#!/usr/bin/env python
from __future__ import unicode_literals

import argparse
import ffmpeg
import logging
import re
import subprocess


logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__file__)
logger.setLevel(logging.INFO)

DEFAULT_DURATION = 0.3
DEFAULT_THRESHOLD = -60

parser = argparse.ArgumentParser(description='Split media into separate chunks wherever silence occurs')
parser.add_argument('in_filename', help='Input filename (`-` for stdin)')
parser.add_argument('out_pattern', help='Output filename pattern (e.g. `out/chunk_%%04d.wav`)')
parser.add_argument('--silence-threshold', default=DEFAULT_THRESHOLD, type=int, help='Silence threshold (in dB)')
parser.add_argument('--silence-duration', default=DEFAULT_DURATION, type=float, help='Silence duration')
parser.add_argument('--start-time', type=float, help='Start time (seconds)')
parser.add_argument('--end-time', type=float, help='End time (seconds)')


silence_start_re = re.compile(' silence_start: (?P<start>[0-9]+(\.?[0-9]*))$')
silence_end_re = re.compile(' silence_end: (?P<end>[0-9]+(\.?[0-9]*)) ')
total_duration_re = re.compile(
    'size=[^ ]+ time=(?P<hours>[0-9]{2}):(?P<minutes>[0-9]{2}):(?P<seconds>[0-9\.]{5}) bitrate=')


def get_chunk_times(in_filename, silence_threshold, silence_duration, start_time=None, end_time=None):
    input_kwargs = {}
    if start_time is not None:
        input_kwargs['ss'] = start_time
    else:
        start_time = 0.
    if end_time is not None:
        input_kwargs['t'] = end_time - start_time

    args = (ffmpeg
        .input(in_filename, **input_kwargs)
        .filter_('silencedetect', n='{}dB'.format(silence_threshold), d=silence_duration)
        .output('-', format='null')
        .get_args()
    )
    p = subprocess.Popen(['ffmpeg'] + args, stderr=subprocess.PIPE)
    output = p.communicate()[1].decode('utf-8')
    lines = output.splitlines()

    # Chunks start when silence ends, and chunks end when silence starts.
    chunk_starts = []
    chunk_ends = []
    for line in lines:
        silence_start_match = silence_start_re.search(line)
        silence_end_match = silence_end_re.search(line)
        total_duration_match = total_duration_re.search(line)
        if silence_start_match:
            chunk_ends.append(float(silence_start_match.group('start')))
            if len(chunk_starts) == 0:
                # Started with non-silence.
                chunk_starts.append(start_time or 0.)
        elif silence_end_match:
            chunk_starts.append(float(silence_end_match.group('end')))
        elif total_duration_match:
            hours = int(total_duration_match.group('hours'))
            minutes = int(total_duration_match.group('minutes'))
            seconds = float(total_duration_match.group('seconds'))
            end_time = hours * 3600 + minutes * 60 + seconds

    if len(chunk_starts) == 0:
        # No silence found.
        chunk_starts.append(start_time)

    if len(chunk_starts) > len(chunk_ends):
        # Finished with non-silence.
        chunk_ends.append(end_time or 10000000.)

    return list(zip(chunk_starts, chunk_ends))


def split_audio(
    in_filename,
    out_pattern,
    silence_threshold=DEFAULT_THRESHOLD,
    silence_duration=DEFAULT_DURATION,
    start_time=None,
    end_time=None,
):
    chunk_times = get_chunk_times(in_filename, silence_threshold, silence_duration, start_time, end_time)
    for i, (start_time, end_time) in enumerate(chunk_times):
        time = end_time - start_time
        out_filename = out_pattern % i
        logger.info('{}: start={:.02f}, end={:.02f}, duration={:.02f}'.format(out_filename, start_time, end_time,
            time))
        subprocess.Popen(
            (ffmpeg
                .input(in_filename, ss=start_time, t=time)
                .output(out_filename)
                .overwrite_output()
                .compile()
            ),
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        ).communicate()


if __name__ == '__main__':
    args = parser.parse_args()
    split_audio(**vars(args))