Added a WatchService to watch the beatmap directory tree for changes.

Any CREATE and DELETE that occur in the song menu state will now show a notification and modify the behavior of the 'F5' key. Changes that occur in other states will force a reload upon entering the song menu.

This is part of osu!, but as it's not incredibly helpful, I've left it disabled by default.  It can be enabled in the options menu.

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

src/itdelatrisu/opsu/Container.java

@@ -21,6 +21,7 @@ package itdelatrisu.opsu;
 import itdelatrisu.opsu.audio.MusicController;
 import itdelatrisu.opsu.beatmap.Beatmap;
 import itdelatrisu.opsu.beatmap.BeatmapSetList;
+import itdelatrisu.opsu.beatmap.BeatmapWatchService;
 import itdelatrisu.opsu.downloads.DownloadList;
 import itdelatrisu.opsu.downloads.Updater;
 import itdelatrisu.opsu.render.CurveRenderState;
@@ -136,6 +137,11 @@ public class Container extends AppGameContainer {
 
 		// delete OpenGL objects involved in the Curve rendering
 		CurveRenderState.shutdown();
+
+		// destroy watch service
+		if (!Options.isWatchServiceEnabled())
+			BeatmapWatchService.destroy();
+		BeatmapWatchService.removeListeners();
 	}
 
 	@Override

src/itdelatrisu/opsu/Options.java

@@ -456,7 +456,8 @@ public class Options {
 		},
 		ENABLE_THEME_SONG ("Enable Theme Song", "MenuMusic", "Whether to play the theme song upon starting opsu!", true),
 		REPLAY_SEEKING ("Replay Seeking", "ReplaySeeking", "Enable a seeking bar on the left side of the screen during replays.", false),
-		DISABLE_UPDATER ("Disable Automatic Updates", "DisableUpdater", "Disable automatic checking for updates upon starting opsu!.", false);
+		DISABLE_UPDATER ("Disable Automatic Updates", "DisableUpdater", "Disable automatic checking for updates upon starting opsu!.", false),
+		ENABLE_WATCH_SERVICE ("Enable Watch Service", "WatchService", "Watch the beatmap directory for changes. Requires a restart.", false);
 
 		/** Option name. */
 		private final String name;
@@ -973,6 +974,12 @@ public class Options {
 	 */
 	public static boolean isUpdaterDisabled() { return GameOption.DISABLE_UPDATER.getBooleanValue(); }
 
+	/**
+	 * Returns whether or not the beatmap watch service is enabled.
+	 * @return true if enabled
+	 */
+	public static boolean isWatchServiceEnabled() { return GameOption.ENABLE_WATCH_SERVICE.getBooleanValue(); }
+
 	/**
 	 * Sets the track checkpoint time, if within bounds.
 	 * @param time the track position (in ms)

src/itdelatrisu/opsu/beatmap/BeatmapParser.java

@@ -19,6 +19,7 @@
 package itdelatrisu.opsu.beatmap;
 
 import itdelatrisu.opsu.ErrorHandler;
+import itdelatrisu.opsu.Options;
 import itdelatrisu.opsu.Utils;
 import itdelatrisu.opsu.db.BeatmapDB;
 import itdelatrisu.opsu.io.MD5InputStreamWrapper;
@@ -83,6 +84,10 @@ public class BeatmapParser {
 		// create a new BeatmapSetList
 		BeatmapSetList.create();
 
+		// create a new watch service
+		if (Options.isWatchServiceEnabled())
+			BeatmapWatchService.create();
+
 		// parse all directories
 		parseDirectories(root.listFiles());
 	}
@@ -110,6 +115,9 @@ public class BeatmapParser {
 		List<Beatmap> cachedBeatmaps = new LinkedList<Beatmap>();  // loaded from database
 		List<Beatmap> parsedBeatmaps = new LinkedList<Beatmap>();  // loaded from parser
 
+		// watch service
+		BeatmapWatchService ws = (Options.isWatchServiceEnabled()) ? BeatmapWatchService.get() : null;
+
 		// parse directories
 		BeatmapSetNode lastNode = null;
 		for (File dir : dirs) {
@@ -162,6 +170,8 @@ public class BeatmapParser {
 			if (!beatmaps.isEmpty()) {
 				beatmaps.trimToSize();
 				allBeatmaps.add(beatmaps);
+				if (ws != null)
+					ws.registerAll(dir.toPath());
 			}
 
