nanobot/channels/telegram_media.py

@@ -0,0 +1,47 @@
+"""Media handling utilities for Telegram channel."""
+
+from __future__ import annotations
+
+import mimetypes
+from pathlib import Path
+
+try:
+    import magic
+    HAS_MAGIC = True
+except ImportError:
+    HAS_MAGIC = False
+
+
+def detect_mime(path: str, content: bytes | None = None) -> str:
+    """
+    Detect MIME type of media file.
+
+    Priority:
+    1. python-magic sniff (if available and content provided)
+    2. Extension-based lookup
+    3. Fallback to application/octet-stream
+
+    Args:
+        path: File path (used for extension detection)
+        content: Optional file content bytes for magic sniffing
+
+    Returns:
+        MIME type string (e.g., "image/jpeg")
+    """
+    # Try magic detection first if we have content
+    if HAS_MAGIC and content:
+        try:
+            mime = magic.from_buffer(content, mime=True)
+            # Avoid generic types if we can be more specific from extension
+            if mime and mime != "application/octet-stream":
+                return mime
+        except Exception:
+            pass  # Fall through to extension-based detection
+
+    # Extension-based detection
+    mime_type, _ = mimetypes.guess_type(path)
+    if mime_type:
+        return mime_type
+
+    # Fallback
+    return "application/octet-stream"

tests/test_telegram_media.py

@@ -0,0 +1,42 @@
+"""Tests for Telegram media handling."""
+
+import pytest
+from pathlib import Path
+
+
+def test_detect_mime_from_jpeg():
+    """Test MIME detection for JPEG images."""
+    from nanobot.channels.telegram_media import detect_mime
+
+    # Create minimal JPEG bytes (FF D8 FF = JPEG magic bytes)
+    jpeg_bytes = b'\xff\xd8\xff\xe0\x00\x10JFIF'
+
+    mime = detect_mime("test.jpg", jpeg_bytes)
+    assert mime == "image/jpeg"
+
+
+def test_detect_mime_from_png():
+    """Test MIME detection for PNG images."""
+    from nanobot.channels.telegram_media import detect_mime
+
+    # PNG magic bytes
+    png_bytes = b'\x89PNG\r\n\x1a\n'
+
+    mime = detect_mime("test.png", png_bytes)
+    assert mime == "image/png"
+
+
+def test_detect_mime_from_extension_fallback():
+    """Test MIME detection falls back to extension when no content provided."""
+    from nanobot.channels.telegram_media import detect_mime
+
+    mime = detect_mime("video.mp4", None)
+    assert mime == "video/mp4"
+
+
+def test_detect_mime_unknown():
+    """Test MIME detection returns generic type for unknown files."""
+    from nanobot.channels.telegram_media import detect_mime
+
+    mime = detect_mime("unknown.xyz", None)
+    assert mime == "application/octet-stream"