'use strict';

const Promise = require("bluebird");
const bhttp = require("bhttp");
const events = require("events");

function getHighestMediaID(items) {
    return Math.max.apply(null, items.map(item => item.media_id));
}

module.exports = function createPlaylist(url) {
    let queuedTracks = [];
    let lastKnownID = 0;

    function getNewTracks() {
        return Promise.try(() => {
            console.log("CHECKING for new tracks...");
            return bhttp.get(url);
        }).then((response) => {
            let newTracks = response.body.filter((track) => {
                return track.media_id > lastKnownID;
            });

            if (newTracks.length > 0) {
                console.log(`FOUND ${newTracks.length} new tracks!`);
                queuedTracks = queuedTracks.concat(newTracks);
                lastKnownID = getHighestMediaID(response.body);
            } else {
                console.log("NO new tracks found.")
            }
        });
    }

    return Promise.try(() => {
        return bhttp.get(url);
    }).then((response) => {
        lastKnownID = getHighestMediaID(response.body) - 2;

        return Object.assign(new events.EventEmitter(), {
            reportFinished: function() {
                return Promise.try(() => {
                    return getNewTracks();
                }).then(() => {
                    if (queuedTracks.length > 0) {
                        this.emit("track", queuedTracks.shift());
                    } else {
                        return Promise.try(() => {
                            return Promise.delay(5000);
                        }).then(() => {
                            return this.reportFinished();
                        })
                    }
                });
            }
        });
    })
};