Check for cachedFiles existing

.vscode/settings.json

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

build.gradle

@@ -7,7 +7,11 @@ plugins {
 
 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 {
@@ -26,9 +30,19 @@ jar {
     }
 }
 
-// Commons CLI is already included in packwiz-installer-bootstrap
+// 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

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

@@ -1,99 +0,0 @@
-package link.infra.packwiz.installer;
-
-import java.awt.BorderLayout;
-import java.awt.Component;
-import java.awt.EventQueue;
-import java.awt.GridBagConstraints;
-import java.awt.GridBagLayout;
-
-import javax.swing.JButton;
-import javax.swing.JFrame;
-import javax.swing.JLabel;
-import javax.swing.JPanel;
-import javax.swing.JProgressBar;
-import javax.swing.UIManager;
-import javax.swing.border.EmptyBorder;
-import java.awt.event.ActionListener;
-import java.awt.event.ActionEvent;
-
-public class InstallWindow {
-	
-	// TODO: move to seperate file, make usable without GUI
-
-	private JFrame frmPackwizlauncher;
-	private UpdateManager updateManager = new UpdateManager();
-
-	/**
-	 * Launch the application.
-	 */
-	public static void main(String[] args) {
-		EventQueue.invokeLater(new Runnable() {
-			public void run() {
-				try {
-					UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-					InstallWindow window = new InstallWindow();
-					window.frmPackwizlauncher.setVisible(true);
-				} catch (Exception e) {
-					e.printStackTrace();
-				}
-			}
-		});
-	}
-
-	/**
-	 * Create the application.
-	 */
-	public InstallWindow() {
-		initialize();
-	}
-
-	/**
-	 * Initialize the contents of the frame.
-	 */
-	private void initialize() {
-		frmPackwizlauncher = new JFrame();
-		frmPackwizlauncher.setTitle("Updating modpack...");
-		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));
-		
-		JProgressBar progressBar = new JProgressBar();
-		progressBar.setValue(50);
-		panel.add(progressBar, BorderLayout.CENTER);
-		
-		JLabel 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) {
-				updateManager.cleanup();
-				frmPackwizlauncher.dispose();
-			}
-		});
-		btnCancel.setAlignmentX(Component.CENTER_ALIGNMENT);
-		GridBagConstraints gbc_btnCancel = new GridBagConstraints();
-		gbc_btnCancel.gridx = 0;
-		gbc_btnCancel.gridy = 1;
-		panel_1.add(btnCancel, gbc_btnCancel);
-	}
-
-}

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

@@ -1,5 +1,10 @@
 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;
 
@@ -9,11 +14,40 @@ 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);
@@ -33,21 +67,93 @@ public class Main {
 			System.exit(1);
 		}
 
-		System.out.println("Hello World!");
+		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("w", "welp", false, "Testing 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");
+		options.addOption("h", "help", false, "Display this message"); // Implemented in packwiz-installer-bootstrap!
 	}
 	
 }

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

@@ -1,9 +1,427 @@
 package link.infra.packwiz.installer;
 
-public class UpdateManager {
+import java.io.FileNotFoundException;
-	Thread updateThread = new Thread(new UpdateThread());
+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;
 
-	public void cleanup() {
+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;
+		}
+
+		ui.submitProgress(new InstallProgress("Checking local files..."));
+
+		List<URI> invalidatedUris = new ArrayList<>();
+		if (manifest.cachedFiles != null) {
+			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) {
+					if (!Files.exists(Paths.get(opts.packFolder, entry.getValue().cachedLocation))) {
+						URI fileUri = entry.getKey();
+						System.out.println("File " + fileUri.toString() + " invalidated, marked for redownloading");
+						invalidatedUris.add(fileUri);
+					}
+				}
+			}
+		}
+
+		if (manifest.packFileHash != null && packFileSource.hashIsEqual(manifest.packFileHash) && invalidatedUris.size() == 0) {
+			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, invalidatedUris);
+		} 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, List<URI> invalidatedUris) {
+		if (manifest.indexFileHash != null && manifest.indexFileHash.equals(indexHash) && invalidatedUris.size() == 0) {
+			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..."));
+		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) {
+				if (!indexFile.files.stream().anyMatch(f -> f.file.equals(entry.getKey()))) {
+					// File has been removed from the index
+					try {
+						Files.deleteIfExists(Paths.get(opts.packFolder, entry.getValue().cachedLocation));
+					} catch (IOException e) {
+						// TODO: should this be shown to the user in some way?
+						e.printStackTrace();
+					}
+					it.remove();
+				}
+			}
+		}
+		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/UpdateThread.java

@@ -1,10 +0,0 @@
-package link.infra.packwiz.installer;
-
-public class UpdateThread implements Runnable {
-
-	@Override
-	public void run() {
-		
-	}
-
-}

