Merge pull request #135 from Grasscutters/plugin-system

Implement a plugin system

src/main/java/emu/grasscutter/Config.java

 package emu.grasscutter;
 
-import java.util.ArrayList;
-
 public final class Config {
 
 	public String DatabaseUrl = "mongodb://localhost:27017";
@@ -12,6 +10,7 @@ public final class Config {
 	public String PACKETS_FOLDER = "./packets/";
 	public String DUMPS_FOLDER = "./dumps/";
 	public String KEY_FOLDER = "./keys/";
+	public String PLUGINS_FOLDER = "./plugins/";
 
 	public String RunMode = "HYBRID"; // HYBRID, DISPATCH_ONLY, GAME_ONLY
 	public GameServerOptions GameServer = new GameServerOptions();

src/main/java/emu/grasscutter/Grasscutter.java

@@ -8,6 +8,7 @@ import java.io.InputStreamReader;
 import java.net.InetSocketAddress;
 
 import emu.grasscutter.command.CommandMap;
+import emu.grasscutter.plugin.PluginManager;
 import emu.grasscutter.utils.Utils;
 import org.reflections.Reflections;
 import org.slf4j.LoggerFactory;
@@ -33,8 +34,9 @@ public final class Grasscutter {
 	public static RunMode MODE = RunMode.BOTH;
 	private static DispatchServer dispatchServer;
 	private static GameServer gameServer;
+	private static PluginManager pluginManager;
 	
-	public static final Reflections reflector = new Reflections("emu.grasscutter");
+	public static final Reflections reflector = new Reflections();
 	
 	static {
 		// Declare logback configuration.
@@ -52,15 +54,11 @@ public final class Grasscutter {
     	
 		for (String arg : args) {
 			switch (arg.toLowerCase()) {
-				case "-auth":
-					MODE = RunMode.AUTH;
-					break;
-				case "-game":
-					MODE = RunMode.GAME;
-					break;
-				case "-handbook":
-					Tools.createGmHandbook();
-					return;
+				case "-auth" -> MODE = RunMode.AUTH;
+				case "-game" -> MODE = RunMode.GAME;
+				case "-handbook" -> {
+					Tools.createGmHandbook(); return;
+				}
 			}
 		}
 		
@@ -71,19 +69,21 @@ public final class Grasscutter {
 		ResourceLoader.loadAll();
 		// Database
 		DatabaseManager.initialize();
+
+		// Create server instances.
+		dispatchServer = new DispatchServer();
+		gameServer = new GameServer(new InetSocketAddress(getConfig().getGameServerOptions().Ip, getConfig().getGameServerOptions().Port));
+		
+		// Create plugin manager instance.
+		pluginManager = new PluginManager();
 		
 		// Start servers.
 		if(getConfig().RunMode.equalsIgnoreCase("HYBRID")) {
-			dispatchServer = new DispatchServer();
 			dispatchServer.start();
-
-			gameServer = new GameServer(new InetSocketAddress(getConfig().getGameServerOptions().Ip, getConfig().getGameServerOptions().Port));
 			gameServer.start();
-		} else if(getConfig().RunMode.equalsIgnoreCase("DISPATCH_ONLY")) {
-			dispatchServer = new DispatchServer();
+		} else if (getConfig().RunMode.equalsIgnoreCase("DISPATCH_ONLY")) {
 			dispatchServer.start();
-		} else if(getConfig().RunMode.equalsIgnoreCase("GAME_ONLY")) {
-			gameServer = new GameServer(new InetSocketAddress(getConfig().getGameServerOptions().Ip, getConfig().getGameServerOptions().Port));
+		} else if (getConfig().RunMode.equalsIgnoreCase("GAME_ONLY")) {
 			gameServer.start();
 		} else {
 			getLogger().error("Invalid server run mode. " + getConfig().RunMode);
@@ -91,12 +91,23 @@ public final class Grasscutter {
 			getLogger().error("Shutting down...");
 			System.exit(1);
 		}
-
-
+		
+		// Enable all plugins.
+		pluginManager.enablePlugins();
 		
