jakciehan
85 lines
1.9 KiB
JavaScript
85 lines
1.9 KiB
JavaScript
/**
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* EventBus.js
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* Simple publish/subscribe event system for decoupled communication
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* between game systems.
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*/
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class EventBus {
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constructor() {
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/** @type {Map<string, Array<{fn: Function, once: boolean}>>} */
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this._listeners = new Map();
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}
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/**
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* Subscribe to an event.
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* @param {string} event
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* @param {Function} fn
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* @returns {Function} Unsubscribe function.
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*/
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on(event, fn) {
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if (!this._listeners.has(event)) {
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this._listeners.set(event, []);
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}
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const entry = { fn, once: false };
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this._listeners.get(event).push(entry);
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return () => this.off(event, fn);
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}
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/**
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* Subscribe to an event, but only fire once.
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* @param {string} event
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* @param {Function} fn
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*/
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once(event, fn) {
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if (!this._listeners.has(event)) {
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this._listeners.set(event, []);
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}
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this._listeners.get(event).push({ fn, once: true });
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}
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/**
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* Unsubscribe from an event.
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* @param {string} event
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* @param {Function} fn
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*/
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off(event, fn) {
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const list = this._listeners.get(event);
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if (!list) return;
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const idx = list.findIndex((entry) => entry.fn === fn);
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if (idx !== -1) list.splice(idx, 1);
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}
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/**
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* Emit an event with optional data.
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* @param {string} event
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* @param {*} [data]
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*/
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emit(event, data) {
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const list = this._listeners.get(event);
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if (!list || list.length === 0) return;
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// Iterate in reverse so we can safely remove "once" entries
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for (let i = list.length - 1; i >= 0; i--) {
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const entry = list[i];
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entry.fn(data);
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if (entry.once) {
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list.splice(i, 1);
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}
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}
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}
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/**
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* Remove all listeners for a specific event, or all events.
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* @param {string} [event]
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*/
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clear(event) {
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if (event) {
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this._listeners.delete(event);
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} else {
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this._listeners.clear();
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}
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}
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}
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module.exports = EventBus;
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