"""GIF 倒放 —— 业务逻辑(Service 层)。"""

from __future__ import annotations

from io import BytesIO

import httpx
from PIL import Image, ImageSequence
from nonebot.log import logger


async def reverse_gif_bytes(image_urls: list[str]) -> tuple[bytes | None, str | None]:
    """下载并翻转 GIF。

    Returns:
        (bytes, None)  成功；
        (None, msg)    失败原因(无 GIF / 帧数过多 / 处理失败)。
    """
    gif_img = []
    async with httpx.AsyncClient(timeout=30) as client:
        for image_url in image_urls:
            try:
                resp = await client.get(image_url)
                resp.raise_for_status()
                image = Image.open(BytesIO(resp.content))
                if getattr(image, "n_frames", 1) == 1:
                    continue
                gif_img.append(image)
            except Exception as e:  # noqa: BLE001
                logger.warning(f"下载或解析图片失败: {e}")

    if not gif_img:
        return None, "没有发现GIF图片"

    suit_gifs = [gif for gif in gif_img if gif.n_frames <= 400]
    if not suit_gifs:
        return None, "GIF帧数太多了，懒得倒放😅"

    suit_image = suit_gifs[0]
    sequence = [f.copy() for f in ImageSequence.Iterator(suit_image)]
    logger.info(f"GIF帧数: {len(sequence)}")
    if len(sequence) <= 2:
        return None, "写入文件时发生未知错误"

    sequence.reverse()
    bio = BytesIO()
    sequence[0].save(
        bio,
        format="GIF",
        save_all=True,
        append_images=sequence[1:],
        disposal=1,
        loop=0,
    )
    bio.seek(0)
    return bio.getvalue(), None


def image_to_bytes(image: Image.Image, input_format: str) -> bytes:
    with BytesIO() as bio:
        image.save(bio, format=input_format)
        return bio.getvalue()