| 1 | """Shared helpers for decoding ``data:...;base64,...`` URLs to disk. |
| 2 | |
| 3 | Historically lived in ``nanobot.api.server``; now shared by the WebSocket |
| 4 | channel so the ``api`` + ``websocket`` ingress paths apply the same parsing, |
| 5 | size guard, and filesystem layout. |
| 6 | """ |
| 7 | |
| 8 | from __future__ import annotations |
| 9 | |
| 10 | import base64 |
| 11 | import mimetypes |
| 12 | import re |
| 13 | import uuid |
| 14 | from pathlib import Path |
| 15 | |
| 16 | from nanobot.utils.helpers import safe_filename |
| 17 | |
| 18 | DEFAULT_MAX_BYTES = 10 * 1024 * 1024 |
| 19 | MAX_FILE_SIZE = DEFAULT_MAX_BYTES |
| 20 | |
| 21 | _DATA_URL_RE = re.compile(r"^data:([^;]+);base64,(.+)$", re.DOTALL) |
| 22 | |
| 23 | |
| 24 | class FileSizeExceeded(Exception): |
| 25 | """Raised when a decoded payload exceeds the caller's size limit.""" |
| 26 | |
| 27 | |
| 28 | def save_base64_data_url( |
| 29 | data_url: str, |
| 30 | media_dir: Path, |
| 31 | *, |
| 32 | max_bytes: int | None = None, |
| 33 | ) -> str | None: |
| 34 | """Decode a ``data:<mime>;base64,<payload>`` URL and persist it. |
| 35 | |
| 36 | Returns the absolute path on success, ``None`` when the URL shape or the |
| 37 | base64 payload itself is malformed. Raises :class:`FileSizeExceeded` |
| 38 | when the decoded payload is larger than ``max_bytes`` (default 10 MB). |
| 39 | """ |
| 40 | m = _DATA_URL_RE.match(data_url) |
| 41 | if not m: |
| 42 | return None |
| 43 | mime_type, b64_payload = m.group(1), m.group(2) |
| 44 | try: |
| 45 | raw = base64.b64decode(b64_payload) |
| 46 | except Exception: |
| 47 | return None |
| 48 | limit = DEFAULT_MAX_BYTES if max_bytes is None else max_bytes |
| 49 | if len(raw) > limit: |
| 50 | raise FileSizeExceeded(f"File exceeds {limit // (1024 * 1024)}MB limit") |
| 51 | ext = mimetypes.guess_extension(mime_type) or ".bin" |
| 52 | filename = f"{uuid.uuid4().hex[:12]}{ext}" |
| 53 | dest = media_dir / safe_filename(filename) |
| 54 | dest.write_bytes(raw) |
| 55 | return str(dest) |
| 56 |