import argparse
import subprocess
import pathlib


BASE_COMMAND = 'ffmpeg -fflags +genpts -i {input}'
BASE_COMMAND += ' -c:a copy -c:v copy -threads 8 -sn -y {output}'


def load_arguments():
    parser = argparse.ArgumentParser()
    parser.add_argument('root_dir')
    parser.add_argument('--dry-run', action='store_true')
    return parser.parse_args()


def traverse(base_dir):
    return pathlib.Path(base_dir).glob('**/*.VOB')


def noop_or_create_dir(path):
    path.parent.mkdir(parents=True, exist_ok=True)


def convert(input_file, output_file, dry_run):
    command = BASE_COMMAND.format(input=input_file.as_posix(),
                                  output=output_file.as_posix())

    if dry_run:
        print(command)
    else:
        subprocess.call(command, shell=True)


def to_output_path(root_dir, path):
    def decorate_dir(base_dir):
        if base_dir[-1] != '/':
            base_dir += '/'
        return base_dir

    root_dir_str = decorate_dir(root_dir)
    output_path = path.as_posix().replace(root_dir_str, '')
    output_path = output_path.replace('/', '_')
    output_path = output_path.replace('.VOB', '.mov')
    return pathlib.Path(output_path)


def main():
    args = load_arguments()

    for input_path in traverse((args.root_dir)):
        output_path = to_output_path(args.root_dir, input_path)
        noop_or_create_dir(output_path)
        convert(input_path, output_path, dry_run=args.dry_run)


if __name__ == '__main__':
    main()