Added configurable extension whitelist on the scanner

Closes #8

README.md

@@ -42,6 +42,8 @@ Available settings are:
     I personnaly use SQLite (`sqlite:////var/supysonic/supysonic.db`), but it might not be the brightest idea for large libraries.
   * **cache_dir**: path to a cache folder. Mostly used for resized cover art images. Defaults to `<system temp dir>/supysonic`.
   * **log_file**: path and base name of a rolling log file.
+  * **scanner_extensions**: space-separated list of file extensions the scanner is restricted to. If omitted, files will be scanned
+    regardless of their extension
 * Section **lastfm**:
   * **api_key**: Last.FM [API key](http://www.last.fm/api/accounts) to enable scrobbling
   * **secret**: Last.FM API secret matching the key.

scanner.py

@@ -25,6 +25,9 @@ class Scanner:
 		self.__deleted_albums  = 0
 		self.__deleted_tracks  = 0
 
+		extensions = config.get('base', 'scanner_extensions')
+		self.__extensions = map(str.lower, extensions.split()) if extensions else None
+
 	def scan(self, folder):
 		print "scanning", folder.path
 		valid = [x.lower() for x in config.get('base','filetypes').split(',')]
@@ -39,7 +42,7 @@ class Scanner:
 		folder.last_scan = int(time.time())
 
 	def prune(self, folder):
-		for track in [ t for t in self.__tracks if t.root_folder.id == folder.id and not os.path.exists(t.path) ]:
+		for track in [ t for t in self.__tracks if t.root_folder.id == folder.id and not self.__is_valid_path(t.path) ]:
 			self.__remove_track(track)
 
 		for album in [ album for artist in self.__artists for album in artist.albums if len(album.tracks) == 0 ]:
@@ -58,6 +61,13 @@ class Scanner:
 		for f in folder.children:
 			self.check_cover_art(f)
 
+	def __is_valid_path(self, path):
+		if not os.path.exists(path):
+			return False
+		if not self.__extensions:
+			return True
+		return os.path.splitext(path)[1][1:].lower() in self.__extensions
+
 	def __scan_file(self, path, folder):
 		if path in self.__tracks:
 			tr = self.__tracks[path]