#!/usr/bin/env python3
"""Write a golden's supplied floor in the CMAF form (extensions/packaging.md §7.7) from
another golden's supplied floor in the OBU form (§7.3).

A CMAF floor is a ladder's own initialization segment and media segments, as a media
muxer wrote them, so this golden's are written by one: each `<name>.obu` of the source
golden's floor is muxed, without re-encoding (`-c copy`), by ffmpeg's HLS muxer into fMP4
segments, cutting at every key frame (`-hls_time` of one frame), so each media segment
holds one piece of the plan; its `init.mp4` and `seg_<k>.m4s` files, `<k>` four digits, are
`floor/<name>/`. The policy's `floor.supplied_listing` is set to the SHA-256 of the floor
directory's listing (SPEC §3.1), which `wai-pack listing` prints.

A muxer is not a pure function of its input across versions, so the files are committed
and pinned by the listing: a packer reads them and checks them against the plan, and
never writes them. This script is how the committed files were written, not a step of
verification.

    python3 supplied_cmaf.py <ffmpeg> <wai-pack binary> <packs/<from>> <packs/<to>> <fps num/den>
"""
import hashlib
import os
import re
import shutil
import subprocess
import sys
import tempfile


def main(argv):
    if len(argv) != 6:
        print(__doc__)
        return 2
    ffmpeg, wai_pack, src, dst, rate = argv[1:]
    num, den = (int(x) for x in rate.split("/"))
    floor_in, floor_out = os.path.join(src, "floor"), os.path.join(dst, "floor")
    if os.path.isdir(floor_out):
        shutil.rmtree(floor_out)
    os.makedirs(floor_out)
    for f in sorted(os.listdir(floor_in)):
        if not f.endswith(".obu"):
            continue
        name = f[:-len(".obu")]
        with tempfile.TemporaryDirectory() as tmp:
            subprocess.run([ffmpeg, "-nostdin", "-v", "error", "-f", "obu", "-framerate", f"{num}/{den}",
                            "-i", os.path.join(floor_in, f), "-c", "copy", "-f", "hls", "-hls_time", f"{den / num:.6f}",
                            "-hls_segment_type", "fmp4", "-hls_fmp4_init_filename", "init.mp4",
                            "-hls_segment_filename", os.path.join(tmp, "seg_%04d.m4s"), "-hls_playlist_type", "vod",
                            os.path.join(tmp, "index.m3u8")], check=True)
            out = os.path.join(floor_out, name)
            os.makedirs(out)
            for g in sorted(os.listdir(tmp)):
                if g == "init.mp4" or g.endswith(".m4s"):
                    shutil.copyfile(os.path.join(tmp, g), os.path.join(out, g))
        print(f"{out}: {sorted(os.listdir(out))}")
    listing = hashlib.sha256(subprocess.run([wai_pack, "listing", floor_out], check=True, capture_output=True).stdout).hexdigest()
    p = os.path.join(dst, "policy.toml")
    policy = open(p, encoding="utf-8").read()
    open(p, "w", encoding="utf-8").write(re.sub(r'supplied_listing = "[0-9a-f]{64}"', f'supplied_listing = "{listing}"', policy))
    print(f"listing {listing}")
    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv))