import {AbortError} from "../utils/error.js"; import {BaseObservable} from "./BaseObservable.js"; // like an EventEmitter, but doesn't have an event type export class BaseObservableValue extends BaseObservable { emit(argument) { for (const h of this._handlers) { h(argument); } } } class WaitForHandle { constructor(observable, predicate) { this._promise = new Promise((resolve, reject) => { this._reject = reject; this._subscription = observable.subscribe(v => { if (predicate(v)) { this._reject = null; resolve(v); this.dispose(); } }); }); } get promise() { return this._promise; } dispose() { if (this._subscription) { this._subscription(); this._subscription = null; } if (this._reject) { this._reject(new AbortError()); this._reject = null; } } } class ResolvedWaitForHandle { constructor(promise) { this.promise = promise; } dispose() {} } export class ObservableValue extends BaseObservableValue { constructor(initialValue) { super(); this._value = initialValue; } get() { return this._value; } set(value) { if (value !== this._value) { this._value = value; this.emit(this._value); } } waitFor(predicate) { if (predicate(this.get())) { return new ResolvedWaitForHandle(Promise.resolve(this.get())); } else { return new WaitForHandle(this, predicate); } } } export function tests() { return { "set emits an update": assert => { const a = new ObservableValue(); let fired = false; const subscription = a.subscribe(v => { fired = true; assert.strictEqual(v, 5); }); a.set(5); assert(fired); subscription(); }, "set doesn't emit if value hasn't changed": assert => { const a = new ObservableValue(5); let fired = false; const subscription = a.subscribe(() => { fired = true; }); a.set(5); a.set(5); assert(!fired); subscription(); }, "waitFor promise resolves on matching update": async assert => { const a = new ObservableValue(5); const handle = a.waitFor(v => v === 6); Promise.resolve().then(() => { a.set(6); }); await handle.promise; assert.strictEqual(a.get(), 6); }, "waitFor promise rejects when disposed": async assert => { const a = new ObservableValue(); const handle = a.waitFor(() => false); Promise.resolve().then(() => { handle.dispose(); }); await assert.rejects(handle.promise, AbortError); }, } }