"""
Per-session video recorder (ByteTrack-counter style).

Encode pending MP4 into SHM (tmpfs), then background-copy to VIDEO_OUTPUT_DIR
when the session ends. Triggers: webhook OFF→IN/OUT start, IN/OUT→OFF stop.

Uses ffmpeg subprocess when available (reliable on RK3588); falls back to OpenCV
VideoWriter with multiple fourcc values.
"""

from __future__ import annotations

import os
import shutil
import subprocess
import threading
import time
from datetime import datetime, timedelta
from pathlib import Path

import cv2

_CODEC_CANDIDATES = ("avc1", "mp4v", "H264", "X264")


class _FrameWriter:
    def write(self, frame) -> None:
        raise NotImplementedError

    def close(self) -> None:
        raise NotImplementedError

    def is_open(self) -> bool:
        raise NotImplementedError


class _OpenCVFrameWriter(_FrameWriter):
    def __init__(self, path: str, w: int, h: int, fps: float, crf: int, preset: str):
        self._writer = None
        self._codec = None
        if crf > 0 or preset:
            opts = []
            if crf > 0:
                opts.append(f"crf;{crf}")
            if preset:
                opts.append(f"preset;{preset}")
            os.environ["OPENCV_FFMPEG_WRITE_OPTIONS"] = "|".join(opts)

        for codec in _CODEC_CANDIDATES:
            writer = cv2.VideoWriter(
                path, cv2.VideoWriter_fourcc(*codec), fps, (int(w), int(h))
            )
            if writer.isOpened():
                self._writer = writer
                self._codec = codec
                print(f"[RECORD] OpenCV writer codec={codec} fps={fps} size={w}x{h}")
                return

        if self._writer is not None:
            self._writer.release()

    def is_open(self) -> bool:
        return self._writer is not None and self._writer.isOpened()

    def write(self, frame) -> None:
        if self.is_open():
            self._writer.write(frame)

    def close(self) -> None:
        if self._writer is not None:
            try:
                self._writer.release()
            except Exception:
                pass
            self._writer = None


class _FfmpegPipeWriter(_FrameWriter):
    """Pipe raw BGR frames to ffmpeg (needs even width/height for libx264)."""

    def __init__(self, path: str, w: int, h: int, fps: float, crf: int, preset: str):
        self._proc = None
        self._w = int(w) - (int(w) % 2)
        self._h = int(h) - (int(h) % 2)
        self._use_crop = self._w != int(w) or self._h != int(h)
        if self._w < 2 or self._h < 2:
            return

        preset_v = preset or "medium"
        crf_v = str(crf) if crf > 0 else "23"
        cmd = [
            "ffmpeg",
            "-y",
            "-hide_banner",
            "-loglevel",
            "error",
            "-f",
            "rawvideo",
            "-vcodec",
            "rawvideo",
            "-s",
            f"{self._w}x{self._h}",
            "-pix_fmt",
            "bgr24",
            "-r",
            str(fps),
            "-i",
            "-",
            "-an",
            "-c:v",
            "libx264",
            "-preset",
            preset_v,
            "-crf",
            crf_v,
            "-pix_fmt",
            "yuv420p",
            str(path),
        ]
        try:
            self._proc = subprocess.Popen(
                cmd,
                stdin=subprocess.PIPE,
                stdout=subprocess.DEVNULL,
                stderr=subprocess.PIPE,
            )
            print(
                f"[RECORD] ffmpeg pipe libx264 fps={fps} size={self._w}x{self._h} → {path}"
            )
        except FileNotFoundError:
            print("[RECORD] ffmpeg not found in PATH")
        except Exception as exc:
            print(f"[RECORD] ffmpeg pipe failed to start: {exc}")

    def is_open(self) -> bool:
        return self._proc is not None and self._proc.poll() is None

    def write(self, frame) -> None:
        if not self.is_open():
            return
        if self._use_crop:
            frame = frame[: self._h, : self._w]
        try:
            self._proc.stdin.write(frame.tobytes())
        except (BrokenPipeError, OSError) as exc:
            print(f"[RECORD] ffmpeg pipe write error: {exc}")
            self.close()

