from subprocess import call, Popen, PIPE, check_output, DEVNULL
from os import listdir, remove
from os.path import splitext, exists
from re import match
from sys import argv
from enum import Enum
from datetime import timedelta
from math import ceil



class Stream(Enum):
    AUDIO = 1
    VIDEO = 2

class File(Enum):
    LIST = 1
    LOOP = 2
    OUTPUT = 3

def getCmdStdErr(command):
    process = Popen(command, stderr=PIPE, stdout=PIPE)
    out, err = process.communicate()
    return err

def getDuration(ffprobe_output):
    durationPattern = r'.*Duration:\s(.+),\sstart.*'
    regex = match(durationPattern, str(ffprobe_output))
    duration = regex.groups()[0] if regex else None
    if not duration:
        raise ValueError('Cannot process ffprobe output!')
    return duration

def downloadStreams():
    print('Downloading audio stream... ', end='', flush=True)
    call(('/usr/bin/env', 'youtube-dl', '--extract-audio',
                                        '--output', '{}.%(ext)s'.format(FILES[Stream.AUDIO]),
                                        URL),
         stdout=DEVNULL, stderr=DEVNULL)
    print('Done!')
    print('Downloading video stream... ', end='', flush=True)
    call(('/usr/bin/env', 'youtube-dl', '--output', '{}.%(ext)s'.format(FILES[Stream.VIDEO]),
                                        URL),
         stdout=DEVNULL, stderr=DEVNULL)
    print('Done!')

def readExtensions():
    for file in listdir():
        for filename in FILES:
            if match('^{}.*'.format(FILES[filename]), file):
                FILES[filename] = file

def yes_no_question(question, default):
    valid = {"yes": True, "y": True, "ye": True,
             "no": False, "n": False}
    if default is None:
        prompt = " [y/n] "
    elif default == "yes":
        prompt = " [Y/n] "
    elif default == "no":
        prompt = " [y/N] "
    else:
        raise ValueError("Invalid default answer: {}!".format(default))

    while True:
        print(question + prompt)
        choice = input().lower()
        if default is not None and choice == '':
            return valid[default]
        elif choice in valid:
            return valid[choice]
        else:
            print("Please respond with 'yes'(y) or 'no'(n)!")


FILES = {Stream.AUDIO: 'audio', Stream.VIDEO: 'video',
         File.LIST: 'list.txt', File.LOOP: 'loop', File.OUTPUT: 'output.mp4'}
OUTPUT_KEYS = [File.OUTPUT]
URL = argv[1] if len(argv) > 0 else ''  # youtube-dl error message will be shown if ''


# fetch video title
FILES[File.OUTPUT] = check_output(('/usr/bin/env', 'youtube-dl', '--get-title', argv[1])).decode('utf-8').strip() + '.mp4'

# ask what to do if output exists
if exists(FILES[File.OUTPUT]):
    answer = yes_no_question('A file named "{}" already exists! Overwrite?'.format(FILES[File.OUTPUT]), default='no')
    if not answer:
        print('Exiting!')
        exit()
    else:
        remove(FILES[File.OUTPUT])

# download streams and update FILE dict with extensions
downloadStreams()
readExtensions()

# get stream lengths via ffprobe
audioData= getDuration(getCmdStdErr(('/usr/bin/env', 'ffprobe', FILES[Stream.AUDIO]))).split(':')
videoData = getDuration(getCmdStdErr(('/usr/bin/env', 'ffprobe', FILES[Stream.VIDEO]))).split(':')

audioLen = timedelta(hours=float(audioData[0]), minutes=float(audioData[1]), seconds=float(audioData[2]))
videoLen = timedelta(hours=float(videoData[0]), minutes=float(videoData[1]), seconds=float(videoData[2]))

# decide which stream needs some looping
longer = audioLen if audioLen > videoLen else videoLen
shorter = audioLen if audioLen < videoLen else videoLen
shorterFile = FILES[Stream.AUDIO] if audioLen < videoLen else FILES[Stream.VIDEO]
FILES[File.LOOP] += splitext(shorterFile)[1]

timesLoop = ceil(longer.seconds / shorter.seconds)

# write concat helper file for ffmpeg
with open(FILES[File.LIST], 'w') as f:
    for i in range(timesLoop):
        print("file '{}'".format(shorterFile), file=f)

# loop & mux
print('Looping shorter stream... ', end='', flush=True)
call(('/usr/bin/env', 'ffmpeg', '-f', 'concat', '-i', FILES[File.LIST], '-c', 'copy', FILES[File.LOOP]),
     stdout=DEVNULL, stderr=DEVNULL)
print('Done!')
print('Muxing streams... ', end='', flush=True)
call(('/usr/bin/env', 'ffmpeg', '-i', FILES[File.LOOP],
                                '-i', FILES[Stream.AUDIO],
                                '-map', '0', '-map', '1',
                                '-c', 'copy', FILES[File.OUTPUT]),
     stdout=DEVNULL, stderr=DEVNULL)
print('Done!')

# cleanup
for key in FILES:
    if key not in OUTPUT_KEYS:
        remove(FILES[key])