"""Hardware video encoders that actually encode a frame on this host."""

from __future__ import annotations

import functools
import os
import re
import subprocess

from .media_io import FFMPEG

CANDIDATE = re.compile(r"^\s*V\S*\s+((?:h264|hevc|av1)_(?:nvenc|vaapi|qsv|amf|videotoolbox|v4l2m2m))\s")
RENDER_NODE = "/dev/dri/renderD128"


def _works(name: str) -> bool:
    argv = [FFMPEG, "-v", "error", "-nostdin"]
    if name.endswith("_vaapi"):
        if not os.path.exists(RENDER_NODE):
            return False
        argv += ["-vaapi_device", RENDER_NODE]
    argv += ["-f", "lavfi", "-i", "color=c=black:s=256x256:d=0.1", "-frames:v", "1"]
    if name.endswith("_vaapi"):
        argv += ["-vf", "format=nv12,hwupload"]
    argv += ["-c:v", name, "-f", "null", "-"]
    try:
        return subprocess.run(argv, capture_output=True, timeout=15, shell=False).returncode == 0
    except (OSError, subprocess.TimeoutExpired):
        return False


@functools.cache
def hardware_encoders() -> tuple[str, ...]:
    try:
        listing = subprocess.run(
            [FFMPEG, "-hide_banner", "-encoders"], capture_output=True, timeout=15, shell=False, text=True
        ).stdout
    except (OSError, subprocess.TimeoutExpired):
        return ()
    names = [m.group(1) for line in listing.splitlines() if (m := CANDIDATE.match(line))]
    return tuple(name for name in names if _works(name))