    def close(self) -> None:
        if self._proc is None:
            return
        try:
            if self._proc.stdin:
                self._proc.stdin.close()
        except Exception:
            pass
        try:
            self._proc.wait(timeout=30)
        except subprocess.TimeoutExpired:
            self._proc.kill()
        if self._proc.returncode not in (0, None):
            err = ""
            try:
                err = (self._proc.stderr.read() if self._proc.stderr else b"").decode(
                    "utf-8", errors="replace"
                ).strip()
            except Exception:
                pass
            if err:
                print(f"[RECORD] ffmpeg exit {self._proc.returncode}: {err[:500]}")
        self._proc = None


def _open_frame_writer(path: str, w: int, h: int, fps: float, crf: int, preset: str):
    if shutil.which("ffmpeg"):
        writer = _FfmpegPipeWriter(path, w, h, fps, crf, preset)
        if writer.is_open():
            return writer
        writer.close()

    writer = _OpenCVFrameWriter(path, w, h, fps, crf, preset)
    if writer.is_open():
        return writer
    writer.close()
    print(f"[RECORD] Failed to open any writer for {path}")
    return None


def _copy_and_clean(src: str, dst: str) -> None:
    try:
        src_p = Path(src)
        if not src_p.is_file() or src_p.stat().st_size == 0:
            print(f"[RECORD] Skip move — missing or empty: {src}")
            src_p.unlink(missing_ok=True)
            return
        Path(dst).parent.mkdir(parents=True, exist_ok=True)
        shutil.copy2(src, dst)
        src_p.unlink(missing_ok=True)
        print(f"[RECORD] Moved: {src} -> {dst}")
    except Exception as exc:
        print(f"[RECORD] Move failed {src} -> {dst}: {exc}")


class VideoSessionWriter:
    """IDLE → RECORDING → STOPPING → save/discard → IDLE."""

    IDLE = "IDLE"
    RECORDING = "RECORDING"
    STOPPING = "STOPPING"

    def __init__(
        self,
        shm_dir: str,
        video_output_dir: str,
        w: int,
        h: int,
        fps: float,
        end_delay_sec: float = 1.0,
        retention_days: int = 3,
        crf: int = -1,
        preset: str = "",
        discard_empty: bool = True,
    ):
        self.shm_dir = Path(shm_dir)
        self.video_output_dir = Path(video_output_dir)
        self.w = int(w)
        self.h = int(h)
        self.fps = float(fps) if fps and fps > 1 else 15.0
        self.end_delay_sec = float(end_delay_sec)
        self.retention_days = int(retention_days)
        self.crf = int(crf)
        self.preset = preset or ""
        self.discard_empty = bool(discard_empty)

        self.state = self.IDLE
        self.state_start = 0.0
        self.writer: _FrameWriter | None = None
        self.current_path = None
        self.direction = "SESSION"
        self.counting_date = datetime.now().strftime("%Y-%m-%d")
        self.had_crossing = False
        self._frames_written = 0
        self._move_threads: list[threading.Thread] = []

        self.shm_dir.mkdir(parents=True, exist_ok=True)
        try:
            self.video_output_dir.mkdir(parents=True, exist_ok=True)
        except OSError as exc:
            print(f"[RECORD] WARNING: cannot create VIDEO_OUTPUT_DIR {video_output_dir}: {exc}")

        for stale in self.shm_dir.glob("pending_*.mp4"):
            try:
                stale.unlink()
            except OSError:
                pass
        self.cleanup_retention()

    def note_session_start(self, direction: str, counting_date: str | None = None) -> None:
        direction = (direction or "SESSION").strip().upper()
        if direction not in ("IN", "OUT"):
            direction = "SESSION"
        if counting_date:
            self.counting_date = counting_date

        if self.state != self.IDLE:
            print(f"[RECORD] Session start ignored (state={self.state})")
            return

        if not self._start_recording(direction):
            print("[RECORD] Session start failed — no encoder opened")
            return

        self.state = self.RECORDING
        self.state_start = time.monotonic()
        self.had_crossing = False
        self._frames_written = 0
        print(f"[RECORD] Session active ({direction})")

