#!/bin/python
"""jsonclips.py - generate highlights based on JSON

usage: jsonclips.py clips.json

JSON file can specify:
    - output filename
    - source filepath
    - start time
    - duration
    - transition type [default: luma]
    - transition duration [default: 30]
"""

DEFAULT_TRANSITION_DURATION = 30  # 30 frames, ie 0.5s at 60FPS
DEFAULT_TRANSITION_TYPE = "luma"


def process_highlights(jsonfile):
    """Go through highlights, make clips, join to a video"""
    import tempfile

    def make_clips(sources=None, outputdir=None):
        """Use ffmpeg to create output from processed JSON"""
        import subprocess
        import os

        ffmpeg_common_args = ["ffmpeg", "-loglevel", "quiet", "-hide_banner"]
        clipnum = 0

        for source in sources:
            print("Making {}s clip from {} at {}".format(
                source["duration"], source["filepath"], source["time"]))

            ffmpeg_file_args = ["-ss", str(source["time"]),
                                "-i", source["filepath"],
                                "-t", str(source["duration"]),
                                "-c", "copy",
                                os.path.join(outputdir,
                                             "clip{}.mkv".format(clipnum))]

            ffmpeg_args = ffmpeg_common_args + ffmpeg_file_args
            print("Running ffmpeg with args:\n\n{}".
                  format(ffmpeg_args))
            subprocess.run(ffmpeg_args)

            clipnum += 1

    def make_output(workingdir=None, outputfile=None, numsources=None):
        """Use MLT (melt) to join clips"""
        import subprocess
        import os

        melt_args = ["melt"]

        for i in range(numsources):
            if i == 0:
                melt_args.extend([os.path.join(workingdir, "clip{}.mkv"
                                               .format(i))])
            else:
                melt_args.extend([
                    os.path.join(workingdir, "clip{}.mkv".format(i)),
                    "-mix", str(DEFAULT_TRANSITION_DURATION),
                    "-mixer", str(DEFAULT_TRANSITION_TYPE)])

        melt_args.extend(["-consumer", "avformat:{}".format(outputfile),
                          "crf=20"])

        print("Running melt with args:\n\n{}".format(melt_args))
        subprocess.run(melt_args)

    def parse_json(jsonfile=None):
        """Parse global / per--clip options from jsonfile

        Requires:
            - outputfile
            - list of sources
        """
        import json
        import sys

        if jsonfile:
            with open(jsonfile, "r") as fh:
                json_in = json.load(fh)

        if "outputfile" not in json_in:
            print("Please specify an outputfile to write to")
            sys.exit(1)

        if "sources" not in json_in:
            print("Please specify some sources to process")
            sys.exit(1)

        return json_in

    # Start

    if jsonfile:
        json_in = parse_json(jsonfile)

    # in temporary dir
    with tempfile.TemporaryDirectory() as tmpdir:
        # make clips
        make_clips(sources=json_in["sources"], outputdir=tmpdir)
        # join clips using melt
        make_output(workingdir=tmpdir, outputfile=json_in["outputfile"],
                    numsources=len(json_in["sources"]))


if __name__ == "__main__":
    import sys

    process_highlights(sys.argv[1])