"""声呐视频发布前：在 FishMeasure ``optical_flow/visualize_optical_flow.py`` 中做稠密光流 overlay。"""

from __future__ import annotations

import importlib.util
import threading
import time
from pathlib import Path
from types import ModuleType
from typing import Optional

from loguru import logger

from app.settings import Settings

_mod_lock = threading.Lock()
_cached_mod: Optional[ModuleType] = None
_cached_mod_path: Optional[str] = None


def _load_optical_flow_module(settings: Settings) -> Optional[ModuleType]:
    global _cached_mod, _cached_mod_path
    path = settings.fish_measure_root / "optical_flow" / "visualize_optical_flow.py"
    path_str = str(path)
    with _mod_lock:
        if _cached_mod is not None and _cached_mod_path == path_str:
            return _cached_mod
        if not path.is_file():
            logger.warning("[sonar-video] optical flow module not found: {}", path)
            return None
        spec = importlib.util.spec_from_file_location("fishmeasure_optical_flow_viz", path)
        if spec is None or spec.loader is None:
            return None
        mod = importlib.util.module_from_spec(spec)
        spec.loader.exec_module(mod)
        _cached_mod = mod
        _cached_mod_path = path_str
        return mod


def run_sonar_optical_flow_overlay(
    src: Path,
    flow_out: Path,
    settings: Settings,
) -> bool:
    """将 ``src`` 处理为 overlay 光流视频写入 ``flow_out``。失败返回 False（调用方应回退直转码）。"""
    if not settings.biomass_sonar_optical_flow:
        return False
    mod = _load_optical_flow_module(settings)
    if mod is None:
        return False
    run_fn = getattr(mod, "run_optical_flow_video", None)
    if not callable(run_fn):
        logger.warning("[sonar-video] run_optical_flow_video missing in optical flow module")
        return False
    src_size_mb = src.stat().st_size / (1024 * 1024) if src.is_file() else 0
    logger.info("[sonar-video] optical flow starting: {} ({:.1f} MB), resize={}", src.name, src_size_mb, settings.biomass_sonar_optical_flow_resize)
    t0 = time.monotonic()
    try:
        ok = run_fn(
            src,
            flow_out,
            mode="overlay",
            resize=float(settings.biomass_sonar_optical_flow_resize),
            progress_log=False,
        )
        elapsed = time.monotonic() - t0
        if ok:
            out_size_mb = flow_out.stat().st_size / (1024 * 1024) if flow_out.is_file() else 0
            logger.info("[sonar-video] optical flow done in {:.1f}s: {} -> {} ({:.1f} MB)", elapsed, src.name, flow_out.name, out_size_mb)
        else:
            logger.warning("[sonar-video] optical flow returned False after {:.1f}s for {}", elapsed, src.name)
        return bool(ok)
    except Exception:
        elapsed = time.monotonic() - t0
        logger.exception("[sonar-video] optical flow raised exception after {:.1f}s for {}", elapsed, src.name)
        return False