 @@
+package link.infra.packwiz.installer.request.handlers
+
+import link.infra.packwiz.installer.metadata.SpaceSafeURI
+import okio.Buffer
+import okio.Source
+import okio.buffer
+import okio.source
+import java.util.*
+import java.util.concurrent.locks.ReentrantLock
+import java.util.concurrent.locks.ReentrantReadWriteLock
+import java.util.function.Predicate
+import java.util.zip.ZipEntry
+import java.util.zip.ZipInputStream
+import kotlin.concurrent.read
+import kotlin.concurrent.withLock
+import kotlin.concurrent.write
+
+abstract class RequestHandlerZip(private val modeHasFolder: Boolean) : RequestHandlerHTTP() {
+	private fun removeFolder(name: String): String {
+		return if (modeHasFolder) {
+			// TODO: replace with proper path checks once switched to Path??
+			name.substring(name.indexOf("/") + 1)
+		} else {
+			name
+		}
+	}
+
+	private inner class ZipReader(zip: Source) {
+		private val zis = ZipInputStream(zip.buffer().inputStream())
+		private val readFiles: MutableMap<SpaceSafeURI, Buffer> = HashMap()
+		// Write lock implies access to ZipInputStream - only 1 thread must read at a time!
+		val filesLock = ReentrantLock()
+		private var entry: ZipEntry? = null
+
+		private val zipSource = zis.source().buffer()
+
+		// File lock must be obtained before calling this function
+		private fun readCurrFile(): Buffer {
+			val fileBuffer = Buffer()
+			zipSource.readFully(fileBuffer, entry!!.size)
+			return fileBuffer
+		}
+
+		// File lock must be obtained before calling this function
+		private fun findFile(loc: SpaceSafeURI): Buffer? {
+			while (true) {
+				entry = zis.nextEntry
+				entry?.also {
+					val data = readCurrFile()
+					val fileLoc = SpaceSafeURI(removeFolder(it.name))
+					if (loc == fileLoc) {
+						return data
+					} else {
+						readFiles[fileLoc] = data
+					}
+				} ?: return null
+			}
+		}
+
+		fun getFileSource(loc: SpaceSafeURI): Source? {
+			filesLock.withLock {
+				// Assume files are only read once, allow GC by removing
+				readFiles.remove(loc)?.also { return it }
+				return findFile(loc)
+			}
+		}
+
+		fun findInZip(matches: Predicate<SpaceSafeURI>): SpaceSafeURI? {
+			filesLock.withLock {
+				readFiles.keys.find { matches.test(it) }?.let { return it }
+
+				do {
+					val entry = zis.nextEntry?.also {
+						val data = readCurrFile()
+						val fileLoc = SpaceSafeURI(removeFolder(it.name))
+						readFiles[fileLoc] = data
+						if (matches.test(fileLoc)) {
+							return fileLoc
+						}
+					}
+				} while (entry != null)
+				return null
+			}
+		}
+	}
+
+	private val cache: MutableMap<SpaceSafeURI, ZipReader> = HashMap()
+	private val cacheLock = ReentrantReadWriteLock()
+
+	protected abstract fun getZipUri(loc: SpaceSafeURI): SpaceSafeURI
+	protected abstract fun getLocationInZip(loc: SpaceSafeURI): SpaceSafeURI
+	abstract override fun matchesHandler(loc: SpaceSafeURI): Boolean
+
+	override fun getFileSource(loc: SpaceSafeURI): Source? {
+		val zipUri = getZipUri(loc)
+		var zr = cacheLock.read { cache[zipUri] }
+		if (zr == null) {
+			cacheLock.write {
+				// Recheck, because unlocking read lock allows another thread to modify it
+				zr = cache[zipUri]
+
+				if (zr == null) {
+					val src = super.getFileSource(zipUri) ?: return null
+					zr = ZipReader(src).also { cache[zipUri] = it }
+				}
+			}
+		}
+		return zr?.getFileSource(getLocationInZip(loc))
+	}
+
+	protected fun findInZip(loc: SpaceSafeURI, matches: Predicate<SpaceSafeURI>): SpaceSafeURI? {
+		val zipUri = getZipUri(loc)
+		return (cacheLock.read { cache[zipUri] } ?: cacheLock.write {
+			// Recheck, because unlocking read lock allows another thread to modify it
+			cache[zipUri] ?: run {
+				// Create the ZipReader if it doesn't exist, return null if getFileSource returns null
+				super.getFileSource(zipUri)?.let { ZipReader(it) }
+						?.also { cache[zipUri] = it }
+			}
+		})?.findInZip(matches)
+	}
+
+}

src/main/kotlin/link/infra/packwiz/installer/target/CachedTarget.kt

@@ -0,0 +1,23 @@
+package link.infra.packwiz.installer.target
+
+import link.infra.packwiz.installer.metadata.hash.Hash
+import java.nio.file.Path
+
+data class CachedTarget(
+	/**
+	 * @see Target.name
+	 */
+	val name: String,
+	/**
+	 * The location where the target was last downloaded to.
+	 * This is used for removing old files when the destination path changes.
+	 * This shouldn't be set to the .disabled path (that is manually appended and checked)
+	 */
+	val cachedLocation: Path,
+	val enabled: Boolean,
+	val hash: Hash,
+	/**
+	 * For detecting when a target transitions non-optional -> optional and showing the option selection screen
+	 */
+	val isOptional: Boolean
+)

