Restructure relationship b/w Songs and Archives

Songs now have a ForeignKey to Archive - one song can not be part of
many Archives.

archiver/archive.py

@@ -1,7 +1,5 @@
 from django.db import models
 
-from song import Song
-
 """
 This is the archive model for the archiving backend of Melodia.
 It's purpose is to control the high-level functionality of managing
@@ -31,8 +29,8 @@ class Archive (models.Model):
 	#Note that we're not using FilePathField since this is actually a folder
 	root_folder = models.CharField(max_length = 255)
 
-	#And a reference to the songs in this archive
-	songs       = models.ManyToManyField(Song)
+	#We've removed the reference to "songs" - instead define it as a ForeignKey,
+	#and do lookups via song_set
 
 	#Backup settings
 	backup_location  = models.CharField(max_length = 255, default = "/dev/null")
@@ -53,7 +51,7 @@ class Archive (models.Model):
 
 		#It's hackish, but far fewer transactions to delete everything first, and add it all back.
 		#If we get interrupted, just re-run it.
-		self.songs.all().delete()
+		song_set.all().delete()
 
 		#Add new songs
 		for dirname, dirnames, filenames in os.walk(self.root_folder):
@@ -63,16 +61,16 @@ class Archive (models.Model):
 				full_url = os.path.abspath(rel_url)
 				new_song = Song(url = full_url)
 				new_song.save()
-				self.songs.add(new_song)
+				song_set.add(new_song)
 
 	def _update_song_metadata(self, use_echonest = False, progress_callback = lambda x, y: None):
 		"""Scan every song in this archive (database only) and make sure all songs are correct
 		The progress_callback function is called with the current song being operated on first, and the total songs second."""
 		#This method operates only on the songs that are in the database - if you need to make
 		#sure that new songs are added, use the _scan_filesystem() method in addition
-		total_songs  = self.songs.count()
+		total_songs  = song_set.count()
 
-		for index, song in enumerate(self.songs.all()):
+		for index, song in enumerate(song_set.all()):
 			song.populate_metadata(use_echonest = use_echonest)
 			song.save()
 			progress_callback(index + 1, total_songs)
@@ -133,9 +131,9 @@ class Archive (models.Model):
 		"""
 		import os, shutil, errno
 
-		total_songs = self.songs.count()
+		total_songs = song_set.count()
 
-		for index, song in enumerate(self.songs.all()):
+		for index, song in enumerate(song_set.all()):
 			_current_filename              = os.path.basename(song.url)
 			_current_filename_no_extension = os.path.splitext(_current_filename)[0]
 

archiver/song.py

@@ -1,7 +1,10 @@
 from django.db import models
 from Melodia import melodia_settings
 
+from archive import Archive
+
 import datetime
+import os.path
 """
 The Song model
 Each instance of a Song represents a single music file.
@@ -63,6 +66,9 @@ class Song (models.Model):
 	skip_count = models.IntegerField(default = _default_int)
 	rating     = models.IntegerField(default = _default_int, choices = _default_rating_choices)
 
+	#Link back to the archive this comes from
+	parent_archive = models.ForeignKey(Archive)
+
 	#Set a static reference to the rating options
 	RATING_DEFAULT   = _default_rating
 	RATING_BAD       = _default_rating_bad
@@ -71,6 +77,10 @@ class Song (models.Model):
 	RATING_GOOD      = _default_rating_good
 	RATING_EXCELLENT = _default_rating_excellent
 
+	def _get_full_url(self):
+		"Combine this song's URL with the URL of its parent"
+		return os.path.join(parent_archive.root_folder, self.url)
+
 	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
@@ -79,7 +89,7 @@ class Song (models.Model):
 		#Check if there's a hash entry - if there is, the song may not have changed,
 		#and we can go ahead and return
 		if self.file_hash != None:
-			song_file = open(self.url, 'rb')
+			song_file = open(self._get_full_url, 'rb')
 			current_file_hash = hash(song_file.read())
 
 			if current_file_hash == self.file_hash:
@@ -94,10 +104,10 @@ class Song (models.Model):
 		#Overload the hash function with whatever Melodia as a whole is using
 		from Melodia.melodia_settings import HASH_FUNCTION as hash
 		
-		file_handle = open(self.url, 'rb')
+		file_handle = open(self._get_full_url, 'rb')
 		
 		self.file_hash = hash(file_handle.read())
-		self.file_size = os.stat(self.url).st_size
+		self.file_size = os.stat(self._get_full_url).st_size
 
 	def _grab_metadata_echonest(self):
 		"Populate this song's metadata using EchoNest"
@@ -110,8 +120,8 @@ class Song (models.Model):
 
 		try:
 			#Use mutagen to scan local metadata - don't update anything else (i.e. play_count)
-			track             = mutagen.File(self.url)
-			track_easy        = mutagen.File(self.url, easy=True)
+			track             = mutagen.File(self._get_full_url)
+			track_easy        = mutagen.File(self._get_full_url, easy=True)
 
 			self.title        = track_easy['title'][0]  or _default_string
 			self.artist       = track_easy['artist'][0] or _default_string