-module(msg).
-compile([export_all]).
%%分布式聊天,
start_server()->
    register (server,spawn(msg,server,[[]])).
server(UserList)->
    receive
	{logon,UserInfo} ->
	    server(handle_logon(UserInfo,UserList));
	{message2,[To,From,Msg]}->
	    io:format("a conn~n",[]),
	    io:format("~w~n",[UserList]),
	    case lists:keysearch(To,1,UserList) of
		false ->
		    io:format("user ~p doesnt exists ~n", [To]);
		{value,{_,UserPid}}->
		    io:format("Msg to ~p ~n", [To]),
		    UserPid!{message2,{From,Msg}}
	    end,
	    server(UserList);
	_ ->
	    server(UserList)
    end.
handle_logon(UserInfo,UserList)->
    [Username,From]=UserInfo,
    case lists:keymember(Username,1,UserList) of
	true ->
	    From ! reject,
	    io:format("server rejected ~p\n",[Username]),
	    UserList;
	false ->
	    From!accept,
	    io:format("server acceped ~p\n",[Username]),
	    [{Username,From}|UserList]
    end
	.

message(To,Msg)->
    case whereis(client) of
	undefined->
	    you_are_not_logged_on;
	_ ->
	    client!{message_req,{To,Msg}}
    end
    %% {server,server@jf.org} !{message2,[To,self(),Msg]}
    %% receive
    %%     {message2,{From,Msg}}->
    %%         io:format(" ~p: ~p\n",[To,Msg])
    %% end
	.
receive_msg()->
    receive
	{message2,{From,Msg}}->
	    io:format(" ~p: ~p\n",[From,Msg]);
	{message_req,{To,Msg}} ->
	    {server,server@jf.org} !{message2,[To,self(),Msg]};
	accept->
	    io:format("acceped~n",[]),
	    true;
	reject->
	    io:format("rej~n",[]),
	    false
    end,
    receive_msg()
	.
logon(Username)->
    case whereis(client) of
	undefined ->
	    register(client, spawn(msg,receive_msg,[])),
	    {server,server@jf.org} !{logon,[Username,whereis(client)]};
	_ ->
	    already_logged_on
    end.
%% erl -name server
%% msg:start_server().
%% erl -name c1
%%  msg:logon("c1").
%%  erl -name c2
%%  msg:logon("c2").
%%  msg:message("c1","hello,c1,I am c2").
%%  msg:message("c2","hello,c2,I am c1").


%% whereis(RegName) ->pid or port or undefined.