src/main/kotlin/link/infra/packwiz/installer/target/CachedTargetValidation.kt

@@ -0,0 +1,95 @@
+package link.infra.packwiz.installer.target
+
+import java.io.IOException
+import java.nio.file.*
+import java.nio.file.attribute.BasicFileAttributes
+import kotlin.io.path.relativeTo
+
+data class CachedTargetStatus(val target: CachedTarget, var isValid: Boolean, var markDisabled: Boolean)
+
+fun validate(targets: List<CachedTarget>, baseDir: Path) = runCatching {
+	val results = targets.map {
+		CachedTargetStatus(it, isValid = false, markDisabled = false)
+	}
+	val tree = buildTree(results, baseDir)
+
+	// Efficient file exists checking using directory listing, several orders of magnitude faster than Files.exists calls
+	Files.walkFileTree(baseDir, setOf(FileVisitOption.FOLLOW_LINKS), Int.MAX_VALUE, object : FileVisitor<Path> {
+		var currentNode: PathNode<CachedTargetStatus> = tree
+
+		override fun preVisitDirectory(dir: Path?, attrs: BasicFileAttributes?): FileVisitResult {
+			if (dir == null) {
+				return FileVisitResult.SKIP_SUBTREE
+			}
+			val subdirNode = currentNode.subdirs[dir.getName(dir.nameCount - 1)]
+			return if (subdirNode != null) {
+				currentNode = subdirNode
+				FileVisitResult.CONTINUE
+			} else {
+				FileVisitResult.SKIP_SUBTREE
+			}
+		}
+
+		override fun visitFile(file: Path?, attrs: BasicFileAttributes?): FileVisitResult {
+			if (file == null) {
+				return FileVisitResult.CONTINUE
+			}
+			// TODO: these are relative paths to baseDir
+			// TODO: strip the .disabled for lookup
+			val target = currentNode.files[file.getName(file.nameCount - 1)]
+			if (target != null) {
+				val disabledFile = file.endsWith(".disabled")
+				// If a .disabled file and the actual file both exist, mark as invalid if the target is disabled
+				if ((disabledFile )) {
+
+				}
+			}
+			return FileVisitResult.CONTINUE
+		}
+
+		@Throws(IOException::class)
+		override fun visitFileFailed(file: Path?, exc: IOException?): FileVisitResult {
+			if (exc != null) {
+				throw exc
+			}
+			throw IOException("visitFileFailed called with no exception")
+		}
+
+		@Throws(IOException::class)
+		override fun postVisitDirectory(dir: Path?, exc: IOException?): FileVisitResult {
+			if (exc != null) {
+				throw exc
+			} else {
+				val parent = currentNode.parent
+				if (parent != null) {
+					currentNode = parent
+				} else {
+					throw IOException("Invalid visitor tree structure")
+				}
+				return FileVisitResult.CONTINUE
+			}
+		}
+	})
+
+	results
+}
+
+fun buildTree(targets: List<CachedTargetStatus>, baseDir: Path): PathNode<CachedTargetStatus> {
+	val root = PathNode<CachedTargetStatus>()
+	for (target in targets) {
+		val relPath = target.target.cachedLocation.relativeTo(baseDir)
+		var node = root
+		// Traverse all the directory components, except for the last one
+		for (i in 0 until (relPath.nameCount - 1)) {
+			node = node.createSubdir(relPath.getName(i))
+		}
+		node.files[relPath.getName(relPath.nameCount - 1)] = target
+	}
+	return root
+}
+
+data class PathNode<T>(val subdirs: MutableMap<Path, PathNode<T>>, val files: MutableMap<Path, T>, val parent: PathNode<T>?) {
+	constructor() : this(mutableMapOf(), mutableMapOf(), null)
+
+	fun createSubdir(nextComponent: Path) = subdirs.getOrPut(nextComponent, { PathNode(mutableMapOf(), mutableMapOf(), this) })
+}

src/main/kotlin/link/infra/packwiz/installer/target/ClientHolder.kt

@@ -0,0 +1,12 @@
+package link.infra.packwiz.installer.target
+
+import okhttp3.OkHttpClient
+import okio.FileSystem
+
+class ClientHolder {
+	// TODO: timeouts?
+	// TODO: a button to increase timeouts temporarily when retrying?
+	val okHttpClient by lazy { OkHttpClient.Builder().build() }
+
+	val fileSystem = FileSystem.SYSTEM
+}

src/main/kotlin/link/infra/packwiz/installer/target/OverwriteMode.kt

@@ -0,0 +1,13 @@
+package link.infra.packwiz.installer.target
+
+enum class OverwriteMode {
+	/**
+	 * Overwrite the destination with the source file, if the source file has changed.
+	 */
+	IF_SRC_CHANGED,
+
+	/**
+	 * Never overwrite the destination; if it exists, it should not be written to.
+	 */
+	NEVER
+}

src/main/kotlin/link/infra/packwiz/installer/target/Side.kt

@@ -0,0 +1,54 @@
+package link.infra.packwiz.installer.target
+
+import com.google.gson.annotations.SerializedName
+
+enum class Side {
+	@SerializedName("client")
+	CLIENT("client"),
+	@SerializedName("server")
+	SERVER("server"),
+	@SerializedName("both")
+	@Suppress("unused")
+	BOTH("both", arrayOf(CLIENT, SERVER));
+
+	private val sideName: String
+	private val depSides: Array<Side>?
+
+	constructor(sideName: String) {
+		this.sideName = sideName.toLowerCase()
+		depSides = null
+	}
+
+	constructor(sideName: String, depSides: Array<Side>) {
+		this.sideName = sideName.toLowerCase()
+		this.depSides = depSides
+	}
+
+	override fun toString() = sideName
+
+	fun hasSide(tSide: Side): Boolean {
+		if (this == tSide) {
+			return true
+		}
+		if (depSides != null) {
+			for (depSide in depSides) {
+				if (depSide == tSide) {
+					return true
+				}
+			}
+		}
+		return false
+	}
+
+	companion object {
+		fun from(name: String): Side? {
+			val lowerName = name.toLowerCase()
+			for (side in values()) {
+				if (side.sideName == lowerName) {
+					return side
+				}
+			}
+			return null
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/target/Target.kt

@@ -0,0 +1,45 @@
+package link.infra.packwiz.installer.target
+
+import link.infra.packwiz.installer.target.path.PackwizPath
+
+// TODO: rename to avoid conflicting with @Target
+interface Target {
+	val src: PackwizPath
+	val dest: PackwizPath
+	val validityToken: ValidityToken
+
+	/**
+	 * Token interface for types used to compare Target identity. Implementations should use equals to indicate that
+	 * these tokens represent the same file; used to preserve optional target choices between file renames.
+	 */
+	interface IdentityToken
+
+	/**
+	 * Default implementation of IdentityToken that assumes files are not renamed; so optional choices do not need to
+	 * be preserved across renames.
+	 */
+	@JvmInline
+	value class PathIdentityToken(val path: String): IdentityToken
+
+	val ident: IdentityToken
+		get() = PathIdentityToken(dest.path)
+
+	/**
+	 * A user-friendly name; defaults to the destination path of the file.
+	 */
+	val name: String
+		get() = dest.path
+	val side: Side
+		get() = Side.BOTH
+	val overwriteMode: OverwriteMode
+		get() = OverwriteMode.IF_SRC_CHANGED
+
+	interface Optional: Target {
+		val optional: Boolean
+		val optionalDefaultValue: Boolean
+	}
+
+	interface OptionalDescribed: Optional {
+		val optionalDescription: String
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/target/ValidityToken.kt

@@ -0,0 +1,16 @@
+package link.infra.packwiz.installer.target
+
+import link.infra.packwiz.installer.metadata.hash.Hash
+
+/**
+ * A token used to determine if the source or destination file is changed, and ensure that the destination file is valid.
+ */
+interface ValidityToken {
+	// TODO: functions to allow validating this from file metadata, from file, or during the download process
+
+	/**
+	 * Default implementation of ValidityToken based on a single hash.
+	 */
+	@JvmInline
+	value class HashValidityToken(val hash: Hash): ValidityToken
+}

src/main/kotlin/link/infra/packwiz/installer/target/path/FilePathBase.kt

@@ -0,0 +1,29 @@
+package link.infra.packwiz.installer.target.path
+
+import link.infra.packwiz.installer.request.RequestException
+import link.infra.packwiz.installer.target.ClientHolder
+import okio.*
+
+data class FilePathBase(private val path: Path): PackwizPath.Base, PackwizPath.SinkableBase {
+	override fun source(path: String, clientHolder: ClientHolder): BufferedSource {
+		val resolved = this.path.resolve(path, true)
+		try {
+			return clientHolder.fileSystem.source(resolved).buffer()
+		} catch (e: FileNotFoundException) {
+			throw RequestException.Response.File.FileNotFound(resolved.toString())
+		} catch (e: IOException) {
+			throw RequestException.Response.File.Other(e)
+		}
+	}
+
+	override fun sink(path: String, clientHolder: ClientHolder): BufferedSink {
+		val resolved = this.path.resolve(path, true)
+		try {
+			return clientHolder.fileSystem.sink(resolved).buffer()
+		} catch (e: FileNotFoundException) {
+			throw RequestException.Response.File.FileNotFound(resolved.toString())
+		} catch (e: IOException) {
+			throw RequestException.Response.File.Other(e)
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/target/path/HttpUrlBase.kt