 			// stop parsing files (interrupted)

src/itdelatrisu/opsu/beatmap/BeatmapWatchService.java

@@ -0,0 +1,275 @@
+/*
+ * opsu! - an open-source osu! client
+ * Copyright (C) 2014, 2015 Jeffrey Han
+ *
+ * opsu! is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * opsu! is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with opsu!.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package itdelatrisu.opsu.beatmap;
+
+import itdelatrisu.opsu.ErrorHandler;
+import itdelatrisu.opsu.Options;
+
+import java.io.IOException;
+import java.nio.file.ClosedWatchServiceException;
+import java.nio.file.FileSystems;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.StandardWatchEventKinds;
+import java.nio.file.WatchEvent;
+import java.nio.file.WatchKey;
+import java.nio.file.WatchService;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import org.newdawn.slick.util.Log;
+
+/*
+ * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   - Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *
+ *   - Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ *   - Neither the name of Oracle nor the names of its
+ *     contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * Watches the beatmap directory tree for changes.
+ *
+ * @author The Java Tutorials (http://docs.oracle.com/javase/tutorial/essential/io/examples/WatchDir.java) (base)
+ */
+public class BeatmapWatchService {
+	/** Beatmap watcher service instance. */
+	private static BeatmapWatchService ws;
+
+	/**
+	 * Creates a new watch service instance (overwriting any previous instance),
+	 * registers the beatmap directory, and starts processing events.
+	 */
+	public static void create() {
+		// close the existing watch service
+		destroy();
+
+		// create a new watch service
+		try {
+			ws = new BeatmapWatchService();
+			ws.register(Options.getBeatmapDir().toPath());
+		} catch (IOException e) {
+			ErrorHandler.error("An I/O exception occurred while creating the watch service.", e, true);
+			return;
+		}
+
+		// start processing events
+		ws.start();
+	}
+
+	/**
+	 * Destroys the watch service instance, if any.
+	 * Subsequent calls to {@link #get()} will return {@code null}.
+	 */
+	public static void destroy() {
+		if (ws == null)
+			return;
+
+		try {
+			ws.watcher.close();
+			ws.service.shutdownNow();
+			ws = null;
+		} catch (IOException e) {
+			ws = null;
+			ErrorHandler.error("An I/O exception occurred while closing the previous watch service.", e, true);
+		}
+	}
+
+	/**
+	 * Returns the single instance of this class.
+	 */
+	public static BeatmapWatchService get() { return ws; }
+
+	/** Watch service listener interface. */
+	public interface BeatmapWatchServiceListener {
+		/** Indication that an event was received. */
+		public void eventReceived(WatchEvent.Kind<?> kind, Path child);
+	}
+
+	/** The list of listeners. */
+	private static final List<BeatmapWatchServiceListener> listeners = new ArrayList<BeatmapWatchServiceListener>();
+
+	/**
+	 * Adds a listener.
+	 * @param listener the listener to add
+	 */
+	public static void addListener(BeatmapWatchServiceListener listener) { listeners.add(listener); }
+
+	/**
+	 * Removes a listener.
+	 * @param listener the listener to remove
+	 */
+	public static void removeListener(BeatmapWatchServiceListener listener) { listeners.remove(listener); }
+
+	/**
+	 * Removes all listeners.
+	 */
+	public static void removeListeners() { listeners.clear(); }
+
+	/** The watch service. */
+	private final WatchService watcher;
+
+	/** The WatchKey -> Path mapping for registered directories. */
+	private final Map<WatchKey, Path> keys;
+
+	/** The Executor. */
+	private ExecutorService service;
+
+	/**
+	 * Creates the WatchService.
+	 * @throws IOException if an I/O error occurs
+	 */
+	private BeatmapWatchService() throws IOException {
+		this.watcher = FileSystems.getDefault().newWatchService();
+		this.keys = new ConcurrentHashMap<WatchKey, Path>();
+	}
+
+	/**
+	 * Register the given directory with the WatchService.
+	 * @param dir the directory to register
+	 * @throws IOException if an I/O error occurs
+	 */
+	private void register(Path dir) throws IOException {
+		WatchKey key = dir.register(watcher,
+				StandardWatchEventKinds.ENTRY_CREATE,
+				StandardWatchEventKinds.ENTRY_DELETE,
+				StandardWatchEventKinds.ENTRY_MODIFY);
+		keys.put(key, dir);
+	}
+
+	/**
+	 * Register the given directory, and all its sub-directories, with the WatchService.
+	 * @param start the root directory to register
+	 */
+	public void registerAll(final Path start) {
+		try {
+			Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
+				@Override
+				public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
+					try {
+						register(dir);
+					} catch (IOException e) {
+						Log.warn(String.format("Failed to register path '%s' with the watch service.", dir.toString()), e);
+					}
+					return FileVisitResult.CONTINUE;
+				}
+			});
+		} catch (IOException e) {
+			Log.warn(String.format("Failed to register paths from root directory '%s' with the watch service.", start.toString()), e);
+		}
+	}
+
+	@SuppressWarnings("unchecked")
+	private static <T> WatchEvent<T> cast(WatchEvent<?> event) {
+		return (WatchEvent<T>) event;
+	}
+
+	/**
+	 * Start processing events in a new thread.
+	 */
+	private void start() {
+		if (service != null)
+			return;
+
+		this.service = Executors.newCachedThreadPool();
+		service.submit(new Runnable() {
+			@Override
+			public void run() { ws.processEvents(); }
+		});
+	}
+
+	/**
+	 * Process all events for keys queued to the watcher
+	 */
+	private void processEvents() {
+		while (true) {
+			// wait for key to be signaled
+			WatchKey key;
+			try {
+				key = watcher.take();
+			} catch (InterruptedException | ClosedWatchServiceException e) {
+				return;
+			}
+
+			Path dir = keys.get(key);
+			if (dir == null)
+				continue;
+
+			for (WatchEvent<?> event : key.pollEvents()) {
+				WatchEvent.Kind<?> kind = event.kind();
+				if (kind == StandardWatchEventKinds.OVERFLOW)
+					continue;
+
+				// context for directory entry event is the file name of entry
+				WatchEvent<Path> ev = cast(event);
+				Path name = ev.context();
+				Path child = dir.resolve(name);
+				//System.out.printf("%s: %s\n", kind.name(), child);
+
+				// fire listeners
+				for (BeatmapWatchServiceListener listener : listeners)
+					listener.eventReceived(kind, child);
+
+				// if directory is created, then register it and its sub-directories
+				if (kind == StandardWatchEventKinds.ENTRY_CREATE) {
+					if (Files.isDirectory(child, LinkOption.NOFOLLOW_LINKS))
+						registerAll(child);
+				}
+			}
+
+			// reset key and remove from set if directory no longer accessible
+			if (!key.reset()) {
+				keys.remove(key);
+				if (keys.isEmpty())
+					break;  // all directories are inaccessible
+			}
+		}
+	}
+}

