"""Detector factory: build a Detector from AppConfig.

Kept separate from ``app.py`` so both the app bootstrap and the UI can build
detectors without an import cycle. Raises ``ValueError`` (not ``SystemExit``) on
bad config so the GUI can show the message instead of exiting.
"""

from __future__ import annotations

from ...config import AppConfig
from .base import Detector
from .classic_cv import ClassicCVDetector
from .types import CensorType


def _require_model(config: AppConfig) -> str:
    if not config.model_path:
        raise ValueError(
            "Для детектора YOLO укажите путь к весам (.pt) в Параметрах "
            "или скачайте модель LADA — см. README."
        )
    return config.model_path


def build_detector(config: AppConfig) -> Detector:
    if config.detector == "classic":
        return ClassicCVDetector(config.detection)
    if config.detector == "yolo":
        from .yolo import YoloDetector  # lazy: pulls torch/ultralytics

        return YoloDetector(_require_model(config), config.detection)
    if config.detector == "combined":
        # YOLO handles mosaic; classic-CV handles black bars / blur.
        from .composite import CompositeDetector
        from .yolo import YoloDetector

        return CompositeDetector([
            YoloDetector(_require_model(config), config.detection),
            ClassicCVDetector(config.detection, types={CensorType.BLACK_BAR, CensorType.BLUR}),
        ])
    raise ValueError(f"Неизвестный детектор: {config.detector!r}")