@@ -0,0 +1,41 @@
+package link.infra.packwiz.installer.target.path
+
+import link.infra.packwiz.installer.request.RequestException
+import link.infra.packwiz.installer.target.ClientHolder
+import okhttp3.HttpUrl
+import okhttp3.Request
+import okio.BufferedSource
+import okio.IOException
+
+data class HttpUrlBase(private val url: HttpUrl): PackwizPath.Base {
+	private fun resolve(path: String) = url.newBuilder().addPathSegments(path).build()
+
+	override fun source(path: String, clientHolder: ClientHolder): BufferedSource {
+		val req = Request.Builder()
+			.url(resolve(path))
+			.header("Accept", "application/octet-stream")
+			.header("User-Agent", "packwiz-installer")
+			.get()
+			.build()
+		try {
+			val res = clientHolder.okHttpClient.newCall(req).execute()
+			// Can't use .use since it would close the response body before returning it to the caller
+			try {
+				if (!res.isSuccessful) {
+					throw RequestException.Response.HTTP.ErrorCode(res)
+				}
+
+				val body = res.body ?: throw RequestException.Internal.HTTP.NoResponseBody()
+				return body.source()
+			} catch (e: Exception) {
+				// If an exception is thrown, close the response and rethrow
+				res.close()
+				throw e
+			}
+		} catch (e: IOException) {
+			throw RequestException.Internal.HTTP.RequestFailed(e)
+		} catch (e: IllegalStateException) {
+			throw RequestException.Internal.HTTP.IllegalState(e)
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/target/path/PackwizPath.kt

@@ -0,0 +1,124 @@
+package link.infra.packwiz.installer.target.path
+
+import link.infra.packwiz.installer.request.RequestException
+import link.infra.packwiz.installer.target.ClientHolder
+import okio.BufferedSink
+import okio.BufferedSource
+
+class PackwizPath(path: String, base: Base) {
+	val path: String
+	val base: Base
+
+	init {
+		this.base = base
+
+		// Check for NUL bytes
+		if (path.contains('\u0000')) { throw RequestException.Validation.PathContainsNUL(path) }
+		// Normalise separator, to prevent differences between Unix/Windows
+		val pathNorm = path.replace('\\', '/')
+		// Split, create new lists for output
+		val split = pathNorm.split('/')
+		val canonicalised = mutableListOf<String>()
+
+		// Backward pass: collapse ".." components, remove "." components and empty components (except an empty component at the end; indicating a folder)
+		var parentComponentCount = 0
+		var first = true
+		for (component in split.asReversed()) {
+			if (first) {
+				first = false
+				if (component == "") {
+					canonicalised += component
+				}
+			}
+			// URL-encoded . is normalised
+			val componentNorm = component.replace("%2e", ".")
+			if (componentNorm == "." || componentNorm == "") {
+				// Do nothing
+			} else if (componentNorm == "..") {
+				parentComponentCount++
+			} else if (parentComponentCount > 0) {
+				parentComponentCount--
+			} else {
+				canonicalised += componentNorm
+				// Don't allow volume letters (allows traversal to the root on Windows)
+				if (componentNorm[0] in 'a'..'z' || componentNorm[0] in 'A'..'Z') {
+					if (componentNorm[1] == ':') {
+						throw RequestException.Validation.PathContainsVolumeLetter(path)
+					}
+				}
+			}
+		}
+
+		// Join path
+		this.path = canonicalised.asReversed().joinToString("/")
+	}
+
+	val folder: Boolean get() = path.endsWith("/")
+
+	fun resolve(path: String): PackwizPath {
+		return if (path.startsWith('/') || path.startsWith('\\')) {
+			// Absolute (but still relative to base of pack)
+			PackwizPath(path, base)
+		} else if (folder) {
+			// File in folder; append
+			PackwizPath(this.path + path, base)
+		} else {
+			// File in parent folder; append with parent component
+			PackwizPath(this.path + "/../" + path, base)
+		}
+	}
+
+	/**
+	 * Obtain a BufferedSource for this path
+	 * @throws RequestException When resolving the file failed
+	 */
+	fun source(clientHolder: ClientHolder): BufferedSource = base.source(path, clientHolder)
+
+	/**
+	 * Obtain a BufferedSink for this path
+	 * @throws RequestException.Internal.UnsinkableBase When the base of this path does not have a sink
+	 * @throws RequestException When resolving the file failed
+	 */
+	fun sink(clientHolder: ClientHolder): BufferedSink =
+		if (base is SinkableBase) { base.sink(path, clientHolder) } else { throw RequestException.Internal.UnsinkableBase() }
+
+	interface Base {
+		/**
+		 * Resolve the given (canonical) path against the base, and get a BufferedSource for this file.
+		 * @throws RequestException
+		 */
+		fun source(path: String, clientHolder: ClientHolder): BufferedSource
+
+		operator fun div(path: String) = PackwizPath(path, this)
+	}
+
+	interface SinkableBase: Base {
+		/**
+		 * Resolve the given (canonical) path against the base, and get a BufferedSink for this file.
+		 * @throws RequestException
+		 */
+		fun sink(path: String, clientHolder: ClientHolder): BufferedSink
+	}
+
+	override fun equals(other: Any?): Boolean {
+		if (this === other) return true
+		if (javaClass != other?.javaClass) return false
+
+		other as PackwizPath
+
+		if (path != other.path) return false
+		if (base != other.base) return false
+
+		return true
+	}
+
+	override fun hashCode(): Int {
+		var result = path.hashCode()
+		result = 31 * result + base.hashCode()
+		return result
+	}
+
+	override fun toString(): String {
+		return "base=$base; $path"
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/task/CacheKey.kt

