Add a component for sending event to remote matrix servers using fede… (#148)

* Add a component for sending event to remote matrix servers using federation

* Use named constants

* Comment on why we combine the deltas

* Comments

* Copyright headers!

* Fix the copy+Pasted comment

* Add tests for combineDeltas

* Review comments

* More review comments

* More comments

* Even more comments

* Name the mutexes

* Document what the mutexes are protecting

* Simplify the SQL, and more comments

src/github.com/matrix-org/dendrite/federationsender/consumers/roomserver_test.go

@@ -0,0 +1,53 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package consumers
+
+import (
+	"testing"
+)
+
+func TestCombineNoOp(t *testing.T) {
+	inputAdd1 := []string{"a", "b", "c"}
+	inputDel1 := []string{"a", "b", "d"}
+	inputAdd2 := []string{"a", "d", "e"}
+	inputDel2 := []string{"a", "c", "e", "e"}
+
+	gotAdd, gotDel := combineDeltas(inputAdd1, inputDel1, inputAdd2, inputDel2)
+
+	if len(gotAdd) != 0 {
+		t.Errorf("wanted combined adds to be an empty list, got %#v", gotAdd)
+	}
+
+	if len(gotDel) != 0 {
+		t.Errorf("wanted combined removes to be an empty list, got %#v", gotDel)
+	}
+}
+
+func TestCombineDedup(t *testing.T) {
+	inputAdd1 := []string{"a", "a"}
+	inputDel1 := []string{"b", "b"}
+	inputAdd2 := []string{"a", "a"}
+	inputDel2 := []string{"b", "b"}
+
+	gotAdd, gotDel := combineDeltas(inputAdd1, inputDel1, inputAdd2, inputDel2)
+
+	if len(gotAdd) != 1 || gotAdd[0] != "a" {
+		t.Errorf("wanted combined adds to be %#v, got %#v", []string{"a"}, gotAdd)
+	}
+
+	if len(gotDel) != 1 || gotDel[0] != "b" {
+		t.Errorf("wanted combined removes to be %#v, got %#v", []string{"b"}, gotDel)
+	}
+}