64 lines
2.2 KiB
Python
64 lines
2.2 KiB
Python
"""大屏封面图：放本地磁盘，文件名就是封面 ID；每次上传换新 ID，旧图删掉
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图片类 URL 要能被 <img src> 匿名访问，靠不可猜的 ID 兜底
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"""
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import re
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import secrets
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from pathlib import Path
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from app.core.exceptions import BizException
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MAX_BYTES = 1024 * 1024
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# 按文件头判断类型，不信任客户端声明的 Content-Type
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MAGIC = {b"\x89PNG\r\n\x1a\n": "image/png", b"\xff\xd8\xff": "image/jpeg"}
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# ID 进了文件路径，读写前必须过这个格式检查，防路径穿越
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ID_PATTERN = re.compile(r"th_[A-Za-z0-9_-]{16,64}")
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def sniff(head: bytes) -> str | None:
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for magic, media_type in MAGIC.items():
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if head.startswith(magic):
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return media_type
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return None
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class ThumbnailStorage:
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def __init__(self, root: Path):
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self._root = root
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def _path(self, thumbnail_id: str) -> Path | None:
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if not ID_PATTERN.fullmatch(thumbnail_id):
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return None
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return self._root / thumbnail_id
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def save(self, data: bytes) -> str:
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if len(data) > MAX_BYTES:
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raise BizException(413, "封面图不能超过 1 MB")
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if sniff(data[:8]) is None:
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raise BizException(422, "封面图只支持 PNG 或 JPEG")
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thumbnail_id = f"th_{secrets.token_urlsafe(16)}"
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self._root.mkdir(parents=True, exist_ok=True)
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self._path(thumbnail_id).write_bytes(data)
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return thumbnail_id
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def open(self, thumbnail_id: str) -> tuple[Path, str] | None:
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"""文件路径和图片类型；ID 不合法、文件不存在或内容不是图片时返回 None"""
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path = self._path(thumbnail_id)
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if path is None or not path.is_file():
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return None
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with path.open("rb") as file:
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media_type = sniff(file.read(8))
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return None if media_type is None else (path, media_type)
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def copy(self, thumbnail_id: str) -> str | None:
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path = self._path(thumbnail_id)
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if path is None or not path.is_file():
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return None
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return self.save(path.read_bytes())
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def delete(self, thumbnail_id: str | None) -> None:
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path = None if thumbnail_id is None else self._path(thumbnail_id)
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if path is not None:
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path.unlink(missing_ok=True)
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