@@ -0,0 +1,3 @@
+package link.infra.packwiz.installer.task
+
+data class CacheKey<T>(val key: String, val version: Int)

src/main/kotlin/link/infra/packwiz/installer/task/CacheManager.kt

@@ -0,0 +1,22 @@
+package link.infra.packwiz.installer.task
+
+import kotlin.reflect.KProperty
+
+class CacheManager {
+	class CacheValue<T> {
+		operator fun getValue(thisVal: Any?, property: KProperty<*>): T {
+			TODO("Not yet implemented")
+		}
+
+		operator fun setValue(thisVal: Any?, property: KProperty<*>, value: T) {
+			TODO("Not yet implemented")
+		}
+
+	}
+
+	operator fun <T> get(cacheKey: CacheKey<T>): CacheValue<T> {
+		return CacheValue()
+	}
+
+
+}

src/main/kotlin/link/infra/packwiz/installer/task/Task.kt

@@ -0,0 +1,20 @@
+package link.infra.packwiz.installer.task
+
+import kotlin.reflect.KMutableProperty0
+
+// TODO: task processing on 1 background thread; actual resolving of values calls out to a thread group
+// TODO: progress bar is updated from each of these tasks
+// TODO: have everything be lazy so there's no need to determine task ordering upfront? a bit like rust async - task results must be queried to occur
+
+abstract class Task<T>(protected val ctx: TaskContext): TaskInput<T> {
+	// TODO: lazy wrapper for fallible results
+	// TODO: multithreaded fanout subclass/helper
+
+	protected fun <T> wasUpdated(value: KMutableProperty0<T>, newValue: T): Boolean {
+		if (value.get() == newValue) {
+			return false
+		}
+		value.set(newValue)
+		return true
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/task/TaskCombinedResult.kt

@@ -0,0 +1,6 @@
+package link.infra.packwiz.installer.task
+
+/**
+ * An object for storing results where result and upToDate are calculated simultaneously
+ */
+data class TaskCombinedResult<T>(val result: T, val upToDate: Boolean)

src/main/kotlin/link/infra/packwiz/installer/task/TaskContext.kt

@@ -0,0 +1,12 @@
+package link.infra.packwiz.installer.task
+
+import link.infra.packwiz.installer.target.ClientHolder
+
+class TaskContext {
+	// TODO: thread pools, protocol roots
+	// TODO: cache management
+
+	val cache = CacheManager()
+
+	val clients = ClientHolder()
+}

src/main/kotlin/link/infra/packwiz/installer/task/TaskInput.kt

@@ -0,0 +1,29 @@
+package link.infra.packwiz.installer.task
+
+import kotlin.reflect.KProperty
+
+interface TaskInput<T> {
+	/**
+	 * The value of this task input. May be lazily evaluated; must be threadsafe.
+	 */
+	val value: T
+
+	/**
+	 * True if the effective value of this input has changed since the task was last run.
+	 * Doesn't require evaluation of the input value; should use cached data if possible.
+	 * May be lazily evaluated; must be threadsafe.
+	 */
+	val upToDate: Boolean
+
+	operator fun getValue(thisVal: Any?, property: KProperty<*>): T = value
+
+	companion object {
+		fun <T> raw(value: T): TaskInput<T> {
+			return object: TaskInput<T> {
+				override val value = value
+				override val upToDate: Boolean
+					get() = false
+			}
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/task/formats/packwizv1/PackwizV1PackFile.kt

@@ -0,0 +1,6 @@
+package link.infra.packwiz.installer.task.formats.packwizv1
+
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.target.path.PackwizPath
+
+data class PackwizV1PackFile(val name: String, val indexPath: PackwizPath, val indexHash: Hash)

src/main/kotlin/link/infra/packwiz/installer/task/formats/packwizv1/PackwizV1PackTomlTask.kt

@@ -0,0 +1,48 @@
+package link.infra.packwiz.installer.task.formats.packwizv1
+
+import com.google.gson.annotations.SerializedName
+import com.moandjiezana.toml.Toml
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashUtils
+import link.infra.packwiz.installer.target.path.PackwizPath
+import link.infra.packwiz.installer.task.CacheKey
+import link.infra.packwiz.installer.task.Task
+import link.infra.packwiz.installer.task.TaskCombinedResult
+import link.infra.packwiz.installer.task.TaskContext
+import java.io.InputStreamReader
+
+class PackwizV1PackTomlTask(ctx: TaskContext, val path: PackwizPath): Task<PackwizV1PackFile>(ctx) {
+	// TODO: make hierarchically defined by caller? - then changing the pack format type doesn't leave junk in the cache
+	private var cache by ctx.cache[CacheKey<Hash>("packwiz.v1.packtoml.hash", 1)]
+
+	private class PackFile {
+		var name: String? = null
+		var index: IndexFileLoc? = null
+
+		class IndexFileLoc {
+			var file: String? = null
+			@SerializedName("hash-format")
+			var hashFormat: String? = null
+			var hash: String? = null
+		}
+
+		var versions: Map<String, String>? = null
+	}
+
+	private val internalResult by lazy {
+		// TODO: query, parse JSON
+		val packFile = Toml().read(InputStreamReader(path.source(ctx.clients).inputStream(), "UTF-8")).to(PackFile::class.java)
+
+		val resolved = PackwizV1PackFile(packFile.name ?: throw RuntimeException("Name required"), // TODO: better exception handling
+			path.resolve(packFile.index?.file ?: throw RuntimeException("File required")),
+			HashUtils.getHash(packFile.index?.hashFormat ?: throw RuntimeException("Hash format required"),
+				packFile.index?.hash ?: throw RuntimeException("Hash required"))
+		)
+		val hash = HashUtils.getHash("sha256", "whatever was just read")
+
+		TaskCombinedResult(resolved, wasUpdated(::cache, hash))
+	}
+
+	override val value by internalResult::result
+	override val upToDate by internalResult::upToDate
+}

src/main/kotlin/link/infra/packwiz/installer/ui/IUserInterface.kt

@@ -0,0 +1,40 @@
+package link.infra.packwiz.installer.ui
+
+import link.infra.packwiz.installer.ui.data.ExceptionDetails
+import link.infra.packwiz.installer.ui.data.IOptionDetails
+import link.infra.packwiz.installer.ui.data.InstallProgress
+
+interface IUserInterface {
+	fun show()
+	fun dispose()
+
+	fun showErrorAndExit(message: String): Nothing {
+		showErrorAndExit(message, null)
+	}
+	fun showErrorAndExit(message: String, e: Exception?): Nothing
+
+	var title: String
+	fun submitProgress(progress: InstallProgress)
+	// Return true if the installation was cancelled!
+	fun showOptions(options: List<IOptionDetails>): Boolean
+
+	fun showExceptions(exceptions: List<ExceptionDetails>, numTotal: Int, allowsIgnore: Boolean): ExceptionListResult
+	fun disableOptionsButton(hasOptions: Boolean) {}
+
+	fun showCancellationDialog(): CancellationResult = CancellationResult.QUIT
+
+	fun awaitOptionalButton(showCancel: Boolean)
+
+	enum class ExceptionListResult {
+		CONTINUE, CANCEL, IGNORE
+	}
+
+	enum class CancellationResult {
+		QUIT, CONTINUE
+	}
+
+	var optionsButtonPressed: Boolean
+	var cancelButtonPressed: Boolean
+
+	var firstInstall: Boolean
+}