src/itdelatrisu/opsu/states/OptionsMenu.java

@@ -97,7 +97,8 @@ public class OptionsMenu extends BasicGameState {
 			GameOption.FIXED_OD,
 			GameOption.CHECKPOINT,
 			GameOption.REPLAY_SEEKING,
-			GameOption.DISABLE_UPDATER
+			GameOption.DISABLE_UPDATER,
+			GameOption.ENABLE_WATCH_SERVICE
 		});
 
 		/** Total number of tabs. */

src/itdelatrisu/opsu/states/SongMenu.java

@@ -36,6 +36,8 @@ import itdelatrisu.opsu.beatmap.BeatmapParser;
 import itdelatrisu.opsu.beatmap.BeatmapSetList;
 import itdelatrisu.opsu.beatmap.BeatmapSetNode;
 import itdelatrisu.opsu.beatmap.BeatmapSortOrder;
+import itdelatrisu.opsu.beatmap.BeatmapWatchService;
+import itdelatrisu.opsu.beatmap.BeatmapWatchService.BeatmapWatchServiceListener;
 import itdelatrisu.opsu.db.BeatmapDB;
 import itdelatrisu.opsu.db.ScoreDB;
 import itdelatrisu.opsu.states.ButtonMenu.MenuState;
@@ -47,6 +49,9 @@ import itdelatrisu.opsu.ui.animations.AnimatedValue;
 import itdelatrisu.opsu.ui.animations.AnimationEquation;
 
 import java.io.File;
+import java.nio.file.Path;
+import java.nio.file.StandardWatchEventKinds;
+import java.nio.file.WatchEvent.Kind;
 import java.util.Map;
 import java.util.Stack;
 
