MultiMC metadata: Support updating NeoForge version (#75)

Removed a deleteIfExists call - this should be handled by DownloadTask instead

.github/workflows/pr.yml

@@ -0,0 +1,27 @@
+name: Java Gradle Build
+
+on:
+  pull_request
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Set up JDK 8
+        uses: actions/setup-java@v2
+        with:
+          java-version: '8'
+          distribution: 'temurin'
+          cache: gradle
+      - name: Build with Gradle
+        run: ./gradlew build
+      - name: Cleanup Gradle Cache
+        # Remove some files from the Gradle cache, so they aren't cached by GitHub Actions.
+        # Restoring these files from a GitHub Actions cache might cause problems for future builds.
+        run: |
+          rm -f ~/.gradle/caches/modules-2/modules-2.lock
+          rm -f ~/.gradle/caches/modules-2/gc.properties

.github/workflows/release.yml

@@ -0,0 +1,29 @@
+name: Java Gradle Release
+
+on:
+  push:
+    tags:
+      - 'v\d+.\d+.\d+'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Set up JDK 8
+        uses: actions/setup-java@v2
+        with:
+          java-version: '8'
+          distribution: 'temurin'
+          cache: gradle
+      - name: Publish with Gradle
+        run: ./gradlew publish -Pgithub.token="${{ secrets.GITHUB_TOKEN }}" -Pbunnycdn.token="${{ secrets.BUNNYCDN_TOKEN }}" -Prelease=true
+      - name: Cleanup Gradle Cache
+        # Remove some files from the Gradle cache, so they aren't cached by GitHub Actions.
+        # Restoring these files from a GitHub Actions cache might cause problems for future builds.
+        run: |
+          rm -f ~/.gradle/caches/modules-2/modules-2.lock
+          rm -f ~/.gradle/caches/modules-2/gc.properties

.github/workflows/snapshot.yml

@@ -0,0 +1,29 @@
+name: Java Gradle Snapshot
+
+on:
+  push:
+    branches:
+      - 'main'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Set up JDK 8
+        uses: actions/setup-java@v2
+        with:
+          java-version: '8'
+          distribution: 'temurin'
+          cache: gradle
+      - name: Publish with Gradle
+        run: ./gradlew publish -Pgithub.token="${{ secrets.GITHUB_TOKEN }}" -Pbunnycdn.token="${{ secrets.BUNNYCDN_TOKEN }}"
+      - name: Cleanup Gradle Cache
+        # Remove some files from the Gradle cache, so they aren't cached by GitHub Actions.
+        # Restoring these files from a GitHub Actions cache might cause problems for future builds.
+        run: |
+          rm -f ~/.gradle/caches/modules-2/modules-2.lock
+          rm -f ~/.gradle/caches/modules-2/gc.properties

.gitignore

@@ -1,74 +1,95 @@
-# Created by https://www.gitignore.io/api/java,gradle,eclipse
-# Edit at https://www.gitignore.io/?templates=java,gradle,eclipse
 
-### Eclipse ###
-.metadata
-bin/
-tmp/
-*.tmp
-*.bak
-*.swp
-*~.nib
-local.properties
-.settings/
-.loadpath
-.recommenders
+# 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
 
-# External tool builders
-.externalToolBuilders/
+### 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
 
-# Locally stored "Eclipse launch configurations"
-*.launch
+# User-specific stuff
+.idea/**/workspace.xml
+.idea/**/tasks.xml
+.idea/**/usage.statistics.xml
+.idea/**/dictionaries
+.idea/**/shelf
 
-# PyDev specific (Python IDE for Eclipse)
-*.pydevproject
+# Generated files
+.idea/**/contentModel.xml
 
-# CDT-specific (C/C++ Development Tooling)
-.cproject
+# Sensitive or high-churn files
+.idea/**/dataSources/
+.idea/**/dataSources.ids
+.idea/**/dataSources.local.xml
+.idea/**/sqlDataSources.xml
+.idea/**/dynamic.xml
+.idea/**/uiDesigner.xml
+.idea/**/dbnavigator.xml
 
-# CDT- autotools
-.autotools
+# Gradle
+.idea/**/gradle.xml
+.idea/**/libraries
 
-# Java annotation processor (APT)
-.factorypath
+# Gradle and Maven with auto-import
+# 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
+# *.iml
+# *.ipr
 
-# PDT-specific (PHP Development Tools)
-.buildpath
+# CMake
+cmake-build-*/
 
-# sbteclipse plugin
-.target
+# Mongo Explorer plugin
+.idea/**/mongoSettings.xml
 
-# Tern plugin
-.tern-project
+# File-based project format
+*.iws
 
-# TeXlipse plugin
-.texlipse
+# IntelliJ
+out/
 
-# STS (Spring Tool Suite)
-.springBeans
+# mpeltonen/sbt-idea plugin
+.idea_modules/
 
-# Code Recommenders
-.recommenders/
+# JIRA plugin
+atlassian-ide-plugin.xml
 
-# Annotation Processing
-.apt_generated/
+# Cursive Clojure plugin
+.idea/replstate.xml
 
-# Scala IDE specific (Scala & Java development for Eclipse)
-.cache-main
-.scala_dependencies
-.worksheet
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+fabric.properties
 
-### Eclipse Patch ###
-# Eclipse Core
-.project
+# Editor-based Rest Client
+.idea/httpRequests
 
-# JDT-specific (Eclipse Java Development Tools)
-.classpath
+# Android studio 3.1+ serialized cache file
+.idea/caches/build_file_checksums.ser
 
-# Annotation Processing
-.apt_generated
+### 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
 
-.sts4-cache/
+.idea/
+
+# Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-249601023
+
+*.iml
+modules.xml
+.idea/misc.xml
+*.ipr
+
+# Sonarlint plugin
+.idea/sonarlint
 
 ### Java ###
 # Compiled class file
@@ -114,4 +135,4 @@ gradle-app.setting
 ### Gradle Patch ###
 **/build/
 
-# End of https://www.gitignore.io/api/java,gradle,eclipse
+# End of https://www.toptal.com/developers/gitignore/api/java,gradle,intellij+all

.vscode/settings.json

@@ -1,9 +0,0 @@
-{
-	"files.exclude": {
-		"**/.classpath": true,
-		"**/.project": true,
-		"**/.settings": true,
-		"**/.factorypath": true
-	},
-	"java.configuration.updateBuildConfiguration": "interactive"
-}

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

@@ -1,48 +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'
-}
-
-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

build.gradle.kts

@@ -0,0 +1,206 @@
+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 "2.4.1"
+	kotlin("jvm") version "1.7.10"
+	id("com.github.jk1.dependency-license-report") version "2.0"
+	`maven-publish`
+}
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
+
+repositories {
+	mavenCentral()
+	google()
+	maven {
+		url = uri("https://jitpack.io")
+	}
+}
+
+val r8 by configurations.creating
+val distJarOutput by configurations.creating {
+	isCanBeResolved = false
+	isCanBeConsumed = true
+
+	attributes {
+		attribute(Usage.USAGE_ATTRIBUTE, project.objects.named(Usage::class.java, Usage.JAVA_RUNTIME))
+		attribute(Bundling.BUNDLING_ATTRIBUTE, project.objects.named(Bundling::class.java, Bundling.EMBEDDED))
+	}
+}
+
+dependencies {
+	implementation("commons-cli:commons-cli:1.5.0")
+	implementation("com.google.code.gson:gson:2.9.0")
+	implementation("com.squareup.okio:okio:3.1.0")
+	implementation(kotlin("stdlib-jdk8"))
+	implementation("com.squareup.okhttp3:okhttp:4.10.0")
+	implementation("cc.ekblad:4koma:1.1.0")
+
+	r8("com.android.tools:r8:3.3.28")
+}
+
+application {
+	mainClass.set("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 {
+	// 4koma uses kotlin-reflect; requires Kotlin metadata
+	//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")
+}
+
+val shrinkJar by tasks.registering(JavaExec::class) {
+	val rules = file("src/main/proguard.txt")
+	val r8File = base.libsDirectory.file(provider {
+		base.archivesName.get() + "-" + project.version + "-all-shrink.jar"
+	})
+	dependsOn(configurations.named("runtimeClasspath"))
+	inputs.files(tasks.shadowJar, rules)
+	outputs.file(r8File)
+
+	classpath(r8)
+	mainClass.set("com.android.tools.r8.R8")
+	args = mutableListOf(
+		"--release",
+		"--classfile",
+		"--output", r8File.get().toString(),
+		"--pg-conf", rules.toString(),
+		"--lib", System.getProperty("java.home"),
+		*(if (System.getProperty("java.version").startsWith("1.")) {
+			// javax.crypto, necessary on <1.9 for compiling Okio
+			arrayOf("--lib", System.getProperty("java.home") + "/lib/jce.jar")
+		} else { arrayOf() }),
+		tasks.shadowJar.get().archiveFile.get().asFile.toString()
+	)
+}
+
+// MANIFEST.MF must be one of the first 2 entries in the zip for JarInputStream to see it
+// Gradle's JAR creation handles this whereas R8 doesn't, so the dist JAR is repacked
+val distJar by tasks.registering(Jar::class) {
+	from(shrinkJar.map { zipTree(it.outputs.files.singleFile) })
+	archiveClassifier.set("all-repacked")
+	manifest {
+		from(shrinkJar.map { zipTree(it.outputs.files.singleFile).matching {
+			include("META-INF/MANIFEST.MF")
+		}.singleFile })
+	}
+}
+
+artifacts {
+	add("distJarOutput", distJar) {
+		classifier = "dist"
+	}
+}
+
+// Used for vscode launch.json
+val copyJar by tasks.registering(Copy::class) {
+	from(distJar)
+	rename("packwiz-installer-(.*)\\.jar", "packwiz-installer.jar")
+	into(layout.buildDirectory.dir("dist"))
+	outputs.file(layout.buildDirectory.dir("dist").map { it.file("packwiz-installer.jar") })
+}
+
+tasks.build {
+	dependsOn(copyJar)
+}
+
+githubRelease {
+	owner("comp500")
+	repo("packwiz-installer")
+	tagName("${project.version}")
+	releaseName("Release ${project.version}")
+	draft(true)
+	token(findProperty("github.token") as String?)
+	releaseAssets(layout.buildDirectory.dir("dist").map { it.file("packwiz-installer.jar") }.get())
+}
+
+tasks.githubRelease {
+	dependsOn(copyJar)
+	enabled = project.hasProperty("github.token") && project.findProperty("release") == "true"
+}
+
+tasks.publish {
+	dependsOn(tasks.githubRelease)
+}
+
+tasks.compileKotlin {
+	kotlinOptions {
+		jvmTarget = "1.8"
+		freeCompilerArgs = listOf("-Xjvm-default=all", "-Xallow-result-return-type", "-opt-in=kotlin.io.path.ExperimentalPathApi", "-Xlambdas=indy")
+	}
+}
+tasks.compileTestKotlin {
+	kotlinOptions {
+		jvmTarget = "1.8"
+		freeCompilerArgs = listOf("-Xjvm-default=all", "-Xallow-result-return-type", "-opt-in=kotlin.io.path.ExperimentalPathApi", "-Xlambdas=indy")
+	}
+}
+
+val javaComponent = components["java"] as AdhocComponentWithVariants
+javaComponent.addVariantsFromConfiguration(distJarOutput) {
+	mapToMavenScope("runtime")
+	mapToOptional()
+}
+javaComponent.withVariantsFromConfiguration(configurations["shadowRuntimeElements"]) {
+	skip()
+}
+
+if (project.hasProperty("bunnycdn.token")) {
+	publishing {
+		publications {
+			create<MavenPublication>("maven") {
+				groupId = "link.infra.packwiz"
+				artifactId = "packwiz-installer"
+
+				from(components["java"])
+			}
+		}
+		repositories {
+			maven {
+				url = if (project.findProperty("release") == "true") {
+					uri("https://storage.bunnycdn.com/comp-maven/repository/release")
+				} else {
+					uri("https://storage.bunnycdn.com/comp-maven/repository/snapshot")
+				}
+				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-7.5-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

gradlew

@@ -1,13 +1,13 @@
-#!/usr/bin/env sh
+#!/bin/sh
 
 #
-# Copyright 2015 the original author or authors.
+# Copyright © 2015-2021 the original authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
-#      http://www.apache.org/licenses/LICENSE-2.0
+#      https://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ -17,78 +17,113 @@
 #
 
 ##############################################################################
-##
-##  Gradle start up script for UN*X
-##
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
 ##############################################################################
 
 # Attempt to set APP_HOME
+
 # Resolve links: $0 may be a link
-PRG="$0"
-# Need this for relative symlinks.
-while [ -h "$PRG" ] ; do
-    ls=`ls -ld "$PRG"`
-    link=`expr "$ls" : '.*-> \(.*\)$'`
-    if expr "$link" : '/.*' > /dev/null; then
-        PRG="$link"
-    else
-        PRG=`dirname "$PRG"`"/$link"
-    fi
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
 done
-SAVED="`pwd`"
-cd "`dirname \"$PRG\"`/" >/dev/null
-APP_HOME="`pwd -P`"
-cd "$SAVED" >/dev/null
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
 
 APP_NAME="Gradle"
-APP_BASE_NAME=`basename "$0"`
+APP_BASE_NAME=${0##*/}
 
 # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
 DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
-MAX_FD="maximum"
+MAX_FD=maximum
 
 warn () {
     echo "$*"
-}
+} >&2
 
 die () {
     echo
     echo "$*"
     echo
     exit 1
-}
+} >&2
 
 # OS specific support (must be 'true' or 'false').
 cygwin=false
 msys=false
 darwin=false
 nonstop=false
-case "`uname`" in
-  CYGWIN* )
-    cygwin=true
-    ;;
-  Darwin* )
-    darwin=true
-    ;;
-  MINGW* )
-    msys=true
-    ;;
-  NONSTOP* )
-    nonstop=true
-    ;;
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
 esac
 
 CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 
+
 # Determine the Java command to use to start the JVM.
 if [ -n "$JAVA_HOME" ] ; then
     if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
         # IBM's JDK on AIX uses strange locations for the executables
-        JAVACMD="$JAVA_HOME/jre/sh/java"
+        JAVACMD=$JAVA_HOME/jre/sh/java
     else
-        JAVACMD="$JAVA_HOME/bin/java"
+        JAVACMD=$JAVA_HOME/bin/java
     fi
     if [ ! -x "$JAVACMD" ] ; then
         die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
@@ -97,7 +132,7 @@ Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
     fi
 else
-    JAVACMD="java"
+    JAVACMD=java
     which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
@@ -105,84 +140,95 @@ location of your Java installation."
 fi
 
 # Increase the maximum file descriptors if we can.
-if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
-    MAX_FD_LIMIT=`ulimit -H -n`
-    if [ $? -eq 0 ] ; then
-        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
-            MAX_FD="$MAX_FD_LIMIT"
-        fi
-        ulimit -n $MAX_FD
-        if [ $? -ne 0 ] ; then
-            warn "Could not set maximum file descriptor limit: $MAX_FD"
-        fi
-    else
-        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
-    fi
-fi
-
-# For Darwin, add options to specify how the application appears in the dock
-if $darwin; then
-    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
-fi
-
-# For Cygwin, switch paths to Windows format before running java
-if $cygwin ; then
-    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
-    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
-    JAVACMD=`cygpath --unix "$JAVACMD"`
-
-    # We build the pattern for arguments to be converted via cygpath
-    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
-    SEP=""
-    for dir in $ROOTDIRSRAW ; do
-        ROOTDIRS="$ROOTDIRS$SEP$dir"
-        SEP="|"
-    done
-    OURCYGPATTERN="(^($ROOTDIRS))"
-    # Add a user-defined pattern to the cygpath arguments
-    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
-        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
-    fi
-    # Now convert the arguments - kludge to limit ourselves to /bin/sh
-    i=0
-    for arg in "$@" ; do
-        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
-        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
-
-        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
-            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
-        else
-            eval `echo args$i`="\"$arg\""
-        fi
-        i=$((i+1))
-    done
-    case $i in
-        (0) set -- ;;
-        (1) set -- "$args0" ;;
-        (2) set -- "$args0" "$args1" ;;
-        (3) set -- "$args0" "$args1" "$args2" ;;
-        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
-        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
-        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
-        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
-        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
-        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
 fi
 
-# Escape application args
-save () {
-    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
-    echo " "
-}
-APP_ARGS=$(save "$@")
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
 
-# Collect all arguments for the java command, following the shell quoting and substitution rules
-eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
 
-# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
-if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
-  cd "$(dirname "$0")"
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
 fi
 
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
 exec "$JAVACMD" "$@"

gradlew.bat

@@ -5,7 +5,7 @@
 @rem you may not use this file except in compliance with the License.
 @rem You may obtain a copy of the License at
 @rem
-@rem      http://www.apache.org/licenses/LICENSE-2.0
+@rem      https://www.apache.org/licenses/LICENSE-2.0
 @rem
 @rem Unless required by applicable law or agreed to in writing, software
 @rem distributed under the License is distributed on an "AS IS" BASIS,
@@ -29,6 +29,9 @@ if "%DIRNAME%" == "" set DIRNAME=.
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
 @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
 set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
 
@@ -37,7 +40,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto init
+if "%ERRORLEVEL%" == "0" goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -51,7 +54,7 @@ goto fail
 set JAVA_HOME=%JAVA_HOME:"=%
 set JAVA_EXE=%JAVA_HOME%/bin/java.exe
 
-if exist "%JAVA_EXE%" goto init
+if exist "%JAVA_EXE%" goto execute
 
 echo.
 echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
@@ -61,28 +64,14 @@ echo location of your Java installation.
 
 goto fail
 
-:init
-@rem Get command-line arguments, handling Windows variants
-
-if not "%OS%" == "Windows_NT" goto win9xME_args
-
-:win9xME_args
-@rem Slurp the command line arguments.
-set CMD_LINE_ARGS=
-set _SKIP=2
-
-:win9xME_args_slurp
-if "x%~1" == "x" goto execute
-
-set CMD_LINE_ARGS=%*
-
 :execute
 @rem Setup the command line
 
 set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
+
 @rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
 
 :end
 @rem End local scope for the variables with windows NT shell

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

@@ -1,159 +0,0 @@
-package link.infra.packwiz.installer;
-
-import java.awt.EventQueue;
-import java.awt.GraphicsEnvironment;
-import java.net.URI;
-import java.net.URISyntaxException;
-
-import javax.swing.JOptionPane;
-import javax.swing.UIManager;
-
-import org.apache.commons.cli.CommandLine;
-import org.apache.commons.cli.CommandLineParser;
-import org.apache.commons.cli.DefaultParser;
-import org.apache.commons.cli.Options;
-import org.apache.commons.cli.ParseException;
-
-import link.infra.packwiz.installer.ui.CLIHandler;
-import link.infra.packwiz.installer.ui.IUserInterface;
-import link.infra.packwiz.installer.ui.InstallWindow;
-
-public class Main {
-
-	// Actual main() is in RequiresBootstrap!
-
-	public Main(String[] args) {
-		// Big overarching try/catch just in case everything breaks
-		try {
-			this.startup(args);
-		} catch (Exception e) {
-			e.printStackTrace();
-			EventQueue.invokeLater(new Runnable() {
-				public void run() {
-					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);
-		}
-	}
-
-	protected 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);
-		}
-
-		ui.show();
-
-		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 URI(unparsedArgs[0]);
-		} catch (URISyntaxException e) {
-			// TODO: better error message?
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-
-		// Start update process!
-		// TODO: start in SwingWorker?
-		try {
-			ui.executeManager(new Runnable(){
-				@Override
-				public void run() {
-					try {
-						new UpdateManager(uOptions, ui);
-					} catch (Exception e) {
-						// TODO: better error message?
-						ui.handleExceptionAndExit(e);
-						return;
-					}
-				}
-			});
-		} catch (Exception e) {
-			// TODO: better error message?
-			ui.handleExceptionAndExit(e);
-			return;
-		}
-	}
-
-	// Called by packwiz-installer-bootstrap to set up the help command
-	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

@@ -1,24 +1,20 @@
 package link.infra.packwiz.installer;
 
+import javax.swing.*;
 import java.util.Arrays;
 
-import javax.swing.JOptionPane;
-import javax.swing.UIManager;
-
 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("--")) {
-				return str.substring(2, str.length());
+				return str.substring(2);
 			}
 			if (str.startsWith("-")) {
-				return str.substring(1, str.length());
+				return str.substring(1);
 			}
 			return "";
 		}).anyMatch(str -> str.equals("g") || str.equals("no-gui"))) {

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

@@ -1,417 +0,0 @@
-package link.infra.packwiz.installer;
-
-import java.io.FileNotFoundException;
-import java.io.FileReader;
-import java.io.FileWriter;
-import java.io.IOException;
-import java.io.Writer;
-import java.net.URI;
-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.HashMap;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-import java.util.concurrent.Callable;
-import java.util.concurrent.CompletionService;
-import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.ExecutorCompletionService;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.stream.Collectors;
-
-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.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.IUserInterface;
-import link.infra.packwiz.installer.ui.InstallProgress;
-import okio.Buffer;
-import okio.Okio;
-import okio.Source;
-
-public class UpdateManager {
-
-	public final Options opts;
-	public final IUserInterface ui;
-
-	public static class Options {
-		public URI downloadURI = null;
-		public String manifestFile = "packwiz.json"; // TODO: make configurable
-		public String packFolder = ".";
-		public Side side = Side.CLIENT;
-
-		public static 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 (int i = 0; i < this.depSides.length; i++) {
-						if (this.depSides[i].equals(tSide)) {
-							return true;
-						}
-					}
-				}
-				return false;
-			}
-
-			public static Side from(String name) {
-				String lowerName = name.toLowerCase();
-				for (Side side : Side.values()) {
-					if (side.sideName == lowerName) {
-						return side;
-					}
-				}
-				return null;
-			}
-		}
-	}
-
-	public UpdateManager(Options opts, IUserInterface ui) {
-		this.opts = opts;
-		this.ui = ui;
-		this.start();
-	}
-
-	protected 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;
-		}
-
-		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 (manifest.packFileHash != null && packFileSource.hashIsEqual(manifest.packFileHash)) {
-			System.out.println("Modpack is already up to date!");
-			// todo: --force?
-			return;
-		}
-
-		System.out.println("Modpack name: " + pf.name);
-
-		try {
-			processIndex(HandlerManager.getNewLoc(opts.downloadURI, pf.index.file),
-					HashUtils.getHash(pf.index.hashFormat, pf.index.hash), pf.index.hashFormat, manifest);
-		} catch (Exception e1) {
-			ui.handleExceptionAndExit(e1);
-		}
-
-		// TODO: update MMC params, java args etc
-
-		manifest.packFileHash = packFileSource.getHash();
-		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);
-		}
-
-	}
-
-	protected void checkOptions() {
-		// TODO: implement
-	}
-
-	protected void processIndex(URI indexUri, Hash indexHash, String hashFormat, ManifestFile manifest) {
-		if (manifest.indexFileHash != null && manifest.indexFileHash.equals(indexHash)) {
-			System.out.println("Modpack files are already up to date!");
-			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
-			return;
-		}
-
-		if (manifest.cachedFiles == null) {
-			manifest.cachedFiles = new HashMap<URI, ManifestFile.File>();
-		}
-
-		ui.submitProgress(new InstallProgress("Checking local files..."));
-		List<URI> invalidatedUris = new ArrayList<>();
-		Iterator<Map.Entry<URI, ManifestFile.File>> it = manifest.cachedFiles.entrySet().iterator();
-		while (it.hasNext()) {
-			Map.Entry<URI, ManifestFile.File> entry = it.next();
-			if (entry.getValue().cachedLocation != null) {
-				Path filePath = Paths.get(opts.packFolder, entry.getValue().cachedLocation);
-				URI fileUri = entry.getKey();
-
-				if (!indexFile.files.stream().anyMatch(f -> f.file.equals(fileUri))) {
-					// File has been removed from the index
-					try {
-						Files.deleteIfExists(filePath);
-					} catch (IOException e) {
-						// TODO: should this be shown to the user in some way?
-						e.printStackTrace();
-					}
-					it.remove();
-				} else if (!Files.exists(filePath)) {
-					System.out.println("File " + fileUri.toString() + " invalidated, marked for redownloading");
-					invalidatedUris.add(fileUri);
-				}
-			}
-		}
-		ui.submitProgress(new InstallProgress("Comparing new files..."));
-
-		// TODO: progress bar
-		ConcurrentLinkedQueue<Exception> exceptionQueue = new ConcurrentLinkedQueue<Exception>();
-		List<IndexFile.File> newFiles = indexFile.files.stream().map(f -> {
-			if (f.hashFormat == null || f.hashFormat.length() == 0) {
-				f.hashFormat = indexFile.hashFormat;
-			}
-			return f;
-		}).filter(f -> {
-			if (invalidatedUris.contains(f.file)) {
-				return true;
-			}
-			ManifestFile.File cachedFile = manifest.cachedFiles.get(f.file);
-			Hash newHash;
-			try {
-				newHash = HashUtils.getHash(f.hashFormat, f.hash);
-			} catch (Exception e) {
-				exceptionQueue.add(e);
-				return false;
-			}
-			return cachedFile == null || !newHash.equals(cachedFile.hash);
-		}).parallel().map(f -> {
-			try {
-				f.downloadMeta(indexFile, indexUri);
-			} catch (Exception e) {
-				exceptionQueue.add(e);
-			}
-			return f;
-		}).collect(Collectors.toList());
-
-		for (Exception e : exceptionQueue) {
-			// TODO: collect all exceptions, present in one dialog
-			ui.handleException(e);
-		}
-
-		// TODO: present options
-		// TODO: all options should be presented, not just new files!!!!!!!
-		// and options should be readded to newFiles after option -> true
-		newFiles.stream().filter(f -> f.linkedFile != null).filter(f -> f.linkedFile.option != null).map(f -> {
-			return "option: " + (f.linkedFile.option.description == null ? "null" : f.linkedFile.option.description);
-		}).forEachOrdered(desc -> {
-			System.out.println(desc);
-		});
-
-		// TODO: different thread pool type?
-		ExecutorService threadPool = Executors.newFixedThreadPool(10);
-		CompletionService<DownloadCompletion> completionService = new ExecutorCompletionService<DownloadCompletion>(
-				threadPool);
-
-		for (IndexFile.File f : newFiles) {
-			ManifestFile.File cachedFile = manifest.cachedFiles.get(f.file);
-			completionService.submit(new Callable<DownloadCompletion>() {
-				public DownloadCompletion call() {
-					DownloadCompletion dc = new DownloadCompletion();
-					dc.file = f;
-
-					if (cachedFile != null && cachedFile.linkedFileHash != null && f.linkedFile != null) {
-						try {
-							if (cachedFile.linkedFileHash.equals(f.linkedFile.getHash())) {
-								// Do nothing, the file didn't change
-								// TODO: but if the hash of the metafile changed, what did change?????
-								// should this be checked somehow??
-								return dc;
-							}
-						} catch (Exception e) {}
-					}
-
-					Path destPath = Paths.get(opts.packFolder, f.getDestURI().toString());
-
-					// Don't update files marked with preserve if they already exist on disk
-					if (f.preserve) {
-						if (Files.exists(destPath)) {
-							return dc;
-						}
-					}
-
-					try {
-						Hash hash;
-						String fileHashFormat;
-						if (f.linkedFile != null) {
-							hash = f.linkedFile.getHash();
-							fileHashFormat = f.linkedFile.download.hashFormat;
-						} else {
-							hash = f.getHash();
-							fileHashFormat = f.hashFormat;
-						}
-
-						Source src = f.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 {
-							System.out.println("Invalid hash for " + f.getDestURI().toString());
-							System.out.println("Calculated: " + fileSource.getHash());
-							System.out.println("Expected:   " + hash);
-							dc.err = new Exception("Hash invalid!");
-						}
-
-						if (cachedFile != null && !destPath.equals(Paths.get(opts.packFolder, cachedFile.cachedLocation))) {
-							// Delete old file if location changes
-							Files.delete(Paths.get(opts.packFolder, cachedFile.cachedLocation));
-						}
-						
-						return dc;
-					} catch (Exception e) {
-						dc.err = e;
-						return dc;
-					}
-				}
-			});
-		}
-
-		for (int i = 0; i < newFiles.size(); i++) {
-			DownloadCompletion ret;
-			try {
-				ret = completionService.take().get();
-			} catch (InterruptedException | ExecutionException e) {
-				// TODO: collect all exceptions, present in one dialog
-				ui.handleException(e);
-				ret = null;
-			}
-			// Update manifest
-			if (ret != null && ret.err == null && ret.file != null) {
-				ManifestFile.File newCachedFile = new ManifestFile.File();
-				try {
-					newCachedFile.hash = ret.file.getHash();
-					if (newCachedFile.hash == null) {
-						throw new Exception("Invalid hash!");
-					}
-				} catch (Exception e) {
-					ret.err = e;
-				}
-				if (ret.file.metafile && ret.file.linkedFile != null) {
-					newCachedFile.isOptional = ret.file.linkedFile.isOptional();
-					if (newCachedFile.isOptional) {
-						newCachedFile.optionValue = ret.file.optionValue;
-					}
-					try {
-						newCachedFile.linkedFileHash = ret.file.linkedFile.getHash();
-					} catch (Exception e) {
-						ret.err = e;
-					}
-				}
-				newCachedFile.cachedLocation = ret.file.getDestURI().toString();
-				manifest.cachedFiles.put(ret.file.file, newCachedFile);
-			}
-			// TODO: show errors properly?
-			String progress;
-			if (ret != null) {
-				if (ret.err != null) {
-					if (ret.file != null) {
-						progress = "Failed to download " + ret.file.getName() + ": " + ret.err.getMessage();
-					} else {
-						progress = "Failed to download: " + ret.err.getMessage();
-					}
-					ret.err.printStackTrace();
-				} else if (ret.file != null) {
-					progress = "Downloaded " + ret.file.getName();
-				} else {
-					progress = "Failed to download, unknown reason";
-				}
-			} else {
-				progress = "Failed to download, unknown reason";
-			}
-			ui.submitProgress(new InstallProgress(progress, i + 1, newFiles.size()));
-		}
-		// option = false file hashes should be stored to disk, but not downloaded
-		// TODO: don't include optional files in progress????
-	}
-
-	private class DownloadCompletion {
-		Exception err;
-		IndexFile.File file;
-	}
-}