src/main/kotlin/link/infra/packwiz/installer/ui/cli/CLIHandler.kt

@@ -0,0 +1,66 @@
+package link.infra.packwiz.installer.ui.cli
+
+import link.infra.packwiz.installer.ui.IUserInterface
+import link.infra.packwiz.installer.ui.IUserInterface.ExceptionListResult
+import link.infra.packwiz.installer.ui.data.ExceptionDetails
+import link.infra.packwiz.installer.ui.data.IOptionDetails
+import link.infra.packwiz.installer.ui.data.InstallProgress
+import link.infra.packwiz.installer.util.Log
+import kotlin.system.exitProcess
+
+class CLIHandler : IUserInterface {
+	@Volatile
+	override var optionsButtonPressed = false
+	@Volatile
+	override var cancelButtonPressed = false
+	@Volatile
+	override var firstInstall = false
+
+	override var title: String = ""
+
+	override fun showErrorAndExit(message: String, e: Exception?): Nothing {
+		if (e != null) {
+			Log.fatal(message, e)
+		} else {
+			Log.fatal(message)
+		}
+		exitProcess(1)
+	}
+
+	override fun show() {}
+	override fun dispose() {}
+	override fun submitProgress(progress: InstallProgress) {
+		val sb = StringBuilder()
+		if (progress.hasProgress) {
+			sb.append('(')
+			sb.append(progress.progress)
+			sb.append('/')
+			sb.append(progress.progressTotal)
+			sb.append(") ")
+		}
+		sb.append(progress.message)
+		println(sb.toString())
+	}
+
+	override fun showOptions(options: List<IOptionDetails>): Boolean {
+		for (opt in options) {
+			opt.optionValue = true
+			// TODO: implement option choice in the CLI?
+			Log.warn("Accepting option ${opt.name} as option choosing is not implemented in the CLI")
+		}
+		return false // Can't be cancelled!
+	}
+
+	override fun showExceptions(exceptions: List<ExceptionDetails>, numTotal: Int, allowsIgnore: Boolean): ExceptionListResult {
+		println("Failed to download modpack, the following errors were encountered:")
+		for (ex in exceptions) {
+			print(ex.name + ": ")
+			ex.exception.printStackTrace()
+		}
+		return ExceptionListResult.CANCEL
+	}
+
+	override fun awaitOptionalButton(showCancel: Boolean) {
+		// Do nothing
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/ui/data/ExceptionDetails.kt

@@ -0,0 +1,6 @@
+package link.infra.packwiz.installer.ui.data
+
+data class ExceptionDetails(
+		val name: String,
+		val exception: Exception
+)

src/main/kotlin/link/infra/packwiz/installer/ui/data/IOptionDetails.kt

@@ -0,0 +1,7 @@
+package link.infra.packwiz.installer.ui.data
+
+interface IOptionDetails {
+	val name: String
+	var optionValue: Boolean
+	val optionDescription: String
+}

src/main/kotlin/link/infra/packwiz/installer/ui/data/InstallProgress.kt

@@ -0,0 +1,12 @@
+package link.infra.packwiz.installer.ui.data
+
+data class InstallProgress(
+		val message: String,
+		val hasProgress: Boolean = false,
+		val progress: Int = 0,
+		val progressTotal: Int = 0
+) {
+	constructor(message: String, progress: Int, progressTotal: Int) : this(message, true, progress, progressTotal)
+
+	constructor(message: String) : this(message, false)
+}

src/main/kotlin/link/infra/packwiz/installer/ui/gui/ExceptionListWindow.kt

@@ -0,0 +1,153 @@
+package link.infra.packwiz.installer.ui.gui
+
+import link.infra.packwiz.installer.ui.IUserInterface
+import link.infra.packwiz.installer.ui.data.ExceptionDetails
+import java.awt.BorderLayout
+import java.awt.Desktop
+import java.awt.event.WindowAdapter
+import java.awt.event.WindowEvent
+import java.io.IOException
+import java.io.PrintWriter
+import java.io.StringWriter
+import java.net.URI
+import java.net.URISyntaxException
+import java.util.concurrent.CompletableFuture
+import javax.swing.*
+import javax.swing.border.EmptyBorder
+
+class ExceptionListWindow(eList: List<ExceptionDetails>, future: CompletableFuture<IUserInterface.ExceptionListResult>, numTotal: Int, allowsIgnore: Boolean, parentWindow: JFrame?) : JDialog(parentWindow, "Failed file downloads", true) {
+	private val lblExceptionStacktrace: JTextArea
+
+	private class ExceptionListModel(private val details: List<ExceptionDetails>) : AbstractListModel<String>() {
+		override fun getSize() = details.size
+		override fun getElementAt(index: Int) = details[index].name
+		fun getExceptionAt(index: Int) = details[index].exception
+	}
+
+	/**
+	 * Create the dialog.
+	 */
+	init {
+		setBounds(100, 100, 540, 340)
+		setLocationRelativeTo(parentWindow)
+
+		contentPane.apply {
+			layout = BorderLayout()
+
+			// Error panel
+			add(JPanel().apply {
+				add(JLabel("One or more errors were encountered while installing the modpack!").apply {
+					icon = UIManager.getIcon("OptionPane.warningIcon")
+				})
+			}, BorderLayout.NORTH)
+
+			// Content panel
+			add(JPanel().apply {
+				border = EmptyBorder(5, 5, 5, 5)
+				layout = BorderLayout(0, 0)
+
+				add(JSplitPane().apply {
+					resizeWeight = 0.3
+
+					lblExceptionStacktrace = JTextArea("Select a file")
+					lblExceptionStacktrace.background = UIManager.getColor("List.background")
+					lblExceptionStacktrace.isOpaque = true
+					lblExceptionStacktrace.wrapStyleWord = true
+					lblExceptionStacktrace.lineWrap = true
+					lblExceptionStacktrace.isEditable = false
+					lblExceptionStacktrace.isFocusable = true
+					lblExceptionStacktrace.font = UIManager.getFont("Label.font")
+					lblExceptionStacktrace.border = EmptyBorder(5, 5, 5, 5)
+
+					rightComponent = JScrollPane(lblExceptionStacktrace)
+
+					leftComponent = JScrollPane(JList<String>().apply {
+						selectionMode = ListSelectionModel.SINGLE_SELECTION
+						border = EmptyBorder(5, 5, 5, 5)
+						val listModel = ExceptionListModel(eList)
+						model = listModel
+						addListSelectionListener {
+							val i = selectedIndex
+							if (i > -1) {
+								val sw = StringWriter()
+								listModel.getExceptionAt(i).printStackTrace(PrintWriter(sw))
+								lblExceptionStacktrace.text = sw.toString()
+								// Scroll to the top
+								lblExceptionStacktrace.caretPosition = 0
+							} else {
+								lblExceptionStacktrace.text = "Select a file"
+							}
+						}
+					})
+				})
+			}, BorderLayout.CENTER)
+
+			// Button pane
+			add(JPanel().apply {
+				layout = BorderLayout(0, 0)
+
+				// Right buttons
+				add(JPanel().apply {
+					add(JButton("Continue").apply {
+						toolTipText = "Attempt to continue installing, excluding the failed downloads"
+						addActionListener {
+							future.complete(IUserInterface.ExceptionListResult.CONTINUE)
+							this@ExceptionListWindow.dispose()
+						}
+					})
+
+					add(JButton("Cancel launch").apply {
+						toolTipText = "Stop launching the game"
+						addActionListener {
+							future.complete(IUserInterface.ExceptionListResult.CANCEL)
+							this@ExceptionListWindow.dispose()
+						}
+					})
+
+					add(JButton("Ignore update").apply {
+						toolTipText = "Start the game without attempting to update"
+						isEnabled = allowsIgnore
+						addActionListener {
+							future.complete(IUserInterface.ExceptionListResult.IGNORE)
+							this@ExceptionListWindow.dispose()
+						}
+					})
+				}, BorderLayout.EAST)
+
+				// Errored label
+				add(JLabel(eList.size.toString() + "/" + numTotal + " errored").apply {
+					horizontalAlignment = SwingConstants.CENTER
+				}, BorderLayout.CENTER)
+
+				// Left buttons
+				add(JPanel().apply {
+					add(JButton("Report issue").apply {
+						if (Desktop.isDesktopSupported() && Desktop.getDesktop().isSupported(Desktop.Action.BROWSE)) {
+							addActionListener {
+								try {
+									Desktop.getDesktop().browse(URI("https://github.com/packwiz/packwiz-installer/issues/new"))
+								} catch (e: IOException) {
+									// lol the button just won't work i guess
+								} catch (e: URISyntaxException) {}
+							}
+						} else {
+							isEnabled = false
+						}
+					})
+				}, BorderLayout.WEST)
+			}, BorderLayout.SOUTH)
+		}
+
+		addWindowListener(object : WindowAdapter() {
+			override fun windowClosing(e: WindowEvent) {
+				future.complete(IUserInterface.ExceptionListResult.CANCEL)
+			}
+
+			override fun windowClosed(e: WindowEvent) {
+				// Just in case closing didn't get triggered - if something else called dispose() the
+				// future will have already completed
+				future.complete(IUserInterface.ExceptionListResult.CANCEL)
+			}
+		})
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/ui/gui/GUIHandler.kt

