import util from 'util';

export const YOUTUBE_BASE = 'https://www.youtube.com/%s';
export const WATCH_BASE = util.format(YOUTUBE_BASE, 'watch?v=%s');

/**
 * Hold a queue of promises from which results can be extracted.
 */
export class PromiseQueue
{
    constructor()
    {
        this.pending = new Set();
    }

    /**
     * Add a new promise to the queue.
     *
     * @param Promise promise Promise to be added.
     */
    add(promise)
    {
        const wrapped = promise.then(res => {
            this.pending.delete(wrapped);
            return res;
        });

        this.pending.add(wrapped);
    }

    /**
     * Check whether there is no promise pending in the queue.
     *
     * @return boolean
     */
    empty()
    {
        return this.pending.size === 0;
    }

    /**
     * Extract the next available result from the promise queue.
     *
     * @return any Next result.
     */
    next()
    {
        return Promise.race(this.pending);
    }
}

/**
 * Escape double quotes in a string.
 */
export const escapeQuotes = str => str.replace(/"/g, '\\"');

/**
 * Make a promise that is resolved in a point in the future.
 *
 * @param number time Time to wait before resolving the promise (ms).
 * @return null
 */
export const sleep = time => new Promise(resolve => setTimeout(resolve, time));