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

@@ -1,108 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import java.net.URI;
-import java.nio.file.Paths;
-import java.util.List;
-
-import com.google.gson.annotations.JsonAdapter;
-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;
-
-public class IndexFile {
-	@SerializedName("hash-format")
-	public String hashFormat;
-	public List<File> files;
-	
-	public static class File {
-		@JsonAdapter(SpaceSafeURIParser.class)
-		public URI file;
-		@SerializedName("hash-format")
-		public String hashFormat;
-		public String hash;
-		public URI alias;
-		public boolean metafile;
-		public boolean preserve;
-
-		public transient ModFile linkedFile;
-		public transient URI linkedFileURI;
-		public transient boolean optionValue = true;
-
-		public void downloadMeta(IndexFile parentIndexFile, URI 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(URI indexUri) throws Exception {
-			if (metafile) {
-				if (linkedFile == null) {
-					throw new Exception("Linked file doesn't exist!");
-				}
-				return linkedFile.getSource(linkedFileURI);
-			} else {
-				URI 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) {
-				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();
-			}
-			return file.getPath();
-		}
-
-		public URI getDestURI() {
-			if (alias != null) {
-				return alias;
-			}
-			if (metafile && linkedFile != null) {
-				// TODO: URIs are bad
-				return file.resolve(linkedFile.filename.replace(" ", "%20"));
-			} else {
-				return file;
-			}
-		}
-	}
-}

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

@@ -1,21 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import java.net.URI;
-import java.util.Map;
-
-import link.infra.packwiz.installer.metadata.hash.Hash;
-
-public class ManifestFile {
-	
-	public Hash packFileHash = null;
-	public Hash indexFileHash = null;
-	public Map<URI, File> cachedFiles;
-
-	public static class File {
-		public Hash hash = null;
-		public boolean isOptional = false;
-		public boolean optionValue = true;
-		public Hash linkedFileHash = null;
-		public String cachedLocation = null;
-	}
-}

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

@@ -1,74 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import java.net.URI;
-import java.util.Map;
-
-import com.google.gson.annotations.JsonAdapter;
-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;
-
-public class ModFile {
-	public String name;
-	public String filename;
-	public Side side;
-
-	public Download download;
-	public static class Download {
-		@JsonAdapter(SpaceSafeURIParser.class)
-		public URI 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(URI 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");
-		}
-		URI 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

@@ -1,24 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import java.net.URI;
-import java.util.Map;
-
-import com.google.gson.annotations.JsonAdapter;
-import com.google.gson.annotations.SerializedName;
-
-public class PackFile {
-	public String name;
-
-	public IndexFileLoc index;
-	public static class IndexFileLoc {
-		@JsonAdapter(SpaceSafeURIParser.class)
-		public URI 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/SpaceSafeURIParser.java

@@ -1,31 +0,0 @@
-package link.infra.packwiz.installer.metadata;
-
-import java.lang.reflect.Type;
-import java.net.URI;
-import java.net.URISyntaxException;
-
-import com.google.gson.JsonDeserializationContext;
-import com.google.gson.JsonDeserializer;
-import com.google.gson.JsonElement;
-import com.google.gson.JsonParseException;
-
-/**
- * This class encodes spaces before parsing the URI, so the URI can actually be
- * parsed.
- */
-class SpaceSafeURIParser implements JsonDeserializer<URI> {
-
-	@Override
-	public URI deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
-			throws JsonParseException {
-		String uriString = json.getAsString().replace(" ", "%20");
-		try {
-			return new URI(uriString);
-		} 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

@@ -1,86 +0,0 @@
-package link.infra.packwiz.installer.metadata.hash;
-
-import okio.HashingSource;
-import okio.Source;
-
-public class HashingSourceHasher implements IHasher {
-	String type;
-
-	public HashingSourceHasher(String type) {
-		this.type = type;
-	}
-
-	// i love naming things
-	private class HashingSourceGeneralHashingSource extends GeneralHashingSource {
-		HashingSource delegateHashing;
-		HashingSourceHash value;
-
-		public 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.equals(objHash.value);
-			} else {
-				return objHash.value == null ? true : false;
-			}
-		}
-
-		@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 "sha256":
-			return new HashingSourceGeneralHashingSource(HashingSource.sha256(delegate));
-			// TODO: support other hash types
-		}
-		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

@@ -1,104 +0,0 @@
-package link.infra.packwiz.installer.metadata.hash;
-
-import java.io.IOException;
-
-import okio.Buffer;
-import okio.Source;
-
-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 (int i = 0; i < input.length; i++) {
-				byte b = input[i];
-				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 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 java.net.URI;
-import java.util.ArrayList;
-import java.util.List;
-
-import link.infra.packwiz.installer.request.handlers.RequestHandlerGithub;
-import link.infra.packwiz.installer.request.handlers.RequestHandlerHTTP;
-import okio.Source;
-
-public abstract class HandlerManager {
-	
-	public static List<IRequestHandler> handlers = new ArrayList<IRequestHandler>();
-	
-	static {
-		handlers.add(new RequestHandlerGithub());
-		handlers.add(new RequestHandlerHTTP());
-	}
-	
-	public static URI getNewLoc(URI base, URI 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(URI 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/IRequestHandler.java

@@ -1,27 +0,0 @@
-package link.infra.packwiz.installer.request;
-
-import java.net.URI;
-
-import okio.Source;
-
-/**
- * IRequestHandler handles requests for locations specified in modpack metadata.
- */
-public interface IRequestHandler {
-	
-	public boolean matchesHandler(URI loc);
-	
-	public default URI getNewLoc(URI loc) {
-		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.
-	 * @param loc The location to be read
-	 * @return The Source containing the data of the file
-	 * @throws Exception
-	 */
-	public Source getFileSource(URI loc) throws Exception;
-
-}

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

@@ -1,83 +0,0 @@
-package link.infra.packwiz.installer.request.handlers;
-
-import java.net.URI;
-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 URI getNewLoc(URI loc) {
-		return loc;
-	}
-	
-	// TODO: is caching really needed, if HTTPURLConnection follows redirects correctly?
-	private Map<String, URI> zipUriMap = new HashMap<String, URI>();
-	final ReentrantReadWriteLock zipUriLock = new ReentrantReadWriteLock();
-	private static Pattern repoMatcherPattern = Pattern.compile("/([\\w.-]+/[\\w.-]+).*");
-	
-	private String getRepoName(URI loc) {
-		Matcher matcher = repoMatcherPattern.matcher(loc.getPath());
-		matcher.matches();
-		return matcher.group(1);
-	}
-
-	@Override
-	protected URI getZipUri(URI loc) throws Exception {
-		String repoName = getRepoName(loc);
-		String branchName = getBranch(loc);
-		zipUriLock.readLock().lock();
-		URI zipUri = zipUriMap.get(repoName + "/" + branchName);
-		zipUriLock.readLock().unlock();
-		if (zipUri != null) {
-			return zipUri;
-		}
-		
-		zipUri = new URI("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.
-		URI 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(URI loc) {
-		Matcher matcher = branchMatcherPattern.matcher(loc.getPath());
-		matcher.matches();
-		return matcher.group(1);
-	}
-
-	@Override
-	protected URI getLocationInZip(URI loc) throws Exception {
-		String path = "/" + getRepoName(loc) + "/blob/" + getBranch(loc);
-		return new URI(loc.getScheme(), loc.getAuthority(), path, null, null).relativize(loc);
-	}
-
-	@Override
-	public boolean matchesHandler(URI 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 java.net.URI;
-import java.net.URLConnection;
-
-import link.infra.packwiz.installer.request.IRequestHandler;
-import okio.Okio;
-import okio.Source;
-
-public class RequestHandlerHTTP implements IRequestHandler {
-
-	@Override
-	public boolean matchesHandler(URI loc) {
-		String scheme = loc.getScheme();
-		return "http".equals(scheme) || "https".equals(scheme);
-	}
-
-	@Override
-	public Source getFileSource(URI 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

@@ -1,172 +0,0 @@
-package link.infra.packwiz.installer.request.handlers;
-
-import java.io.IOException;
-import java.net.URI;
-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;
-
-import okio.Buffer;
-import okio.BufferedSource;
-import okio.Okio;
-import okio.Source;
-
-public abstract class RequestHandlerZip extends RequestHandlerHTTP {
-	
-	protected 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<URI, Buffer> readFiles = new HashMap<URI, Buffer>();
-		// 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;
-
-		public 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(URI loc) throws IOException, URISyntaxException {
-			while (true) {
-				entry = zis.getNextEntry();
-				if (entry == null) {
-					return null;
-				}
-				Buffer data = readCurrFile();
-				URI fileLoc = new URI(removeFolder(entry.getName()));
-				if (loc.equals(fileLoc)) {
-					return data;
-				} else {
-					readFiles.put(fileLoc, data);
-				}
-			}
-		}
-		
-		public Source getFileSource(URI 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();
-			if (file != null) {
-				return file;
-			}
-			return null;
-		}
-		
-		public URI findInZip(Predicate<URI> matches) throws Exception {
-			filesLock.lock();
-			for (URI 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();
-				URI fileLoc = new URI(removeFolder(entry.getName()));
-				readFiles.put(fileLoc, data);
-				if (matches.test(fileLoc)) {
-					filesLock.unlock();
-					return fileLoc;
-				}
-			}
-		}
-		
-	}
-	
-	private final Map<URI, ZipReader> cache = new HashMap<URI, ZipReader>();
-	final ReentrantReadWriteLock cacheLock = new ReentrantReadWriteLock();
-	
-	protected abstract URI getZipUri(URI loc) throws Exception;
-	
-	protected abstract URI getLocationInZip(URI loc) throws Exception;
-	
-	@Override
-	public abstract boolean matchesHandler(URI loc);
-
-	@Override
-	public Source getFileSource(URI loc) throws Exception {
-		URI 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 URI findInZip(URI loc, Predicate<URI> matches) throws Exception {
-		URI 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

@@ -1,33 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-public class CLIHandler implements IUserInterface {
-
-	@Override
-	public void handleException(Exception e) {
-		e.printStackTrace();
-	}
-
-	@Override
-	public void show() {}
-
-	@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!");
-	}
-	
-}

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

@@ -1,23 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-public interface IUserInterface {
-	
-	public void show();
-
-	public void handleException(Exception e);
-	
-	/**
-	 * This might not exit straight away, return after calling this!
-	 */
-	public default void handleExceptionAndExit(Exception e) {
-		handleException(e);
-		System.exit(1);
-	};
-	
-	public default void setTitle(String title) {};
-
-	public void submitProgress(InstallProgress progress);
-
-	public void executeManager(Runnable task);
-	
-}