@@ -0,0 +1,179 @@
+package link.infra.packwiz.installer.ui.gui
+
+import link.infra.packwiz.installer.ui.IUserInterface
+import link.infra.packwiz.installer.ui.IUserInterface.ExceptionListResult
+import link.infra.packwiz.installer.ui.data.ExceptionDetails
+import link.infra.packwiz.installer.ui.data.IOptionDetails
+import link.infra.packwiz.installer.ui.data.InstallProgress
+import link.infra.packwiz.installer.util.Log
+import java.awt.EventQueue
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.CountDownLatch
+import javax.swing.JDialog
+import javax.swing.JOptionPane
+import javax.swing.UIManager
+import kotlin.system.exitProcess
+
+class GUIHandler : IUserInterface {
+	private lateinit var frmPackwizlauncher: InstallWindow
+
+	@Volatile
+	override var optionsButtonPressed = false
+		set(value) {
+			optionalSelectedLatch.countDown()
+			field = value
+		}
+	@Volatile
+	override var cancelButtonPressed = false
+		set(value) {
+			optionalSelectedLatch.countDown()
+			field = value
+		}
+	var okButtonPressed = false
+		set(value) {
+			optionalSelectedLatch.countDown()
+			field = value
+		}
+	@Volatile
+	override var firstInstall = false
+
+	override var title = "packwiz-installer"
+		set(value) {
+			field = value
+			EventQueue.invokeLater { frmPackwizlauncher.title = value }
+		}
+
+	init {
+		EventQueue.invokeAndWait {
+			try {
+				UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName())
+			} catch (e: Exception) {
+				Log.warn("Failed to set look and feel", e)
+			}
+			frmPackwizlauncher = InstallWindow(this).apply {
+				title = this@GUIHandler.title
+			}
+		}
+	}
+
+	private val visibleCountdownLatch = CountDownLatch(1)
+	private val optionalSelectedLatch = CountDownLatch(1)
+
+	override fun show() = EventQueue.invokeLater {
+		frmPackwizlauncher.isVisible = true
+		visibleCountdownLatch.countDown()
+	}
+
+	override fun dispose() = EventQueue.invokeAndWait {
+		frmPackwizlauncher.dispose()
+	}
+
+	override fun showErrorAndExit(message: String, e: Exception?): Nothing {
+		val buttons = arrayOf("Quit", if (firstInstall) "Continue without installing" else "Continue without updating")
+		if (e != null) {
+			Log.fatal(message, e)
+			EventQueue.invokeAndWait {
+				val result = JOptionPane.showOptionDialog(frmPackwizlauncher,
+					"$message: $e",
+					title,
+					JOptionPane.YES_NO_OPTION, JOptionPane.ERROR_MESSAGE, null, buttons, buttons[0])
+				if (result == 1) {
+					Log.info("User selected to continue without installing/updating, exiting with code 0...")
+					exitProcess(0)
+				} else {
+					Log.info("User selected to quit, exiting with code 1...")
+					exitProcess(1)
+				}
+			}
+		} else {
+			Log.fatal(message)
+			EventQueue.invokeAndWait {
+				val result = JOptionPane.showOptionDialog(frmPackwizlauncher,
+					message,
+					title,
+					JOptionPane.YES_NO_OPTION, JOptionPane.ERROR_MESSAGE, null, buttons, buttons[0])
+				if (result == 1) {
+					Log.info("User selected to continue without installing/updating, exiting with code 0...")
+					exitProcess(0)
+				} else {
+					Log.info("User selected to quit, exiting with code 1...")
+					exitProcess(1)
+				}
+			}
+		}
+		exitProcess(1)
+	}
+
+	override fun submitProgress(progress: InstallProgress) {
+		val sb = StringBuilder()
+		if (progress.hasProgress) {
+			sb.append('(')
+			sb.append(progress.progress)
+			sb.append('/')
+			sb.append(progress.progressTotal)
+			sb.append(") ")
+		}
+		sb.append(progress.message)
+		Log.info(sb.toString())
+		EventQueue.invokeLater {
+			frmPackwizlauncher.displayProgress(progress)
+		}
+	}
+
+	override fun showOptions(options: List<IOptionDetails>): Boolean {
+		val future = CompletableFuture<Boolean>()
+		EventQueue.invokeAndWait {
+			if (options.isEmpty()) {
+				JOptionPane.showMessageDialog(null,
+					"This modpack has no optional mods!",
+					"Optional mods", JOptionPane.INFORMATION_MESSAGE)
+				future.complete(false)
+			} else {
+				OptionsSelectWindow(options, future, frmPackwizlauncher).apply {
+					defaultCloseOperation = JDialog.DISPOSE_ON_CLOSE
+					isVisible = true
+				}
+			}
+		}
+		return future.get()
+	}
+
+	override fun showExceptions(exceptions: List<ExceptionDetails>, numTotal: Int, allowsIgnore: Boolean): ExceptionListResult {
+		val future = CompletableFuture<ExceptionListResult>()
+		EventQueue.invokeLater {
+			ExceptionListWindow(exceptions, future, numTotal, allowsIgnore, frmPackwizlauncher).apply {
+				defaultCloseOperation = JDialog.DISPOSE_ON_CLOSE
+				isVisible = true
+			}
+		}
+		return future.get()
+	}
+
+	override fun disableOptionsButton(hasOptions: Boolean) = EventQueue.invokeLater {
+		frmPackwizlauncher.disableOptionsButton(hasOptions)
+	}
+
+	override fun showCancellationDialog(): IUserInterface.CancellationResult {
+		val future = CompletableFuture<IUserInterface.CancellationResult>()
+		EventQueue.invokeLater {
+			val buttons = arrayOf("Quit", "Ignore")
+			val result = JOptionPane.showOptionDialog(frmPackwizlauncher,
+					"The installation was cancelled. Would you like to quit the game, or ignore the update and start the game?",
+					"Cancelled installation",
+					JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, buttons, buttons[0])
+			future.complete(if (result == 0) IUserInterface.CancellationResult.QUIT else IUserInterface.CancellationResult.CONTINUE)
+		}
+		return future.get()
+	}
+
+	override fun awaitOptionalButton(showCancel: Boolean) {
+		EventQueue.invokeAndWait {
+			frmPackwizlauncher.showOk(!showCancel)
+		}
+		visibleCountdownLatch.await()
+		optionalSelectedLatch.await()
+		EventQueue.invokeLater {
+			frmPackwizlauncher.hideOk()
+		}
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/ui/gui/InstallWindow.kt

