mirror of
https://github.com/vector-im/element-call.git
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91 lines
2.8 KiB
TypeScript
91 lines
2.8 KiB
TypeScript
/*
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Copyright 2022 New Vector Ltd
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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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http://www.apache.org/licenses/LICENSE-2.0
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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 EventEmitter from "events";
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type NonEmptyArray<T> = [T, ...T[]];
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/**
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* An event emitter that lets events pile up in a backlog until a listener is
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* present, at which point any events that were missed are re-emitted.
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*/
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export class LazyEventEmitter extends EventEmitter {
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// eslint-disable-next-line @typescript-eslint/no-explicit-any
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private eventBacklogs = new Map<string | symbol, NonEmptyArray<any[]>>();
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// eslint-disable-next-line @typescript-eslint/no-explicit-any
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public emit(type: string | symbol, ...args: any[]): boolean {
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const hasListeners = super.emit(type, ...args);
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if (!hasListeners) {
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// The event was missed, so add it to the backlog
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const backlog = this.eventBacklogs.get(type);
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if (backlog) {
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backlog.push(args);
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} else {
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// Start a new backlog
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this.eventBacklogs.set(type, [args]);
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}
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}
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return hasListeners;
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}
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// eslint-disable-next-line @typescript-eslint/no-explicit-any
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public on(type: string | symbol, listener: (...args: any[]) => void): this {
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super.on(type, listener);
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const backlog = this.eventBacklogs.get(type);
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if (backlog) {
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// That was the first listener for this type, so let's send it all the
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// events that have piled up
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for (const args of backlog) super.emit(type, ...args);
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// Backlog is now clear
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this.eventBacklogs.delete(type);
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}
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return this;
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}
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public addListener(
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type: string | symbol,
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// eslint-disable-next-line @typescript-eslint/no-explicit-any
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listener: (...args: any[]) => void,
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): this {
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return this.on(type, listener);
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}
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// eslint-disable-next-line @typescript-eslint/no-explicit-any
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public once(type: string | symbol, listener: (...args: any[]) => void): this {
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super.once(type, listener);
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const backlog = this.eventBacklogs.get(type);
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if (backlog) {
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// That was the first listener for this type, so let's send it the first
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// of the events that have piled up
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super.emit(type, ...backlog[0]);
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// Clear the event from the backlog
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if (backlog.length === 1) {
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this.eventBacklogs.delete(type);
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} else {
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backlog.shift();
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}
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}
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return this;
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}
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}
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