move sender_valid? logic to Retraction and Relayable

lib/diaspora_federation/entities/relayable.rb

@@ -89,6 +89,10 @@ module DiasporaFederation
         verify_parent_author_signature unless parent.local
       end
 
+      def sender_valid?(sender)
+        sender == author || sender == parent.author
+      end
+
       private
 
       # this happens only on downstream federation

lib/diaspora_federation/entities/retraction.rb

@@ -33,6 +33,15 @@ module DiasporaFederation
         super(data)
       end
 
+      def sender_valid?(sender)
+        case target_type
+        when "Comment", "Like", "PollParticipation"
+          sender == target.author || sender == target.parent.author
+        else
+          sender == target.author
+        end
+      end
+
       # @param [Nokogiri::XML::Element] root_node xml nodes
       # @return [Retraction] instance
       def self.populate_entity(root_node)

lib/diaspora_federation/federation/receiver/abstract_receiver.rb

@@ -27,16 +27,8 @@ module DiasporaFederation
         end
 
         def sender_valid?
-          case entity
-          when Entities::Retraction
-            case entity.target_type
-            when "Comment", "Like", "PollParticipation"
-              sender == entity.target.author || sender == entity.target.parent.author
-            else
-              sender == entity.target.author
-            end
-          when Entities::Relayable
-            sender == entity.author || sender == entity.parent.author
+          if entity.respond_to?(:sender_valid?)
+            entity.sender_valid?(sender)
           else
             sender == entity.author
           end

spec/lib/diaspora_federation/entities/relayable_spec.rb

@@ -323,5 +323,26 @@ XML
         expect(entity.parent).to eq(remote_parent)
       end
     end
+
+    describe "#sender_valid?" do
+      it "allows author" do
+        entity = SomeRelayable.new(hash)
+
+        expect(entity.sender_valid?(author)).to be_truthy
+      end
+
+      it "allows parent author" do
+        entity = SomeRelayable.new(hash)
+
+        expect(entity.sender_valid?(local_parent.author)).to be_truthy
+      end
+
+      it "does not allow any random author" do
+        entity = SomeRelayable.new(hash)
+        invalid_author = FactoryGirl.generate(:diaspora_id)
+
+        expect(entity.sender_valid?(invalid_author)).to be_falsey
+      end
+    end
   end
 end

spec/lib/diaspora_federation/entities/retraction_spec.rb

@@ -26,5 +26,54 @@ XML
     it_behaves_like "an XML Entity"
 
     it_behaves_like "a retraction"
+
+    describe "#sender_valid?" do
+      context "unrelayable target" do
+        it "allows target author" do
+          entity = Entities::Retraction.new(data)
+
+          expect(entity.sender_valid?(bob.diaspora_id)).to be_truthy
+        end
+
+        it "does not allow any random author" do
+          entity = Entities::Retraction.new(data)
+          invalid_author = FactoryGirl.generate(:diaspora_id)
+
+          expect(entity.sender_valid?(invalid_author)).to be_falsey
+        end
+      end
+
+      %w(Comment Like PollParticipation).each do |target_type|
+        context "#{target_type} target" do
+          let(:relayable_target) {
+            FactoryGirl.build(
+              :related_entity,
+              author: bob.diaspora_id,
+              parent: FactoryGirl.build(:related_entity, author: alice.diaspora_id)
+            )
+          }
+          let(:relayable_data) { data.merge(target_type: target_type, target: relayable_target) }
+
+          it "allows target author" do
+            entity = Entities::Retraction.new(relayable_data)
+
+            expect(entity.sender_valid?(bob.diaspora_id)).to be_truthy
+          end
+
+          it "allows target parent author" do
+            entity = Entities::Retraction.new(relayable_data)
+
+            expect(entity.sender_valid?(alice.diaspora_id)).to be_truthy
+          end
+
+          it "does not allow any random author" do
+            entity = Entities::Retraction.new(relayable_data)
+            invalid_author = FactoryGirl.generate(:diaspora_id)
+
+            expect(entity.sender_valid?(invalid_author)).to be_falsey
+          end
+        end
+      end
+    end
   end
 end