"""Shared validation and normalization for user-supplied images."""

from __future__ import annotations

from io import BytesIO

from PIL import Image, ImageOps, UnidentifiedImageError

import settings


def normalize_image(data: bytes) -> tuple[bytes, int, int]:
    """Return a bounded, orientation-corrected JPEG safe for model input."""

    try:
        source = Image.open(BytesIO(data))
        width, height = source.size
        if width <= 0 or height <= 0:
            raise ValueError("图片尺寸无效")
        if width * height > settings.INPUT_IMAGE_MAX_PIXELS:
            raise ValueError("图片像素尺寸过大")
        source.load()
    except (UnidentifiedImageError, OSError) as exc:
        raise ValueError("文件不是可识别的图片") from exc

    image = ImageOps.exif_transpose(source)
    image.thumbnail(
        (settings.INPUT_IMAGE_MAX_EDGE, settings.INPUT_IMAGE_MAX_EDGE),
        Image.Resampling.LANCZOS,
    )
    if image.mode in {"RGBA", "LA"} or "transparency" in image.info:
        rgba = image.convert("RGBA")
        background = Image.new("RGB", rgba.size, "white")
        background.paste(rgba, mask=rgba.getchannel("A"))
        image = background
    else:
        image = image.convert("RGB")

    buffer = BytesIO()
    image.save(buffer, format="JPEG", quality=85, optimize=True)
    return buffer.getvalue(), image.width, image.height