#!/usr/bin/env python3
# coding: utf-8

import os
import pathlib
import subprocess


def ffprobe(filepath):
    """ffprobe 実行結果を返す"""
    command = ['ffprobe', str(filepath)]
    cp = subprocess.run(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    if cp.returncode != 0:
        print('ffprobe error: ')
        print(cp.stdout.decode('utf-8'))
        print(cp.stderr.decode('utf-8'))
        return None

    # stderrに出力されている。改行で分割
    return cp.stderr.decode('utf-8').split('\n')    


def ffmpeg_webm(filepath, fileinfo):
    """ffmpeg で WebM に変換する"""
    # 出力先
    dstpath = pathlib.Path(os.path.abspath(__file__)).with_name(filepath.stem + '.webm')

    # ビットレートを得る
    for line in fileinfo:
        line = line.rstrip().lstrip()
        if line.startswith('Stream'):
            _, index, stream, info = line.split(':')
            for item in info.split(','):
                if item.endswith('kb/s'):
                    bitrate = int(item.split()[0])

            if stream.endswith('Audio'):
                # 96 kbps で十分らしいが
                #if bitrate > 96:
                #    bitrate = 96
                bitrate_audio = bitrate

            elif stream.endswith('Video'):
                bitrate_video = bitrate

    # 変換コマンド
    command_pass1 = ['ffmpeg',
                     '-i', str(filepath),
                     '-c:v', 'libvpx-vp9', '-pass', '1', '-b:v', '{0}k'.format(bitrate_video),
                     '-threads', '8', '-speed', '4',
                     '-tile-columns', '6', '-frame-parallel', '1',
                     '-an',
                     '-f', 'webm',
                     '-y', '/dev/null']
    command_pass2 = ['ffmpeg',
                     '-i', str(filepath),
                     '-c:v', 'libvpx-vp9', '-pass', '2', '-b:v', '{0}k'.format(bitrate_video),
                     '-threads', '8', '-speed', '1',
                     '-tile-columns', '6', '-frame-parallel', '1',
                     '-auto-alt-ref', '1', '-lag-in-frames', '25',
                     '-c:a', 'libopus', '-b:a', '{0}k'.format(bitrate_audio),
                     '-f', 'webm',
                     '-y', str(dstpath)]
    cp = subprocess.run(command_pass1)
    if cp.returncode != 0:
        print('ffmpeg error: pass1')
        return None

    cp = subprocess.run(command_pass2)
    if cp.returncode != 0:
        print('ffmpeg error: pass2')
        return None

    return dstpath


def thumbnail_tile(filepath, fileinfo):
    """格子状サムネイルを作成する"""
    # 4x6
    tile_w = 4
    tile_h = 6
    # 144p
    scale_x = 256
    scale_y = 144
    # 出力先
    imgpath = pathlib.Path(os.path.abspath(__file__)).with_name(filepath.stem + '.jpg')

    # 動画の長さからキャプチャ間隔を決定する
    for line in fileinfo:
        line = line.rstrip().lstrip()
        if line.startswith('Duration'):
            hh, mm, ss = line.split(',')[0].split()[1].split(':')
            duration = int(hh) * 3600 + int(mm) * 60 + int(float(ss)) + 1
            rate = 1 + duration // (tile_w * tile_h)

    # 変換コマンド
    fps_filter = 'fps=fps=1/{0}'.format(rate)
    # 高さを固定とする
    scale_filter = 'scale={0}*iw/ih:{0}'.format(scale_y)
    tile_filter = 'tile={0}x{1}'.format(tile_w, tile_h)
    # アスペクト比を揃えたい場合はpadする
    #pad_filter = 'pad={0}:{1}:(ow-iw)/2:0:black'.format(scale_x, scale_y)
    #vf_filter = ','.join([fps_filter, scale_filter, pad_filter, tile_filter])
    vf_filter = ','.join([fps_filter, scale_filter, tile_filter])
    command = ['ffmpeg',
               '-i', str(filepath),
               '-vf', vf_filter,
               '-y', str(imgpath)]
    cp = subprocess.run(command)
    if cp.returncode != 0:
        print('ffmpeg error: capture')
        return None

    return imgpath


def main():
    # 指定のディレクトリ以下のファイルを全て処理する
    working_directory = pathlib.Path('/path/to/video')
    for srcpath in working_directory.glob('**/*'):
        probe = ffprobe(srcpath)
        if probe is not None:
            dst = ffmpeg_webm(srcpath, probe)
            img = thumbnail_tile(srcpath, probe)


if __name__ == '__main__':
    main()