gen_phone.erl

%%%-------------------------------------------------------------------
%%% File:      gen_phone.erl
%%% @author    Sean Cribbs <> []
%%% @copyright 2009 Sean Cribbs
%%% @doc  
%%%
%%% @end  
%%%
%%% @since 2009-01-08 by Sean Cribbs
%%%-------------------------------------------------------------------
-module(gen_phone).
-author('').

-behaviour(gen_server).

%% API
-export([start_link/2, send_message/2, stop/1]).

%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
         terminate/2, code_change/3]).

-record(state, {me, neighbor}).

%%====================================================================
%% API
%%====================================================================
%%--------------------------------------------------------------------
%% @spec start_link() -> {ok,Pid} | ignore | {error,Error}
%% @doc Starts the server
%% @end 
%%--------------------------------------------------------------------
start_link(Me, Neighbor) ->
    gen_server:start_link({global, Me}, ?MODULE, [Me, Neighbor], []).

send_message(Message, Who) ->
  gen_server:call({global, Who}, {send_message, Message}).
  
stop(Who) ->
  gen_server:call({global, Who}, stop).

%%====================================================================
%% gen_server callbacks
%%====================================================================

%%--------------------------------------------------------------------
%% @spec init(Args) -> {ok, State} |
%%                         {ok, State, Timeout} |
%%                         ignore               |
%%                         {stop, Reason}
%% @doc Initiates the server
%% @end 
%%--------------------------------------------------------------------
init([Me, Neighbor]) ->
    {ok, #state{me=Me, neighbor=Neighbor}}.

%%--------------------------------------------------------------------
%% @spec 
%% handle_call(Request, From, State) -> {reply, Reply, State} |
%%                                      {reply, Reply, State, Timeout} |
%%                                      {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, Reply, State} |
%%                                      {stop, Reason, State}
%% @doc Handling call messages
%% @end 
%%--------------------------------------------------------------------
handle_call({send_message, Message}, _From, State) ->
  global:send(State#state.neighbor, {State#state.me, Message}),
  {reply, ok, State};
handle_call(stop, _From, _State) ->
  {stop, normal};
handle_call(_Request, _From, State) ->
    Reply = ok,
    {reply, Reply, State}.

%%--------------------------------------------------------------------
%% @spec handle_cast(Msg, State) -> {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, State}
%% @doc Handling cast messages
%% @end 
%%--------------------------------------------------------------------
handle_cast(_Msg, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% @spec handle_info(Info, State) -> {noreply, State} |
%%                                       {noreply, State, Timeout} |
%%                                       {stop, Reason, State}
%% @doc Handling all non call/cast messages
%% @end 
%%--------------------------------------------------------------------
handle_info(Message, State) when is_tuple(Message) ->
  MyName = State#state.me,
  Neighbor = State#state.neighbor,
  io:format("~p~n", [Message]),
  case check_circle(Message, MyName) of
    true ->
      ok;
    _ ->
      global:send(Neighbor, {MyName, Message})
  end,
  {noreply, State};
handle_info(_Info, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% @spec terminate(Reason, State) -> void()
%% @doc This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any necessary
%% cleaning up. When it returns, the gen_server terminates with Reason.
%% The return value is ignored.
%% @end 
%%--------------------------------------------------------------------
terminate(_Reason, _State) ->
    ok.

%%--------------------------------------------------------------------
%% @spec code_change(OldVsn, State, Extra) -> {ok, NewState}
%% @doc Convert process state when code is changed
%% @end 
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------

check_circle({MyName, _Message}, MyName) ->
  true;
check_circle({_Sender, Message}, MyName) when is_tuple(Message) ->
  check_circle(Message, MyName);
check_circle(_,_) -> false.

telephone.erl

-module(telephone).

-export([start/3, send_message/2, stop/1]).

start(MyName, Neighbor, Node) ->
  pong = net_adm:ping(Node),
  Pid = spawn_link(node(), fun() -> loop(MyName, Neighbor) end),
  global:register_name(MyName, Pid).

send_message(Message, Who) ->
  global:send(Who, {send_message, Message}).

stop(MyName) ->
  global:send(MyName, stop).

loop(MyName, Neighbor) ->
  receive
    stop -> ok;
    {send_message, Message} ->
      global:send(Neighbor, {MyName, Message}),
      loop(MyName, Neighbor);
    Message when is_tuple(Message) ->
      io:format("~p~n", [Message]),
      case check_circle(Message, MyName) of
        true ->
          ok;
        _ ->
          global:send(Neighbor, {MyName, Message})
      end,
      loop(MyName, Neighbor);
    _ ->
      loop(MyName, Neighbor)
  end.

check_circle({MyName, _Message}, MyName) ->
  true;
check_circle({_Sender, Message}, MyName) when is_tuple(Message) ->
  check_circle(Message, MyName);
check_circle(_,_) -> false.