 		// Open console.
 		startConsole();
+		// Hook into shutdown event.
+		Runtime.getRuntime().addShutdownHook(new Thread(Grasscutter::onShutdown));
     }
+
+	/**
+	 * Server shutdown event.
+	 */
+	private static void onShutdown() {
+		// Disable all plugins.
+		pluginManager.disablePlugins();
+	}
 	
 	public static void loadConfig() {
 		try (FileReader file = new FileReader(configFile)) {
@@ -112,7 +123,7 @@ public final class Grasscutter {
 		try (FileWriter file = new FileWriter(configFile)) {
 			file.write(gson.toJson(config));
 		} catch (Exception e) {
-			Grasscutter.getLogger().error("Config save error");
+			Grasscutter.getLogger().error("Unable to save config file.");
 		}
 	}
 	
@@ -123,13 +134,13 @@ public final class Grasscutter {
 			while ((input = br.readLine()) != null) {
 				try {
 					if(getConfig().RunMode.equalsIgnoreCase("DISPATCH_ONLY")) {
-						getLogger().error("Commands are not supported in dispatch only mode");
+						getLogger().error("Commands are not supported in dispatch only mode.");
 						return;
 					}
+					
 					CommandMap.getInstance().invoke(null, input);
 				} catch (Exception e) {
-					Grasscutter.getLogger().error("Command error: ");
-					e.printStackTrace();
+					Grasscutter.getLogger().error("Command error:", e);
 				}
 			}
 		} catch (Exception e) {
@@ -162,4 +173,8 @@ public final class Grasscutter {
 	public static GameServer getGameServer() {
 		return gameServer;
 	}
+	
+	public static PluginManager getPluginManager() {
+		return pluginManager;
+	}
 }

src/main/java/emu/grasscutter/plugin/Plugin.java

+package emu.grasscutter.plugin;
+
+import emu.grasscutter.Grasscutter;
+import emu.grasscutter.server.game.GameServer;
+
+/**
+ * The base class for all plugins to extend.
+ */
+public abstract class Plugin {
+    private PluginIdentifier identifier;
+
+    /**
+     * This method is reflected into.
+     * 
+     * Set plugin variables.
+     * @param identifier The plugin's identifier.
+     */
+    private void initializePlugin(PluginIdentifier identifier) {
+        if(this.identifier == null)
+            this.identifier = identifier;
+        else Grasscutter.getLogger().warn(this.identifier.name + " had a reinitialization attempt.");
+    }
+
+    /**
+     * The plugin's identifier instance.
+     * @return An instance of {@link PluginIdentifier}.
+     */
+    public final PluginIdentifier getIdentifier(){
+        return this.identifier;
+    }
+
+    /**
+     * Get the plugin's name.
+     */
+    public final String getName() {
+        return this.identifier.name;
+    }
+
+    /**
+     * Get the plugin's description.
+     */
+    public final String getDescription() {
+        return this.identifier.description;
+    }
+
+    /**
+     * Get the plugin's version.
+     */
+    public final String getVersion() {
+        return this.identifier.version;
+    }
+
+    /**
+     * Returns the server that initialized the plugin.
+     * @return A server instance.
+     */
+    public final GameServer getServer() {
+        return Grasscutter.getGameServer();
+    }
+    
+    /* Called when the plugin is first loaded. */
+    public void onLoad() { }
+    /* Called after (most of) the server enables. */
+    public void onEnable() { }
+    /* Called before the server disables. */
+    public void onDisable() { }
+}

src/main/java/emu/grasscutter/plugin/PluginConfig.java

+package emu.grasscutter.plugin;
+
+/**
+ * The data contained in the plugin's `plugin.json` file.
+ */
+public final class PluginConfig {
+    public String name, description, version;
+    public String mainClass;
+    public String[] authors;
+
+    /**
+     * Attempts to validate this config instance.
+     * @return True if the config is valid, false otherwise.
+     */
+    public boolean validate() {
+        return name != null && description != null && mainClass != null;
+    }
+}

