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88 lines
2.8 KiB
TypeScript
88 lines
2.8 KiB
TypeScript
/*
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Copyright 2020 The Matrix.org Foundation C.I.C.
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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 { logger } from "matrix-js-sdk/src/logger";
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import { IDestroyable } from "./IDestroyable";
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import { arrayFastClone } from "./arrays";
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export type WhenFn<T> = (w: Whenable<T>) => void;
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/**
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* Whenables are a cheap way to have Observable patterns mixed with typical
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* usage of Promises, without having to tear down listeners or calls. Whenables
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* are intended to be used when a condition will be met multiple times and
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* the consumer needs to know *when* that happens.
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*/
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export abstract class Whenable<T> implements IDestroyable {
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private listeners: {condition: T | null, fn: WhenFn<T>}[] = [];
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/**
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* Sets up a call to `fn` *when* the `condition` is met.
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* @param condition The condition to match.
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* @param fn The function to call.
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* @returns This.
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*/
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public when(condition: T, fn: WhenFn<T>): Whenable<T> {
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this.listeners.push({ condition, fn });
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return this;
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}
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/**
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* Sets up a call to `fn` *when* any of the `conditions` are met.
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* @param conditions The conditions to match.
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* @param fn The function to call.
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* @returns This.
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*/
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public whenAnyOf(conditions: T[], fn: WhenFn<T>): Whenable<T> {
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for (const condition of conditions) {
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this.when(condition, fn);
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}
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return this;
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}
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/**
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* Sets up a call to `fn` *when* any condition is met.
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* @param fn The function to call.
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* @returns This.
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*/
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public whenAnything(fn: WhenFn<T>): Whenable<T> {
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this.listeners.push({ condition: null, fn });
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return this;
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}
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/**
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* Notifies all the listeners of a given condition.
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* @param condition The new condition that has been met.
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*/
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protected notifyCondition(condition: T) {
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const listeners = arrayFastClone(this.listeners); // clone just in case the handler modifies us
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for (const listener of listeners) {
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if (listener.condition === null || listener.condition === condition) {
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try {
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listener.fn(this);
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} catch (e) {
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logger.error(`Error calling whenable listener for ${condition}:`, e);
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}
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}
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}
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}
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public destroy() {
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this.listeners = [];
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}
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}
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