"""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.

Only the YOLO detector is supported — the classic-CV heuristic (and the composite
mode that combined them) were removed: they were noisy/approximate on real footage.
"""

from __future__ import annotations

from ...config import AppConfig
from .base import Detector


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:
    from .yolo import YoloDetector  # lazy: pulls torch/ultralytics

    return YoloDetector(_require_model(config), config.detection)