src/main/java/emu/grasscutter/plugin/PluginIdentifier.java

+package emu.grasscutter.plugin;
+
+// TODO: Potentially replace with Lombok?
+public final class PluginIdentifier {
+    public final String name, description, version;
+    public final String[] authors;
+    
+    public PluginIdentifier(
+            String name, String description, String version,
+            String[] authors
+    ) {
+        this.name = name;
+        this.description = description;
+        this.version = version;
+        this.authors = authors;
+    }
+
+    /**
+     * Converts a {@link PluginConfig} into a {@link PluginIdentifier}.
+     */
+    public static PluginIdentifier fromPluginConfig(PluginConfig config) {
+        if(!config.validate())
+            throw new IllegalArgumentException("A valid plugin config is required to convert into a plugin identifier.");
+        return new PluginIdentifier(
+                config.name, config.description, config.version,
+                config.authors
+        );
+    }
+}

src/main/java/emu/grasscutter/plugin/PluginManager.java

+package emu.grasscutter.plugin;
+
+import emu.grasscutter.Grasscutter;
+import emu.grasscutter.server.event.Event;
+import emu.grasscutter.server.event.EventHandler;
+import emu.grasscutter.server.event.Listener;
+import emu.grasscutter.utils.Utils;
+import org.reflections.Reflections;
+
+import java.io.File;
+import java.io.InputStreamReader;
+import java.lang.reflect.Method;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.*;
+
+/**
+ * Manages the server's plugins & the event system.
+ */
+public final class PluginManager {
+    private final Map<String, Plugin> plugins = new HashMap<>();
+    private final Map<Plugin, List<Listener>> listeners = new HashMap<>();
+    
+    public PluginManager() {
+        this.loadPlugins(); // Load all plugins from the plugins directory.
+    }
+
+    /**
+     * Loads plugins from the config-specified directory.
+     */
+    private void loadPlugins() {
+        String directory = Grasscutter.getConfig().PLUGINS_FOLDER;
+        File pluginsDir = new File(Utils.toFilePath(directory));
+        if(!pluginsDir.exists() && !pluginsDir.mkdirs()) {
+            Grasscutter.getLogger().error("Failed to create plugins directory: " + pluginsDir.getAbsolutePath());
+            return;
+        }
+        
+        File[] files = pluginsDir.listFiles();
+        if(files == null) {
+            // The directory is empty, there aren't any plugins to load.
+            return;
+        }
+        
+        List<File> plugins = Arrays.stream(files)
+                .filter(file -> file.getName().endsWith(".jar"))
+                .toList();
+        
+        plugins.forEach(plugin -> {
+            try {
+                URL url = plugin.toURI().toURL();
+                try (URLClassLoader loader = new URLClassLoader(new URL[]{url})) {
+                    URL configFile = loader.findResource("plugin.json");
+                    InputStreamReader fileReader = new InputStreamReader(configFile.openStream());
+                    
+                    PluginConfig pluginConfig = Grasscutter.getGsonFactory().fromJson(fileReader, PluginConfig.class);
+                    if(!pluginConfig.validate()) {
+                        Utils.logObject(pluginConfig);
+                        Grasscutter.getLogger().warn("Plugin " + plugin.getName() + " has an invalid config file.");
+                        return;
+                    }
+                    
+                    Class<?> pluginClass = loader.loadClass(pluginConfig.mainClass);
+                    Plugin pluginInstance = (Plugin) pluginClass.getDeclaredConstructor().newInstance();
+                    this.loadPlugin(pluginInstance, PluginIdentifier.fromPluginConfig(pluginConfig));
+                    
+                    fileReader.close(); // Close the file reader.
+                } catch (ClassNotFoundException ignored) {
+                    Grasscutter.getLogger().warn("Plugin " + plugin.getName() + " has an invalid main class.");
+                }
+            } catch (Exception exception) {
+                Grasscutter.getLogger().error("Failed to load plugin: " + plugin.getName(), exception);
+            }
+        });
+    }
+
+    /**
+     * Load the specified plugin.
+     * @param plugin The plugin instance.
+     */
+    private void loadPlugin(Plugin plugin, PluginIdentifier identifier) {
+        Grasscutter.getLogger().info("Loading plugin: " + identifier.name);
+        
+        // Add the plugin's identifier.
+        try {
+            Class<Plugin> pluginClass = Plugin.class;
+            Method method = pluginClass.getDeclaredMethod("initializePlugin", PluginIdentifier.class);
+            method.setAccessible(true); method.invoke(plugin, identifier); method.setAccessible(false);
+        } catch (Exception ignored) {
+            Grasscutter.getLogger().warn("Failed to add plugin identifier: " + identifier.name);
+        }
+        
+        // Add the plugin to the list of loaded plugins.
+        this.plugins.put(identifier.name, plugin);
+        // Call the plugin's onLoad method.
+        plugin.onLoad();
+    }
+
+    /**
+     * Enables all registered plugins.
+     */
+    public void enablePlugins() {
+        this.plugins.forEach((name, plugin) -> {
+            Grasscutter.getLogger().info("Enabling plugin: " + name);
+            plugin.onEnable();
+        });
+    }
+    
+    /**
+     * Disables all registered plugins.
+     */
+    public void disablePlugins() {
+        this.plugins.forEach((name, plugin) -> {
+            Grasscutter.getLogger().info("Disabling plugin: " + name);
+            plugin.onDisable();
+        });
+    }
+
+    /**
+     * Registers a plugin's event listener.
+     * @param plugin The plugin instance.
+     * @param listener The event listener.
+     */
+    public void registerListener(Plugin plugin, Listener listener) {
+        this.listeners.computeIfAbsent(plugin, k -> new ArrayList<>()).add(listener);
+    }
+    
+    /**
+     * Invoke the provided event on all registered event listeners.
+     * @param event The event to invoke.
+     */
+    public void invokeEvent(Event event) {
+        this.listeners.values().stream()
+                .flatMap(Collection::stream)
+                .forEach(listener -> this.invokeOnListener(listener, event));
+    }
+    
+    /**
+     * Attempts to invoke the event on the provided listener.
+     */
+    private void invokeOnListener(Listener listener, Event event) {
+        try {
+            Class<?> listenerClass = listener.getClass();
+            Method[] methods = listenerClass.getMethods();
+            for (Method method : methods) {
+                if(!method.isAnnotationPresent(EventHandler.class)) return;
+                if(!method.getParameterTypes()[0].isAssignableFrom(event.getClass())) return;
+                method.invoke(listener, event);
+            }
+        } catch (Exception ignored) { }
+    }
+}
\ No newline at end of file

