Refactor sections of adding song metadata

Last commit before beginning web frontend

Melodia/settings.py

@@ -146,6 +146,9 @@ INSTALLED_APPS = (
 
 	# Melodia apps
 	'archiver',
+
+	#Django management
+	'django_extensions',
 )
 
 # A sample logging configuration. The only tangible logging

archiver/song.py

@@ -29,6 +29,7 @@ class Song (models.Model):
 	"""
 	This class defines the fields and functions related to controlling
 	individual music files.
+	Note that the Playlist model depends on this model's PK being an int.
 	"""
 
 	#Standard user-populated metadata
@@ -50,8 +51,8 @@ class Song (models.Model):
 	url              = models.CharField(max_length = 255)
 	file_hash        = melodia_settings.HASH_RESULT_DB_TYPE
 
-	def populate_metadata(self, use_echonest = False):
-		"Populate the metadata of this song (only if file hash has changed)"
+	def _file_not_changed(self):
+		"Make sure the hash for this file is valid - return True if it has not changed."
 		#Overload the hash function with whatever Melodia as a whole is using
 		from Melodia.melodia_settings import HASH_FUNCTION as hash
 
@@ -63,18 +64,19 @@ class Song (models.Model):
 
 			if current_file_hash == self.file_hash:
 				#The song data hasn't changed at all, we don't need to do anything
-				return
+				return True
 
-		#If we've gotten to here, we do actually need to fully update the metadata
-		if use_echonest:
-			#Code to grab metadata from echonest here
+		return False
+
+	def _grab_metadata_echonest(self):
+		"Populate this song's metadata using EchoNest"
 		pass
 
-		else:
-			#Grab metadata for the database using what is in the track.
+	def _grab_metadata_local(self):
+		"Populate this song's metadata using what is locally available"
+		#It's weird, but we need to wrap importing audiotools
 		from Melodia.resources import add_resource_dir
 		add_resource_dir()
-
 		import audiotools
 
 		try:
@@ -108,6 +110,18 @@ class Song (models.Model):
 			self.duration         = self.bit_rate         or _default_duration
 			self.echonest_song_id = self.echonest_song_id or _default_echonest_song_id
 
+	def populate_metadata(self, use_echonest = False):
+		"Populate the metadata of this song (only if file hash has changed), and save the result."
+		if self._file_not_changed():
+			return
+
+		#If we've gotten to here, we do actually need to fully update the metadata
+		if use_echonest:
+			self._grab_echonest()
+
+		else:
+			self._grab_metadata_local()
+			
 	def convert(self, output_location, output_format, progress_func = lambda x, y: None):
 		"Convert a song to a new format."
 		#Note that output_format over-rides the format guessed by output_location