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

@@ -1,189 +0,0 @@
-package link.infra.packwiz.installer.ui;
-
-import java.awt.BorderLayout;
-import java.awt.Component;
-import java.awt.EventQueue;
-import java.awt.GridBagConstraints;
-import java.awt.GridBagLayout;
-import java.awt.event.ActionEvent;
-import java.awt.event.ActionListener;
-import java.util.List;
-import java.util.concurrent.atomic.AtomicBoolean;
-
-import javax.swing.JButton;
-import javax.swing.JFrame;
-import javax.swing.JLabel;
-import javax.swing.JOptionPane;
-import javax.swing.JPanel;
-import javax.swing.JProgressBar;
-import javax.swing.UIManager;
-import javax.swing.border.EmptyBorder;
-
-public class InstallWindow implements IUserInterface {
-
-	private JFrame frmPackwizlauncher;
-	private JLabel lblProgresslabel;
-	private JProgressBar progressBar;
-
-	private String title = "Updating modpack...";
-	private SwingWorkerButWithPublicPublish<Void, InstallProgress> worker;
-	private AtomicBoolean aboutToCrash = new AtomicBoolean();
-
-	@Override
-	public void show() {
-		EventQueue.invokeLater(new Runnable() {
-			public void run() {
-				try {
-					UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-					InstallWindow.this.initialize();
-					InstallWindow.this.frmPackwizlauncher.setVisible(true);
-				} catch (Exception e) {
-					e.printStackTrace();
-				}
-			}
-		});
-	}
-
-	/**
-	 * Initialize the contents of the frame.
-	 */
-	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);
-		
-		JButton btnOptions = new JButton("Options...");
-		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(new ActionListener() {
-			public void actionPerformed(ActionEvent arg0) {
-				if (worker != null) {
-					worker.cancel(true);
-				}
-				frmPackwizlauncher.dispose();
-				// TODO: show window to ask user what to do
-				System.out.println("Update process cancelled by user!");
-				System.exit(1);
-			}
-		});
-		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(new Runnable() {
-			public void run() {
-				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(new Runnable() {
-			public void run() {
-				JOptionPane.showMessageDialog(null, "A fatal error occurred: \n" + e.getClass().getCanonicalName() + ": " + e.getMessage(), title, JOptionPane.ERROR_MESSAGE);
-				System.exit(1);
-			}
-		});
-	}
-	
-	@Override
-	public void setTitle(String title) {
-		this.title = title;
-		if (frmPackwizlauncher != null) {
-			EventQueue.invokeLater(new Runnable() {
-				public void run() {
-					InstallWindow.this.frmPackwizlauncher.setTitle(title);
-				}
-			});
-		}
-	}
-
-	@Override
-	public void submitProgress(InstallProgress progress) {
-		if (worker != null) {
-			worker.publishPublic(progress);
-		}
-	}
-
-	@Override
-	public void executeManager(Runnable task) {
-		EventQueue.invokeLater(new Runnable() {
-			public void run() {
-				worker = new SwingWorkerButWithPublicPublish<Void, InstallProgress>() {
-
-					@Override
-					protected Void doInBackground() throws Exception {
-						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();
-			}
-		});
-	}
-
-}

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 +1,325 @@
+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.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashFormat
+import link.infra.packwiz.installer.request.RequestException
+import link.infra.packwiz.installer.target.ClientHolder
+import link.infra.packwiz.installer.target.Side
+import link.infra.packwiz.installer.target.path.PackwizFilePath
+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.Buffer
+import okio.HashingSink
+import okio.blackholeSink
+import okio.buffer
+import java.io.IOException
+import java.nio.file.Files
+import java.nio.file.StandardCopyOption
+
+internal class DownloadTask private constructor(val metadata: IndexFile.File, val index: IndexFile, private val downloadSide: Side) : IOptionDetails {
+	var cachedFile: ManifestFile.File? = null
+		private set
+
+	private var err: Exception? = null
+	val exceptionDetails get() = err?.let { e -> ExceptionDetails(name, e) }
+
+	fun failed() = err != null
+
+	var alreadyUpToDate = false
+		private set
+	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
+	var completionStatus = CompletionStatus.INCOMPLETE
+		private set
+
+	enum class CompletionStatus {
+		INCOMPLETE,
+		DOWNLOADED,
+		ALREADY_EXISTS_CACHED,
+		ALREADY_EXISTS_VALIDATED,
+		SKIPPED_DISABLED,
+		SKIPPED_WRONG_SIDE,
+		DELETED_DISABLED,
+		DELETED_WRONG_SIDE;
+	}
+
+	val isOptional get() = metadata.linkedFile?.option?.optional ?: false
+
+	fun isNewOptional() = isOptional && newOptional
+
+	fun correctSide() = metadata.linkedFile?.side?.let { downloadSide.hasSide(it) } ?: 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 ?: ""
+
+	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 {
+				metadata.getHashObj(index)
+			} catch (e: Exception) {
+				err = e
+				return
+			}
+			if (currHash == cachedFile.hash) { // Already up to date
+				alreadyUpToDate = true
+				metadataRequired = false
+				completionStatus = CompletionStatus.ALREADY_EXISTS_CACHED
+			}
+		}
+		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(clientHolder: ClientHolder) {
+		if (err != null) return
+
+		if (metadataRequired) {
+			try {
+				// Retrieve the linked metadata file
+				metadata.downloadMeta(index, clientHolder)
+			} catch (e: Exception) {
+				err = e
+				return
+			}
+			cachedFile?.let { cachedFile ->
+				val linkedFile = metadata.linkedFile
+				if (linkedFile != null) {
+					if (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 = linkedFile.option.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: PackwizFilePath, clientHolder: ClientHolder) {
+		if (!alreadyUpToDate) {
+			try {
+				// TODO: only do this for files that didn't exist before or have been modified since last full update?
+				val destPath = metadata.destURI.rebase(packFolder)
+				destPath.source(clientHolder).use { src ->
+					// TODO: clean up duplicated code
+					val hash: Hash<*>
+					val fileHashFormat: HashFormat<*>
+					val linkedFile = metadata.linkedFile
+
+					if (linkedFile != null) {
+						hash = linkedFile.hash
+						fileHashFormat = linkedFile.download.hashFormat
+					} else {
+						hash = metadata.getHashObj(index)
+						fileHashFormat = metadata.hashFormat(index)
+					}
+
+					val fileSource = fileHashFormat.source(src)
+					fileSource.buffer().readAll(blackholeSink())
+					if (hash == fileSource.hash) {
+						alreadyUpToDate = true
+						completionStatus = CompletionStatus.ALREADY_EXISTS_VALIDATED
+
+						// Update the manifest file
+						cachedFile = (cachedFile ?: ManifestFile.File()).also {
+							try {
+								it.hash = metadata.getHashObj(index)
+							} catch (e: Exception) {
+								err = e
+								return
+							}
+							it.isOptional = isOptional
+							it.cachedLocation = metadata.destURI.rebase(packFolder)
+							metadata.linkedFile?.let { linked ->
+								try {
+									it.linkedFileHash = linked.hash
+								} catch (e: Exception) {
+									err = e
+								}
+							}
+						}
+					}
+				}
+			} catch (e: RequestException) {
+				// Ignore exceptions; if the file doesn't exist we'll be downloading it
+			} catch (e: IOException) {
+				// Ignore exceptions; if the file doesn't exist we'll be downloading it
+			}
+		}
+	}
+
+	fun download(packFolder: PackwizFilePath, clientHolder: ClientHolder) {
+		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 {
+						completionStatus = if (Files.deleteIfExists(it.cachedLocation!!.nioPath)) {
+							if (correctSide()) { CompletionStatus.DELETED_DISABLED } else { CompletionStatus.DELETED_WRONG_SIDE }
+						} else {
+							if (correctSide()) { CompletionStatus.SKIPPED_DISABLED } else { CompletionStatus.SKIPPED_WRONG_SIDE }
+						}
+					} catch (e: IOException) {
+						Log.warn("Failed to delete file", e)
+					}
+				} else {
+					completionStatus =
+						if (correctSide()) { CompletionStatus.SKIPPED_DISABLED }
+						else { CompletionStatus.SKIPPED_WRONG_SIDE }
+				}
+				it.cachedLocation = null
+				return
+			}
+		}
+		if (alreadyUpToDate) return
+
+		val destPath = metadata.destURI.rebase(packFolder)
+
+		// Don't update files marked with preserve if they already exist on disk
+		if (metadata.preserve) {
+			if (destPath.nioPath.toFile().exists()) {
+				return
+			}
+		}
+
+		// TODO: add .disabled support?
+
+		try {
+			val hash: Hash<*>
+			val fileHashFormat: HashFormat<*>
+			val linkedFile = metadata.linkedFile
+
+			if (linkedFile != null) {
+				hash = linkedFile.hash
+				fileHashFormat = linkedFile.download.hashFormat
+			} else {
+				hash = metadata.getHashObj(index)
+				fileHashFormat = metadata.hashFormat(index)
+			}
+
+			val src = metadata.getSource(clientHolder)
+			val fileSource = fileHashFormat.source(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 (hash == fileSource.hash) {
+				// isDirectory follows symlinks, but createDirectories doesn't
+				try {
+					Files.createDirectories(destPath.parent.nioPath)
+				} catch (e: java.nio.file.FileAlreadyExistsException) {
+					if (!Files.isDirectory(destPath.parent.nioPath)) {
+						throw e
+					}
+				}
+				Files.copy(data.inputStream(), destPath.nioPath, 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 != it) {
+					// Delete old file if location changes
+					try {
+						Files.delete(cachedFile!!.cachedLocation!!.nioPath)
+					} 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(index)
+			} catch (e: Exception) {
+				err = e
+				return
+			}
+			it.isOptional = isOptional
+			it.cachedLocation = metadata.destURI.rebase(packFolder)
+			metadata.linkedFile?.let { linked ->
+				try {
+					it.linkedFileHash = linked.hash
+				} catch (e: Exception) {
+					err = e
+				}
+			}
+		}
+
+		completionStatus = CompletionStatus.DOWNLOADED
+	}
+
+	companion object {
+		fun createTasksFromIndex(index: IndexFile, downloadSide: Side): MutableList<DownloadTask> {
+			val tasks = ArrayList<DownloadTask>()
+			for (file in index.files) {
+				tasks.add(DownloadTask(file, index, downloadSide))
+			}
+			return tasks
+		}
+	}
+}

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

@@ -0,0 +1,142 @@
+package link.infra.packwiz.installer
+
+import com.google.gson.Gson
+import com.google.gson.JsonIOException
+import com.google.gson.JsonParser
+import com.google.gson.JsonSyntaxException
+import link.infra.packwiz.installer.metadata.PackFile
+import link.infra.packwiz.installer.ui.IUserInterface
+import link.infra.packwiz.installer.util.Log
+import kotlin.io.path.reader
+import kotlin.io.path.writeText
+
+class LauncherUtils internal constructor(private val opts: UpdateManager.Options, val ui: IUserInterface) {
+	enum class LauncherStatus {
+		SUCCESSFUL,
+		NO_CHANGES,
+		CANCELLED,
+		NOT_FOUND, // When there is no mmc-pack.json file found (i.e. MultiMC is not being used)
+	}
+
+	fun handleMultiMC(pf: PackFile, gson: Gson): LauncherStatus {
+		// MultiMC MC and loader version checker
+		val manifestPath = opts.multimcFolder / "mmc-pack.json"
+
+		if (!manifestPath.nioPath.toFile().exists()) {
+			return LauncherStatus.NOT_FOUND
+		}
+
+		val multimcManifest = manifestPath.nioPath.reader().use {
+			try {
+				JsonParser.parseReader(it)
+			} catch (e: JsonIOException) {
+				throw Exception("Cannot read the MultiMC pack file", e)
+			} catch (e: JsonSyntaxException) {
+				throw Exception("Invalid MultiMC pack file", e)
+			}.asJsonObject
+		}
+
+		Log.info("Loaded MultiMC config")
+
+		// We only support format 1, if it gets updated in the future we'll have to handle that
+		// There's only version 1 for now tho, so that's good
+		if (multimcManifest["formatVersion"]?.asInt != 1) {
+			throw Exception("Unsupported MultiMC format version ${multimcManifest["formatVersion"]}")
+		}
+
+		var manifestModified = false
+		val modLoaders = hashMapOf(
+			"net.minecraft" to "minecraft",
+			"net.minecraftforge" to "forge",
+			"net.neoforged" to "neoforge",
+			"net.fabricmc.fabric-loader" to "fabric",
+			"org.quiltmc.quilt-loader" to "quilt",
+			"com.mumfrey.liteloader" to "liteloader"
+		)
+		// MultiMC requires components to be sorted; this is defined in the MultiMC meta repo, but they seem to
+		// be the same for every version so they are just used directly here
+		val componentOrders = mapOf(
+			"net.minecraft" to -2,
+			"org.lwjgl" to -1,
+			"org.lwjgl3" to -1,
+			"net.minecraftforge" to 5,
+			"net.neoforged" to 5,
+			"net.fabricmc.fabric-loader" to 10,
+			"org.quiltmc.quilt-loader" to 10,
+			"com.mumfrey.liteloader" to 10,
+			"net.fabricmc.intermediary" to 11
+		)
+		val modLoadersClasses = modLoaders.entries.associate{(k,v)-> v to k}
+		val loaderVersionsFound = HashMap<String, String?>()
+		val outdatedLoaders = mutableSetOf<String>()
+		val components = multimcManifest["components"]?.asJsonArray ?: throw Exception("Invalid mmc-pack.json: no components key")
+		components.removeAll {
+			val component = it.asJsonObject
+
+			val version = component["version"]?.asString
+			// If we find any of the modloaders we support, we save it and check the version
+			if (modLoaders.containsKey(component["uid"]?.asString)) {
+				val modLoader = modLoaders.getValue(component["uid"]!!.asString)
+				loaderVersionsFound[modLoader] = version
+				if (version != pf.versions[modLoader]) {
+					outdatedLoaders.add(modLoader)
+					true // Delete component; cached metadata is invalid and will be re-added
+				} else {
+					false // Already up to date; cached metadata is valid
+				}
+			} else { false } // Not a known loader / MC
+		}
+
+		for ((_, loader) in modLoaders
+			.filter {
+				(!loaderVersionsFound.containsKey(it.value) || outdatedLoaders.contains(it.value)) && pf.versions.containsKey(it.value)
+			}
+		) {
+			manifestModified = true
+			components.add(gson.toJsonTree(
+				hashMapOf("uid" to modLoadersClasses[loader], "version" to pf.versions[loader]))
+			)
+		}
+
+		// If inconsistent Intermediary mappings version is found, delete it - MultiMC will add and re-dl the correct one
+		components.find { it.isJsonObject && it.asJsonObject["uid"]?.asString == "net.fabricmc.intermediary" }?.let {
+			if (it.asJsonObject["version"]?.asString != pf.versions["minecraft"]) {
+				components.remove(it)
+				manifestModified = true
+			}
+		}
+
+		if (manifestModified) {
+			// Sort manifest by component order
+			val sortedComponents = components.sortedWith(nullsLast(compareBy {
+				if (it.isJsonObject) {
+					componentOrders[it.asJsonObject["uid"]?.asString]
+				} else { null }
+			}))
+			components.removeAll { true }
+			sortedComponents.forEach { components.add(it) }
+
+			// The manifest has been modified, so before saving it we'll ask the user
+			// if they wanna update it, continue without updating it, or exit
+			val oldVers = loaderVersionsFound.map { Pair(it.key, it.value) }
+			val newVers = pf.versions.map { Pair(it.key, it.value) }
+
+			when (ui.showUpdateConfirmationDialog(oldVers, newVers)) {
+				IUserInterface.UpdateConfirmationResult.CANCELLED -> {
+					return LauncherStatus.CANCELLED
+				}
+				IUserInterface.UpdateConfirmationResult.CONTINUE -> {
+					return LauncherStatus.SUCCESSFUL
+				}
+				else -> {}
+			}
+
+			manifestPath.nioPath.writeText(gson.toJson(multimcManifest))
+			Log.info("Successfully updated mmc-pack.json based on version metadata")
+
+			return LauncherStatus.SUCCESSFUL
+		}
+
+		return LauncherStatus.NO_CHANGES
+	}
+}