@@ -0,0 +1,124 @@
+package link.infra.packwiz.installer.ui.gui
+
+import link.infra.packwiz.installer.ui.data.InstallProgress
+import java.awt.BorderLayout
+import java.awt.Component
+import java.awt.GridBagConstraints
+import java.awt.GridBagLayout
+import javax.swing.*
+import javax.swing.border.EmptyBorder
+
+class InstallWindow(private val handler: GUIHandler) : JFrame() {
+	private var lblProgresslabel: JLabel
+	private var progressBar: JProgressBar
+	private var btnOptions: JButton
+	private val btnCancel: JButton
+	private val btnOk: JButton
+	private val buttonsPanel: JPanel
+
+	init {
+		setBounds(100, 100, 493, 95)
+		// Works better with tiling window managers - there isn't any reason to change window size currently anyway
+		isResizable = false
+		defaultCloseOperation = EXIT_ON_CLOSE
+		setLocationRelativeTo(null)
+
+		// Progress bar and loading text
+		add(JPanel().apply {
+			border = EmptyBorder(10, 10, 10, 10)
+			layout = BorderLayout(0, 0)
+
+			progressBar = JProgressBar().apply {
+				isIndeterminate = true
+			}
+			add(progressBar, BorderLayout.CENTER)
+
+			lblProgresslabel = JLabel("Loading...")
+			add(lblProgresslabel, BorderLayout.SOUTH)
+		}, BorderLayout.CENTER)
+
+		// Buttons
+		buttonsPanel = JPanel().apply {
+			border = EmptyBorder(0, 5, 0, 5)
+			layout = GridBagLayout()
+
+			btnOptions = JButton("Optional mods...").apply {
+				alignmentX = Component.CENTER_ALIGNMENT
+
+				addActionListener {
+					text = "Loading..."
+					isEnabled = false
+					handler.optionsButtonPressed = true
+				}
+			}
+			add(btnOptions, GridBagConstraints().apply {
+				gridx = 1
+				gridy = 0
+			})
+
+			btnCancel = JButton("Cancel").apply {
+				addActionListener {
+					isEnabled = false
+					handler.cancelButtonPressed = true
+				}
+			}
+			add(btnCancel, GridBagConstraints().apply {
+				gridx = 1
+				gridy = 1
+			})
+		}
+
+		btnOk = JButton("Continue").apply {
+			addActionListener {
+				handler.okButtonPressed = true
+			}
+		}
+		add(buttonsPanel, BorderLayout.EAST)
+	}
+
+	fun displayProgress(progress: InstallProgress) {
+		if (progress.hasProgress) {
+			progressBar.isIndeterminate = false
+			progressBar.value = progress.progress
+			progressBar.maximum = progress.progressTotal
+		} else {
+			progressBar.isIndeterminate = true
+			progressBar.value = 0
+		}
+		lblProgresslabel.text = progress.message
+	}
+
+	fun disableOptionsButton(hasOptions: Boolean) {
+		btnOptions.apply {
+			text = if (hasOptions) { "Optional mods..." } else { "No optional mods" }
+ 			isEnabled = false
+		}
+	}
+
+	fun showOk(hideCancel: Boolean) {
+		if (hideCancel) {
+			buttonsPanel.add(btnOk, GridBagConstraints().apply {
+				gridx = 1
+				gridy = 1
+			})
+			buttonsPanel.remove(btnCancel)
+		} else {
+			buttonsPanel.add(btnOk, GridBagConstraints().apply {
+				gridx = 0
+				gridy = 1
+			})
+		}
+		buttonsPanel.revalidate()
+	}
+
+	fun hideOk() {
+		buttonsPanel.remove(btnOk)
+		if (!buttonsPanel.components.contains(btnCancel)) {
+			buttonsPanel.add(btnCancel, GridBagConstraints().apply {
+				gridx = 1
+				gridy = 1
+			})
+		}
+		buttonsPanel.revalidate()
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/ui/gui/OptionTempHandler.kt

@@ -0,0 +1,15 @@
+package link.infra.packwiz.installer.ui.gui
+
+import link.infra.packwiz.installer.ui.data.IOptionDetails
+
+// Serves as a proxy for IOptionDetails, so that setOptionValue isn't called until OK is clicked
+internal class OptionTempHandler(private val opt: IOptionDetails) : IOptionDetails {
+	override var optionValue = opt.optionValue
+
+	override val name get() = opt.name
+	override val optionDescription get() = opt.optionDescription
+
+	fun finalise() {
+		opt.optionValue = optionValue
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/ui/gui/OptionsSelectWindow.kt

