Collection: change collections to be an extension of items

Each collection now has an item and the item's UID is the collections
UID. This lets us manipulate collections just like items, and as part of
transactions. This is significant because it lets us change them as part
of transactions!

django_etebase/serializers.py

@@ -182,15 +182,19 @@ class CollectionItemBulkGetSerializer(serializers.ModelSerializer):
 
 
 class CollectionSerializer(serializers.ModelSerializer):
-    encryptionKey = CollectionEncryptionKeyField()
+    collectionKey = CollectionEncryptionKeyField()
     accessLevel = serializers.SerializerMethodField('get_access_level_from_context')
     stoken = serializers.CharField(read_only=True)
+
+    uid = serializers.CharField(source='main_item.uid')
+    encryptionKey = BinaryBase64Field(source='main_item.encryptionKey')
     etag = serializers.CharField(allow_null=True, write_only=True)
-    content = CollectionItemRevisionSerializer(many=False)
+    version = serializers.IntegerField(min_value=0, source='main_item.version')
+    content = CollectionItemRevisionSerializer(many=False, source='main_item.content')
 
     class Meta:
         model = models.Collection
-        fields = ('uid', 'version', 'accessLevel', 'encryptionKey', 'content', 'stoken', 'etag')
+        fields = ('uid', 'version', 'accessLevel', 'encryptionKey', 'collectionKey', 'content', 'stoken', 'etag')
 
     def get_access_level_from_context(self, obj):
         request = self.context.get('request', None)
@@ -200,9 +204,16 @@ class CollectionSerializer(serializers.ModelSerializer):
 
     def create(self, validated_data):
         """Function that's called when this serializer creates an item"""
+        collection_key = validated_data.pop('collectionKey')
+
         etag = validated_data.pop('etag')
-        revision_data = validated_data.pop('content')
-        encryption_key = validated_data.pop('encryptionKey')
+
+        main_item_data = validated_data.pop('main_item')
+        uid = main_item_data.pop('uid')
+        version = main_item_data.pop('version')
+        revision_data = main_item_data.pop('content')
+        encryption_key = main_item_data.pop('encryptionKey')
+
         instance = self.__class__.Meta.model(**validated_data)
 
         with transaction.atomic():
@@ -211,7 +222,10 @@ class CollectionSerializer(serializers.ModelSerializer):
 
             instance.save()
             main_item = models.CollectionItem.objects.create(
-                uid=None, encryptionKey=None, version=instance.version, collection=instance)
+                uid=uid, encryptionKey=encryption_key, version=version, collection=instance)
+
+            instance.main_item = main_item
+            instance.save()
 
             process_revisions_for_item(main_item, revision_data)
 
@@ -219,26 +233,13 @@ class CollectionSerializer(serializers.ModelSerializer):
                                     stoken=models.Stoken.objects.create(),
                                     user=validated_data.get('owner'),
                                     accessLevel=models.AccessLevels.ADMIN,
-                                    encryptionKey=encryption_key,
+                                    encryptionKey=collection_key,
                                     ).save()
 
         return instance
 
     def update(self, instance, validated_data):
-        """Function that's called when this serializer is meant to update an item"""
-        revision_data = validated_data.pop('content')
-
-        with transaction.atomic():
-            main_item = instance.main_item
-            # We don't have to use select_for_update here because the unique constraint on current guards against
-            # the race condition. But it's a good idea because it'll lock and wait rather than fail.
-            current_revision = main_item.revisions.filter(current=True).select_for_update().first()
-            current_revision.current = None
-            current_revision.save()
-
-            process_revisions_for_item(main_item, revision_data)
-
-        return instance
+        raise NotImplementedError()
 
 
 class CollectionMemberSerializer(serializers.ModelSerializer):