lan-jukebox/routes/index.js

var app = require('express')();

// Body parsing
var bodyParser = require('body-parser');
app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());

// Validation
var expressValidator = require('express-validator');
app.use(expressValidator());

// Child process, for spawning youtube-dl
var child_process = require('child_process');

// The location of the youtube-dl executable
var YOUTUBE_DL_LOC = '/usr/bin/youtube-dl'

// Keep track of music to play, playing, and played
var playlist = [];
var playing = 'None';
var played = [];

var Player = require('player');

// Create a player with the proper error handling.
function playerCreator(song) {
    if (song)
	return new Player(song)
	.on('error', function(err) {playerHandleError(playlist, played)})
    return new Player()
	.on('error', function(err) {playerHandleError(playlist, played)})
}

player = playerCreator();

// Player functionality

// Songs move from playlist (if nothing is playing presently), to playing, to played.

// TODO check if song already exists in played.

// event: on error (No next song was found).
function playerHandleError(playlist, played) {

    // TODO Workaround for a bug in player: wait a couple seconds so the
    // songs don't overlap.
    
    // Move the recently playing song to played.
    played.push(playing);

    if (playlist.length != 0) {
	// Play the next song.
	player = playerCreator(playlist[0]);
	player.play();

	// Remove the added song.
	playing = playlist[0];
	playlist.shift();
    } else {
	// Reset the object, resetting its playlist.
	player = playerCreator();
	playing = 'None';
    }
}

// Add a song and start the playlist, if it's empty.
function playerAddSong(song) {
    if (player.list.length == 0) {
	// If this is the player's first song, start it.
	player = playerCreator(song);
	player.play();
	playing = song;
    } else { 
	// Otherwise add it to the queue
	playlist.push(song);
    }

}


/* GET home page. */
app.get('/', function(req, res, next) {
    var playlist_view;
    if(playlist.length) {
	playlist_view = '<p>Playlist:</p><ul>';
	for(var i=0; i < playlist.length; i++) {
	    playlist_view +=
		'<li>' +
		playlist[i].replace(/^\.\/downloads\//, '') .replace(/\.mp3$/, '') +
		'</li>';
	}
	playlist_view += '</ul>';
    } else {
	playlist_view = '<p>No songs in playlist.</p>';
    }
    var playing_view = '<p>Now playing: ' + playing.replace(/^\.\/downloads\//, '') .replace(/\.mp3$/, '') + '</p>';
    var played_view;
    if(played.length) {
	played_view = '<p>Played:</p><ul>';
	for(var i=0; i < played.length; i++) {
	    played_view +=
		'<li>' +
		played[i].replace(/^\.\/downloads\//, '') .replace(/\.mp3$/, '') +
		'</li>';
	}
	played_view += '</ul>';
    } else {
	played_view = '<p>No played songs.</p>';
    }
    res.render('index', { playlist_view: playlist_view,
			  playing_view: playing_view,
			  played_view: played_view });
});

app.get('/youtube', function(req, res, next) {
  res.render('youtube');
});

app.use(expressValidator({
    customValidators: {
	dlSuccess: function(video) {
	    // Test if the requested video is available.
	    // TODO make this non-blocking so music doesn't stop
	    var youtube_dl = child_process.spawnSync(YOUTUBE_DL_LOC, ['-s', video]);

	    // DEBUG: for when I forget to change the var
	    if(youtube_dl.stderr == null) {
		console.log("Your youtube-dl location is probably invalid.");
	    }

	    if (youtube_dl.stderr.toString()) {
		return false;
	    }
	    return true;
	}
    }
 }
));

app.post('/youtube', function(req, res) {
    var video = req.body.video;
    
    req.checkBody('video', 'URL is not valid.').dlSuccess();
    
    var errors = req.validationErrors();
    
    if(errors){
	res.render('youtube', {
	    errors:errors
	});
    } else {
        var youtube_dl = child_process.spawn(YOUTUBE_DL_LOC, ['-x', '--audio-format', 'mp3', '-o', 'downloads/%(title)s.%(ext)s', video]);
        youtube_dl.on('close', (code) => {
            console.log("Done getting " + video);
            var error;
            youtube_dl.stderr.on('data', (data) => {
                error = data;
                console.log(`Error getting video: ${data}`);
                // TODO give error to user when they return to /
            });

            if(!error) {
                var youtube_dl_get_title = child_process.spawnSync(YOUTUBE_DL_LOC, ['--get-title', video]);
		console.log(youtube_dl_get_title.stdout.toString());
                playerAddSong('./downloads/' + youtube_dl_get_title.stdout.toString()
			      .replace('\n', '')
			      .replace(new RegExp('"', 'g'), '\'')
			      + ".mp3");
            }
            res.redirect('/');
        });
    }
});

app.get('/file', function(req, res, next) {
  res.render('file');
});


module.exports = app;