131 lines
3.5 KiB
TypeScript
131 lines
3.5 KiB
TypeScript
/**
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* @license
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import {
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EventCallback,
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EventEmitterService,
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UnsubscribeMethod,
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} from './gr-event-interface';
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/**
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* An lite implementation of
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* https://nodejs.org/api/events.html#events_class_eventemitter.
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*
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* This is unrelated to the native DOM events, you should use it when you want
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* to enable EventEmitter interface on any class.
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*
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* @example
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*
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* class YourClass extends EventEmitter {
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* // now all instance of YourClass will have this EventEmitter interface
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* }
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*
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*/
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export class EventEmitter implements EventEmitterService {
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private _listenersMap = new Map<string, EventCallback[]>();
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/**
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* Register an event listener to an event.
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*/
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addListener(eventName: string, cb: EventCallback): UnsubscribeMethod {
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if (!eventName || !cb) {
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console.warn('A valid eventname and callback is required!');
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return () => {};
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}
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const listeners = this._listenersMap.get(eventName) || [];
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listeners.push(cb);
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this._listenersMap.set(eventName, listeners);
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return () => {
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this.off(eventName, cb);
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};
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}
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/**
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* Alias for addListener.
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*/
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on(eventName: string, cb: EventCallback): UnsubscribeMethod {
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return this.addListener(eventName, cb);
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}
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/**
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* Attach event handler only once. Automatically removed.
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*/
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once(eventName: string, cb: EventCallback): UnsubscribeMethod {
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const onceWrapper = (...args: any[]) => {
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cb(...args);
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this.off(eventName, onceWrapper);
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};
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return this.on(eventName, onceWrapper);
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}
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/**
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* De-register an event listener to an event.
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*/
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removeListener(eventName: string, cb: EventCallback): void {
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let listeners = this._listenersMap.get(eventName) || [];
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listeners = listeners.filter(listener => listener !== cb);
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this._listenersMap.set(eventName, listeners);
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}
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/**
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* Alias to removeListener
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*/
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off(eventName: string, cb: EventCallback): void {
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this.removeListener(eventName, cb);
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}
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/**
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* Synchronously calls each of the listeners registered for
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* the event named eventName, in the order they were registered,
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* passing the supplied detail to each.
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*
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* @returns true if the event had listeners, false otherwise.
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*/
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emit(eventName: string, detail: any): boolean {
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const listeners = this._listenersMap.get(eventName) || [];
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for (const listener of listeners) {
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try {
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listener(detail);
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} catch (e) {
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console.error(e);
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}
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}
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return listeners.length !== 0;
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}
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/**
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* Alias to emit.
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*/
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dispatch(eventName: string, detail: any): boolean {
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return this.emit(eventName, detail);
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}
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/**
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* Remove listeners for a specific event or all.
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*
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* @param eventName if not provided, will remove all
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*/
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removeAllListeners(eventName: string): void {
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if (eventName) {
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this._listenersMap.set(eventName, []);
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} else {
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this._listenersMap = new Map();
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}
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}
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}
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