src/main/java/emu/grasscutter/server/dispatch/DispatchServer.java

@@ -18,6 +18,8 @@ import emu.grasscutter.net.proto.RegionInfoOuterClass.RegionInfo;
 import emu.grasscutter.net.proto.RegionSimpleInfoOuterClass.RegionSimpleInfo;
 import emu.grasscutter.server.dispatch.json.*;
 import emu.grasscutter.server.dispatch.json.ComboTokenReqJson.LoginTokenData;
+import emu.grasscutter.server.event.dispatch.QueryAllRegionsEvent;
+import emu.grasscutter.server.event.dispatch.QueryCurrentRegionEvent;
 import emu.grasscutter.utils.FileUtils;
 import emu.grasscutter.utils.Utils;
 
@@ -277,7 +279,11 @@ public final class DispatchServer {
 				if (uri.getQuery() != null && uri.getQuery().length() > 0) {
 					response = regionCurrentBase64;
 				}
-				responseHTML(t, response);
+				
+				// Invoke event.
+				QueryCurrentRegionEvent event = new QueryCurrentRegionEvent(response); event.call();
+				// Respond with event result.
+				responseHTML(t, event.getRegionInfo());
 			});
 		}
 

src/main/java/emu/grasscutter/server/event/Cancellable.java

+package emu.grasscutter.server.event;
+
+/**
+ * Implementing this interface marks an event as cancellable.
+ */
+public interface Cancellable {
+    void cancel();
+}

