import subprocess
from pathlib import Path
from typing import List, Optional

from app.config import COVER_DIR, HLS_DIR, PROCESSED_DIR


class FFmpegError(RuntimeError):
    pass


def run_ffmpeg(command: List[str]) -> None:
    completed = subprocess.run(
        command,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
        text=True,
        check=False,
    )
    if completed.returncode != 0:
        raise FFmpegError(completed.stderr.strip() or "ffmpeg command failed")


def build_filter(watermark_text: Optional[str]) -> Optional[str]:
    if not watermark_text:
        return None
    escaped = watermark_text.replace(":", r"\:").replace("'", r"\\'")
    return (
        "drawtext=text='"
        f"{escaped}"
        "':fontcolor=white:fontsize=28:box=1:boxcolor=black@0.45:boxborderw=6:x=w-tw-24:y=h-th-24"
    )


def transcode_to_mp4(
    source: Path, task_id: str, clip_seconds: Optional[int], watermark_text: Optional[str]
) -> Path:
    output = PROCESSED_DIR / f"{task_id}.mp4"
    command = ["ffmpeg", "-y", "-i", str(source)]
    if clip_seconds:
        command.extend(["-t", str(clip_seconds)])

    video_filter = build_filter(watermark_text)
    if video_filter:
        command.extend(["-vf", video_filter])

    command.extend(
        [
            "-c:v",
            "libx264",
            "-preset",
            "veryfast",
            "-c:a",
            "aac",
            "-movflags",
            "+faststart",
            str(output),
        ]
    )
    run_ffmpeg(command)
    return output


def generate_cover(source: Path, task_id: str) -> Path:
    output = COVER_DIR / f"{task_id}.jpg"
    command = [
        "ffmpeg",
        "-y",
        "-ss",
        "00:00:01",
        "-i",
        str(source),
        "-frames:v",
        "1",
        str(output),
    ]
    run_ffmpeg(command)
    return output


def generate_hls(source_mp4: Path, task_id: str) -> Path:
    task_dir = HLS_DIR / task_id
    task_dir.mkdir(parents=True, exist_ok=True)
    playlist = task_dir / "index.m3u8"
    segment_pattern = task_dir / "segment_%03d.ts"
    command = [
        "ffmpeg",
        "-y",
        "-i",
        str(source_mp4),
        "-codec:v",
        "libx264",
        "-codec:a",
        "aac",
        "-hls_time",
        "4",
        "-hls_playlist_type",
        "vod",
        "-hls_segment_filename",
        str(segment_pattern),
        str(playlist),
    ]
    run_ffmpeg(command)
    return playlist