microbit-web-bluetooth/src/promise-queue.ts

Web Bluetooth library for micro:bit

/*
* micro:bit Web Bluetooth
* Copyright (c) 2019 Rob Moran
*
* The MIT License (MIT)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the 'Software'), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/

/**
 * @hidden
 */
interface QueuedPromise {
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    fn: () => Promise<any>;
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    resolve: (value: any | PromiseLike<any>) => void;
    reject: (reason?: Error) => void;
}

/**
 * @hidden
 */
export class PromiseQueue {

    private queue: QueuedPromise[] = [];
    private running = 0;

    constructor(private concurrent = 1) {
    }

    private async pump(): Promise<void> {
        if (this.running >= this.concurrent) {
            return;
        }

        const promise = this.queue.shift();

        if (!promise) {
            return;
        }

        this.running ++;

        try {
            const result = await promise.fn();
            promise.resolve(result);
        } catch (error) {
            promise.reject(error as Error);
        }

        this.running --;
        return this.pump();
    }

    public add<T>(fn: () => Promise<T>): Promise<T> {
        return new Promise((resolve, reject) => {
            this.queue.push({
                fn,
                resolve,
                reject
            });

            return this.pump();
        });
    }
}