"""Resize / letterbox images to a fixed square (default 512×512)."""

from __future__ import annotations

from pathlib import Path
from typing import Optional

import cv2
import numpy as np


def letterbox_square_bgr(bgr: np.ndarray, size: int) -> np.ndarray:
    """Fit image inside size×size with padding (preserves aspect)."""
    h, w = bgr.shape[:2]
    if h <= 0 or w <= 0:
        raise ValueError("empty image")
    scale = min(size / w, size / h)
    nw = max(1, int(round(w * scale)))
    nh = max(1, int(round(h * scale)))
    resized = cv2.resize(bgr, (nw, nh), interpolation=cv2.INTER_AREA)
    # Padding nền trắng để tránh viền đen ảnh hưởng Canny/edge.
    out = np.full((size, size, 3), 255, dtype=np.uint8)
    pad_y = (size - nh) // 2
    pad_x = (size - nw) // 2
    out[pad_y : pad_y + nh, pad_x : pad_x + nw] = resized
    return out


def read_image_bgr(path: Path) -> Optional[np.ndarray]:
    img = cv2.imread(str(path), cv2.IMREAD_COLOR)
    return img


def write_jpg(path: Path, bgr: np.ndarray, quality: int = 92) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)
    cv2.imwrite(str(path), bgr, [int(cv2.IMWRITE_JPEG_QUALITY), quality])


def write_image(path: Path, bgr: np.ndarray) -> None:
    """
    Write image using file extension.
    Supports .jpg/.jpeg/.png/.webp (via OpenCV).
    """
    path.parent.mkdir(parents=True, exist_ok=True)
    suf = path.suffix.lower()
    if suf in {".jpg", ".jpeg"}:
        write_jpg(path, bgr)
        return
    cv2.imwrite(str(path), bgr)