@@ -205,6 +210,9 @@ public class SongMenu extends BasicGameState {
 	/** The text length of the last string in the search TextField. */
 	private int lastSearchTextLength = -1;
 
+	/** Whether the song folder changed (notified via the watch service). */
+	private boolean songFolderChanged = false;
+
 	// game-related variables
 	private GameContainer container;
 	private StateBasedGame game;
@@ -283,6 +291,19 @@ public class SongMenu extends BasicGameState {
 		int loaderDim = GameImage.MENU_MUSICNOTE.getImage().getWidth();
 		SpriteSheet spr = new SpriteSheet(GameImage.MENU_LOADER.getImage(), loaderDim, loaderDim);
 		loader = new Animation(spr, 50);
+
+		// beatmap watch service listener
+		final StateBasedGame game_ = game;
+		BeatmapWatchService.addListener(new BeatmapWatchServiceListener() {
+			@Override
+			public void eventReceived(Kind<?> kind, Path child) {
+				if (!songFolderChanged && kind != StandardWatchEventKinds.ENTRY_MODIFY) {
+					songFolderChanged = true;
+					if (game_.getCurrentStateID() == Opsu.STATE_SONGMENU)
+						UI.sendBarNotification("Changes in Songs folder detected. Hit F5 to refresh.");
+				}
+			}
+		});
 	}
 
 	@Override
@@ -775,8 +796,12 @@ public class SongMenu extends BasicGameState {
 			break;
 		case Input.KEY_F5:
 			SoundController.playSound(SoundEffect.MENUHIT);
+			if (songFolderChanged)
+				reloadBeatmaps(false);
+			else {
 				((ButtonMenu) game.getState(Opsu.STATE_BUTTONMENU)).setMenuState(MenuState.RELOAD);
 				game.enterState(Opsu.STATE_BUTTONMENU);
+			}
 			break;
 		case Input.KEY_DELETE:
 			if (focusNode == null)
@@ -949,8 +974,12 @@ public class SongMenu extends BasicGameState {
 		// reset song stack
 		randomStack = new Stack<SongNode>();
 
+		// reload beatmaps if song folder changed
+		if (songFolderChanged && stateAction != MenuState.RELOAD)
+			reloadBeatmaps(false);
+
 		// set focus node if not set (e.g. theme song playing)
-		if (focusNode == null && BeatmapSetList.get().size() > 0)
+		else if (focusNode == null && BeatmapSetList.get().size() > 0)
 			setFocus(BeatmapSetList.get().getRandomNode(), -1, true, true);
 
 		// reset music track
@@ -1069,44 +1098,7 @@ public class SongMenu extends BasicGameState {
 				}
 				break;
 			case RELOAD:  // reload beatmaps
-				// reset state and node references
-				MusicController.reset();
-				startNode = focusNode = null;
-				scoreMap = null;
-				focusScores = null;
-				oldFocusNode = null;
-				randomStack = new Stack<SongNode>();
-				songInfo = null;
-				hoverOffset.setTime(0);
-				hoverIndex = -1;
-				search.setText("");
-				searchTimer = SEARCH_DELAY;
-				searchTransitionTimer = SEARCH_TRANSITION_TIME;
-				searchResultString = null;
-
-				// reload songs in new thread
-				reloadThread = new Thread() {
-					@Override
-					public void run() {
-						// clear the beatmap cache
-						BeatmapDB.clearDatabase();
-
-						// invoke unpacker and parser
-						File beatmapDir = Options.getBeatmapDir();
-						OszUnpacker.unpackAllFiles(Options.getOSZDir(), beatmapDir);
-						BeatmapParser.parseAllFiles(beatmapDir);
-
-						// initialize song list
-						if (BeatmapSetList.get().size() > 0) {
-							BeatmapSetList.get().init();
-							setFocus(BeatmapSetList.get().getRandomNode(), -1, true, true);
-						} else
-							MusicController.playThemeSong();
-
-						reloadThread = null;
-					}
-				};
-				reloadThread.start();
+				reloadBeatmaps(true);
 				break;
 			default:
 				break;
@@ -1310,6 +1302,58 @@ public class SongMenu extends BasicGameState {
 			return null;  // incorrect map
 	}
 
