"""生成并缓存缩略图。"""
from __future__ import annotations

import hashlib
from pathlib import Path

from PIL import Image

from app.core.config import settings
from app.core.path_utils import path_to_storage


SUPPORTED_EXTS = {".png", ".jpg", ".jpeg", ".webp", ".gif", ".bmp", ".tif", ".tiff"}


def is_supported(path: Path) -> bool:
    """是否为我们支持的图片格式。"""
    return path.suffix.lower() in SUPPORTED_EXTS


def generate_thumbnail(image_path: Path, max_side: int | None = None) -> Path:
    """生成 webp 缩略图，落到缓存目录。返回缓存路径。"""
    max_side = max_side or settings.thumb_size
    # 用文件路径 + mtime 哈希作为缓存键，源文件变化会自动生成新缩略图
    stat = image_path.stat()
    key = hashlib.md5(
        f"{path_to_storage(image_path)}|{stat.st_mtime_ns}|{max_side}".encode("utf-8")
    ).hexdigest()
    out = settings.thumb_dir / f"{key}.webp"
    if out.exists():
        return out
    with Image.open(image_path) as img:
        img = img.convert("RGB")
        img.thumbnail((max_side, max_side), Image.LANCZOS)
        img.save(out, format="WEBP", quality=80)
    return out


def file_hash(image_path: Path, chunk: int = 1024 * 1024) -> str:
    """计算文件 sha256，用作去重键。"""
    h = hashlib.sha256()
    with open(image_path, "rb") as f:
        while True:
            data = f.read(chunk)
            if not data:
                break
            h.update(data)
    return h.hexdigest()