import { EventEmitter } from 'eventemitter3';
import pTimeout, { TimeoutError } from 'p-timeout';
import PriorityQueue from './priority-queue.js';
/**
Promise queue with concurrency control.
*/
export default class PQueue extends EventEmitter {
    #carryoverConcurrencyCount;
    #isIntervalIgnored;
    #intervalCount = 0;
    #intervalCap;
    #interval;
    #intervalEnd = 0;
    #intervalId;
    #timeoutId;
    #queue;
    #queueClass;
    #pending = 0;
    // The `!` is needed because of https://github.com/microsoft/TypeScript/issues/32194
    #concurrency;
    #isPaused;
    #throwOnTimeout;
    /**
    Per-operation timeout in milliseconds. Operations fulfill once `timeout` elapses if they haven't already.

    Applies to each future operation.
    */
    timeout;
    // TODO: The `throwOnTimeout` option should affect the return types of `add()` and `addAll()`
    constructor(options) {
        super();
        // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
        options = {
            carryoverConcurrencyCount: false,
            intervalCap: Number.POSITIVE_INFINITY,
            interval: 0,
            concurrency: Number.POSITIVE_INFINITY,
            autoStart: true,
            queueClass: PriorityQueue,
            ...options,
        };
        if (!(typeof options.intervalCap === 'number' && options.intervalCap >= 1)) {
            throw new TypeError(`Expected \`intervalCap\` to be a number from 1 and up, got \`${options.intervalCap?.toString() ?? ''}\` (${typeof options.intervalCap})`);
        }
        if (options.interval === undefined || !(Number.isFinite(options.interval) && options.interval >= 0)) {
            throw new TypeError(`Expected \`interval\` to be a finite number >= 0, got \`${options.interval?.toString() ?? ''}\` (${typeof options.interval})`);
        }
        this.#carryoverConcurrencyCount = options.carryoverConcurrencyCount;
        this.#isIntervalIgnored = options.intervalCap === Number.POSITIVE_INFINITY || options.interval === 0;
        this.#intervalCap = options.intervalCap;
        this.#interval = options.interval;
        this.#queue = new options.queueClass();
        this.#queueClass = options.queueClass;
        this.concurrency = options.concurrency;
        this.timeout = options.timeout;
        this.#throwOnTimeout = options.throwOnTimeout === true;
        this.#isPaused = options.autoStart === false;
    }
    get #doesIntervalAllowAnother() {
        return this.#isIntervalIgnored || this.#intervalCount < this.#intervalCap;
    }
    get #doesConcurrentAllowAnother() {
        return this.#pending < this.#concurrency;
    }
    #next() {
        this.#pending--;
        this.#tryToStartAnother();
        this.emit('next');
    }
    #onResumeInterval() {
        this.#onInterval();
        this.#initializeIntervalIfNeeded();
        this.#timeoutId = undefined;
    }
    get #isIntervalPaused() {
        const now = Date.now();
        if (this.#intervalId === undefined) {
            const delay = this.#intervalEnd - now;
            if (delay < 0) {
                // Act as the interval was done
                // We don't need to resume it here because it will be resumed on line 160
                this.#intervalCount = (this.#carryoverConcurrencyCount) ? this.#pending : 0;
            }
            else {
                // Act as the interval is pending
                if (this.#timeoutId === undefined) {
                    this.#timeoutId = setTimeout(() => {
                        this.#onResumeInterval();
                    }, delay);
                }
                return true;
            }
        }
        return false;
    }
    #tryToStartAnother() {
        if (this.#queue.size === 0) {
            // We can clear the interval ("pause")
            // Because we can redo it later ("resume")
            if (this.#intervalId) {
                clearInterval(this.#intervalId);
            }
            this.#intervalId = undefined;
            this.emit('empty');
            if (this.#pending === 0) {
                this.emit('idle');
            }
            return false;
        }
        if (!this.#isPaused) {
            const canInitializeInterval = !this.#isIntervalPaused;
            if (this.#doesIntervalAllowAnother && this.#doesConcurrentAllowAnother) {
                const job = this.#queue.dequeue();
                if (!job) {
                    return false;
                }
                this.emit('active');
                job();
                if (canInitializeInterval) {
                    this.#initializeIntervalIfNeeded();
                }
                return true;
            }
        }
        return false;
    }
    #initializeIntervalIfNeeded() {
        if (this.#isIntervalIgnored || this.#intervalId !== undefined) {
            return;
        }
        this.#intervalId = setInterval(() => {
            this.#onInterval();
        }, this.#interval);
        this.#intervalEnd = Date.now() + this.#interval;
    }
    #onInterval() {
        if (this.#intervalCount === 0 && this.#pending === 0 && this.#intervalId) {
            clearInterval(this.#intervalId);
            this.#intervalId = undefined;
        }
        this.#intervalCount = this.#carryoverConcurrencyCount ? this.#pending : 0;
        this.#processQueue();
    }
    /**
    Executes all queued functions until it reaches the limit.
    */
    #processQueue() {
        // eslint-disable-next-line no-empty
        while (this.#tryToStartAnother()) { }
    }
    get concurrency() {
        return this.#concurrency;
    }
    set concurrency(newConcurrency) {
        if (!(typeof newConcurrency === 'number' && newConcurrency >= 1)) {
            throw new TypeError(`Expected \`concurrency\` to be a number from 1 and up, got \`${newConcurrency}\` (${typeof newConcurrency})`);
        }
        this.#concurrency = newConcurrency;
        this.#processQueue();
    }
    async #throwOnAbort(signal) {
        return new Promise((_resolve, reject) => {
            signal.addEventListener('abort', () => {
                reject(signal.reason);
            }, { once: true });
        });
    }
    async add(function_, options = {}) {
        options = {
            timeout: this.timeout,
            throwOnTimeout: this.#throwOnTimeout,
            ...options,
        };
        return new Promise((resolve, reject) => {
            this.#queue.enqueue(async () => {
                this.#pending++;
                this.#intervalCount++;
                try {
                    options.signal?.throwIfAborted();
                    let operation = function_({ signal: options.signal });
                    if (options.timeout) {
                        operation = pTimeout(Promise.resolve(operation), { milliseconds: options.timeout });
                    }
                    if (options.signal) {
                        operation = Promise.race([operation, this.#throwOnAbort(options.signal)]);
                    }
                    const result = await operation;
                    resolve(result);
                    this.emit('completed', result);
                }
                catch (error) {
                    if (error instanceof TimeoutError && !options.throwOnTimeout) {
                        resolve();
                        return;
                    }
                    reject(error);
                    this.emit('error', error);
                }
                finally {
                    this.#next();
                }
            }, options);
            this.emit('add');
            this.#tryToStartAnother();
        });
    }
    async addAll(functions, options) {
        return Promise.all(functions.map(async (function_) => this.add(function_, options)));
    }
    /**
    Start (or resume) executing enqueued tasks within concurrency limit. No need to call this if queue is not paused (via `options.autoStart = false` or by `.pause()` method.)
    */
    start() {
        if (!this.#isPaused) {
            return this;
        }
        this.#isPaused = false;
        this.#processQueue();
        return this;
    }
    /**
    Put queue execution on hold.
    */
    pause() {
        this.#isPaused = true;
    }
    /**
    Clear the queue.
    */
    clear() {
        this.#queue = new this.#queueClass();
    }
    /**
    Can be called multiple times. Useful if you for example add additional items at a later time.

