// From https://github.com/rauschma/async-iter-demo/tree/master/src under MIT license
// http://2ality.com/2016/10/asynchronous-iteration.html
class ArrayQueue extends Array {
    enqueue(value) {
        // Add at the end
        return this.push(value);
    }
    dequeue() {
        // Remove first element
        return this.shift();
    }
}
export default class AsyncQueue {
    _values;
    _settlers;
    _closed;
    constructor() {
        // enqueues > dequeues
        this._values = new ArrayQueue();
        // dequeues > enqueues
        this._settlers = new ArrayQueue();
        this._closed = false;
    }
    close() {
        while (this._settlers.length > 0) {
            this._settlers.dequeue().resolve({ done: true });
        }
        this._closed = true;
    }
    [Symbol.asyncIterator]() {
        return this;
    }
    enqueue(value) {
        if (this._closed) {
            throw new Error('Closed');
        }
        if (this._settlers.length > 0) {
            if (this._values.length > 0) {
                throw new Error('Illegal internal state');
            }
            const settler = this._settlers.dequeue();
            if (value instanceof Error) {
                settler.reject(value);
            }
            else {
                settler.resolve({ value });
            }
        }
        else {
            this._values.enqueue(value);
        }
    }
    /**
     * @returns a Promise for an IteratorResult
     */
    next() {
        if (this._values.length > 0) {
            const value = this._values.dequeue();
            if (value instanceof Error) {
                return Promise.reject(value);
            }
            return Promise.resolve({ value });
        }
        if (this._closed) {
            if (this._settlers.length > 0) {
                throw new Error('Illegal internal state');
            }
            return Promise.resolve({ done: true });
        }
        // Wait for new values to be enqueued
        return new Promise((resolve, reject) => {
            this._settlers.enqueue({ resolve, reject });
        });
    }
}
/**
 * @returns a Promise for an Array with the elements in `asyncIterable`
 */
export async function takeAsync(asyncIterable, count = Infinity) {
    const result = [];
    const iterator = asyncIterable[Symbol.asyncIterator]();
    while (result.length < count) {
        const { value, done } = await iterator.next();
        if (done) {
            break;
        }
        result.push(value);
    }
    return result;
}