src/main/java/emu/grasscutter/server/event/Event.java

+package emu.grasscutter.server.event;
+
+import emu.grasscutter.Grasscutter;
+
+/**
+ * A generic server event.
+ */
+public abstract class Event {
+    private boolean cancelled = false;
+
+    /**
+     * Return the cancelled state of the event.
+     */
+    public boolean isCanceled() {
+        return this.cancelled;
+    }
+
+    /**
+     * Cancels the event if possible.
+     */
+    public void cancel() {
+        if(this instanceof Cancellable)
+            this.cancelled = true;
+    }
+
+    /**
+     * Pushes this event to all listeners.
+     */
+    public void call() {
+        Grasscutter.getPluginManager().invokeEvent(this);
+    }
+}

src/main/java/emu/grasscutter/server/event/EventHandler.java

+package emu.grasscutter.server.event;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * Declares a class as an event listener/handler.
+ */
+@Retention(RetentionPolicy.RUNTIME)
+public @interface EventHandler {
+}
\ No newline at end of file

src/main/java/emu/grasscutter/server/event/Listener.java

+package emu.grasscutter.server.event;
+
+/**
+ * Implementing this interface declares a class as an event listener.
+ */
+public interface Listener {
+}

src/main/java/emu/grasscutter/server/event/ServerEvent.java

+package emu.grasscutter.server.event;
+
+/**
+ * An event that is related to the internals of the server.
+ */
+public abstract class ServerEvent extends Event {
+    protected final Type type;
+    
+    public ServerEvent(Type type) {
+        this.type = type;
+    }
+    
+    public enum Type {
+        DISPATCH,
+        GAME
+    }
+}

src/main/java/emu/grasscutter/server/event/dispatch/QueryAllRegionsEvent.java

+package emu.grasscutter.server.event.dispatch;
+
+import emu.grasscutter.server.event.ServerEvent;
+
+public final class QueryAllRegionsEvent extends ServerEvent {
+    private String regionList;
+    
+    public QueryAllRegionsEvent(String regionList) {
+        super(Type.DISPATCH);
+        
+        this.regionList = regionList;
+    }
+    
+    public void setRegionList(String regionList) {
+        this.regionList = regionList;
+    }
+    
+    public String getRegionList() {
+        return this.regionList;
+    }
+}

src/main/java/emu/grasscutter/server/event/dispatch/QueryCurrentRegionEvent.java

+package emu.grasscutter.server.event.dispatch;
+
+import emu.grasscutter.server.event.ServerEvent;
+
+public final class QueryCurrentRegionEvent extends ServerEvent {
+    private String regionInfo;
+
+    public QueryCurrentRegionEvent(String regionInfo) {
+        super(Type.DISPATCH);
+
+        this.regionInfo = regionInfo;
+    }
+
+    public void setRegionInfo(String regionInfo) {
+        this.regionInfo = regionInfo;
+    }
+
+    public String getRegionInfo() {
+        return this.regionInfo;
+    }
+}

src/main/java/emu/grasscutter/server/event/game/ReceivePacketEvent.java

+package emu.grasscutter.server.event.game;
+
+import emu.grasscutter.server.event.Cancellable;
+import emu.grasscutter.server.event.ServerEvent;
+import emu.grasscutter.server.game.GameSession;
+
+public final class ReceivePacketEvent extends ServerEvent implements Cancellable {
+    private final GameSession gameSession;
+    private final int packetId;
+    private byte[] packetData;
+    
+    public ReceivePacketEvent(GameSession gameSession, int packetId, byte[] packetData) {
+        super(Type.GAME);
+        
+        this.gameSession = gameSession;
+        this.packetId = packetId;
+        this.packetData = packetData;
+    }
+    
+    public GameSession getGameSession() {
+        return this.gameSession;
+    }
+    
+    public int getPacketId() {
+        return this.packetId;
+    }
+    
+    public void setPacketData(byte[] packetData) {
+        this.packetData = packetData;
+    }
+    
+    public byte[] getPacketData() {
+        return this.packetData;
+    }
+}

