Implement room aliases (#167)

* Add database functions to interact with aliases

* Save room alias

* Check if alias already exists

* Implement local alias lookup

* Implement alias removal

* Move alias API

* Handle case with no alias set for a room

* Apply requested changes

src/github.com/matrix-org/dendrite/roomserver/api/alias.go

@@ -0,0 +1,129 @@
+// 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 api
+
+import (
+	"net/http"
+)
+
+// SetRoomAliasRequest is a request to SetRoomAlias
+type SetRoomAliasRequest struct {
+	// ID of the user setting the alias
+	UserID string `json:"user_id"`
+	// New alias for the room
+	Alias string `json:"alias"`
+	// The room ID the alias is referring to
+	RoomID string `json:"room_id"`
+}
+
+// SetRoomAliasResponse is a response to SetRoomAlias
+type SetRoomAliasResponse struct {
+	// Does the alias already refer to a room?
+	AliasExists bool `json:"alias_exists"`
+}
+
+// GetAliasRoomIDRequest is a request to GetAliasRoomID
+type GetAliasRoomIDRequest struct {
+	// Alias we want to lookup
+	Alias string `json:"alias"`
+}
+
+// GetAliasRoomIDResponse is a response to GetAliasRoomID
+type GetAliasRoomIDResponse struct {
+	// The room ID the alias refers to
+	RoomID string `json:"room_id"`
+}
+
+// RemoveRoomAliasRequest is a request to RemoveRoomAlias
+type RemoveRoomAliasRequest struct {
+	// ID of the user removing the alias
+	UserID string `json:"user_id"`
+	// The room alias to remove
+	Alias string `json:"alias"`
+}
+
+// RemoveRoomAliasResponse is a response to RemoveRoomAlias
+type RemoveRoomAliasResponse struct{}
+
+// RoomserverAliasAPI is used to save, lookup or remove a room alias
+type RoomserverAliasAPI interface {
+	// Set a room alias
+	SetRoomAlias(
+		req *SetRoomAliasRequest,
+		response *SetRoomAliasResponse,
+	) error
+
+	// Get the room ID for an alias
+	GetAliasRoomID(
+		req *GetAliasRoomIDRequest,
+		response *GetAliasRoomIDResponse,
+	) error
+
+	// Remove a room alias
+	RemoveRoomAlias(
+		req *RemoveRoomAliasRequest,
+		response *RemoveRoomAliasResponse,
+	) error
+}
+
+// RoomserverSetRoomAliasPath is the HTTP path for the SetRoomAlias API.
+const RoomserverSetRoomAliasPath = "/api/roomserver/setRoomAlias"
+
+// RoomserverGetAliasRoomIDPath is the HTTP path for the GetAliasRoomID API.
+const RoomserverGetAliasRoomIDPath = "/api/roomserver/getAliasRoomID"
+
+// RoomserverRemoveRoomAliasPath is the HTTP path for the RemoveRoomAlias API.
+const RoomserverRemoveRoomAliasPath = "/api/roomserver/removeRoomAlias"
+
+// NewRoomserverAliasAPIHTTP creates a RoomserverAliasAPI implemented by talking to a HTTP POST API.
+// If httpClient is nil then it uses the http.DefaultClient
+func NewRoomserverAliasAPIHTTP(roomserverURL string, httpClient *http.Client) RoomserverAliasAPI {
+	if httpClient == nil {
+		httpClient = http.DefaultClient
+	}
+	return &httpRoomserverAliasAPI{roomserverURL, httpClient}
+}
+
+type httpRoomserverAliasAPI struct {
+	roomserverURL string
+	httpClient    *http.Client
+}
+
+// SetRoomAlias implements RoomserverAliasAPI
+func (h *httpRoomserverAliasAPI) SetRoomAlias(
+	request *SetRoomAliasRequest,
+	response *SetRoomAliasResponse,
+) error {
+	apiURL := h.roomserverURL + RoomserverSetRoomAliasPath
+	return postJSON(h.httpClient, apiURL, request, response)
+}
+
+// GetAliasRoomID implements RoomserverAliasAPI
+func (h *httpRoomserverAliasAPI) GetAliasRoomID(
+	request *GetAliasRoomIDRequest,
+	response *GetAliasRoomIDResponse,
+) error {
+	// RemoveRoomAlias implements RoomserverAliasAPI
+	apiURL := h.roomserverURL + RoomserverGetAliasRoomIDPath
+	return postJSON(h.httpClient, apiURL, request, response)
+}
+
+func (h *httpRoomserverAliasAPI) RemoveRoomAlias(
+	request *RemoveRoomAliasRequest,
+	response *RemoveRoomAliasResponse,
+) error {
+	apiURL := h.roomserverURL + RoomserverRemoveRoomAliasPath
+	return postJSON(h.httpClient, apiURL, request, response)
+}