"""Download a static ffmpeg + ffprobe build for this OS into ./ffmpeg/bin.

Uses the GPL builds from https://github.com/BtbN/FFmpeg-Builds (newest stable
release branch). The app finds ./ffmpeg/bin automatically when run from source,
and build.py --ffmpeg-dir ffmpeg/bin bundles them with the executable, together
with the build's license, which is saved as ./ffmpeg/LICENSE.txt.
"""

from __future__ import annotations

import json
import re
import shutil
import sys
import tarfile
import tempfile
import urllib.request
import zipfile
from pathlib import Path

DEST = Path(__file__).resolve().parent.parent / "ffmpeg" / "bin"
API = "https://api.github.com/repos/BtbN/FFmpeg-Builds/releases/latest"


def pick_asset(assets: list[dict], plat: str) -> dict:
    ext = ".zip" if plat == "win64" else ".tar.xz"
    stable = []
    for a in assets:
        m = re.fullmatch(rf"ffmpeg-n(\d+)\.(\d+)-latest-{plat}-gpl-\d+\.\d+{re.escape(ext)}", a["name"])
        if m:
            stable.append(((int(m.group(1)), int(m.group(2))), a))
    if stable:
        return max(stable, key=lambda x: x[0])[1]
    for a in assets:
        if a["name"] == f"ffmpeg-master-latest-{plat}-gpl{ext}":
            return a
    raise SystemExit(f"No ffmpeg build found for {plat}")


def main() -> int:
    if sys.platform.startswith("win"):
        plat, exe = "win64", ".exe"
    elif sys.platform.startswith("linux"):
        plat, exe = "linux64", ""
    else:
        raise SystemExit("Only Windows and Linux are supported")

    with urllib.request.urlopen(API, timeout=30) as r:
        asset = pick_asset(json.load(r)["assets"], plat)
    print(f"Downloading {asset['name']} ({asset['size'] // 1_000_000} MB)...")

    with tempfile.TemporaryDirectory() as tmp:
        archive = Path(tmp) / asset["name"]
        with urllib.request.urlopen(asset["browser_download_url"], timeout=60) as r, open(archive, "wb") as f:
            shutil.copyfileobj(r, f)
        extract(archive, exe, DEST)
    print(f"Installed ffmpeg and ffprobe into {DEST}, and their license as {DEST.parent / 'LICENSE.txt'}")
    return 0


def extract(archive: Path, exe: str, dest: Path) -> None:
    """Copy ffmpeg + ffprobe from the archive's bin/ into dest, and its LICENSE.txt into dest's parent.

    A BtbN archive holds one top folder with bin/ and LICENSE.txt in it. ffmpeg is GPL, so the
    license has to ship with the binaries; build.py picks it up from there.
    """
    dest.mkdir(parents=True, exist_ok=True)
    license_out = dest.parent / "LICENSE.txt"
    license_out.unlink(missing_ok=True)
    wanted = {f"ffmpeg{exe}", f"ffprobe{exe}"}

    def target(member: str) -> Path | None:
        name = Path(member).name
        if name in wanted and "/bin/" in member:
            return dest / name
        if member.strip("/").count("/") == 1 and name == "LICENSE.txt":
            return license_out
        return None

    if archive.suffix == ".zip":
        with zipfile.ZipFile(archive) as z:
            for info in z.infolist():
                out = target(info.filename)
                if out:
                    out.write_bytes(z.read(info))
    else:
        with tarfile.open(archive) as t:
            for m in t.getmembers():
                out = target(m.name) if m.isfile() else None
                if out:
                    with t.extractfile(m) as src, open(out, "wb") as f:
                        shutil.copyfileobj(src, f)
                    if out.name in wanted:
                        out.chmod(0o755)
    missing = [n for n in sorted(wanted) if not (dest / n).is_file()]
    if not license_out.is_file():
        missing.append("LICENSE.txt")
    if missing:
        raise SystemExit(f"Archive did not contain {missing}")


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