src/main/java/emu/grasscutter/server/event/game/SendPacketEvent.java

+package emu.grasscutter.server.event.game;
+
+import emu.grasscutter.net.packet.GenshinPacket;
+import emu.grasscutter.server.event.Cancellable;
+import emu.grasscutter.server.event.ServerEvent;
+import emu.grasscutter.server.game.GameSession;
+
+public final class SendPacketEvent extends ServerEvent implements Cancellable {
+    private final GameSession gameSession;
+    private GenshinPacket packet;
+
+    public SendPacketEvent(GameSession gameSession, GenshinPacket packet) {
+        super(Type.GAME);
+
+        this.gameSession = gameSession;
+        this.packet = packet;
+    }
+
+    public GameSession getGameSession() {
+        return this.gameSession;
+    }
+
+    public void setPacket(GenshinPacket packet) {
+        this.packet = packet;
+    }
+
+    public GenshinPacket getPacket() {
+        return this.packet;
+    }
+}

src/main/java/emu/grasscutter/server/game/GameServerPacketHandler.java

@@ -2,6 +2,7 @@ package emu.grasscutter.server.game;
 
 import java.util.Set;
 
+import emu.grasscutter.server.event.game.ReceivePacketEvent;
 import org.reflections.Reflections;
 
 import emu.grasscutter.Grasscutter;
@@ -48,9 +49,7 @@ public class GameServerPacketHandler {
 	}
 	
 	public void handle(GameSession session, int opcode, byte[] header, byte[] payload) {
-		PacketHandler handler = null;
-		
-		handler = this.handlers.get(opcode);
+		PacketHandler handler = this.handlers.get(opcode);
 		
 		if (handler != null) {
 			try {
@@ -77,8 +76,10 @@ public class GameServerPacketHandler {
 					}
 				}
 				
-				// Handle
-				handler.handle(session, header, payload);				
+				// Invoke event.
+				ReceivePacketEvent event = new ReceivePacketEvent(session, opcode, payload); event.call();
+				if(!event.isCanceled()) // If event is not canceled, continue.
+					handler.handle(session, header, event.getPacketData());				
 			} catch (Exception ex) {
 				// TODO Remove this when no more needed
 				ex.printStackTrace();

src/main/java/emu/grasscutter/server/game/GameSession.java

@@ -10,6 +10,7 @@ import emu.grasscutter.game.GenshinPlayer;
 import emu.grasscutter.net.packet.GenshinPacket;
 import emu.grasscutter.net.packet.PacketOpcodesUtil;
 import emu.grasscutter.netty.MihoyoKcpChannel;
+import emu.grasscutter.server.event.game.SendPacketEvent;
 import emu.grasscutter.utils.Crypto;
 import emu.grasscutter.utils.FileUtils;
 import emu.grasscutter.utils.Utils;
@@ -161,16 +162,15 @@ public class GameSession extends MihoyoKcpChannel {
     		genshinPacket.buildHeader(this.getNextClientSequence());
     	}
     	
-    	// Build packet
-    	byte[] data = genshinPacket.build();
-    	
     	// Log
     	if (Grasscutter.getConfig().getGameServerOptions().LOG_PACKETS) {
     		logPacket(genshinPacket);
     	}
-    	
-    	// Send
-    	send(data);
+		
+		// Invoke event.
+		SendPacketEvent event = new SendPacketEvent(this, genshinPacket); event.call();
+    	if(!event.isCanceled()) // If event is not cancelled, continue.
+			this.send(event.getPacket().build());
     }
     
     private void logPacket(int opcode) {

src/main/java/emu/grasscutter/utils/Utils.java

@@ -137,6 +137,15 @@ public final class Utils {
 		return nonNull != null ? nonNull : fallback;
 	}
 
+	/**
+	 * Logs an object to the console.
+	 * @param object The object to log.
+	 */
+	public static void logObject(Object object) {
+		String asJson = Grasscutter.getGsonFactory().toJson(object);
+		Grasscutter.getLogger().info(asJson);
+	}
+	
 	/**
 	 * Checks for required files and folders before startup.
 	 */