from __future__ import annotations

from io import BytesIO
import os
from pathlib import Path
from threading import Lock

import numpy as np
from fastapi.concurrency import run_in_threadpool
from loguru import logger
from PIL import Image, UnidentifiedImageError

os.environ["YOLO_CONFIG_DIR"] = "/tmp"

from ultralytics import YOLO

from app.config import settings
from app.services.consumable_classifier import (
    InvalidImageError,
    ModelNotConfiguredError,
    PredictionCandidate,
    PredictionError,
    PredictionResult,
    resolve_classifier_inference_device,
)


class TearActionService:
    """撕扯耗材动作识别（独立权重）：判断是否存在/如何撕扯耗材等行为；与耗材分类 `ConsumableClassifierService` 分离。内部流水线调用，不对外 HTTP。"""

    def __init__(self) -> None:
        self._model: YOLO | None = None
        self._model_lock = Lock()

    @property
    def weights_path(self) -> Path | None:
        if not settings.tear_action_weights:
            return None
        return Path(settings.tear_action_weights).expanduser()

    @property
    def configured(self) -> bool:
        return self.weights_path is not None

    @property
    def weights_found(self) -> bool:
        path = self.weights_path
        return path is not None and path.is_file()

    @property
    def model_loaded(self) -> bool:
        return self._model is not None

    async def predict_image_bytes(
        self,
        payload: bytes,
        *,
        topk: int | None = None,
    ) -> PredictionResult:
        return await run_in_threadpool(self._predict_image_bytes, payload, topk)

    def _predict_image_bytes(
        self,
        payload: bytes,
        topk: int | None,
    ) -> PredictionResult:
        model = self._get_model()
        image = self._decode_image(payload)

        try:
            result = model.predict(
                image,
                imgsz=settings.tear_action_imgsz,
                device=resolve_classifier_inference_device(settings.tear_action_device),
                verbose=False,
            )[0]
        except Exception as exc:  # pragma: no cover
            raise PredictionError(
                f"Failed to run tear-action inference: {exc}"
            ) from exc

        return self._build_prediction_result(result, model, topk=topk)

    def _get_model(self) -> YOLO:
        path = self.weights_path
        if path is None:
            raise ModelNotConfiguredError(
                "Tear-action weights are not configured. Set TEAR_ACTION_WEIGHTS."
            )

        path = path.resolve()
        if not path.is_file():
            raise ModelNotConfiguredError(f"Tear-action weights not found: {path}")

        if self._model is None:
            with self._model_lock:
                if self._model is None:
                    logger.info("Loading tear-action weights from {}", path)
                    self._model = YOLO(str(path))

        return self._model

    def _decode_image(self, payload: bytes) -> np.ndarray:
        if not payload:
            raise InvalidImageError("Uploaded image is empty.")

        try:
            with Image.open(BytesIO(payload)) as image:
                return np.asarray(image.convert("RGB"))
        except (UnidentifiedImageError, OSError) as exc:
            raise InvalidImageError("Uploaded file is not a valid image.") from exc

    def _build_prediction_result(
        self,
        result: object,
        model: YOLO,
        *,
        topk: int | None,
    ) -> PredictionResult:
        probs = getattr(result, "probs", None)
        data = getattr(probs, "data", None)
        if probs is None or data is None:
            raise PredictionError("Model did not return classification probabilities.")

        scores = data.tolist()
        if not isinstance(scores, list):
            scores = [float(scores)]

        names = self._names(model)
        limit = max(1, topk or settings.tear_action_topk)
        ranked = sorted(
            ((index, float(score)) for index, score in enumerate(scores)),
            key=lambda item: item[1],
            reverse=True,
        )[:limit]

        if not ranked:
            raise PredictionError("Model returned an empty prediction result.")

        candidates = [
            PredictionCandidate(
                label=names.get(index, str(index)),
                confidence=confidence,
            )
            for index, confidence in ranked
        ]
        return PredictionResult(
            label=candidates[0].label,
            confidence=candidates[0].confidence,
            topk=candidates,
        )

    def _names(self, model: YOLO) -> dict[int, str]:
        raw = getattr(model.model, "names", None) or {}
        return {int(key): str(value) for key, value in raw.items()}