"""
VideoProcessorService
=====================
Extracts 24 predefined 15-second clips using MoviePy.
No system FFmpeg installation required — MoviePy bundles its own via imageio-ffmpeg.
"""

import asyncio
import logging
import os
from pathlib import Path
from typing import List

from moviepy.editor import VideoFileClip

from app.models.schemas import ClipResult, ProcessingResponse
from app.utils.helpers import get_file_size, seconds_to_hhmmss
from app.utils.segments import MINIMUM_VIDEO_DURATION, SEGMENTS

logger = logging.getLogger(__name__)


# ─────────────────────────────────────────────────────────────────────────────
# Exceptions
# ─────────────────────────────────────────────────────────────────────────────


class VideoProcessingError(Exception):
    """Raised when video processing fails for an expected reason."""


class VideoTooShortError(VideoProcessingError):
    """Raised when the source video is shorter than the last required segment."""


class InvalidVideoError(VideoProcessingError):
    """Raised when MoviePy cannot read the video file."""


# ─────────────────────────────────────────────────────────────────────────────
# Service
# ─────────────────────────────────────────────────────────────────────────────


class VideoProcessorService:
    """
    Handles end-to-end clip extraction using MoviePy.
    """

    def __init__(self, output_dir: str = "outputs") -> None:
        self.output_dir = Path(output_dir)
        self.output_dir.mkdir(parents=True, exist_ok=True)

    async def process(
        self,
        video_path: str,
        upload_id: str,
        original_filename: str,
    ) -> ProcessingResponse:
        duration = self._validate_video(video_path)

        session_output_dir = self.output_dir / upload_id
        session_output_dir.mkdir(parents=True, exist_ok=True)

        semaphore = asyncio.Semaphore(3)
        tasks = [
            self._extract_clip_async(
                video_path=video_path,
                segment=seg,
                output_dir=session_output_dir,
                upload_id=upload_id,
                semaphore=semaphore,
            )
            for seg in SEGMENTS
        ]
        clip_results: List[ClipResult] = await asyncio.gather(*tasks)
        clip_results.sort(key=lambda c: c.clip_index)

        return ProcessingResponse(
            upload_id=upload_id,
            total_clips=len(clip_results),
            clips=clip_results,
            output_directory=str(session_output_dir),
            message=(
                f"Successfully extracted {len(clip_results)} clips "
                f"from '{original_filename}' "
                f"(duration: {seconds_to_hhmmss(duration)})."
            ),
        )

    def _validate_video(self, video_path: str) -> float:
        if not os.path.isfile(video_path):
            raise InvalidVideoError(f"File not found: {video_path}")

        try:
            with VideoFileClip(video_path) as clip:
                duration = clip.duration
        except Exception as exc:
            raise InvalidVideoError(
                f"Cannot read video file. Make sure it is a valid MP4. ({exc})"
            ) from exc

        if duration is None:
            raise InvalidVideoError("Could not determine video duration.")

        if duration < MINIMUM_VIDEO_DURATION:
            raise VideoTooShortError(
                f"Video is too short. "
                f"Duration: {seconds_to_hhmmss(duration)} — "
                f"minimum required: {seconds_to_hhmmss(MINIMUM_VIDEO_DURATION)} (25:00)."
            )

        return duration

    async def _extract_clip_async(self, video_path, segment, output_dir, upload_id, semaphore):
        async with semaphore:
            return await asyncio.get_event_loop().run_in_executor(
                None,
                self._extract_clip_sync,
                video_path,
                segment,
                output_dir,
                upload_id,
            )

    def _extract_clip_sync(self, video_path, segment, output_dir, upload_id):
        filename = self._build_filename(upload_id, segment)
        output_path = str(output_dir / filename)

        logger.info("Extracting clip %d (%s)", segment.index, segment.label)

        try:
            with VideoFileClip(video_path) as video:
                clip = video.subclip(segment.start_seconds, segment.end_seconds)
                clip.write_videofile(
                    output_path,
                    codec="libx264",
                    audio_codec="aac",
                    temp_audiofile=f"{output_path}.temp_audio.m4a",
                    remove_temp=True,
                    logger=None,
                    ffmpeg_params=["-crf", "23", "-preset", "fast"],
                )
        except Exception as exc:
            raise VideoProcessingError(
                f"Failed to extract clip {segment.index} ({segment.label}): {exc}"
            ) from exc

        return ClipResult(
            clip_index=segment.index,
            filename=filename,
            start_time=seconds_to_hhmmss(segment.start_seconds),
            end_time=seconds_to_hhmmss(segment.end_seconds),
            duration_seconds=segment.duration,
            size_bytes=get_file_size(output_path),
        )

    @staticmethod
    def _build_filename(upload_id: str, segment) -> str:
        label_safe = segment.label.replace(":", "").replace("-", "_")
        short_id = upload_id[:8]
        return f"clip_{segment.index:02d}_{label_safe}_{short_id}.mp4"