feat: add error handling to downloader

Added DownloadError exception class that is raised when yt-dlp fails.
The download_space function now wraps yt-dlp calls in a try-except block
to catch any exceptions and raise a custom DownloadError with a clear message.

Test added to verify that DownloadError is raised when yt-dlp fails.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/downloader.py

@@ -4,6 +4,11 @@ from typing import Optional
 from src.validator import validate_space_url
 
 
+class DownloadError(Exception):
+    """Raised when download fails."""
+    pass
+
+
 def download_space(
     space_url: str,
     output_dir: str,
@@ -19,6 +24,9 @@ def download_space(
 
     Returns:
         Path to the downloaded MP3 file
+
+    Raises:
+        DownloadError: If download fails
     """
     # Extract space ID from URL using validator for robustness
     is_valid, space_id, error_message = validate_space_url(space_url)
@@ -45,8 +53,11 @@ def download_space(
         ydl_opts['cookiefile'] = cookies_file
 
     # Download with yt-dlp
+    try:
         with yt_dlp.YoutubeDL(ydl_opts) as ydl:
             ydl.extract_info(space_url, download=True)
+    except Exception as e:
+        raise DownloadError(f"Failed to download Space: {str(e)}")
 
     # Return the expected output path
     return os.path.join(output_dir, f'space_{space_id}.mp3')

tests/test_downloader.py

@@ -1,6 +1,6 @@
 import pytest
 from unittest.mock import Mock, patch
-from src.downloader import download_space
+from src.downloader import download_space, DownloadError
 
 
 def test_download_space_basic(tmp_path):
@@ -83,3 +83,22 @@ def test_download_space_ytdlp_configuration(tmp_path):
         assert len(call_args['postprocessors']) > 0
         assert call_args['postprocessors'][0]['key'] == 'FFmpegExtractAudio'
         assert call_args['postprocessors'][0]['preferredcodec'] == 'mp3'
+
+
+def test_download_space_error_handling(tmp_path):
+    """Test that download errors are properly caught and wrapped."""
+    space_url = "https://x.com/i/spaces/invalid"
+
+    with patch('src.downloader.yt_dlp.YoutubeDL') as mock_ytdl_class:
+        mock_ytdl = Mock()
+        mock_ytdl_class.return_value.__enter__.return_value = mock_ytdl
+        mock_ytdl.extract_info.side_effect = Exception("Video unavailable")
+
+        with pytest.raises(DownloadError) as exc_info:
+            download_space(
+                space_url=space_url,
+                output_dir=str(tmp_path),
+                cookies_file=None
+            )
+
+        assert "Failed to download" in str(exc_info.value)