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

@@ -0,0 +1,170 @@
+@file:JvmName("Main")
+
+package link.infra.packwiz.installer
+
+import link.infra.packwiz.installer.target.Side
+import link.infra.packwiz.installer.target.path.HttpUrlPath
+import link.infra.packwiz.installer.target.path.PackwizFilePath
+import link.infra.packwiz.installer.ui.cli.CLIHandler
+import link.infra.packwiz.installer.ui.gui.GUIHandler
+import link.infra.packwiz.installer.ui.wrap
+import link.infra.packwiz.installer.util.Log
+import okhttp3.HttpUrl.Companion.toHttpUrl
+import okio.Path.Companion.toOkioPath
+import okio.Path.Companion.toPath
+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.URI
+import java.nio.file.Paths
+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 packFileRaw = unparsedArgs[0]
+
+		val packFile = when {
+			// HTTP(s) URLs
+			Regex("^https?://", RegexOption.IGNORE_CASE).containsMatchIn(packFileRaw) -> ui.wrap("Invalid HTTP/HTTPS URL for pack file: $packFileRaw") {
+				HttpUrlPath(packFileRaw.toHttpUrl().resolve(".")!!, packFileRaw.toHttpUrl().pathSegments.last())
+			}
+			// File URIs (uses same logic as old packwiz-installer, for backwards compat)
+			Regex("^file:", RegexOption.IGNORE_CASE).containsMatchIn(packFileRaw) -> {
+				ui.wrap("Failed to parse file path for pack file: $packFileRaw") {
+					val path = Paths.get(URI(packFileRaw)).toOkioPath()
+					PackwizFilePath(path.parent ?: ui.showErrorAndExit("Invalid pack file path: $packFileRaw"), path.name)
+				}
+			}
+			// Other URIs (unsupported)
+			Regex("^[a-z][a-z\\d+\\-.]*://", RegexOption.IGNORE_CASE).containsMatchIn(packFileRaw) -> ui.showErrorAndExit("Unsupported scheme for pack file: $packFileRaw")
+			// None of the above matches -> interpret as file path
+			else -> PackwizFilePath(packFileRaw.toPath().parent ?: ui.showErrorAndExit("Invalid pack file path: $packFileRaw"), packFileRaw.toPath().name)
+		}
+		val side = cmd.getOptionValue("side")?.let {
+			Side.from(it) ?: ui.showErrorAndExit("Unknown side name: $it")
+		} ?: Side.CLIENT
+		val packFolder = ui.wrap("Invalid pack folder path") {
+			cmd.getOptionValue("pack-folder")?.let{ PackwizFilePath(it.toPath()) } ?: PackwizFilePath(".".toPath())
+		}
+		val multimcFolder = ui.wrap("Invalid MultiMC folder path") {
+			cmd.getOptionValue("multimc-folder")?.let{ PackwizFilePath(it.toPath()) } ?: PackwizFilePath("..".toPath())
+		}
+		val manifestFile = ui.wrap("Invalid manifest file path") {
+			packFolder / (cmd.getOptionValue("meta-file") ?: "packwiz.json")
+		}
+		val timeout = ui.wrap("Invalid timeout value") {
+			cmd.getOptionValue("timeout")?.toLong() ?: 10
+		}
+
+		// Start update process!
+		try {
+			UpdateManager(UpdateManager.Options(packFile, manifestFile, packFolder, multimcFolder, side, timeout), 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, "multimc-folder", true, "The MultiMC pack folder (defaults to the parent of the pack directory)")
+			options.addOption(null, "meta-file", true, "JSON file to store pack metadata, relative to the pack folder (defaults to packwiz.json)")
+			options.addOption("t", "timeout", true, "Seconds to wait before automatically launching when asking about optional mods (defaults to 10)")
+		}
+
+		// 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!
+		}
+
+		@JvmStatic
+		fun main(args: Array<String>) {
+			Log.info("packwiz-installer was started without packwiz-installer-bootstrap. Use the bootstrapper for automatic updates! (Disregard this message if you have your own update mechanism)")
+			Main(args)
+		}
+	}
+
+	// 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 +1,487 @@
+package link.infra.packwiz.installer
+
+import cc.ekblad.toml.decode
+import com.google.gson.GsonBuilder
+import com.google.gson.JsonIOException
+import com.google.gson.JsonSyntaxException
+import link.infra.packwiz.installer.DownloadTask.Companion.createTasksFromIndex
+import link.infra.packwiz.installer.metadata.DownloadMode
+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.curseforge.resolveCfMetadata
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashFormat
+import link.infra.packwiz.installer.request.RequestException
+import link.infra.packwiz.installer.target.ClientHolder
+import link.infra.packwiz.installer.target.Side
+import link.infra.packwiz.installer.target.path.PackwizFilePath
+import link.infra.packwiz.installer.target.path.PackwizPath
+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 okio.buffer
+import java.io.IOException
+import java.io.InputStreamReader
+import java.nio.charset.StandardCharsets
+import java.nio.file.Files
+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 packFile: PackwizPath<*>,
+		val manifestFile: PackwizFilePath,
+		val packFolder: PackwizFilePath,
+		val multimcFolder: PackwizFilePath,
+		val side: Side,
+		val timeout: Long,
+	)
+
+	// TODO: make this return a value based on results?
+	private fun start() {
+		val clientHolder = ClientHolder()
+		ui.cancelCallback = {
+			clientHolder.close()
+		}
+
+		ui.submitProgress(InstallProgress("Loading manifest file..."))
+		val gson = GsonBuilder()
+			.registerTypeAdapter(Hash::class.java, Hash.TypeHandler())
+			.registerTypeAdapter(PackwizFilePath::class.java, PackwizPath.adapterRelativeTo(opts.packFolder))
+			.enableComplexMapKeySerialization()
+			.create()
+		val manifest = try {
+			// TODO: kotlinx.serialisation?
+			InputStreamReader(opts.manifestFile.source(clientHolder).inputStream(), StandardCharsets.UTF_8).use { reader ->
+				gson.fromJson(reader, ManifestFile::class.java)
+			}
+		} catch (e: RequestException.Response.File.FileNotFound) {
+			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 = opts.packFile.source(clientHolder)
+			HashFormat.SHA256.source(src)
+		} catch (e: Exception) {
+			// TODO: ensure suppressed/caused exceptions are shown?
+			ui.showErrorAndExit("Failed to download pack.toml", e)
+		}
+		val pf = packFileSource.buffer().use {
+			try {
+				PackFile.mapper(opts.packFile).decode<PackFile>(it.inputStream())
+			} catch (e: IllegalStateException) {
+				ui.showErrorAndExit("Failed to parse pack.toml", e)
+			}
+		}
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			handleCancellation()
+		}
+
+		// Launcher checks
+		val lu = LauncherUtils(opts, ui)
+
+		// MultiMC MC and loader version checker
+		ui.submitProgress(InstallProgress("Loading MultiMC pack file..."))
+		try {
+			when (lu.handleMultiMC(pf, gson)) {
+				LauncherUtils.LauncherStatus.CANCELLED -> cancelled = true
+				LauncherUtils.LauncherStatus.NOT_FOUND -> Log.info("MultiMC not detected")
+				else -> {}
+			}
+			handleCancellation()
+		} catch (e: Exception) {
+			ui.showErrorAndExit(e.message!!, e)
+		}
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			handleCancellation()
+		}
+
+		ui.submitProgress(InstallProgress("Checking local files..."))
+
+		// If the side changes, invalidate EVERYTHING (even when the index hasn't changed)
+		val invalidateAll = opts.side != manifest.cachedSide
+		val invalidatedUris: MutableList<PackwizFilePath> = ArrayList()
+		if (!invalidateAll) {
+			// Invalidation checking must be done here, as it must happen before pack/index hashes are checked
+			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 (!file.cachedLocation!!.nioPath.toFile().exists()) {
+							invalid = true
+						}
+					} else {
+						// if cachedLocation == null, should probably be installed!!
+						invalid = true
+					}
+				}
+				if (invalid) {
+					Log.info("File ${fileUri.filename} invalidated, marked for redownloading")
+					invalidatedUris.add(fileUri)
+				}
+			}
+
+			if (manifest.packFileHash?.let { it == packFileSource.hash } == 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, opts.timeout)
+				}
+				if (!ui.optionsButtonPressed) {
+					return
+				}
+			}
+		}
+
+		Log.info("Modpack name: ${pf.name}")
+
+		if (ui.cancelButtonPressed) {
+			showCancellationDialog()
+			handleCancellation()
+		}
+		try {
+			processIndex(
+				pf.index.file,
+				pf.index.hashFormat.fromString(pf.index.hash),
+				pf.index.hashFormat,
+				manifest,
+				invalidatedUris,
+				invalidateAll,
+				clientHolder
+			)
+		} catch (e1: Exception) {
+			ui.showErrorAndExit("Failed to process index file", e1)
+		}
+
+		handleCancellation()
+
+
+		// 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 {
+			Files.newBufferedWriter(opts.manifestFile.nioPath, StandardCharsets.UTF_8).use { writer -> gson.toJson(manifest, writer) }
+		} catch (e: IOException) {
+			ui.showErrorAndExit("Failed to save local manifest file", e)
+		}
+	}
+
+	private fun processIndex(indexUri: PackwizPath<*>, indexHash: Hash<*>, hashFormat: HashFormat<*>, manifest: ManifestFile, invalidatedFiles: List<PackwizFilePath>, invalidateAll: Boolean, clientHolder: ClientHolder) {
+		if (!invalidateAll) {
+			if (manifest.indexFileHash == indexHash && invalidatedFiles.isEmpty()) {
+				ui.submitProgress(InstallProgress("Modpack files are already up to date!", 1, 1))
+				if (manifest.cachedFiles.any { it.value.isOptional }) {
+					ui.awaitOptionalButton(false, opts.timeout)
+				}
+				if (!ui.optionsButtonPressed) {
+					return
+				}
+				if (ui.cancelButtonPressed) {
+					showCancellationDialog()
+					return
+				}
+			}
+		}
+		manifest.indexFileHash = indexHash
+
+		val indexFileSource = try {
+			val src = indexUri.source(clientHolder)
+			hashFormat.source(src)
+		} catch (e: Exception) {
+			ui.showErrorAndExit("Failed to download index file", e)
+		}
+
+		val indexFile = try {
+			IndexFile.mapper(indexUri).decode<IndexFile>(indexFileSource.buffer().inputStream())
+		} catch (e: IllegalStateException) {
+			ui.showErrorAndExit("Failed to parse index file", e)
+		}
+		if (indexHash != indexFileSource.hash) {
+			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..."))
+		val it: MutableIterator<Map.Entry<PackwizFilePath, ManifestFile.File>> = manifest.cachedFiles.entries.iterator()
+		while (it.hasNext()) {
+			val (uri, file) = it.next()
+			if (file.cachedLocation != null) {
+				if (indexFile.files.none { it.file.rebase(opts.packFolder) == uri }) { // File has been removed from the index
+					try {
+						Files.deleteIfExists(file.cachedLocation!!.nioPath)
+					} catch (e: IOException) {
+						Log.warn("Failed to delete file removed from index", e)
+					}
+					Log.info("Deleted ${file.cachedLocation!!.filename} (removed from pack)")
+					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, opts.side)
+		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 (invalidatedFiles.contains(f.metadata.file.rebase(opts.packFolder))) {
+				f.invalidate()
+			}
+			val file = manifest.cachedFiles[f.metadata.file.rebase(opts.packFolder)]
+			// 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(clientHolder) }
+
+		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, opts.timeout)
+				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, clientHolder)) {
+				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, clientHolder)
+				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) {
+						manifest.cachedFiles.putIfAbsent(task.metadata.file.rebase(opts.packFolder), oldFile)
+					} else { null }
+				} else {
+					manifest.cachedFiles.putIfAbsent(task.metadata.file.rebase(opts.packFolder), file)
+				}
+			}
+
+			val exDetails = task.exceptionDetails
+			val progress = if (exDetails != null) {
+				"Failed to download ${exDetails.name}: ${exDetails.exception.message}"
+			} else {
+				when (task.completionStatus) {
+					DownloadTask.CompletionStatus.INCOMPLETE -> "${task.name} pending (you should never see this...)"
+					DownloadTask.CompletionStatus.DOWNLOADED -> "Downloaded ${task.name}"
+					DownloadTask.CompletionStatus.ALREADY_EXISTS_CACHED -> "${task.name} already exists (cached)"
+					DownloadTask.CompletionStatus.ALREADY_EXISTS_VALIDATED -> "${task.name} already exists (validated)"
+					DownloadTask.CompletionStatus.SKIPPED_DISABLED -> "Skipped ${task.name} (disabled)"
+					DownloadTask.CompletionStatus.SKIPPED_WRONG_SIDE -> "Skipped ${task.name} (wrong side)"
+					DownloadTask.CompletionStatus.DELETED_DISABLED -> "Deleted ${task.name} (disabled)"
+					DownloadTask.CompletionStatus.DELETED_WRONG_SIDE -> "Deleted ${task.name} (wrong side)"
+				}
+			}
+			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!)
+				// TODO: close client holder in more places?
+				clientHolder.close()
+				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>, clientHolder: ClientHolder): ResolveResult {
+		ui.submitProgress(InstallProgress("Validating existing files..."))
+
+		// Validate existing files
+		for (downloadTask in nonFailedFirstTasks.filter(DownloadTask::correctSide)) {
+			downloadTask.validateExistingFile(opts.packFolder, clientHolder)
+		}
+
+		// 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 == DownloadMode.CURSEFORGE }.toList()
+		if (cfFiles.isNotEmpty()) {
+			ui.submitProgress(InstallProgress("Resolving CurseForge metadata..."))
+			val resolveFailures = resolveCfMetadata(cfFiles, opts.packFolder, clientHolder)
+			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/DownloadMode.kt

