awaitqueue/lib/AwaitQueue.js

TypeScript utility to enqueue asynchronous tasks and run them sequentially one after another

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.AwaitQueue = void 0;
const Logger_1 = require("./Logger");
const errors_1 = require("./errors");
const logger = new Logger_1.Logger('AwaitQueue');
class AwaitQueue {
    // Queue of pending tasks (map of PendingTasks indexed by id).
    pendingTasks = new Map();
    // Incrementing PendingTask id.
    nextTaskId = 0;
    // Whether stop() method is stopping all pending tasks.
    stopping = false;
    constructor() {
        logger.debug('constructor()');
    }
    get size() {
        return this.pendingTasks.size;
    }
    async push(task, name) {
        name = name ?? task.name;
        logger.debug(`push() [name:${name}]`);
        if (typeof task !== 'function') {
            throw new TypeError('given task is not a function');
        }
        if (name) {
            try {
                Object.defineProperty(task, 'name', { value: name });
            }
            catch (error) { }
        }
        return new Promise((resolve, reject) => {
            const pendingTask = {
                id: this.nextTaskId++,
                task: task,
                name: name,
                enqueuedAt: Date.now(),
                executedAt: undefined,
                completed: false,
                resolve: (result) => {
                    // pendingTask.resolve() can only be called in execute() method. Since
                    // resolve() was called it means that the task successfully completed.
                    // However the task may have been stopped before it completed (via
                    // stop() or remove()) so its completed flag was already set. If this
                    // is the case, abort here since next task (if any) is already being
                    // executed.
                    if (pendingTask.completed) {
                        return;
                    }
                    pendingTask.completed = true;
                    // Remove the task from the queue.
                    this.pendingTasks.delete(pendingTask.id);
                    logger.debug(`resolving task [name:${pendingTask.name}]`);
                    // Resolve the task with the obtained result.
                    resolve(result);
                    // Execute the next pending task (if any).
                    const [nextPendingTask] = this.pendingTasks.values();
                    // NOTE: During the resolve() callback the user app may have interacted
                    // with the queue. For instance, the app may have pushed a task while
                    // the queue was empty so such a task is already being executed. If so,
                    // don't execute it twice.
                    if (nextPendingTask && !nextPendingTask.executedAt) {
                        void this.execute(nextPendingTask);
                    }
                },
                reject: (error) => {
                    // pendingTask.reject() can be called within execute() method if the
                    // task completed with error. However it may have also been called in
                    // stop() or remove() methods (before or while being executed) so its
                    // completed flag was already set. If so, abort here since next task
                    // (if any) is already being executed.
                    if (pendingTask.completed) {
                        return;
                    }
                    pendingTask.completed = true;
                    // Remove the task from the queue.
                    this.pendingTasks.delete(pendingTask.id);
                    logger.debug(`rejecting task [name:${pendingTask.name}]: %s`, String(error));
                    // Reject the task with the obtained error.
                    reject(error);
                    // Execute the next pending task (if any) unless stop() is running.
                    if (!this.stopping) {
                        const [nextPendingTask] = this.pendingTasks.values();
                        // NOTE: During the reject() callback the user app may have interacted
                        // with the queue. For instance, the app may have pushed a task while
                        // the queue was empty so such a task is already being executed. If so,
                        // don't execute it twice.
                        if (nextPendingTask && !nextPendingTask.executedAt) {
                            void this.execute(nextPendingTask);
                        }
                    }
                },
            };
            // Append task to the queue.
            this.pendingTasks.set(pendingTask.id, pendingTask);
            // And execute it if this is the only task in the queue.
            if (this.pendingTasks.size === 1) {
                void this.execute(pendingTask);
            }
        });
    }
    stop() {
        logger.debug('stop()');
        this.stopping = true;
        for (const pendingTask of this.pendingTasks.values()) {
            logger.debug(`stop() | stopping task [name:${pendingTask.name}]`);
            pendingTask.reject(new errors_1.AwaitQueueStoppedError());
        }
        this.stopping = false;
    }
    remove(taskIdx) {
        logger.debug(`remove() [taskIdx:${taskIdx}]`);
        const pendingTask = Array.from(this.pendingTasks.values())[taskIdx];
        if (!pendingTask) {
            logger.debug(`stop() | no task with given idx [taskIdx:${taskIdx}]`);
            return;
        }
        pendingTask.reject(new errors_1.AwaitQueueRemovedTaskError());
    }
    dump() {
        const now = Date.now();
        let idx = 0;
        return Array.from(this.pendingTasks.values()).map(pendingTask => ({
            idx: idx++,
            task: pendingTask.task,
            name: pendingTask.name,
            enqueuedTime: pendingTask.executedAt
                ? pendingTask.executedAt - pendingTask.enqueuedAt
                : now - pendingTask.enqueuedAt,
            executionTime: pendingTask.executedAt ? now - pendingTask.executedAt : 0,
        }));
    }
    async execute(pendingTask) {
        logger.debug(`execute() [name:${pendingTask.name}]`);
        if (pendingTask.executedAt) {
            throw new Error('task already being executed');
        }
        pendingTask.executedAt = Date.now();
        try {
            const result = await pendingTask.task();
            // Resolve the task with its resolved result (if any).
            pendingTask.resolve(result);
        }
        catch (error) {
            // Reject the task with its rejected error.
            pendingTask.reject(error);
        }
    }
}
exports.AwaitQueue = AwaitQueue;