    def note_crossing(self) -> None:
        if self.state in (self.RECORDING, self.STOPPING):
            self.had_crossing = True

    def note_session_end(self) -> None:
        if self.state != self.RECORDING:
            return

        if self.discard_empty and not self.had_crossing:
            print("[RECORD] Session end — discarding (no crossings)")
            self._stop_and_delete()
            self.state = self.IDLE
            return

        self.state = self.STOPPING
        self.state_start = time.monotonic()
        print(f"[RECORD] Session stopping (+{self.end_delay_sec}s tail)")

    def feed_frame(self, raw) -> None:
        now = time.monotonic()

        if self.state == self.STOPPING:
            if self.writer is not None and self.writer.is_open():
                self.writer.write(raw)
                self._frames_written += 1
            if now - self.state_start >= self.end_delay_sec:
                self._stop_and_move()
                self.state = self.IDLE
            return

        if self.state == self.RECORDING and self.writer is not None and self.writer.is_open():
            self.writer.write(raw)
            self._frames_written += 1

    def cleanup_retention(self) -> None:
        if self.retention_days <= 0:
            return
        cutoff = (datetime.now() - timedelta(days=self.retention_days)).strftime("%Y-%m-%d")
        try:
            for entry in self.video_output_dir.iterdir():
                if entry.is_dir() and entry.name < cutoff:
                    shutil.rmtree(entry, ignore_errors=True)
                    print(f"[RECORD] Retention removed: {entry}")
        except OSError as exc:
            print(f"[RECORD] Retention scan failed: {exc}")

    def shutdown(self) -> None:
        prev = self.state
        self._close_writer()

        self.state = self.IDLE
        path = self.current_path
        self.current_path = None

        if not path:
            return

        keep = prev in (self.RECORDING, self.STOPPING) and (
            not self.discard_empty or self.had_crossing
        )
        if keep:
            dst = self._final_path()
            self._spawn_move(str(path), str(dst))
        else:
            try:
                Path(path).unlink(missing_ok=True)
                print(f"[RECORD] Discarding on shutdown: {path}")
            except OSError:
                pass

        for t in self._move_threads:
            t.join(timeout=30.0)
        self._move_threads.clear()

    def _start_recording(self, direction: str) -> bool:
        self._close_writer()

        self.direction = direction
        ts = datetime.now().strftime("%Y%m%d_%H%M%S")
        path = self.shm_dir / f"pending_{direction}_{ts}.mp4"
        self.current_path = path

        self.writer = _open_frame_writer(
            str(path), self.w, self.h, self.fps, self.crf, self.preset
        )
        if self.writer is not None and self.writer.is_open():
            return True

        self._close_writer()
        self.current_path = None
        return False

    def _close_writer(self) -> None:
        if self.writer is not None:
            try:
                self.writer.close()
            except Exception:
                pass
            self.writer = None

    def _stop_and_delete(self) -> None:
        path = self.current_path
        self._close_writer()
        self.current_path = None
        if path:
            try:
                Path(path).unlink(missing_ok=True)
                print(f"[RECORD] Discarded: {path} ({self._frames_written} frames)")
            except OSError:
                pass

    def _stop_and_move(self) -> None:
        path = self.current_path
        self._close_writer()
        self.current_path = None
        if not path:
            return
        size = Path(path).stat().st_size if Path(path).is_file() else 0
        print(f"[RECORD] Stopped: {path} ({self._frames_written} frames, {size} bytes)")
        if size == 0:
            Path(path).unlink(missing_ok=True)
            print(f"[RECORD] Skip move — empty file removed: {path}")
            return
        dst = self._final_path()
        self._spawn_move(str(path), str(dst))

    def _final_path(self) -> Path:
        day = self.counting_date or datetime.now().strftime("%Y-%m-%d")
        date_part = day.replace("-", "")
        ts = datetime.now().strftime("%H%M%S")
        name = f"{self.direction}_{date_part}_{ts}.mp4"
        return self.video_output_dir / day / name

    def _spawn_move(self, src: str, dst: str) -> None:
        t = threading.Thread(
            target=_copy_and_clean,
            args=(src, dst),
            name="record-move",
            daemon=True,
        )
        t.start()
        self._move_threads.append(t)