@@ -0,0 +1,19 @@
+package link.infra.packwiz.installer.metadata
+
+import cc.ekblad.toml.model.TomlValue
+import cc.ekblad.toml.tomlMapper
+
+enum class DownloadMode {
+	URL,
+	CURSEFORGE;
+
+	companion object {
+		fun mapper() = tomlMapper {
+			decoder { it: TomlValue.String -> when (it.value) {
+				"", "url" -> URL
+				"metadata:curseforge" -> CURSEFORGE
+				else -> throw Exception("Unsupported download mode ${it.value}")
+			} }
+		}
+	}
+}

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 +1,97 @@
+package link.infra.packwiz.installer.metadata
+
+import cc.ekblad.toml.decode
+import cc.ekblad.toml.tomlMapper
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashFormat
+import link.infra.packwiz.installer.target.ClientHolder
+import link.infra.packwiz.installer.target.path.PackwizPath
+import link.infra.packwiz.installer.util.delegateTransitive
+import okio.Source
+import okio.buffer
+
+data class IndexFile(
+	val hashFormat: HashFormat<*>,
+	val files: List<File> = listOf()
+) {
+	data class File(
+		val file: PackwizPath<*>,
+		private val hashFormat: HashFormat<*>? = null,
+		val hash: String,
+		val alias: PackwizPath<*>?,
+		val metafile: Boolean = false,
+		val preserve: Boolean = false,
+	) {
+		var linkedFile: ModFile? = null
+
+		fun hashFormat(index: IndexFile) = hashFormat ?: index.hashFormat
+		@Throws(Exception::class)
+		fun getHashObj(index: IndexFile): Hash<*> {
+			// TODO: more specific exceptions?
+			return hashFormat(index).fromString(hash)
+		}
+
+		@Throws(Exception::class)
+		fun downloadMeta(index: IndexFile, clientHolder: ClientHolder) {
+			if (!metafile) {
+				return
+			}
+			val fileHash = getHashObj(index)
+			val src = file.source(clientHolder)
+			val fileStream = hashFormat(index).source(src)
+			linkedFile = ModFile.mapper(file).decode<ModFile>(fileStream.buffer().inputStream())
+			if (fileHash != fileStream.hash) {
+				// TODO: propagate details about hash, and show better error!
+				throw Exception("Invalid mod file hash")
+			}
+		}
+
+		@Throws(Exception::class)
+		fun getSource(clientHolder: ClientHolder): Source {
+			return if (metafile) {
+				if (linkedFile == null) {
+					throw Exception("Linked file doesn't exist!")
+				}
+				linkedFile!!.getSource(clientHolder)
+			} else {
+				file.source(clientHolder)
+			}
+		}
+
+		val name: String
+			get() {
+				if (metafile) {
+					return linkedFile?.name ?: file.filename
+				}
+				return file.filename
+			}
+
+		val destURI: PackwizPath<*>
+			get() {
+				if (alias != null) {
+					return alias
+				}
+				return if (metafile) {
+					linkedFile!!.filename
+				} else {
+					file
+				}
+			}
+
+		companion object {
+			fun mapper(base: PackwizPath<*>) = tomlMapper {
+				mapping<File>("hash-format" to "hashFormat")
+				delegateTransitive<HashFormat<*>>(HashFormat.mapper())
+				delegateTransitive<PackwizPath<*>>(PackwizPath.mapperRelativeTo(base))
+			}
+		}
+	}
+
+	companion object {
+		fun mapper(base: PackwizPath<*>) = tomlMapper {
+			mapping<IndexFile>("hash-format" to "hashFormat")
+			delegateTransitive<HashFormat<*>>(HashFormat.mapper())
+			delegateTransitive<File>(File.mapper(base))
+		}
+	}
+}

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
+import link.infra.packwiz.installer.target.path.PackwizFilePath
+
+class ManifestFile {
+	var packFileHash: Hash<*>? = null
+	var indexFileHash: Hash<*>? = null
+	var cachedFiles: MutableMap<PackwizFilePath, File> = HashMap()
+	// If the side changes, EVERYTHING invalidates. FUN!!!
+	var cachedSide = Side.CLIENT
+
+	class File {
+		@Transient
+		var revert: File? = null
+			private set
+
+		var hash: Hash<*>? = null
+		var linkedFileHash: Hash<*>? = null
+		var cachedLocation: PackwizFilePath? = 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 +1,96 @@
+package link.infra.packwiz.installer.metadata
+
+import cc.ekblad.toml.delegate
+import cc.ekblad.toml.model.TomlValue
+import cc.ekblad.toml.tomlMapper
+import link.infra.packwiz.installer.metadata.curseforge.UpdateData
+import link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashFormat
+import link.infra.packwiz.installer.target.ClientHolder
+import link.infra.packwiz.installer.target.Side
+import link.infra.packwiz.installer.target.path.HttpUrlPath
+import link.infra.packwiz.installer.target.path.PackwizPath
+import link.infra.packwiz.installer.util.delegateTransitive
+import okhttp3.HttpUrl.Companion.toHttpUrl
+import okio.Source
+import kotlin.reflect.KType
+
+data class ModFile(
+	val name: String,
+	val filename: PackwizPath<*>,
+	val side: Side = Side.BOTH,
+	val download: Download,
+	val update: Map<String, UpdateData> = mapOf(),
+	val option: Option = Option(false)
+) {
+	data class Download(
+		val url: PackwizPath<*>?,
+		val hashFormat: HashFormat<*>,
+		val hash: String,
+		val mode: DownloadMode = DownloadMode.URL
+	) {
+		companion object {
+			fun mapper() = tomlMapper {
+				decoder<TomlValue.String, PackwizPath<*>> { it -> HttpUrlPath(it.value.toHttpUrl()) }
+				mapping<Download>("hash-format" to "hashFormat")
+
+				delegateTransitive<HashFormat<*>>(HashFormat.mapper())
+				delegate<DownloadMode>(DownloadMode.mapper())
+			}
+		}
+	}
+
+	@Transient
+	val resolvedUpdateData = mutableMapOf<String, PackwizPath<*>>()
+
+	data class Option(
+		val optional: Boolean,
+		val description: String = "",
+		val defaultValue: Boolean = false
+	) {
+		companion object {
+			fun mapper() = tomlMapper {
+				mapping<Option>("default" to "defaultValue")
+			}
+		}
+	}
+
+	@Throws(Exception::class)
+	fun getSource(clientHolder: ClientHolder): Source {
+		return when (download.mode) {
+			DownloadMode.URL -> {
+				(download.url ?: throw Exception("No download URL provided")).source(clientHolder)
+			}
+			DownloadMode.CURSEFORGE -> {
+				if (!resolvedUpdateData.contains("curseforge")) {
+					throw Exception("Metadata file specifies CurseForge mode, but is missing metadata")
+				}
+				return resolvedUpdateData["curseforge"]!!.source(clientHolder)
+			}
+		}
+	}
+
+	@get:Throws(Exception::class)
+	val hash: Hash<*>
+		get() = download.hashFormat.fromString(download.hash)
+
+	companion object {
+		fun mapper(base: PackwizPath<*>) = tomlMapper {
+			delegateTransitive<PackwizPath<*>>(PackwizPath.mapperRelativeTo(base))
+
+			delegateTransitive<Option>(Option.mapper())
+			delegateTransitive<Download>(Download.mapper())
+
+			delegateTransitive<Side>(Side.mapper())
+
+			val updateDataMapper = UpdateData.mapper()
+			decoder { type: KType, it: TomlValue.Map ->
+				if (type.arguments[1].type?.classifier == UpdateData::class) {
+					updateDataMapper.decode<Map<String, UpdateData>>(it)
+				} else {
+					pass()
+				}
+			}
+		}
+	}
+}

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

@@ -0,0 +1,37 @@
+package link.infra.packwiz.installer.metadata
+
+import cc.ekblad.toml.model.TomlValue
+import cc.ekblad.toml.tomlMapper
+import link.infra.packwiz.installer.metadata.hash.HashFormat
+import link.infra.packwiz.installer.target.path.PackwizPath
+import link.infra.packwiz.installer.util.delegateTransitive
+
+data class PackFile(
+	val name: String,
+	val packFormat: PackFormat = PackFormat.DEFAULT,
+	val index: IndexFileLoc,
+	val versions: Map<String, String> = mapOf()
+) {
+	data class IndexFileLoc(
+		val file: PackwizPath<*>,
+		val hashFormat: HashFormat<*>,
+		val hash: String,
+	) {
+		companion object {
+			fun mapper(base: PackwizPath<*>) = tomlMapper {
+				mapping<IndexFileLoc>("hash-format" to "hashFormat")
+				delegateTransitive<PackwizPath<*>>(PackwizPath.mapperRelativeTo(base))
+				delegateTransitive<HashFormat<*>>(HashFormat.mapper())
+			}
+		}
+	}
+
+	companion object {
+		fun mapper(base: PackwizPath<*>) = tomlMapper {
+			mapping<PackFile>("pack-format" to "packFormat")
+			decoder { it: TomlValue.String -> PackFormat(it.value) }
+			encoder { it: PackFormat -> TomlValue.String(it.format) }
+			delegateTransitive<IndexFileLoc>(IndexFileLoc.mapper(base))
+		}
+	}
+}

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

@@ -0,0 +1,10 @@
+package link.infra.packwiz.installer.metadata
+
+@JvmInline
+value class PackFormat(val format: String) {
+	companion object {
+		val DEFAULT = PackFormat("packwiz:1.0.0")
+	}
+
+	// TODO: implement validation, errors for too new / invalid versions
+}

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

@@ -0,0 +1,159 @@
+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.target.ClientHolder
+import link.infra.packwiz.installer.target.path.HttpUrlPath
+import link.infra.packwiz.installer.target.path.PackwizFilePath
+import link.infra.packwiz.installer.ui.data.ExceptionDetails
+import okhttp3.HttpUrl.Companion.toHttpUrl
+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
+import kotlin.io.path.absolute
+
+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: String? = 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)
+
+@Throws(JsonSyntaxException::class, JsonIOException::class)
+fun resolveCfMetadata(mods: List<IndexFile.File>, packFolder: PackwizFilePath, clientHolder: ClientHolder): List<ExceptionDetails> {
+	val failures = mutableListOf<ExceptionDetails>()
+	val fileIdMap = mutableMapOf<Int, List<IndexFile.File>>()
+
+	for (mod in mods) {
+		if (!mod.linkedFile!!.update.contains("curseforge")) {
+			failures.add(ExceptionDetails(mod.linkedFile!!.name, Exception("Failed to resolve CurseForge metadata: no CurseForge update section")))
+			continue
+		}
+		val fileId = (mod.linkedFile!!.update["curseforge"] as CurseForgeUpdateData).fileId
+		fileIdMap[fileId] = (fileIdMap[fileId] ?: listOf()) + 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, List<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] = (manualDownloadMods[file.modId] ?: listOf()) + file.id
+			continue
+		}
+		try {
+			for (indexFile in fileIdMap[file.id]!!) {
+				indexFile.linkedFile!!.resolvedUpdateData["curseforge"] =
+					HttpUrlPath(file.downloadUrl!!.toHttpUrl())
+			}
+		} catch (e: IllegalArgumentException) {
+			failures.add(ExceptionDetails(file.id.toString(),
+				Exception("Failed to parse URL: ${file.downloadUrl} for ID ${file.id}, Project ID ${file.modId}", e)))
+		}
+	}
+
+	// Some file types don't show up in the API at all! (e.g. shaderpacks)
+	// Add unresolved files to manualDownloadMods
+	for ((fileId, indexFiles) in fileIdMap) {
+		for (file in indexFiles) {
+			if (file.linkedFile != null) {
+				if (file.linkedFile!!.resolvedUpdateData["curseforge"] == null) {
+					val projectId = (file.linkedFile!!.update["curseforge"] as CurseForgeUpdateData).projectId
+					manualDownloadMods[projectId] = (manualDownloadMods[projectId] ?: listOf()) + fileId
+				}
+			}
+		}
+	}
+
+	if (manualDownloadMods.isNotEmpty()) {
+		val reqModsData = GetModsRequest(manualDownloadMods.keys.toList())
+		val reqMods = Request.Builder()
+			.url("https://${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
+			}
+
+			for (fileId in manualDownloadMods[mod.id]!!) {
+				if (!fileIdMap.contains(fileId)) {
+					failures.add(ExceptionDetails(mod.name,
+						Exception("Failed to find file from result: file ID $fileId")))
+					continue
+				}
+
+				for (indexFile in fileIdMap[fileId]!!) {
+					var modUrl = "${mod.links?.websiteUrl}/files/${fileId}"
+					failures.add(ExceptionDetails(indexFile.name, Exception("This mod is excluded from the CurseForge API and must be downloaded manually.\n" +
+						"Please go to ${modUrl} and save this file to ${indexFile.destURI.rebase(packFolder).nioPath.absolute()}"), modUrl))
+				}
+			}
+		}
+	}
+
+	return failures
+}

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

@@ -0,0 +1,14 @@
+package link.infra.packwiz.installer.metadata.curseforge
+
+import cc.ekblad.toml.tomlMapper
+
+data class CurseForgeUpdateData(
+	val fileId: Int,
+	val projectId: Int,
+): UpdateData {
+	companion object {
+		fun mapper() = tomlMapper {
+			mapping<CurseForgeUpdateData>("file-id" to "fileId", "project-id" to "projectId")
+		}
+	}
+}

