import os
from functools import lru_cache
from typing import Callable, Dict, Optional

from models.detectors.base import ObjectDetector
from models.detectors.owlv2 import Owlv2Detector
from models.detectors.yolov8 import HuggingFaceYoloV8Detector
from models.detectors.yolov8_defence import HuggingFaceYoloV8DefenceDetector
from models.detectors.yolov12_bot_sort import HuggingFaceYoloV12BotSortDetector

DEFAULT_DETECTOR = "owlv2"

_REGISTRY: Dict[str, Callable[[], ObjectDetector]] = {
    "owlv2": Owlv2Detector,
    "hf_yolov8": HuggingFaceYoloV8Detector,
    "hf_yolov8_defence": HuggingFaceYoloV8DefenceDetector,
    "hf_yolov12_bot_sort": HuggingFaceYoloV12BotSortDetector,
}


def _create_detector(name: str) -> ObjectDetector:
    try:
        factory = _REGISTRY[name]
    except KeyError as exc:
        available = ", ".join(sorted(_REGISTRY))
        raise ValueError(f"Unknown detector '{name}'. Available: {available}") from exc
    return factory()


@lru_cache(maxsize=None)
def _get_cached_detector(name: str) -> ObjectDetector:
    return _create_detector(name)


def load_detector(name: Optional[str] = None) -> ObjectDetector:
    """Return a cached detector instance selected via arg or OBJECT_DETECTOR env."""
    detector_name = name or os.getenv("OBJECT_DETECTOR", DEFAULT_DETECTOR)
    return _get_cached_detector(detector_name)


# Backwards compatibility for existing callers.
def load_model():
    return load_detector()