Pony.fm/app/Http/Controllers/PlaylistsController.php

<?php

namespace App\Http\Controllers;

use App;
use App\Playlist;
use App\ResourceLogItem;
use App\Track;
use App\PlaylistDownloader;
use Auth;
use Illuminate\Support\Facades\Redirect;
use View;

class PlaylistsController extends Controller
{
    public function getIndex()
    {
        return View::make('playlists.index');
    }

    public function getPlaylist($id, $slug)
    {
        $playlist = Playlist::find($id);
        if (!$playlist || !$playlist->canView(Auth::user())) {
            App::abort(404);
        }

        if ($playlist->slug != $slug) {
            return Redirect::action('PlaylistsController@getPlaylist', [$id, $playlist->slug]);
        }

        return View::make('playlists.show');
    }

    public function getShortlink($id)
    {
        $playlist = Playlist::find($id);
        if (!$playlist || !$playlist->canView(Auth::user())) {
            App::abort(404);
        }

        return Redirect::action('PlaylistsController@getPlaylist', [$id, $playlist->slug]);
    }

    public function getDownload($id, $extension)
    {
        $playlist = Playlist::with('tracks', 'user', 'tracks.album')->find($id);
        if (!$playlist || !$playlist->is_public) {
            App::abort(404);
        }

        $format = null;
        $formatName = null;

        foreach (Track::$Formats as $name => $item) {
            if ($item['extension'] == $extension) {
                $format = $item;
                $formatName = $name;
                break;
            }
        }

        if ($format == null) {
            App::abort(404);
        }

        ResourceLogItem::logItem('playlist', $id, ResourceLogItem::DOWNLOAD, $format['index']);
        $downloader = new PlaylistDownloader($playlist, $formatName);
        $downloader->download();
    }
}