Implement client get state event endpoint

README.md

@@ -62,6 +62,7 @@ Here, implemented and some unimplemented features are listed.
 - PUT /_matrix/client/r0/rooms/{roomId}/send/{eventType}/{txnId}
 - GET /_matrix/client/r0/rooms/{roomId}/messages: Except filtering.
 - GET /_matrix/client/r0/rooms/{roomId}/state
+- GET /_matrix/client/r0/rooms/{roomId}/state/{eventType}/{stateKey}
 - GET /_matrix/client/r0/directory/list/room/{roomId}
 - PUT /_matrix/client/r0/directory/list/room/{roomId}
 - GET /_matrix/client/r0/capabilities

lib/architex/room_server.ex

@@ -200,6 +200,12 @@ defmodule Architex.RoomServer do
     GenServer.call(pid, {:get_current_state, account})
   end
 
+  @spec get_state_event(pid(), Account.t(), String.t(), String.t()) ::
+          {:ok, map()} | {:error, :unauthorized} | {:error, :not_found}
+  def get_state_event(pid, account, event_type, state_key) do
+    GenServer.call(pid, {:get_state_event, account, event_type, state_key})
+  end
+
   ### Implementation
 
   @impl true
@@ -445,6 +451,10 @@ defmodule Architex.RoomServer do
 
       %Event{content: %{"membership" => "leave"}} = event ->
         # Get the state of the room, after leaving.
+        # TODO: This does not work properly, as a user's membership can change to "leave"
+        # even after they left/are banned.
+        # I think it is best to seperately keep track when a user left, maybe in the
+        # Membership table.
         state_set = StateResolution.resolve(event)
         {:reply, {:ok, Map.values(state_set)}, state}
 
@@ -453,6 +463,34 @@ defmodule Architex.RoomServer do
     end
   end
 
+  def handle_call(
+        {:get_state_event, account, event_type, state_key},
+        _from,
+        %{state_set: state_set} = state
+      ) do
+    mxid = Account.get_mxid(account)
+
+    case state_set[{"m.room.member", mxid}] do
+      %Event{content: %{"membership" => "join"}} ->
+        case state_set[{event_type, state_key}] do
+          %Event{content: content} -> {:reply, {:ok, content}, state}
+          nil -> {:reply, {:error, :not_found}, state}
+        end
+
+      %Event{content: %{"membership" => "leave"}} = event ->
+        # TODO: See get_current_state.
+        state_set = StateResolution.resolve(event)
+
+        case state_set[{event_type, state_key}] do
+          %Event{content: content} -> {:reply, {:ok, content}, state}
+          nil -> {:reply, {:error, :not_found}, state}
+        end
+
+      _ ->
+        {:reply, {:error, :unauthorized}, state}
+    end
+  end
+
   @spec process_event_with_txn(t(), Room.t(), Device.t(), %Event{}, String.t()) ::
           (() -> {t(), Room.t(), String.t()} | {:error, atom()})
   defp process_event_with_txn(

lib/architex_web/client/controllers/room_controller.ex

@@ -317,7 +317,7 @@ defmodule ArchitexWeb.Client.RoomController do
 
   Action for GET /_matrix/client/r0/rooms/{roomId}/state.
   """
-  def state(%Conn{assigns: %{account: account}} = conn, %{"room_id" => room_id}) do
+  def get_state(%Conn{assigns: %{account: account}} = conn, %{"room_id" => room_id}) do
     case RoomServer.get_room_server(room_id) do
       {:ok, pid} ->
         case RoomServer.get_current_state(pid, account) do
@@ -340,4 +340,46 @@ defmodule ArchitexWeb.Client.RoomController do
         put_error(conn, :not_found, "The given room was not found.")
     end
   end
+
+  @doc """
+  Looks up the contents of a state event in a room.
+
+  Action for GET /_matrix/client/r0/rooms/{roomId}/state/{eventType}/{stateKey}.
+  """
+  def get_state_event(conn, %{"state_key" => [state_key | _]} = params) do
+    do_get_state_event(conn, params, state_key)
+  end
+
+  def get_state_event(conn, params) do
+    do_get_state_event(conn, params, "")
+  end
+
+  defp do_get_state_event(
+         %Conn{assigns: %{account: account}} = conn,
+         %{"room_id" => room_id, "event_type" => event_type},
+         state_key
+       ) do
+    case RoomServer.get_room_server(room_id) do
+      {:ok, pid} ->
+        case RoomServer.get_state_event(pid, account, event_type, state_key) do
+          {:ok, content} ->
+            conn
+            |> put_status(200)
+            |> json(content)
+
+          {:error, :unauthorized} ->
+            put_error(
+              conn,
+              :forbidden,
+              "You aren't a member of the room and weren't previously a member of the room."
+            )
+
+          {:error, :not_found} ->
+            put_error(conn, :not_found, "The room has no state with the given type or key.")
+        end
+
+      {:error, :not_found} ->
+        put_error(conn, :not_found, "The given room was not found.")
+    end
+  end
 end

lib/architex_web/router.ex

@@ -61,13 +61,16 @@ defmodule ArchitexWeb.Router do
 
     scope "/r0" do
       get "/account/whoami", AccountController, :whoami
-      post "/logout", AccountController, :logout
-      post "/logout/all", AccountController, :logout_all
       post "/createRoom", RoomController, :create
       get "/joined_rooms", RoomController, :joined_rooms
       get "/capabilities", InfoController, :capabilities
       get "/sync", SyncController, :sync
 
+      scope "/logout" do
+        post "/", AccountController, :logout
+        post "/all", AccountController, :logout_all
+      end
+
       scope "/profile/:user_id" do
         put "/avatar_url", ProfileController, :set_avatar_url
         put "/displayname", ProfileController, :set_displayname
@@ -89,8 +92,12 @@ defmodule ArchitexWeb.Router do
         get "/messages", RoomController, :messages
 
         scope "/state" do
-          get "/", RoomController, :state
-          put "/:event_type/*state_key", RoomController, :send_state_event
+          get "/", RoomController, :get_state
+
+          scope "/:event_type/*state_key" do
+            get "/", RoomController, :get_state_event
+            put "/", RoomController, :send_state_event
+          end
         end
       end
     end