"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.Lock = void 0;
// Based on https://github.com/jsoendermann/semaphore-async-await/blob/master/src/Semaphore.ts
class Lock {
constructor() {
this.permits = 1;
this.promiseResolverQueue = [];
}
/**
* Returns a promise used to wait for a permit to become available. This method should be awaited on.
* @returns A promise that gets resolved when execution is allowed to proceed.
*/
async acquire() {
if (this.permits > 0) {
this.permits -= 1;
return Promise.resolve(true);
}
// If there is no permit available, we return a promise that resolves once the semaphore gets
// signaled enough times that permits is equal to one.
return new Promise((resolver) => this.promiseResolverQueue.push(resolver));
}
/**
* Increases the number of permits by one. If there are other functions waiting, one of them will
* continue to execute in a future iteration of the event loop.
*/
release() {
this.permits += 1;
if (this.permits > 1 && this.promiseResolverQueue.length > 0) {
// eslint-disable-next-line no-console
console.warn('Lock.permits should never be > 0 when there is someone waiting.');
}
else if (this.permits === 1 && this.promiseResolverQueue.length > 0) {
// If there is someone else waiting, immediately consume the permit that was released
// at the beginning of this function and let the waiting function resume.
this.permits -= 1;
const nextResolver = this.promiseResolverQueue.shift();
if (nextResolver) {
nextResolver(true);
}
}
}
}
exports.Lock = Lock;
//# sourceMappingURL=lock.js.map