Add leave room method

internal/backend.go

@@ -29,5 +29,6 @@ type User interface {
 	ID() string
 	Password() string
 	CreateRoom(request createroom.Request) (Room, *models.ApiError)
+	LeaveRoom(room Room) *models.ApiError
 	SetTopic(room Room, topic string) *models.ApiError
 }

internal/backends/memory/rooms_test.go

@@ -99,3 +99,25 @@ func TestSetRoomTopicWithnprivelegedUser(t *testing.T) {
 	err := user2.SetTopic(room, newTopic)
 	assert.NotNil(t, err)
 }
+
+func TestLeaveRoom(t *testing.T) {
+	backend := NewBackend("localhost")
+
+	user, _, _ := backend.Register("user1", "", "")
+
+	request := createroom.Request{
+		RoomAliasName: "room1",
+		Name:          "room1",
+		Topic:         "topic"}
+
+	room, _ := user.CreateRoom(request)
+
+	assert.Equal(t, 1, len(room.(*Room).joined))
+
+	err := user.LeaveRoom(room)
+	assert.Equal(t, 0, len(room.(*Room).joined))
+
+	// Try to leave room again must throw error
+	err = user.LeaveRoom(room)
+	assert.NotNil(t, err)
+}

internal/backends/memory/user.go

@@ -114,3 +114,17 @@ func (user *User) SetTopic(room internal.Room, topic string) *models.ApiError {
 
 	return nil
 }
+
+func (user *User) LeaveRoom(room internal.Room) *models.ApiError {
+	room.(*Room).mutex.Lock()
+	defer room.(*Room).mutex.Unlock()
+
+	for i, roomMember := range room.(*Room).joined {
+		if roomMember.ID() == user.ID() {
+			room.(*Room).joined = append(room.(*Room).joined[:i], room.(*Room).joined[i+1:]...)
+			return nil
+		}
+	}
+
+	return internal.NewError(models.M_BAD_STATE, "you are not a member of group") // TODO: check error code
+}