mirror of
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54 lines
2.3 KiB
Python
54 lines
2.3 KiB
Python
"""HTTP response helpers."""
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from pathlib import Path
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from urllib.parse import quote
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from starlette.responses import PlainTextResponse
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def download_error_response(status_code: int, message: str) -> PlainTextResponse:
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"""Answer a browser-native download with a file that says what went wrong.
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These URLs are reached by an ``<a download>`` click, and a browser saves
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whatever comes back under the name it was going to use. A JSON error body
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therefore lands on the user's disk as a .zip that will not open, with
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nothing on screen to explain it -- the download simply appears to have
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produced a broken file. A short text file, named for the failure rather
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than for the download, is at least legible when opened.
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"""
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return PlainTextResponse(
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f"{message}\n",
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status_code=status_code,
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headers={"Content-Disposition": build_content_disposition("download-failed.txt")},
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)
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def safe_download_filename(filename: str, fallback: str = "download", max_chars: int = 200) -> str:
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"""Return a basename safe for a bounded download response header."""
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basename = Path(filename.replace("\\", "/")).name
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cleaned = "".join("_" if ord(char) < 32 or ord(char) == 127 else char for char in basename).strip(" .")
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if not cleaned:
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return fallback
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if len(cleaned) <= max_chars:
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return cleaned
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suffixes = "".join(Path(cleaned).suffixes)
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suffix = suffixes if len(suffixes) <= 32 else ""
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stem_chars = max(1, max_chars - len(suffix))
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return f"{cleaned[:stem_chars]}{suffix}"
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def build_content_disposition(filename: str, disposition: str = "attachment") -> str:
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"""Build an RFC 6266-compliant Content-Disposition header value.
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Starlette/uvicorn encodes response headers as latin-1, so any non-ASCII
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character in a raw `filename="..."` parameter raises UnicodeEncodeError.
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The fix is RFC 5987's `filename*=UTF-8''<percent-encoded>` form alongside
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a stripped ASCII fallback in the legacy `filename="..."` parameter — every
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modern browser prefers the `*` form when present.
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"""
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ascii_fallback = filename.encode("ascii", "ignore").decode("ascii").strip(" ._-") or "download"
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ascii_fallback = ascii_fallback.replace('"', "").replace("\\", "")
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return f"{disposition}; filename=\"{ascii_fallback}\"; filename*=UTF-8''{quote(filename)}"
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