from __future__ import annotations

from PIL import Image


def smart_cover_crop(
    img: Image.Image,
    target_w: int,
    target_h: int,
) -> tuple[Image.Image, tuple[int, int, int, int]]:
    """Center-weighted cover crop that fills target_w × target_h exactly.

    The crop box is returned alongside the cropped image so callers can
    record it for metadata or later focal-point refinement.
    """
    src_w, src_h = img.size
    target_ratio = target_w / target_h
    src_ratio = src_w / src_h

    if src_ratio > target_ratio:
        # Image is wider than needed — crop sides
        crop_h = src_h
        crop_w = int(crop_h * target_ratio)
        left = max((src_w - crop_w) // 2, 0)
        top = 0
    else:
        # Image is taller than needed — crop top/bottom
        crop_w = src_w
        crop_h = int(crop_w / target_ratio)
        left = 0
        top = max((src_h - crop_h) // 2, 0)

    right = min(left + crop_w, src_w)
    bottom = min(top + crop_h, src_h)
    box = (left, top, right, bottom)

    cropped = img.crop(box).resize((target_w, target_h), Image.LANCZOS)
    return cropped, box