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

@@ -0,0 +1,108 @@
+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

@@ -0,0 +1,21 @@
+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

@@ -0,0 +1,74 @@
+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

@@ -0,0 +1,24 @@
+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

@@ -0,0 +1,31 @@
+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

@@ -0,0 +1,18 @@
+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

@@ -0,0 +1,48 @@
+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

@@ -0,0 +1,29 @@
+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

@@ -0,0 +1,86 @@
+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

@@ -0,0 +1,8 @@
+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

@@ -0,0 +1,104 @@
+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

@@ -0,0 +1,166 @@
+// Obtained from https://github.com/prasanthj/hasher/blob/master/src/main/java/hasher/Murmur2.java
+/**
+ *   Copyright 2014 Prasanth Jayachandran
+ *
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package link.infra.packwiz.installer.metadata.hash;
+
+/**
+ * Murmur2 32 and 64 bit variants.
+ * 32-bit Java port of https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash2.cpp#37
+ * 64-bit Java port of https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash2.cpp#96
+ */
+public class Murmur2Lib {
+  // Constants for 32-bit variant
+  private static final int M_32 = 0x5bd1e995;
+  private static final int R_32 = 24;
+
+  // Constants for 64-bit variant
+  private static final long M_64 = 0xc6a4a7935bd1e995L;
+  private static final int R_64 = 47;
+  private static final int DEFAULT_SEED = 0;
+
+  /**
+   * Murmur2 32-bit variant.
+   *
+   * @param data - input byte array
+   * @return - hashcode
+   */
+  public static int hash32(byte[] data) {
+    return hash32(data, data.length, DEFAULT_SEED);
+  }
+
+  /**
+   * Murmur2 32-bit variant.
+   *
+   * @param data   - input byte array
+   * @param length - length of array
+   * @param seed   - seed. (default 0)
+   * @return - hashcode
+   */
+  public static int hash32(byte[] data, int length, int seed) {
+    int h = seed ^ length;
+    int len_4 = length >> 2;
+
+    // body
+    for (int i = 0; i < len_4; i++) {
+      int i_4 = i << 2;
+      int k = (data[i_4] & 0xff)
+          | ((data[i_4 + 1] & 0xff) << 8)
+          | ((data[i_4 + 2] & 0xff) << 16)
+          | ((data[i_4 + 3] & 0xff) << 24);
+
+      // mix functions
+      k *= M_32;
+      k ^= k >>> R_32;
+      k *= M_32;
+      h *= M_32;
+      h ^= k;
+    }
+
+    // tail
+    int len_m = len_4 << 2;
+    int left = length - len_m;
+    if (left != 0) {
+      if (left >= 3) {
+        h ^= (int) data[length - 3] << 16;
+      }
+      if (left >= 2) {
+        h ^= (int) data[length - 2] << 8;
+      }
+      if (left >= 1) {
+        h ^= (int) data[length - 1];
+      }
+
+      h *= M_32;
+    }
+
+    // finalization
+    h ^= h >>> 13;
+    h *= M_32;
+    h ^= h >>> 15;
+
+    return h;
+  }
+
+  /**
+   * Murmur2 64-bit variant.
+   *
+   * @param data - input byte array
+   * @return - hashcode
+   */
+  public static long hash64(final byte[] data) {
+    return hash64(data, data.length, DEFAULT_SEED);
+  }
+
+  /**
+   * Murmur2 64-bit variant.
+   *
+   * @param data   - input byte array
+   * @param length - length of array
+   * @param seed   - seed. (default 0)
+   * @return - hashcode
+   */
+  public static long hash64(final byte[] data, int length, int seed) {
+    long h = (seed & 0xffffffffl) ^ (length * M_64);
+    int length8 = length >> 3;
+
+    // body
+    for (int i = 0; i < length8; i++) {
+      final int i8 = i << 3;
+      long k = ((long) data[i8] & 0xff)
+          | (((long) data[i8 + 1] & 0xff) << 8)
+          | (((long) data[i8 + 2] & 0xff) << 16)
+          | (((long) data[i8 + 3] & 0xff) << 24)
+          | (((long) data[i8 + 4] & 0xff) << 32)
+          | (((long) data[i8 + 5] & 0xff) << 40)
+          | (((long) data[i8 + 6] & 0xff) << 48)
+          | (((long) data[i8 + 7] & 0xff) << 56);
+
+      // mix functions
+      k *= M_64;
+      k ^= k >>> R_64;
+      k *= M_64;
+      h ^= k;
+      h *= M_64;
+    }
+
+    // tail
+    int tailStart = length8 << 3;
+    switch (length - tailStart) {
+      case 7:
+        h ^= (long) (data[tailStart + 6] & 0xff) << 48;
+      case 6:
+        h ^= (long) (data[tailStart + 5] & 0xff) << 40;
+      case 5:
+        h ^= (long) (data[tailStart + 4] & 0xff) << 32;
+      case 4:
+        h ^= (long) (data[tailStart + 3] & 0xff) << 24;
+      case 3:
+        h ^= (long) (data[tailStart + 2] & 0xff) << 16;
+      case 2:
+        h ^= (long) (data[tailStart + 1] & 0xff) << 8;
+      case 1:
+        h ^= (long) (data[tailStart] & 0xff);
+        h *= M_64;
+    }
+
+    // finalization
+    h ^= h >>> R_64;
+    h *= M_64;
+    h ^= h >>> R_64;
+
+    return h;
+  }
+}

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

@@ -0,0 +1,59 @@
+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

@@ -0,0 +1,27 @@
+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

@@ -0,0 +1,83 @@
+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

@@ -0,0 +1,29 @@
+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

@@ -0,0 +1,172 @@
+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

@@ -0,0 +1,33 @@
+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

@@ -0,0 +1,23 @@
+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

@@ -0,0 +1,22 @@
+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

@@ -0,0 +1,189 @@
+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

@@ -0,0 +1,13 @@
+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);
+	}
+}