Add ListenerUtil

It's helpful I swear

package.json

@@ -36,7 +36,8 @@
     "glob": "7.1.1",
     "node-json-db": "0.7.3",
     "performance-now": "^2.0.0",
-    "postinstall-build": "^3.0.0"
+    "postinstall-build": "^3.0.0",
+    "reflect-metadata": "^0.1.10"
   },
   "devDependencies": {
     "@types/chalk": "^0.4.31",

src/client/Client.ts

@@ -1,6 +1,22 @@
 import * as Discord from 'discord.js';
 import * as path from 'path';
-import { Channel, ClientOptions, Collection, Emoji, Guild, GuildMember, Message, MessageReaction, Role, User, UserResolvable, ClientUserSettings, Snowflake } from 'discord.js';
+
+import {
+	Channel,
+	ClientOptions,
+	Collection,
+	Emoji,
+	Guild,
+	GuildMember,
+	Message,
+	MessageReaction,
+	Role,
+	User,
+	UserResolvable,
+	ClientUserSettings,
+	Snowflake
+} from 'discord.js';
+
 import { Command } from '../command/Command';
 import { CommandDispatcher } from '../command/CommandDispatcher';
 import { CommandLoader } from '../command/CommandLoader';
@@ -16,6 +32,9 @@ import { MiddlewareFunction } from '../types/MiddlewareFunction';
 import { StorageProviderConstructor } from '../types/StorageProviderConstructor';
 import { BaseCommandName } from '../types/BaseCommandName';
 import { Logger, logger } from '../util/logger/Logger';
+import { ListenerUtil } from '../util/ListenerUtil';
+
+const { registerListeners } = ListenerUtil;
 
 /**
  * The YAMDBF Client through which you can access [storage]{@link Client#storage}
@@ -173,6 +192,8 @@ export class Client extends Discord.Client
 
 		// Load commands
 		if (!this.passive) this.loadCommand('all');
+
+		registerListeners(this);
 	}
 
 	/**

src/index.ts

@@ -28,6 +28,8 @@ export { LogLevel } from './types/LogLevel';
 
 export { deprecated } from './util/DeprecatedDecorator';
 
+export { ListenerUtil } from './util/ListenerUtil';
+
 export { ArgOpts } from './types/ArgOpts';
 export { BaseCommandName } from './types/BaseCommandName';
 export { ClientStorage } from './types/ClientStorage';

