wehub-resource-sync
73 lines
2.3 KiB
Python
73 lines
2.3 KiB
Python
"""Shared helpers for decoding ``data:...;base64,...`` URLs to disk.
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Historically lived in ``nanobot.api.server``; now shared by the WebSocket
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channel so the ``api`` + ``websocket`` ingress paths apply the same parsing,
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size guard, and filesystem layout.
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"""
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from __future__ import annotations
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import base64
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import mimetypes
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import re
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import uuid
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from pathlib import Path
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from nanobot.utils.helpers import safe_filename
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DEFAULT_MAX_BYTES = 10 * 1024 * 1024
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MAX_FILE_SIZE = DEFAULT_MAX_BYTES
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_DATA_URL_RE = re.compile(r"^data:([^;,]+)(?:;[^,]*)*;base64,(.+)$", re.DOTALL)
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_MIME_EXTENSION_OVERRIDES = {
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# Python's ``mimetypes`` maps browser-recorded audio/webm to ``.weba`` and
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# audio/ogg to ``.oga`` on macOS. Some transcription APIs validate by the
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# file extension and accept the canonical container extensions instead.
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"application/ogg": ".ogg",
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"audio/ogg": ".ogg",
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"audio/mpga": ".mpga",
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"audio/wav": ".wav",
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"audio/webm": ".webm",
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"audio/x-m4a": ".m4a",
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"audio/x-wav": ".wav",
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"audio/vnd.wave": ".wav",
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"video/webm": ".webm",
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}
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class FileSizeExceededError(Exception):
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"""Raised when a decoded payload exceeds the caller's size limit."""
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FileSizeExceeded = FileSizeExceededError
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def save_base64_data_url(
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data_url: str,
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media_dir: Path,
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*,
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max_bytes: int | None = None,
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) -> str | None:
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"""Decode a ``data:<mime>;base64,<payload>`` URL and persist it.
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Returns the absolute path on success, ``None`` when the URL shape or the
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base64 payload itself is malformed. Raises :class:`FileSizeExceeded`
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when the decoded payload is larger than ``max_bytes`` (default 10 MB).
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"""
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m = _DATA_URL_RE.match(data_url)
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if not m:
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return None
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mime_type, b64_payload = m.group(1).strip().lower(), m.group(2)
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try:
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raw = base64.b64decode(b64_payload)
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except Exception:
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return None
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limit = DEFAULT_MAX_BYTES if max_bytes is None else max_bytes
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if len(raw) > limit:
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raise FileSizeExceeded(f"File exceeds {limit // (1024 * 1024)}MB limit")
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ext = _MIME_EXTENSION_OVERRIDES.get(mime_type) or mimetypes.guess_extension(mime_type) or ".bin"
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filename = f"{uuid.uuid4().hex[:12]}{ext}"
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dest = media_dir / safe_filename(filename)
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dest.write_bytes(raw)
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return str(dest)
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