pref: choose rxjs-like style to write `lib.announce`.

game/src/lib/announce.js

@@ -0,0 +1,133 @@
+// TODO: 补充一点描述
+
+/**
+ * @type {WeakMap<AnnounceSubscriber, EventTarget>}
+ */
+const vm = new WeakMap();
+
+/**
+ *
+ */
+export class Announce {
+	/**
+	 * @type {EventTarget}
+	 */
+	#handler;
+
+	/**
+	 * @type {WeakMap<function(any): void, AnnounceSubscriber>}
+	 */
+	#records;
+
+	constructor() {
+		this.#handler = new EventTarget();
+		this.#records = new WeakMap();
+	}
+
+	/**
+	 * 推送任意数据给所有监听了指定事件的订阅者，并返回给定的数据
+	 *
+	 * 若不存在订阅指定事件的订阅者，则推送的数据将无意义
+	 *
+	 * @template T
+	 * @param {string} name - 要推送事件的名称
+	 * @param {T} values - 要推送的数据
+	 * @returns {T}
+	 */
+	publish(name, values) {
+		this.#handler.dispatchEvent(new CustomEvent(name, {
+			detail: [values, name]
+		}));
+		return values;
+	}
+
+	/**
+	 * 订阅给定名字的事件，并返回给定的函数
+	 *
+	 * 在事件触发时执行给定的函数
+	 *
+	 * 给定的函数将被存储至当前实例中，用于取消订阅时获取
+	 *
+	 * @template T
+	 * @param {string} name - 要订阅事件的名称
+	 * @param {(values: T) => void} method - 事件触发时执行的函数
+	 * @returns {(values: T) => void}
+	 */
+	subscribe(name, method) {
+		let subscriber;
+		if (this.#records.has(method))
+			subscriber = this.#records.get(method);
+		else {
+			subscriber = new AnnounceSubscriber(method, this.#handler);
+			this.#records.set(method, subscriber);
+		}
+		subscriber.subscribe(name);
+		return method;
+	}
+
+	/**
+	 * 取消指定事件某一个函数的订阅，并返回该函数
+	 *
+	 * 给定的函数将不再于事件触发时执行，其余同事件需触发的函数不受限制
+	 *
+	 * @template T
+	 * @param {string} name - 要取消订阅事件的名称
+	 * @param {(values: T) => void} method - 订阅指定事件的函数
+	 * @returns {(values: T) => void}
+	 */
+	unsubscribe(name, method) {
+		if (this.#records.has(method)) {
+			const subscriber = this.#records.get(method);
+			subscriber.unsubscribe(name);
+			if (subscriber.isEmpty)
+				this.#records.delete(method);
+		}
+		return method;
+	}
+}
+
+/**
+ * @template T
+ */
+class AnnounceSubscriber {
+	/**
+	 * @type {function(CustomEvent): void}
+	 */
+	#content;
+
+	/**
+	 * @type {string[]}
+	 */
+	#listening
+
+	/**
+	 *
+	 * @param {function(T, string): void} content
+	 * @param {EventTarget} target
+	 */
+	constructor(content, target) {
+		this.#content = function (event) {
+			content(event.detail[0], event.detail[1]);
+		}
+		this.#listening = [];
+
+		vm.set(this, target);
+	}
+
+	get isEmpty() {
+		return this.#listening.length <= 0;
+	}
+
+	/**
+	 * @param {string} name
+	 */
+	subscribe(name) {
+		vm.get(this).addEventListener(name, this.#content);
+		this.#listening.add(name);
+	}
+
+	unsubscribe() {
+		vm.get(this).removeEventListener(name, this.#content);
+		this.#listening.remove(name);
+	}
+}