restviews: add additional layer view with extra nested fields

It was a bit awkward to query layers externally - you had to do multiple
queries and you couldn't get the YP Compatible version info at all. Add
an additional LayerBranch-based view that exposes the branch name,
layer fields, YP Compatible Version and active maintainer information
with just one call.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

layerindex/restviews.py

@@ -1,7 +1,28 @@
-from layerindex.models import Branch, LayerItem, LayerMaintainer, LayerNote, LayerBranch, LayerDependency, Recipe, Machine, Distro, BBClass
+from layerindex.models import Branch, LayerItem, LayerMaintainer, YPCompatibleVersion, LayerNote, LayerBranch, LayerDependency, Recipe, Machine, Distro, BBClass
 from rest_framework import viewsets, serializers
 from layerindex.querysethelper import params_to_queryset, get_search_tuple
 
+class DynamicFieldsModelSerializer(serializers.ModelSerializer):
+    """
+    A ModelSerializer that takes an additional "fields" argument that
+    controls which fields should be displayed. Borrowed from the Django
+    REST Framework documentation.
+    """
+
+    def __init__(self, *args, **kwargs):
+        # Don't pass the 'fields' arg up to the superclass
+        fields = kwargs.pop('fields', None)
+
+        # Instantiate the superclass normally
+        super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)
+
+        if fields is not None:
+            # Drop any fields that are not specified in the `fields` argument.
+            allowed = set(fields)
+            existing = set(self.fields)
+            for field_name in existing - allowed:
+                self.fields.pop(field_name)
+
 class ParametricSearchableModelViewSet(viewsets.ReadOnlyModelViewSet):
     def get_queryset(self):
         model = self.__class__.serializer_class.Meta.model
@@ -9,7 +30,7 @@ class ParametricSearchableModelViewSet(viewsets.ReadOnlyModelViewSet):
         (filter_string, search_term, ordering_string) = get_search_tuple(self.request, model)
         return params_to_queryset(model, qs, filter_string, search_term, ordering_string)
 
-class BranchSerializer(serializers.ModelSerializer):
+class BranchSerializer(DynamicFieldsModelSerializer):
     class Meta:
         model = Branch
         fields = '__all__'
@@ -45,7 +66,7 @@ class LayerDependencyViewSet(ParametricSearchableModelViewSet):
     queryset = LayerDependency.objects.filter(layerbranch__layer__status__in=['P', 'X'])
     serializer_class = LayerDependencySerializer
 
-class LayerMaintainerSerializer(serializers.ModelSerializer):
+class LayerMaintainerSerializer(DynamicFieldsModelSerializer):
     class Meta:
         model = LayerMaintainer
         fields = '__all__'
@@ -98,3 +119,34 @@ class ClassSerializer(serializers.ModelSerializer):
 class ClassViewSet(ParametricSearchableModelViewSet):
     queryset = BBClass.objects.all()
     serializer_class = ClassSerializer
+
+class YPCompatibleVersionSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = YPCompatibleVersion
+        fields = '__all__'
+
+class LayerSerializer(serializers.ModelSerializer):
+    """
+    A more fleshed-out LayerBranch serializer for external applications
+    """
+    branch = BranchSerializer(read_only=True, fields=('id', 'name'))
+    layer = LayerItemSerializer(read_only=True)
+    yp_compatible_version = YPCompatibleVersionSerializer(read_only=True)
+    maintainers = serializers.SerializerMethodField()
+
+    class Meta:
+        model = LayerBranch
+        fields = '__all__'
+
+    def get_maintainers(self, layerbranch):
+        qs = layerbranch.layermaintainer_set.filter(status='A')
+        serializer = LayerMaintainerSerializer(instance=qs, many=True, read_only=True, fields=('name', 'email', 'responsibility'))
+        return serializer.data
+
+class LayerViewSet(ParametricSearchableModelViewSet):
+    """
+    A more fleshed-out LayerBranch viewset for external applications
+    """
+    queryset = LayerBranch.objects.filter(layer__status__in=['P', 'X'])
+    serializer_class = LayerSerializer
+

layerindex/urls.py

@@ -25,6 +25,7 @@ router.register(r'recipes', restviews.RecipeViewSet)
 router.register(r'machines', restviews.MachineViewSet)
 router.register(r'distros', restviews.DistroViewSet)
 router.register(r'classes', restviews.ClassViewSet)
+router.register(r'layers', restviews.LayerViewSet)
 
 urlpatterns = patterns('',
     url(r'^$',