add api method to get selection data

src/documents/serialisers.py

@@ -393,3 +393,11 @@ class PostDocumentSerializer(serializers.Serializer):
             return [tag.id for tag in tags]
         else:
             return None
+
+
+class SelectionDataSerializer(serializers.Serializer):
+
+    documents = serializers.ListField(
+        required=True,
+        child=serializers.IntegerField()
+    )

src/documents/views.py

@@ -4,7 +4,7 @@ from datetime import datetime
 from time import mktime
 
 from django.conf import settings
-from django.db.models import Count, Max
+from django.db.models import Count, Max, Case, When, IntegerField
 from django.http import HttpResponse, HttpResponseBadRequest, Http404
 from django.views.decorators.cache import cache_control
 from django.views.generic import TemplateView
@@ -48,7 +48,7 @@ from .serialisers import (
     DocumentTypeSerializer,
     PostDocumentSerializer,
     SavedViewSerializer,
-    BulkEditSerializer
+    BulkEditSerializer, SelectionDataSerializer
 )
 
 
@@ -372,6 +372,62 @@ class PostDocumentView(APIView):
         return Response("OK")
 
 
+class SelectionDataView(APIView):
+
+    permission_classes = (IsAuthenticated,)
+    serializer_class = SelectionDataSerializer
+    parser_classes = (parsers.MultiPartParser, parsers.JSONParser)
+
+    def get_serializer_context(self):
+        return {
+            'request': self.request,
+            'format': self.format_kwarg,
+            'view': self
+        }
+
+    def get_serializer(self, *args, **kwargs):
+        kwargs['context'] = self.get_serializer_context()
+        return self.serializer_class(*args, **kwargs)
+
+    def post(self, request, format=None):
+        serializer = self.get_serializer(data=request.data)
+        serializer.is_valid(raise_exception=True)
+
+        ids = serializer.validated_data.get('documents')
+
+        correspondents = Correspondent.objects.annotate(dcount=Count(Case(
+            When(documents__id__in=ids, then=1),
+            output_field=IntegerField()
+        )))
+
+        tags = Tag.objects.annotate(dcount=Count(Case(
+            When(documents__id__in=ids, then=1),
+            output_field=IntegerField()
+        )))
+
+        types = DocumentType.objects.annotate(dcount=Count(Case(
+            When(documents__id__in=ids, then=1),
+            output_field=IntegerField()
+        )))
+
+        r = Response({
+            "selected_correspondents": [{
+                "id": t.id,
+                "dcount": t.dcount
+            } for t in correspondents],
+            "selected_tags": [{
+                "id": t.id,
+                "dcount": t.dcount
+            } for t in tags],
+            "selected_types": [{
+                "id": t.id,
+                "dcount": t.dcount
+            } for t in types]
+        })
+
+        return r
+
+
 class SearchView(APIView):
 
     permission_classes = (IsAuthenticated,)

src/paperless/urls.py

@@ -19,7 +19,8 @@ from documents.views import (
     StatisticsView,
     PostDocumentView,
     SavedViewViewSet,
-    BulkEditView
+    BulkEditView,
+    SelectionDataView
 )
 from paperless.views import FaviconView
 
@@ -53,10 +54,12 @@ urlpatterns = [
         re_path(r"^documents/post_document/", PostDocumentView.as_view(),
                 name="post_document"),
 
-
         re_path(r"^documents/bulk_edit/", BulkEditView.as_view(),
                 name="bulk_edit"),
 
+        re_path(r"^documents/selection_data/", SelectionDataView.as_view(),
+                name="selection_data"),
+
         path('token/', views.obtain_auth_token)
 
     ] + api_router.urls)),