"""HLS transcoding via ffmpeg. Background-runs and updates DB."""
import asyncio
import logging
import shutil
from pathlib import Path
from typing import Optional

logger = logging.getLogger("kino.transcode")


async def transcode_to_hls(
    source: Path,
    out_dir: Path,
    on_status,
):
    """
    Run ffmpeg to produce HLS playlist + segments.
    `on_status(status, error=None)` is awaited at start/end with status one of
    'running'|'done'|'failed'.
    Uses stream-copy where possible (fast, no re-encode).
    """
    if not source.is_file():
        await on_status("failed", error=f"Source missing: {source}")
        return
    out_dir.mkdir(parents=True, exist_ok=True)
    playlist = out_dir / "playlist.m3u8"

    cmd = [
        "ffmpeg", "-y",
        "-i", str(source),
        "-c:v", "copy",
        "-c:a", "copy",
        "-bsf:v", "h264_mp4toannexb",
        "-f", "hls",
        "-hls_time", "6",
        "-hls_list_size", "0",
        "-hls_playlist_type", "vod",
        "-hls_segment_filename", str(out_dir / "seg_%04d.ts"),
        str(playlist),
    ]

    await on_status("running")
    try:
        proc = await asyncio.create_subprocess_exec(
            *cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE,
        )
        _stdout, stderr = await proc.communicate()
        if proc.returncode != 0:
            err = stderr.decode("utf-8", errors="ignore")[-500:]
            logger.error(f"ffmpeg failed: {err}")
            await on_status("failed", error=err[:200])
            # cleanup partial files
            shutil.rmtree(out_dir, ignore_errors=True)
            return
        await on_status("done")
    except FileNotFoundError:
        await on_status("failed", error="ffmpeg not installed")
    except Exception as e:
        logger.exception("transcode crashed")
        await on_status("failed", error=str(e))
        shutil.rmtree(out_dir, ignore_errors=True)


def srt_to_vtt(srt_text: str) -> str:
    """Convert SRT subtitles to WebVTT format (simple, no styling)."""
    lines = srt_text.replace("\r\n", "\n").split("\n")
    out = ["WEBVTT", ""]
    for line in lines:
        # Replace SRT timestamp commas with VTT dots
        if "-->" in line:
            out.append(line.replace(",", "."))
        else:
            out.append(line)
    return "\n".join(out)