"""Geometry — bounding boxes, cropping, resizing."""

from __future__ import annotations

from dataclasses import dataclass
from typing import Tuple

import cv2
import numpy as np


@dataclass
class BBox:
    """Axis-aligned bounding box."""
    x: int
    y: int
    w: int
    h: int

    def to_dict(self) -> dict:
        return {"x": self.x, "y": self.y, "w": self.w, "h": self.h}

    @property
    def area(self) -> int:
        return self.w * self.h

    def to_face_recognition_tuple(self) -> Tuple[int, int, int, int]:
        """Convert to (top, right, bottom, left) tuple used by face_recognition."""
        return (self.y, self.x + self.w, self.y + self.h, self.x)


def crop_region(img: np.ndarray, bbox: BBox, margin: float = 0.0) -> np.ndarray:
    """Crop a region with optional fractional margin.  Clamps to image bounds."""
    dx = int(bbox.w * margin)
    dy = int(bbox.h * margin)
    x0 = max(0, bbox.x - dx)
    y0 = max(0, bbox.y - dy)
    x1 = min(img.shape[1], bbox.x + bbox.w + dx)
    y1 = min(img.shape[0], bbox.y + bbox.h + dy)
    return img[y0:y1, x0:x1]


def resize_with_aspect(img: np.ndarray, max_dim: int = 1024) -> np.ndarray:
    """Resize so the longest side is at most max_dim, preserving aspect."""
    h, w = img.shape[:2]
    if max(h, w) <= max_dim:
        return img
    scale = max_dim / max(h, w)
    return cv2.resize(img, (int(w * scale), int(h * scale)), interpolation=cv2.INTER_AREA)


def clamp_box(bbox: BBox, width: int, height: int) -> BBox:
    """Clamp a bounding box to image bounds."""
    x = max(0, min(bbox.x, width - 1))
    y = max(0, min(bbox.y, height - 1))
    x2 = max(0, min(bbox.x + bbox.w, width))
    y2 = max(0, min(bbox.y + bbox.h, height))
    return BBox(x, y, max(0, x2 - x), max(0, y2 - y))


def boxes_iou(a: BBox, b: BBox) -> float:
    """Intersection-over-Union between two bounding boxes."""
    x1 = max(a.x, b.x)
    y1 = max(a.y, b.y)
    x2 = min(a.x + a.w, b.x + b.w)
    y2 = min(a.y + a.h, b.y + b.h)
    inter = max(0, x2 - x1) * max(0, y2 - y1)
    union = a.area + b.area - inter
    return inter / union if union > 0 else 0.0