@@ -0,0 +1,167 @@
+package link.infra.packwiz.installer.ui.gui
+
+import link.infra.packwiz.installer.ui.data.IOptionDetails
+import java.awt.BorderLayout
+import java.awt.FlowLayout
+import java.awt.event.ActionEvent
+import java.awt.event.ActionListener
+import java.awt.event.WindowAdapter
+import java.awt.event.WindowEvent
+import java.util.*
+import java.util.concurrent.CompletableFuture
+import javax.swing.*
+import javax.swing.border.EmptyBorder
+import javax.swing.event.TableModelListener
+import javax.swing.table.TableModel
+
+class OptionsSelectWindow internal constructor(optList: List<IOptionDetails>, future: CompletableFuture<Boolean>, parentWindow: JFrame?) : JDialog(parentWindow, "Select optional mods...", true), ActionListener {
+	private val lblOptionDescription: JTextArea
+	private val tableModel: OptionTableModel
+	private val future: CompletableFuture<Boolean>
+
+	private class OptionTableModel(givenOpts: List<IOptionDetails>) : TableModel {
+		private val opts: List<OptionTempHandler>
+
+		init {
+			val mutOpts = ArrayList<OptionTempHandler>()
+			for (opt in givenOpts) {
+				mutOpts.add(OptionTempHandler(opt))
+			}
+			opts = mutOpts
+		}
+
+		override fun getRowCount() = opts.size
+		override fun getColumnCount() = 2
+
+		private val columnNames = arrayOf("Enabled", "Mod name")
+		private val columnTypes = arrayOf(Boolean::class.javaObjectType, String::class.java)
+		private val columnEditables = booleanArrayOf(true, false)
+
+		override fun getColumnName(columnIndex: Int) = columnNames[columnIndex]
+		override fun getColumnClass(columnIndex: Int) = columnTypes[columnIndex]
+		override fun isCellEditable(rowIndex: Int, columnIndex: Int) = columnEditables[columnIndex]
+
+		override fun getValueAt(rowIndex: Int, columnIndex: Int): Any {
+			val opt = opts[rowIndex]
+			return if (columnIndex == 0) opt.optionValue else opt.name
+		}
+
+		override fun setValueAt(aValue: Any, rowIndex: Int, columnIndex: Int) {
+			if (columnIndex == 0) {
+				val opt = opts[rowIndex]
+				opt.optionValue = aValue as Boolean
+			}
+		}
+
+		// Noop, the table model doesn't change!
+		override fun addTableModelListener(l: TableModelListener) {}
+		override fun removeTableModelListener(l: TableModelListener) {}
+
+		fun getDescription(rowIndex: Int) = opts[rowIndex].optionDescription
+
+		fun finalise() {
+			for (opt in opts) {
+				opt.finalise()
+			}
+		}
+	}
+
+	override fun actionPerformed(e: ActionEvent) {
+		if (e.actionCommand == "OK") {
+			tableModel.finalise()
+			future.complete(false)
+			dispose()
+		} else if (e.actionCommand == "Cancel") {
+			future.complete(true)
+			dispose()
+		}
+	}
+
+	/**
+	 * Create the dialog.
+	 */
+	init {
+		tableModel = OptionTableModel(optList)
+		this.future = future
+
+		setBounds(100, 100, 450, 300)
+		setLocationRelativeTo(parentWindow)
+
+		contentPane.apply {
+			layout = BorderLayout()
+			add(JPanel().apply {
+				border = EmptyBorder(5, 5, 5, 5)
+				layout = BorderLayout(0, 0)
+
+				add(JSplitPane().apply {
+					resizeWeight = 0.5
+
+					lblOptionDescription = JTextArea("Select an option...").apply {
+						background = UIManager.getColor("List.background")
+						isOpaque = true
+						wrapStyleWord = true
+						lineWrap = true
+						isEditable = false
+						isFocusable = false
+						font = UIManager.getFont("Label.font")
+						border = EmptyBorder(10, 10, 10, 10)
+					}
+
+					leftComponent = JScrollPane(JTable().apply {
+						showVerticalLines = false
+						showHorizontalLines = false
+						setSelectionMode(ListSelectionModel.SINGLE_SELECTION)
+						setShowGrid(false)
+						model = tableModel
+						columnModel.getColumn(0).resizable = false
+						columnModel.getColumn(0).preferredWidth = 15
+						columnModel.getColumn(0).maxWidth = 15
+						columnModel.getColumn(1).resizable = false
+						selectionModel.addListSelectionListener {
+							val i = selectedRow
+							if (i > -1) {
+								lblOptionDescription.text = tableModel.getDescription(i)
+							} else {
+								lblOptionDescription.text = "Select an option..."
+							}
+						}
+						tableHeader = null
+					}).apply {
+						viewport.background = UIManager.getColor("List.background")
+						horizontalScrollBarPolicy = ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER
+					}
+
+					rightComponent = JScrollPane(lblOptionDescription)
+				})
+
+				add(JPanel().apply {
+					layout = FlowLayout(FlowLayout.RIGHT)
+
+					add(JButton("OK").apply {
+						actionCommand = "OK"
+						addActionListener(this@OptionsSelectWindow)
+
+						this@OptionsSelectWindow.rootPane.defaultButton = this
+					})
+
+					add(JButton("Cancel").apply {
+						actionCommand = "Cancel"
+						addActionListener(this@OptionsSelectWindow)
+					})
+				}, BorderLayout.SOUTH)
+			}, BorderLayout.CENTER)
+		}
+
+		addWindowListener(object : WindowAdapter() {
+			override fun windowClosing(e: WindowEvent) {
+				future.complete(true)
+			}
+
+			override fun windowClosed(e: WindowEvent) {
+				// Just in case closing didn't get triggered - if something else called dispose() the
+				// future will have already completed
+				future.complete(true)
+			}
+		})
+	}
+}

src/main/kotlin/link/infra/packwiz/installer/util/Exts.kt

@@ -0,0 +1,38 @@
+package link.infra.packwiz.installer.util
+
+import link.infra.packwiz.installer.ui.IUserInterface
+
+inline fun <T> iflet(value: T?, whenNotNull: (T) -> Unit) {
+	if (value != null) {
+		whenNotNull(value)
+	}
+}
+
+inline fun <T, U> IUserInterface.ifletOrErr(value: T?, message: String, whenNotNull: (T) -> U): U =
+	if (value != null) {
+		whenNotNull(value)
+	} else {
+		this.showErrorAndExit(message)
+	}
+
+inline fun <T, U, V> IUserInterface.ifletOrErr(value: T?, value2: U?, message: String, whenNotNull: (T, U) -> V): V =
+	if (value != null && value2 != null) {
+		whenNotNull(value, value2)
+	} else {
+		this.showErrorAndExit(message)
+	}
+
+inline fun <T> ifletOrWarn(value: T?, message: String, whenNotNull: (T) -> Unit) {
+	if (value != null) {
+		whenNotNull(value)
+	} else {
+		Log.warn(message)
+	}
+}
+
+inline fun <T, U> iflet(value: T?, whenNotNull: (T) -> U, whenNull: () -> U): U =
+	if (value != null) {
+		whenNotNull(value)
+	} else {
+		whenNull()
+	}

src/main/kotlin/link/infra/packwiz/installer/util/Log.kt

@@ -0,0 +1,16 @@
+package link.infra.packwiz.installer.util
+
+object Log {
+	fun info(message: String) = println(message)
+
+	fun warn(message: String) = println("[Warning] $message")
+	fun warn(message: String, exception: Exception) = println("[Warning] $message: $exception")
+
+	fun fatal(message: String) {
+		println("[FATAL] $message")
+	}
+	fun fatal(message: String, exception: Exception) {
+		println("[FATAL] $message: ")
+		exception.printStackTrace()
+	}
+}