Added a chat server to make life hilarious

src/chats_server.erl

@@ -0,0 +1,103 @@
+-module(chats_server).
+
+-behaviour(gen_server).
+
+-export([start/0, add_user/2, remove_user/2, send_message/2, list_users/0]).
+
+-include_lib("src/models.hrl").
+
+%% gen_server callbacks
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
+         terminate/2, code_change/3]).
+
+-record(state, {active_users}).
+
+start() ->
+  gen_server:start_link({local, chats_server}, chats_server, [], []).
+
+add_user(User, Pid) ->
+  gen_server:cast(chats_server, {add_user, User, Pid}).
+
+remove_user(User, Pid) ->
+  gen_server:cast(chats_server, {remove_user, User, Pid}).
+
+send_message(User, Message) ->
+  gen_server:cast(chats_server, {message, User, Message}).
+
+list_users() ->
+  gen_server:call(chats_server, list_users).
+
+
+init([]) ->
+  {ok, #state{active_users=dict:new()}}.
+
+handle_call(list_users, _From, State) ->
+  {reply, dict:fetch_keys(State#state.active_users), State};
+
+handle_call(_Request, _From, State) ->
+  Reply = ok,
+  {reply, Reply, State}.
+
+% Message
+handle_cast({message, User, Message}, State) ->
+  send_message_to_all_users(User, Message, 
+    users_to_pids(State#state.active_users)),
+  {noreply, refresh_active_users(State)};
+
+% Add User
+handle_cast({add_user, User, Pid}, State) -> 
+  NewState = refresh_active_users(add_user_to_active_users(User, Pid, State)),
+  {noreply, NewState};
+% Remove User
+handle_cast({remove_user, User, Pid}, State) ->
+  NewState = refresh_active_users(remove_user_from_active_users(User, Pid, State)),
+  {noreply, NewState};
+
+handle_cast(_Msg, State) ->
+  {noreply, State}.
+
+handle_info(_Info, State) ->
+  {noreply, State}.
+
+terminate(_Reason, _State) ->
+  ok.
+
+code_change(_OldVsn, State, _Extra) ->
+  {ok, State}.
+
+refresh_active_users(State) ->
+  State#state{
+    active_users=
+      dict:filter(
+        fun(_, V) ->
+          try is_pid(V) andalso is_process_alive(V)
+          catch
+            _ -> false
+          end
+        end,
+        State#state.active_users)}.
+
+users_to_pids(Users) ->
+  list:map(fun({_, Pid}) -> Pid end, dict:to_list(Users)).
+
+send_message_to_all_users(User, Message, UserPids) -> 
+  [X!{message, User#user.username, Message} || X <- UserPids],
+  ok.
+
+add_user_to_active_users(User, Pid, State) ->
+  ActiveUsers = State#state.active_users,
+  NewActiveUsers = 
+    case dict:find(User, ActiveUsers) of
+      {ok, _} -> dict:update(User, Pid, ActiveUsers);
+      _ -> dict:append(User, Pid, ActiveUsers)
+    end,
+  State#state{active_users=NewActiveUsers}.
+
+remove_user_from_active_users(User, Pid, State) ->
+  ActiveUsers = State#state.active_users,
+  NewActiveUsers =
+    case dict:find(User, ActiveUsers) of
+      {ok, Pid} -> dict:erase(User, ActiveUsers);
+      _ -> ActiveUsers
+    end,
+  State#state{active_users=NewActiveUsers}.