import subprocess
import os

def song(input_song, output_song, avconv=False, verbose=False):
    if not input_song == output_song:
        input_song = input_song.encode('utf-8')
        output_song = output_song.encode('utf-8')
        print('Converting ' + input_song + ' to ' + output_song.split('.')[-1])
        if avconv:
            exit_code = convert_with_avconv(input_song, output_song, verbose)
        else:
            exit_code = convert_with_FFmpeg(input_song, output_song, verbose)
        return exit_code
    return None

def convert_with_avconv(input_song, output_song, verbose):
    # different path for windows
    if os.name == 'nt':
        avconv_path = 'Scripts\\avconv.exe'
    else:
        avconv_path = 'avconv'

    if verbose:
        level = 'debug'
    else:
        level = '0'

    command = [avconv_path,
               '-loglevel', level,
               '-i',        'Music/' + input_song,
               '-ab',       '192k',
               'Music/' + output_song]

    subprocess.call(command)


def convert_with_FFmpeg(input_song, output_song, verbose):
    # What are the differences and similarities between ffmpeg, libav, and avconv?
    # https://stackoverflow.com/questions/9477115
    # ffmeg encoders high to lower quality
    # libopus > libvorbis >= libfdk_aac > aac > libmp3lame
    # libfdk_aac due to copyrights needs to be compiled by end user
    # on MacOS brew install ffmpeg --with-fdk-aac will do just that. Other OS?
    # https://trac.ffmpeg.org/wiki/Encode/AAC

    if os.name == "nt":
        ffmpeg_pre = 'Scripts\\ffmpeg.exe '
    else:
        ffmpeg_pre = 'ffmpeg '

    ffmpeg_pre += '-y '
    if not verbose:
        ffmpeg_pre += '-hide_banner -nostats -v panic '

    input_ext = input_song.split('.')[-1]
    output_ext = output_song.split('.')[-1]

    if input_ext == 'm4a':
        if output_ext == 'mp3':
            ffmpeg_params = '-codec:v copy -codec:a libmp3lame -q:a 2 '
        elif output_ext == 'webm':
            ffmpeg_params = '-c:a libopus -vbr on -b:a 192k -vn '

    elif input_ext == 'webm':
        if output_ext == 'mp3':
            ffmpeg_params = ' -ab 192k -ar 44100 -vn '
        elif output_ext == 'm4a':
            ffmpeg_params = '-cutoff 20000 -c:a libfdk_aac -b:a 192k -vn '

    command = (ffmpeg_pre +
              '-i Music/' + input_song + ' ' +
               ffmpeg_params +
              'Music/' + output_song + '').split(' ')

    subprocess.call(command)