+	/**
+	 * Reloads all beatmaps.
+	 * @param fullReload if true, also clear the beatmap cache and invoke the unpacker
+	 */
+	private void reloadBeatmaps(final boolean fullReload) {
+		songFolderChanged = false;
+
+		// reset state and node references
+		MusicController.reset();
+		startNode = focusNode = null;
+		scoreMap = null;
+		focusScores = null;
+		oldFocusNode = null;
+		randomStack = new Stack<SongNode>();
+		songInfo = null;
+		hoverOffset.setTime(0);
+		hoverIndex = -1;
+		search.setText("");
+		searchTimer = SEARCH_DELAY;
+		searchTransitionTimer = SEARCH_TRANSITION_TIME;
+		searchResultString = null;
+
+		// reload songs in new thread
+		reloadThread = new Thread() {
+			@Override
+			public void run() {
+				File beatmapDir = Options.getBeatmapDir();
+
+				if (fullReload) {
+					// clear the beatmap cache
+					BeatmapDB.clearDatabase();
+	
+					// invoke unpacker
+					OszUnpacker.unpackAllFiles(Options.getOSZDir(), beatmapDir);
+				}
+
+				// invoke parser
+				BeatmapParser.parseAllFiles(beatmapDir);
+
+				// initialize song list
+				if (BeatmapSetList.get().size() > 0) {
+					BeatmapSetList.get().init();
+					setFocus(BeatmapSetList.get().getRandomNode(), -1, true, true);
+				} else
+					MusicController.playThemeSong();
+
+				reloadThread = null;
+			}
+		};
+		reloadThread.start();
+	}
+
 	/**
 	 * Starts the game.
 	 */

src/itdelatrisu/opsu/states/Splash.java

@@ -27,6 +27,7 @@ import itdelatrisu.opsu.audio.MusicController;
 import itdelatrisu.opsu.audio.SoundController;
 import itdelatrisu.opsu.beatmap.BeatmapParser;
 import itdelatrisu.opsu.beatmap.BeatmapSetList;
+import itdelatrisu.opsu.beatmap.BeatmapWatchService;
 import itdelatrisu.opsu.replay.ReplayImporter;
 import itdelatrisu.opsu.ui.UI;
 import itdelatrisu.opsu.ui.animations.AnimatedValue;
@@ -63,6 +64,9 @@ public class Splash extends BasicGameState {
 	/** Whether the skin being loaded is a new skin (for program restarts). */
 	private boolean newSkin = false;
 
+	/** Whether the watch service is newly enabled (for program restarts). */
+	private boolean watchServiceChange = false;
+
 	/** Logo alpha level. */
 	private AnimatedValue logoAlpha;
 
@@ -84,6 +88,9 @@ public class Splash extends BasicGameState {
 		if (Options.getSkin() != null)
 			this.newSkin = (Options.getSkin().getDirectory() != Options.getSkinDir());
 
+		// check if watch service newly enabled
+		this.watchServiceChange = Options.isWatchServiceEnabled() && BeatmapWatchService.get() == null;
+
 		// load Utils class first (needed in other 'init' methods)
 		Utils.init(container, game);
 
@@ -108,12 +115,17 @@ public class Splash extends BasicGameState {
 
 			// resources already loaded (from application restart)
 			if (BeatmapSetList.get() != null) {
-				// reload sounds if skin changed
-				if (newSkin) {
+				if (newSkin || watchServiceChange) {  // need to reload resources
 					thread = new Thread() {
 						@Override
 						public void run() {
+							// reload beatmaps if watch service newly enabled
+							if (watchServiceChange)
+								BeatmapParser.parseAllFiles(Options.getBeatmapDir());
+
+							// reload sounds if skin changed
 							// TODO: only reload each sound if actually needed?
+							if (newSkin)
 								SoundController.init();
 
 							finished = true;

src/itdelatrisu/opsu/ui/UI.java

@@ -64,7 +64,7 @@ public class UI {
 	private static int barNotifTimer = -1;
 
 	/** Duration, in milliseconds, to display bar notifications. */
-	private static final int BAR_NOTIFICATION_TIME = 1250;
+	private static final int BAR_NOTIFICATION_TIME = 1500;
 
 	/** The current tooltip. */
 	private static String tooltip;