#!/usr/bin/env python
# -*- coding:utf-8 -*-

"""
使用 ffmpeg 截取视频片段并且重新拼接

使用方式:
提供文件格式如下：比如 input.txt

./input.mp4
00:01:00 00:02:00
00:04:00 00:08:00
"""

import os
import sys

CONCAT_FILE = '_concat.txt'


def read_input(filepath):
    with open(filepath) as f:
        lines = f.readlines()
        input_mp4 = lines[0].strip()
        suffix = input_mp4.split('.')[-1]
        for idx, start_end_time in enumerate(lines[1:]):
            pair = start_end_time.split()
            start, end = pair[0], pair[1]
            part_name = 'part_' + str(idx) + '.' + suffix
            cmd = "ffmpeg -i {} -ss {} -to {} -c copy {}".format(
                input_mp4, start, end, part_name
            )
            print(cmd)
            os.system(cmd)
            yield part_name


def write_part_to_file(part_list):
    dir_path = os.path.dirname(os.path.realpath(__file__))
    filepath_list = []
    for part_name in part_list:
        print(part_name)
        path = os.path.join(dir_path, part_name)
        filepath_list.append(path)

    with open(CONCAT_FILE, 'w') as f:
        for path in filepath_list:
            f.write("file '{}'\n".format(path))
    return filepath_list


def concat_video():
    cmd = "ffmpeg -f concat -safe 0 -i {} -c copy output.mp4".format(CONCAT_FILE)
    os.system(cmd)


def remove(filepath_list):
    """移除中间文件"""
    for path in filepath_list + [CONCAT_FILE]:
        if os.path.exists(path):
            os.remove(path)


def main():
    try:
        inputfile = sys.argv[1]
    except KeyError:
        print('must need input.txt')
    partnames = list(read_input(inputfile))
    filepath_list = write_part_to_file(partnames)
    concat_video()
    remove(filepath_list)


if __name__ == '__main__':
    main()