src/util/ListenerUtil.ts

@@ -0,0 +1,98 @@
+import 'reflect-metadata';
+import { EventEmitter } from 'events';
+
+/**
+ * Contains static methods for declaring class methods (within a class extending `EventEmitter`)
+ * as listeners for events that will be emitted by the class or parent classes
+ * @module ListenerUtil
+ */
+export class ListenerUtil
+{
+	/**
+	 * Attaches any listeners registered via the `on` or `once` decorators.
+	 * Must be called ***after*** `super()`, and only in classes extending `EventEmitter`
+	 * (which includes the Discord.js Client class and thus the YAMDBF Client class);
+	 * @static
+	 * @method registerListeners
+	 * @param {EventEmitter} emitter EventEmitter to register listeners for
+	 * @returns {void}
+	 */
+	public static registerListeners(emitter: EventEmitter): void
+	{
+		if (!(emitter instanceof EventEmitter))
+			throw new TypeError('Listeners can only be registered on classes extending EventEmitter');
+		if (typeof Reflect.getMetadata('listeners', emitter.constructor.prototype) === 'undefined') return;
+
+		for (const listener of <ListenerMetadata[]> Reflect.getMetadata('listeners', emitter.constructor.prototype))
+		{
+			if (!(<any> emitter)[listener.method]) continue;
+			if (listener.attached) continue;
+			listener.attached = true;
+			emitter[listener.once ? 'once' : 'on'](listener.event,
+				(...eventArgs: any[]) => (<any> emitter)[listener.method](...eventArgs));
+		}
+	}
+
+	/**
+	 * Declares the decorated method as an event handler for the specified event
+	 * Must be registered by calling {@link ListenerUtil.registerListeners()}
+	 *
+	 * > **Note:** `registerListeners()` is already called in the YAMDBF
+	 * {@link Client} constructor and does not need to be called in classes
+	 * extending it
+	 * @static
+	 * @method on
+	 * @param {string} event The name of the event to handle
+	 * @returns {MethodDecorator}
+	 */
+	public static on(event: string): MethodDecorator
+	{
+		return ListenerUtil._setListenerMetadata(event);
+	}
+
+	/**
+	 * Declares the decorated method as a single-use event handler for the
+	 * specified event. Must be registered by calling
+	 * {@link ListenerUtil.registerListeners()}
+	 *
+	 * > **Note:** `registerListeners()` is already called in the YAMDBF
+	 * {@link Client} constructor and does not need to be called in classes
+	 * extending it
+	 * @static
+	 * @method once
+	 * @param {string} event The name of the event to handle
+	 * @returns {MethodDecorator}
+	 */
+	public static once(event: string): MethodDecorator
+	{
+		return ListenerUtil._setListenerMetadata(event, true);
+	}
+
+	/**
+	 * Returns a MethodDecorator that handles setting the appropriate listener
+	 * metadata for a class method
+	 * @private
+	 */
+	private static _setListenerMetadata(event: string, once: boolean = false): MethodDecorator
+	{
+		return function<T extends EventEmitter>(target: T, key: string, descriptor: PropertyDescriptor): PropertyDescriptor
+		{
+			const listeners: ListenerMetadata[] = Reflect.getMetadata('listeners', target) || [];
+			listeners.push({ event: event, method: key, once: once });
+			Reflect.defineMetadata('listeners', listeners, target);
+			return descriptor;
+		};
+	}
+}
+
+/**
+ * Represents metadata used to build an event listener
+ * and assign it to a class method at runtime
+ */
+type ListenerMetadata =
+{
+	event: string;
+	method: string;
+	once: boolean;
+	attached?: boolean;
+};

test/test_client.ts

@@ -1,20 +1,55 @@
-import { Client, LogLevel, Logger } from '../bin/';
+import { Client, LogLevel, Logger, ListenerUtil } from '../bin/';
 const config: any = require('./config.json');
 const logger: Logger = Logger.instance();
+const { once } = ListenerUtil;
 
-const client: Client = new Client({
-	name: 'test',
-	token: config.token,
-	config: config,
-	commandsDir: './commands',
-	logLevel: LogLevel.DEBUG
-}).start();
+// const client: Client = new Client({
+// 	name: 'test',
+// 	token: config.token,
+// 	config: config,
+// 	commandsDir: './commands',
+// 	logLevel: LogLevel.DEBUG
+// }).start();
 
-client.on('waiting', async () =>
+// client.on('waiting', async () =>
+// {
+// 	await client.setDefaultSetting('prefix', '.');
+// 	client.emit('finished');
+// });
+// logger.warn('Test', 'Testing Logger#warn()');
+// logger.error('Test', 'Testing Logger#error()');
+// logger.debug('Test', 'Testing Logger#debug()');
+
+class Test extends Client
 {
-	await client.setDefaultSetting('prefix', '.');
-	client.emit('finished');
-});
-logger.warn('Test', 'Testing Logger#warn()');
-logger.error('Test', 'Testing Logger#error()');
-logger.debug('Test', 'Testing Logger#debug()');
+	public constructor()
+	{
+		super({
+			name: 'test',
+			token: config.token,
+			config: config,
+			commandsDir: './commands',
+			logLevel: LogLevel.DEBUG
+		});
+	}
+
+	@once('waiting')
+	private async _onWaiting(): Promise<void>
+	{
+		logger.debug('Test', 'Waiting...');
+		await this.setDefaultSetting('prefix', '?');
+		this.emit('finished');
+	}
+
+	@once('finished')
+	private _onFinished(): void
+	{
+		logger.debug('Test', 'Finished');
+
+		logger.warn('Test', 'Testing Logger#warn()');
+		logger.debug('Test', 'Testing Logger#debug()');
+		logger.error('Test', 'Testing Logger#error()');
+	}
+}
+const test: Test = new Test();
+test.start();