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

@@ -0,0 +1,17 @@
+package link.infra.packwiz.installer.metadata.curseforge
+
+import cc.ekblad.toml.model.TomlValue
+import cc.ekblad.toml.tomlMapper
+
+interface UpdateData {
+	companion object {
+		fun mapper() = tomlMapper {
+			val cfMapper = CurseForgeUpdateData.mapper()
+			decoder { it: TomlValue.Map ->
+				if (it.properties.contains("curseforge")) {
+					mapOf("curseforge" to cfMapper.decode<CurseForgeUpdateData>(it.properties["curseforge"]!!))
+				} else { mapOf() }
+			}
+		}
+	}
+}

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/Hash.kt

@@ -0,0 +1,76 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import com.google.gson.*
+import link.infra.packwiz.installer.metadata.hash.Hash.SourceProvider
+import okio.ByteString
+import okio.ByteString.Companion.decodeHex
+import okio.ForwardingSource
+import okio.HashingSource
+import okio.Source
+import java.lang.reflect.Type
+
+data class Hash<T>(val type: HashFormat<T>, val value: T) {
+	interface Encoding<T> {
+		fun encodeToString(value: T): String
+		fun decodeFromString(str: String): T
+
+		object Hex: Encoding<ByteString> {
+			override fun encodeToString(value: ByteString) = value.hex()
+			override fun decodeFromString(str: String) = str.decodeHex()
+		}
+
+		object UInt: Encoding<kotlin.UInt> {
+			override fun encodeToString(value: kotlin.UInt) = value.toString()
+			override fun decodeFromString(str: String) =
+				try {
+					str.toUInt()
+				} catch (e: NumberFormatException) {
+					// Old packwiz.json values are signed; if they are negative they should be parsed as signed integers
+					// and reinterpreted as unsigned integers
+					str.toInt().toUInt()
+				}
+		}
+	}
+
+	fun interface SourceProvider<T> {
+		fun source(type: HashFormat<T>, delegate: Source): HasherSource<T>
+
+		companion object {
+			fun fromOkio(provider: ((Source) -> HashingSource)): SourceProvider<ByteString> {
+				return SourceProvider { type, delegate ->
+					val delegateHashing = provider.invoke(delegate)
+					object : ForwardingSource(delegateHashing), HasherSource<ByteString> {
+						override val hash: Hash<ByteString> by lazy(LazyThreadSafetyMode.NONE) { Hash(type, delegateHashing.hash) }
+					}
+				}
+			}
+		}
+	}
+
+	class TypeHandler : JsonDeserializer<Hash<*>>, JsonSerializer<Hash<*>> {
+		override fun serialize(src: Hash<*>, typeOfSrc: Type, context: JsonSerializationContext): JsonElement = JsonObject().apply {
+			add("type", JsonPrimitive(src.type.formatName))
+			// Local function for generics
+			fun <T> addValue(src: Hash<T>) = add("value", JsonPrimitive(src.type.encodeToString(src.value)))
+			addValue(src)
+		}
+
+		@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 {
+				(HashFormat.fromName(type) ?: throw JsonParseException("Unknown hash type $type")).fromString(value)
+			} catch (e: Exception) {
+				throw JsonParseException("Failed to create hash object", e)
+			}
+		}
+	}
+}

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

@@ -0,0 +1,39 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import cc.ekblad.toml.model.TomlValue
+import cc.ekblad.toml.tomlMapper
+import link.infra.packwiz.installer.metadata.hash.Hash.Encoding
+import link.infra.packwiz.installer.metadata.hash.Hash.SourceProvider
+import link.infra.packwiz.installer.metadata.hash.Hash.SourceProvider.Companion.fromOkio
+import okio.ByteString
+import okio.Source
+import okio.HashingSource.Companion as OkHashes
+
+sealed class HashFormat<T>(val formatName: String): Encoding<T>, SourceProvider<T> {
+	object SHA1: HashFormat<ByteString>("sha1"),
+		Encoding<ByteString> by Encoding.Hex, SourceProvider<ByteString> by fromOkio(OkHashes::sha1)
+	object SHA256: HashFormat<ByteString>("sha256"),
+		Encoding<ByteString> by Encoding.Hex, SourceProvider<ByteString> by fromOkio(OkHashes::sha256)
+	object SHA512: HashFormat<ByteString>("sha512"),
+		Encoding<ByteString> by Encoding.Hex, SourceProvider<ByteString> by fromOkio(OkHashes::sha512)
+	object MD5: HashFormat<ByteString>("md5"),
+		Encoding<ByteString> by Encoding.Hex, SourceProvider<ByteString> by fromOkio(OkHashes::md5)
+	object MURMUR2: HashFormat<UInt>("murmur2"),
+		Encoding<UInt> by Encoding.UInt, SourceProvider<UInt> by SourceProvider(::Murmur2HasherSource)
+
+	fun source(delegate: Source): HasherSource<T> = source(this, delegate)
+	fun fromString(str: String) = Hash(this, decodeFromString(str))
+	override fun toString() = formatName
+
+	companion object {
+		// lazy used to prevent initialisation issues!
+		private val values by lazy { listOf(SHA1, SHA256, SHA512, MD5, MURMUR2) }
+		fun fromName(formatName: String) = values.find { formatName == it.formatName }
+
+		fun mapper() = tomlMapper {
+			// TODO: better exception?
+			decoder { it: TomlValue.String -> fromName(it.value) ?: throw Exception("Hash format ${it.value} not supported") }
+			encoder { it: HashFormat<*> -> TomlValue.String(it.formatName) }
+		}
+	}
+}

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

@@ -0,0 +1,7 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import okio.Source
+
+interface HasherSource<T>: Source {
+	val hash: Hash<T>
+}

src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Murmur2HasherSource.kt

@@ -0,0 +1,43 @@
+package link.infra.packwiz.installer.metadata.hash
+
+import okio.Buffer
+import okio.ForwardingSource
+import okio.Source
+import java.io.IOException
+
+class Murmur2HasherSource(type: HashFormat<UInt>, delegate: Source) : ForwardingSource(delegate), HasherSource<UInt> {
+	private val internalBuffer = Buffer()
+	private val tempBuffer = Buffer()
+
+	override val hash: Hash<UInt> by lazy(LazyThreadSafetyMode.NONE) {
+		// TODO: remove internal buffering?
+		val data = internalBuffer.readByteArray()
+		Hash(type, Murmur2Lib.hash32(data, data.size, 1).toUInt())
+	}
+
+	@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 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)
+	}
+}

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

@@ -0,0 +1,67 @@
+package link.infra.packwiz.installer.request
+
+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)
+
+		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", 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 res: okhttp3.Response
+
+			constructor(req: okhttp3.Request, res: okhttp3.Response, message: String, cause: Throwable) : super("Failed to make HTTP request to ${req.url}: $message", cause) {
+				this.res = res
+			}
+			constructor(req: okhttp3.Request, res: okhttp3.Response, message: String) : super("Failed to make HTTP request to ${req.url}: $message") {
+				this.res = res
+			}
+
+			class ErrorCode(req: okhttp3.Request, res: okhttp3.Response): HTTP(req, 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/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 +1,57 @@
+package link.infra.packwiz.installer.target
+
+import link.infra.packwiz.installer.util.Log
+import okhttp3.OkHttpClient
+import okhttp3.Response
+import okio.FileSystem
+import java.net.SocketTimeoutException
+import java.util.concurrent.TimeUnit
+
+class ClientHolder {
+	// Tries 10s timeouts (default), then 15s timeouts, then 60s timeouts
+	private val retryTimes = arrayOf(15, 60)
+
+	// TODO: a button to increase timeouts temporarily when retrying? manual retry button?
+	val okHttpClient by lazy { OkHttpClient.Builder()
+		// Retry requests according to retryTimes list
+		.addInterceptor {
+			val req = it.request()
+
+			var lastException: SocketTimeoutException? = null
+			var res: Response? = null
+
+			try {
+				res = it.proceed(req)
+			} catch (e: SocketTimeoutException) {
+				lastException = e
+			}
+
+			var tryCount = 0
+			while (res == null && tryCount < retryTimes.size) {
+				Log.info("OkHttp connection to ${req.url} timed out; retrying... (${tryCount + 1}/${retryTimes.size})")
+
+				val longerTimeoutChain = it
+					.withConnectTimeout(retryTimes[tryCount], TimeUnit.SECONDS)
+					.withReadTimeout(retryTimes[tryCount], TimeUnit.SECONDS)
+					.withWriteTimeout(retryTimes[tryCount], TimeUnit.SECONDS)
+				try {
+					res = longerTimeoutChain.proceed(req)
+				} catch (e: SocketTimeoutException) {
+					lastException = e
+				}
+
+				tryCount++
+			}
+
+			res ?: throw lastException!!
+		}
+		.build() }
+
+	val fileSystem = FileSystem.SYSTEM
+
+	fun close() {
+		okHttpClient.dispatcher.cancelAll()
+		okHttpClient.dispatcher.executorService.shutdown()
+		okHttpClient.connectionPool.evictAll()
+	}
+}

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 +1,48 @@
+package link.infra.packwiz.installer.target
+
+import cc.ekblad.toml.model.TomlValue
+import cc.ekblad.toml.tomlMapper
+import com.google.gson.annotations.SerializedName
+
+enum class Side(sideName: String) {
+	@SerializedName("client")
+	CLIENT("client"),
+	@SerializedName("server")
+	SERVER("server"),
+	@SerializedName("both")
+	@Suppress("unused")
+	BOTH("both") {
+		override fun hasSide(tSide: Side): Boolean {
+			return true
+		}
+	};
+
+	private val sideName: String
+
+	init {
+		this.sideName = sideName.lowercase()
+	}
+
+	override fun toString() = sideName
+
+	open fun hasSide(tSide: Side): Boolean {
+		return this == tSide || tSide == BOTH
+	}
+
+	companion object {
+		fun from(name: String): Side? {
+			val lowerName = name.lowercase()
+			for (side in values()) {
+				if (side.sideName == lowerName) {
+					return side
+				}
+			}
+			return null
+		}
+
+		fun mapper() = tomlMapper {
+			encoder { it: Side -> TomlValue.String(it.sideName) }
+			decoder { it: TomlValue.String -> from(it.value) ?: throw Exception("Invalid side name ${it.value}") }
+		}
+	}
+}

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: PackwizPath<*>): IdentityToken
+
+	val ident: IdentityToken
+		get() = PathIdentityToken(dest) // TODO: should use local-rebased path?
+
+	/**
+	 * A user-friendly name; defaults to the destination path of the file.
+	 */
+	val name: String
+		get() = dest.filename
+	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/HttpUrlPath.kt

@@ -0,0 +1,69 @@
+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
+
+class HttpUrlPath(private val url: HttpUrl, path: String? = null): PackwizPath<HttpUrlPath>(path) {
+	private fun build() = if (path == null) { url } else { url.newBuilder().addPathSegments(path).build() }
+
+	@Throws(RequestException::class)
+	override fun source(clientHolder: ClientHolder): BufferedSource {
+		val req = Request.Builder()
+			.url(build())
+			.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(req, 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)
+		}
+	}
+
+	override fun construct(path: String): HttpUrlPath = HttpUrlPath(url, path)
+
+	override val folder: Boolean
+		get() = pathFolder ?: (url.pathSegments.last() == "")
+	override val filename: String
+		get() = pathFilename ?: url.pathSegments.last()
+
+	override fun equals(other: Any?): Boolean {
+		if (this === other) return true
+		if (javaClass != other?.javaClass) return false
+		if (!super.equals(other)) return false
+
+		other as HttpUrlPath
+
+		if (url != other.url) return false
+
+		return true
+	}
+
+	override fun hashCode(): Int {
+		var result = super.hashCode()
+		result = 31 * result + url.hashCode()
+		return result
+	}
+
+	override fun toString() = build().toString()
+}

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

@@ -0,0 +1,51 @@
+package link.infra.packwiz.installer.target.path
+
+import link.infra.packwiz.installer.request.RequestException
+import link.infra.packwiz.installer.target.ClientHolder
+import okio.*
+
+class PackwizFilePath(private val base: Path, path: String? = null): PackwizPath<PackwizFilePath>(path) {
+	@Throws(RequestException::class)
+	override fun source(clientHolder: ClientHolder): BufferedSource {
+		val resolved = if (path == null) { base } else { this.base.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)
+		}
+	}
+
+	val nioPath: java.nio.file.Path get() {
+		val resolved = if (path == null) { base } else { this.base.resolve(path, true) }
+		return resolved.toNioPath()
+	}
+
+	override fun construct(path: String): PackwizFilePath = PackwizFilePath(base, path)
+
+	override val folder: Boolean
+		get() = pathFolder ?: (base.segments.last() == "")
+	override val filename: String
+		get() = pathFilename ?: base.segments.last()
+
+	override fun equals(other: Any?): Boolean {
+		if (this === other) return true
+		if (javaClass != other?.javaClass) return false
+		if (!super.equals(other)) return false
+
+		other as PackwizFilePath
+
+		if (base != other.base) return false
+
+		return true
+	}
+
+	override fun hashCode(): Int {
+		var result = super.hashCode()
+		result = 31 * result + base.hashCode()
+		return result
+	}
+
+	override fun toString() = nioPath.toString()
+}

