"""Camera enumeration — discovers available video input devices."""

from __future__ import annotations

from dataclasses import dataclass, field

from PySide6.QtMultimedia import QCameraDevice, QMediaDevices


@dataclass
class CameraInfo:
    """Lightweight descriptor of a detected camera."""

    device: QCameraDevice
    name: str
    id: str
    formats: list[tuple[int, int, float]] = field(default_factory=list)
    # formats: list of (width, height, max_fps)

    def __str__(self) -> str:
        return f"{self.name} [{self.id}]"


class CameraEnumerator:
    """Discovers available video input devices via QMediaDevices."""

    @staticmethod
    def list_cameras() -> list[CameraInfo]:
        """Return all available camera devices with their supported formats."""
        devices = QMediaDevices.videoInputs()
        cameras: list[CameraInfo] = []

        for device in devices:
            formats: list[tuple[int, int, float]] = []
            for fmt in device.videoFormats():
                res = fmt.resolution()
                fps = fmt.maxFrameRate()
                formats.append((res.width(), res.height(), fps))

            # deduplicate and sort: largest resolution first, then fps descending
            seen: set[tuple[int, int, float]] = set()
            unique_formats: list[tuple[int, int, float]] = []
            for f in sorted(formats, key=lambda x: (x[0] * x[1], x[2]), reverse=True):
                if f not in seen:
                    seen.add(f)
                    unique_formats.append(f)

            cameras.append(
                CameraInfo(
                    device=device,
                    name=device.description(),
                    id=device.id().toStdString()
                    if hasattr(device.id(), "toStdString")
                    else device.id().data().decode("utf-8", errors="replace"),
                    formats=unique_formats,
                )
            )

        return cameras

    @staticmethod
    def default_camera() -> CameraInfo | None:
        """Return the system default camera, or None if no camera is available."""
        device = QMediaDevices.defaultVideoInput()
        if device.isNull():
            return None

        cameras = CameraEnumerator.list_cameras()
        # find by id match
        default_id = (
            device.id().toStdString()
            if hasattr(device.id(), "toStdString")
            else device.id().data().decode("utf-8", errors="replace")
        )
        for cam in cameras:
            if cam.id == default_id:
                return cam

        # fallback: wrap directly
        return cameras[0] if cameras else None