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import PendingTask from './PendingTask';
import getLogger from './getLogger';
const log = getLogger('utils.ConditionVariable');
export type Condition = () => boolean;
export default class ConditionVariable {
private readonly condition: Condition;
private readonly defaultTimeout: number;
private listeners: PendingTask<void>[] = [];
constructor(condition: Condition, defaultTimeout = 0) {
this.condition = condition;
this.defaultTimeout = defaultTimeout;
}
async waitFor(timeoutMs?: number | undefined): Promise<void> {
if (this.condition()) {
return;
}
const timeoutOrDefault = timeoutMs ?? this.defaultTimeout;
let nowMs = Date.now();
const endMs = nowMs + timeoutOrDefault;
while (!this.condition() && nowMs < endMs) {
const remainingMs = endMs - nowMs;
const promise = new Promise<void>((resolve, reject) => {
if (this.condition()) {
resolve();
return;
}
const task = new PendingTask(resolve, reject, remainingMs);
this.listeners.push(task);
});
// We must keep waiting until the update has completed,
// so the tasks can't be started in parallel.
// eslint-disable-next-line no-await-in-loop
await promise;
nowMs = Date.now();
}
if (!this.condition()) {
log.error('Condition still does not hold after', timeoutOrDefault, 'ms');
throw new Error('Failed to wait for condition');
}
}
notifyAll(): void {
this.clearListenersWith((listener) => listener.resolve());
}
rejectAll(error: unknown): void {
this.clearListenersWith((listener) => listener.reject(error));
}
private clearListenersWith(callback: (listener: PendingTask<void>) => void) {
// Copy `listeners` so that we don't get into a race condition
// if one of the listeners adds another listener.
const { listeners } = this;
this.listeners = [];
listeners.forEach(callback);
}
}
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