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

@@ -0,0 +1,128 @@
+package link.infra.packwiz.installer.target.path
+
+import cc.ekblad.toml.model.TomlValue
+import cc.ekblad.toml.tomlMapper
+import com.google.gson.TypeAdapter
+import com.google.gson.stream.JsonReader
+import com.google.gson.stream.JsonWriter
+import link.infra.packwiz.installer.request.RequestException
+import link.infra.packwiz.installer.target.ClientHolder
+import okio.BufferedSource
+
+abstract class PackwizPath<T: PackwizPath<T>>(path: String? = null) {
+	protected val path: String?
+
+	init {
+		if (path != null) {
+			// 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.length == 2) {
+						if (componentNorm[0] in 'a'..'z' || componentNorm[0] in 'A'..'Z') {
+							if (componentNorm[1] == ':') {
+								throw RequestException.Validation.PathContainsVolumeLetter(path)
+							}
+						}
+					}
+				}
+			}
+
+			if (canonicalised.isEmpty()) {
+				this.path = null
+			} else {
+				// Join path
+				this.path = canonicalised.asReversed().joinToString("/")
+			}
+		} else {
+			this.path = null
+		}
+	}
+
+	protected abstract fun construct(path: String): T
+
+	protected val pathFolder: Boolean? get() = path?.endsWith("/")
+	abstract val folder: Boolean
+	protected val pathFilename: String? get() = path?.split("/")?.last()
+	abstract val filename: String
+
+	fun resolve(path: String): T {
+		return if (path.startsWith('/') || path.startsWith('\\')) {
+			// Absolute (but still relative to base of pack)
+			construct(path)
+		} else if (folder) {
+			// File in folder; append
+			construct((this.path ?: "") + path)
+		} else {
+			// File in parent folder; append with parent component
+			construct((this.path ?: "") + "/../" + path)
+		}
+	}
+
+	operator fun div(path: String) = resolve(path)
+
+	fun <U: PackwizPath<U>> rebase(path: U) = path.resolve(this.path ?: "")
+
+	val parent: T get() = resolve(if (folder) { ".." } else { "." })
+
+	/**
+	 * Obtain a BufferedSource for this path
+	 * @throws RequestException When resolving the file failed
+	 */
+	@Throws(RequestException::class)
+	abstract fun source(clientHolder: ClientHolder): BufferedSource
+
+	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
+
+		return true
+	}
+
+	override fun hashCode() = path.hashCode()
+
+	companion object {
+		fun mapperRelativeTo(base: PackwizPath<*>) = tomlMapper {
+			encoder { it: PackwizPath<*> -> TomlValue.String(it.path ?: "") }
+			decoder { it: TomlValue.String -> base.resolve(it.value) }
+		}
+
+		fun <T: PackwizPath<T>> adapterRelativeTo(base: T) = object : TypeAdapter<T>() {
+			override fun write(writer: JsonWriter, value: T?) {
+				writer.value(value?.path)
+			}
+			override fun read(reader: JsonReader) = base.resolve(reader.nextString())
+		}
+	}
+
+	override fun toString() = "(Unknown 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 link.infra.packwiz.installer.metadata.hash.Hash
+import link.infra.packwiz.installer.metadata.hash.HashFormat
+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
+
+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: HashFormat<*>? = null
+			var hash: String? = null
+		}
+
+		var versions: Map<String, String>? = null
+	}
+
+	private val internalResult by lazy {
+		// TODO: query, parse JSON
+		val packFile = PackFile()
+			//Toml().read(InputStreamReader(path.source(ctx.clients).inputStream(), "UTF-8")).to(PackFile::class.java)
+
+		val hashFormat = (packFile.index?.hashFormat ?: throw RuntimeException("Hash format required"))
+		val resolved = PackwizV1PackFile(
+			packFile.name ?: throw RuntimeException("Name required"), // TODO: better exception handling
+			path.resolve(packFile.index?.file ?: throw RuntimeException("File required")),
+			hashFormat.fromString(packFile.index?.hash ?: throw RuntimeException("Hash required"))
+		)
+		val hash = hashFormat.fromString("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 +1,59 @@
+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 showUpdateConfirmationDialog(oldVersions: List<Pair<String, String?>>, newVersions: List<Pair<String, String?>>): UpdateConfirmationResult {
+		// Always update metadata when using the CLI
+		return UpdateConfirmationResult.UPDATE
+	}
+
+	fun awaitOptionalButton(showCancel: Boolean, timeout: Long)
+
+	enum class ExceptionListResult {
+		CONTINUE, CANCEL, IGNORE
+	}
+
+	enum class CancellationResult {
+		QUIT, CONTINUE
+	}
+
+	enum class UpdateConfirmationResult {
+		CANCELLED, CONTINUE, UPDATE
+	}
+
+	var optionsButtonPressed: Boolean
+	var cancelButtonPressed: Boolean
+	var cancelCallback: (() -> Unit)?
+
+	var firstInstall: Boolean
+
+}
+
+inline fun <T> IUserInterface.wrap(message: String, inner: () -> T): T {
+	return try {
+		inner.invoke()
+	} catch (e: Exception) {
+		showErrorAndExit(message, e)
+	}
+}

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

@@ -0,0 +1,69 @@
+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
+	// TODO: treat ctrl+c as cancel?
+	@Volatile
+	override var cancelButtonPressed = false
+	@Volatile
+	override var cancelCallback: (() -> Unit)? = null
+	@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, timeout: Long) {
+		// Do nothing
+	}
+}

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

@@ -0,0 +1,7 @@
+package link.infra.packwiz.installer.ui.data
+
+data class ExceptionDetails(
+		val name: String,
+		val exception: Exception,
+		val modUrl: String? = null
+)

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 +1,177 @@
+package link.infra.packwiz.installer.ui.gui
+
+import link.infra.packwiz.installer.util.Log
+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
+	}
+
+	private fun openUrl(url: String) {
+		try {
+			if (Desktop.isDesktopSupported() && Desktop.getDesktop().isSupported(Desktop.Action.BROWSE)) {
+				Desktop.getDesktop().browse(URI(url))
+			} else {
+				val process = Runtime.getRuntime().exec(arrayOf("xdg-open", url));
+				val exitValue = process.waitFor()
+				if (exitValue > 0) {
+					Log.warn("Failed to open $url: xdg-open exited with code $exitValue")
+				}
+			}
+		} catch (e: IOException) {
+			Log.warn("Failed to open $url", e)
+		} catch (e: URISyntaxException) {
+			Log.warn("Failed to open $url", e)
+		}
+	}
+
+	/**
+	 * 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()
+						}
+					})
+
+					val missingMods = eList.filter { it.modUrl != null }.map { it.modUrl!! }.toSet()
+
+					if (!missingMods.isEmpty()) {
+						add(JButton("Open missing mods").apply {
+							toolTipText = "Open missing mods in your browser"
+							addActionListener {
+								missingMods.forEach {
+									openUrl(it)
+								}
+							}
+						})
+					}
+				}, 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 {
+						addActionListener {
+							openUrl("https://github.com/packwiz/packwiz-installer/issues/new")
+						}
+					})
+				}, 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 +1,251 @@
+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.Timer
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.CountDownLatch
+import javax.swing.JDialog
+import javax.swing.JOptionPane
+import javax.swing.UIManager
+import kotlin.concurrent.timer
+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
+			cancelCallback?.invoke()
+		}
+	@Volatile
+	override var cancelCallback: (() -> Unit)? = null
+	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 showUpdateConfirmationDialog(oldVersions: List<Pair<String, String?>>, newVersions: List<Pair<String, String?>>): IUserInterface.UpdateConfirmationResult {
+		assert(newVersions.isNotEmpty())
+		val future = CompletableFuture<IUserInterface.UpdateConfirmationResult>()
+		EventQueue.invokeLater {
+			val oldVersIndex = oldVersions.map { it.first to it.second }.toMap()
+			val newVersIndex = newVersions.map { it.first to it.second }.toMap()
+			val message = StringBuilder()
+			message.append("<html>" +
+					"This modpack uses newer versions of the following:<br>" +
+					"<ul>")
+
+			for (oldVer in oldVersions) {
+				val correspondingNewVer = newVersIndex[oldVer.first]
+				message.append("<li>")
+				message.append(oldVer.first.replaceFirstChar { it.uppercase() })
+				message.append(": <font color=${if (oldVer.second != correspondingNewVer) "#ff0000" else "#000000"}>")
+				message.append(oldVer.second ?: "Not found")
+				message.append("</font></li>")
+			}
+			message.append("</ul>")
+
+			message.append("New versions:" +
+					"<ul>")
+			for (newVer in newVersions) {
+				val correspondingOldVer = oldVersIndex[newVer.first]
+				message.append("<li>")
+				message.append(newVer.first.replaceFirstChar { it.uppercase() })
+				message.append(": <font color=${if (newVer.second != correspondingOldVer) "#00ff00" else "#000000"}>")
+				message.append(newVer.second ?: "Not found")
+				message.append("</font></li>")
+			}
+			message.append("</ul><br>" +
+					"Would you like to update the versions, launch without updating, or cancel the launch?")
+
+
+			val options = arrayOf("Cancel", "Continue anyways", "Update")
+			val result = JOptionPane.showOptionDialog(frmPackwizlauncher, message,
+					"Updating MultiMC versions",
+					JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options[2])
+			future.complete(
+				when (result) {
+					JOptionPane.CLOSED_OPTION, 0 -> IUserInterface.UpdateConfirmationResult.CANCELLED
+					1 -> IUserInterface.UpdateConfirmationResult.CONTINUE
+					2 -> IUserInterface.UpdateConfirmationResult.UPDATE
+					else -> IUserInterface.UpdateConfirmationResult.CANCELLED
+				}
+			)
+		}
+		return future.get()
+	}
+
+	override fun awaitOptionalButton(showCancel: Boolean, timeout: Long) {
+		EventQueue.invokeAndWait {
+			frmPackwizlauncher.showOk(!showCancel)
+		}
+		visibleCountdownLatch.await()
+
+		var closeTimer: Timer? = null
+		if (timeout >= 0) {
+			var count = 0
+			closeTimer = timer("timeout", true, 0, 1000) {
+				if (count >= timeout) {
+					optionalSelectedLatch.countDown()
+					cancel()
+				} else {
+					frmPackwizlauncher.timeoutOk(timeout - count)
+					count += 1
+				}
+			};
+		}
+
+		optionalSelectedLatch.await()
+		closeTimer?.cancel()
+		EventQueue.invokeLater {
+			frmPackwizlauncher.hideOk()
+		}
+	}
+}

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

@@ -0,0 +1,128 @@
+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()
+	}
+
+	fun timeoutOk(remaining: Long) {
+		btnOk.text = "Continue ($remaining)"
+	}
+}

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/4KDelegation.kt

@@ -0,0 +1,10 @@
+package link.infra.packwiz.installer.util
+
+import cc.ekblad.toml.TomlMapper
+import cc.ekblad.toml.configuration.TomlMapperConfigurator
+import cc.ekblad.toml.model.TomlValue
+
+inline fun <reified T: Any> TomlMapperConfigurator.delegateTransitive(mapper: TomlMapper) {
+	decoder { it: TomlValue -> mapper.decode<T>(it) }
+	encoder { it: T -> mapper.encode(it) }
+}

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()
+	}
+}

src/main/proguard.txt

@@ -0,0 +1,19 @@
+-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.**
+
+-keep class !link.infra.packwiz.installer.deps.**,link.infra.packwiz.installer.** { *; }
+
+-keep class com.google.gson.reflect.TypeToken { *; }
+-keep class * extends com.google.gson.reflect.TypeToken
+
+-keep @interface kotlin.Metadata { *; }
+
+-renamesourcefileattribute SourceFile
+-keepattributes *Annotation*,SourceFile,LineNumberTable,Signature

src/main/resources/META-INF/LICENSES.md

@@ -0,0 +1,264 @@
+# Licenses
+
+packwiz-installer itself is under the MIT license ([Source](https://github.com/packwiz/packwiz-installer)), except for Murmur2Lib and bundled dependencies as follows:
+
+- Murmur2Lib: Apache 2.0 ([Source](https://github.com/prasanthj/hasher/blob/master/src/main/java/hasher/Murmur2.java))
+  - Copyright 2014 Prasanth Jayachandran
+- Google Gson 2.9.0: Apache 2.0 ([Source](https://github.com/google/gson))
+  - Copyright 2008 Google Inc.
+- Okio 3.1.0: Apache 2.0 ([Source](https://github.com/square/okio/))
+  - Copyright 2013 Square, Inc.
+- Commons CLI 1.5: Apache 2.0 ([Source](http://commons.apache.org/proper/commons-cli/))
+- Jetbrains Annotations 13.0: Apache 2.0 ([Source](https://github.com/JetBrains/java-annotations))
+  - Copyright 2000-2016 JetBrains s.r.o.
+- Kotlin Standard Library 1.7.10: Apache 2.0 ([Source](https://github.com/JetBrains/kotlin))
+  - Copyright 2010-2020 JetBrains s.r.o and respective authors and developers
+- 4koma 1.1.0: MIT ([Source](https://github.com/valderman/4koma))
+  - Copyright (c) 2021 Anton Ekblad
+
+## Associated notices
+
+### Commons CLI
+Apache Commons CLI
+Copyright 2001-2017 The Apache Software Foundation
+
+This product includes software developed at
+The Apache Software Foundation (http://www.apache.org/).
+
+## Full license texts
+
+### MIT
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+### Apache 2.0
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
+
+   "Licensor" shall mean the copyright owner or entity authorized by
+   the copyright owner that is granting the License.
+
+   "Legal Entity" shall mean the union of the acting entity and all
+   other entities that control, are controlled by, or are under common
+   control with that entity. For the purposes of this definition,
+   "control" means (i) the power, direct or indirect, to cause the
+   direction or management of such entity, whether by contract or
+   otherwise, or (ii) ownership of fifty percent (50%) or more of the
+   outstanding shares, or (iii) beneficial ownership of such entity.
+
+   "You" (or "Your") shall mean an individual or Legal Entity
+   exercising permissions granted by this License.
+
+   "Source" form shall mean the preferred form for making modifications,
+   including but not limited to software source code, documentation
+   source, and configuration files.
+
+   "Object" form shall mean any form resulting from mechanical
+   transformation or translation of a Source form, including but
+   not limited to compiled object code, generated documentation,
+   and conversions to other media types.
+
+   "Work" shall mean the work of authorship, whether in Source or
+   Object form, made available under the License, as indicated by a
+   copyright notice that is included in or attached to the work
+   (an example is provided in the Appendix below).
+
+   "Derivative Works" shall mean any work, whether in Source or Object
+   form, that is based on (or derived from) the Work and for which the
+   editorial revisions, annotations, elaborations, or other modifications
+   represent, as a whole, an original work of authorship. For the purposes
+   of this License, Derivative Works shall not include works that remain
+   separable from, or merely link (or bind by name) to the interfaces of,
+   the Work and Derivative Works thereof.
+
+   "Contribution" shall mean any work of authorship, including
+   the original version of the Work and any modifications or additions
+   to that Work or Derivative Works thereof, that is intentionally
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+
+4. Redistribution. You may reproduce and distribute copies of the
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+
+   (a) You must give any other recipients of the Work or
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+
+   (b) You must cause any modified files to carry prominent notices
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+   (c) You must retain, in the Source form of any Derivative Works
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+   (d) If the Work includes a "NOTICE" text file as part of its
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