adds vote posting

also moves some validation code to the model

playlist/serializers/vote.py

@@ -1,5 +1,5 @@
 from rest_framework import serializers
-from playlist.models import Vote
+from playlist.models import Vote, Track
 
 class VoteSerializer(serializers.HyperlinkedModelSerializer):
     class Meta:
@@ -10,3 +10,19 @@ class VoteSerializer(serializers.HyperlinkedModelSerializer):
             'track': {'view_name': 'api-track', 'lookup_field': 'id'},
             'user': {'view_name': 'api-user', 'lookup_field': 'id'}
         }
+
+class VoteSaveSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = Vote
+        fields = ['track', 'points', 'skipped']
+
+    def create(self, validated_data):
+        """
+        Create a new vote. Deletes a previous skipped vote if it exists.
+        """
+        user = self.context['request'].user
+        track = validated_data['track']
+        previous_vote = Vote.objects.filter(user=user, track=track).first()
+        if previous_vote and previous_vote.skipped:
+            previous_vote.delete()
+        return Vote.objects.create(**validated_data)