    @returns A promise that settles when the queue becomes empty.
    */
    async onEmpty() {
        // Instantly resolve if the queue is empty
        if (this.#queue.size === 0) {
            return;
        }
        await this.#onEvent('empty');
    }
    /**
    @returns A promise that settles when the queue size is less than the given limit: `queue.size < limit`.

    If you want to avoid having the queue grow beyond a certain size you can `await queue.onSizeLessThan()` before adding a new item.

    Note that this only limits the number of items waiting to start. There could still be up to `concurrency` jobs already running that this call does not include in its calculation.
    */
    async onSizeLessThan(limit) {
        // Instantly resolve if the queue is empty.
        if (this.#queue.size < limit) {
            return;
        }
        await this.#onEvent('next', () => this.#queue.size < limit);
    }
    /**
    The difference with `.onEmpty` is that `.onIdle` guarantees that all work from the queue has finished. `.onEmpty` merely signals that the queue is empty, but it could mean that some promises haven't completed yet.

    @returns A promise that settles when the queue becomes empty, and all promises have completed; `queue.size === 0 && queue.pending === 0`.
    */
    async onIdle() {
        // Instantly resolve if none pending and if nothing else is queued
        if (this.#pending === 0 && this.#queue.size === 0) {
            return;
        }
        await this.#onEvent('idle');
    }
    async #onEvent(event, filter) {
        return new Promise(resolve => {
            const listener = () => {
                if (filter && !filter()) {
                    return;
                }
                this.off(event, listener);
                resolve();
            };
            this.on(event, listener);
        });
    }
    /**
    Size of the queue, the number of queued items waiting to run.
    */
    get size() {
        return this.#queue.size;
    }
    /**
    Size of the queue, filtered by the given options.

    For example, this can be used to find the number of items remaining in the queue with a specific priority level.
    */
    sizeBy(options) {
        // eslint-disable-next-line unicorn/no-array-callback-reference
        return this.#queue.filter(options).length;
    }
    /**
    Number of running items (no longer in the queue).
    */
    get pending() {
        return this.#pending;
    }
    /**
    Whether the queue is currently paused.
    */
    get isPaused() {
        return this.#isPaused;
    }
}