%% Author: amk, mmu
%% Created: 02.01.2008
%% Description: Serverloser chat. Problemchen:
%% Partner werden nur aus den PIDs entfernt, wenn sie sich ordnungsgemäß
%% verabschieden. Ansonsten werden ihnen auf ewig alle Nachrichten zugeschickt
%% -> funktioniert, aber nicht effizient.
-module(chat).

%%
%% Include files
%%
-import(base).

%%
%% Exported Functions
%%
-export([start/1,start/3,reader/1]).

%%
%% API Functions
%%
start(Nick) ->
    spawn_link(chat,reader,[self()]),
    register(Nick,self()),
    chat(Nick,[self()]).
    
%% Beispiel: chat:start(myNick,'nodename@1.2.3.4',partnerNick).
start(Nick,Node,NodeNick) ->
	{NodeNick,Node}!{getlist,self()},
    start(Nick).
    
    
reader(P) ->
    Line = base:getLn("> "),
    P!{input,Line},
    reader(P).


%%
%% Local Functions
%%
chat(Nick,PIDs) ->
    receive
        {input,"/quit"} ->
            lists:foreach(fun(P) -> P!{quit,Nick,self()} end, PIDs),
            exit(-1);
        {input,Line} ->
            Hash = hash(PIDs),
            lists:foreach(fun(P) -> P!{message,Nick,Line,Hash,self()} end, PIDs),
            chat(Nick,PIDs);
        {getlist,PID} ->
            PID!{list,PIDs},
            chat(Nick,PIDs);
        {list,ReceivedPIDs} ->
            NewPIDs = lists:subtract(ReceivedPIDs, PIDs),
            lists:foreach(fun(P) -> P!{join,Nick,self()} end,NewPIDs),
            chat(Nick,lists:append(NewPIDs,PIDs));
        {join,SendNick,PID} ->
            case lists:any(fun(P) -> P == PID end, PIDs) of
                false ->
                    base:print(SendNick),
                    base:printLn(" has joined the Chat."),
                    NewPIDs = [PID|PIDs],
                    chat(Nick,NewPIDs);
                true ->
                    chat(Nick,PIDs)
            end;
        {quit,SendNick,PID} ->
            base:print(SendNick),
            base:printLn(" has left the Chat."),
            chat(Nick,lists:delete(PID,PIDs));
        {message,SendNick,Line,Hash,PID} ->
            base:print(SendNick),base:print(" "),
            base:printLn(Line),
            case hash(PIDs) of
                Hash ->
                    42;
                _ ->
                    PID!{getlist,self()},
                    PID!{list,PIDs}
            end,
            chat(Nick,PIDs)
    end.

hash(Val) -> erlang:phash2(lists:sort(Val), 4294967296).