-module(ebb_chain_fsm).

-behaviour(gen_fsm).

%% API
-export([start_link/2]).

%% gen_fsm callbacks
-export([init/1, handle_event/3, handle_sync_event/4, handle_info/3,
	 terminate/3, code_change/4]).

%% state callbacks
-export([forwarding/2]).

-define(DICT, orddict).

-record(state, {arity, vals, receiver}).

%%====================================================================
%% API
%%====================================================================
%%--------------------------------------------------------------------
%% Function: start_link() -> {ok,Pid} | ignore | {error,Error}
%% Description:Creates a gen_fsm process which calls Module:init/1 to
%% initialize. To ensure a synchronized start-up procedure, this function
%% does not return until Module:init/1 has returned.  
%%--------------------------------------------------------------------
start_link(Arity, Receiver) when is_number(Arity), is_pid(Receiver) ->
    gen_fsm:start_link(?MODULE, {Arity, Receiver}, []).

%%====================================================================
%% gen_fsm callbacks
%%====================================================================
%%--------------------------------------------------------------------
%% Function: init(Args) -> {ok, StateName, State} |
%%                         {ok, StateName, State, Timeout} |
%%                         ignore                              |
%%                         {stop, StopReason}                   
%% Description:Whenever a gen_fsm is started using gen_fsm:start/[3,4] or
%% gen_fsm:start_link/3,4, this function is called by the new process to 
%% initialize. 
%%--------------------------------------------------------------------
init({Arity, Receiver}) ->
    State = #state{arity=Arity, vals=?DICT:new(), receiver=Receiver},
    {ok, forwarding, State}.

%%--------------------------------------------------------------------
%% Function: 
%% state_name(Event, State) -> {next_state, NextStateName, NextState}|
%%                             {next_state, NextStateName, 
%%                                NextState, Timeout} |
%%                             {stop, Reason, NewState}
%% Description:There should be one instance of this function for each possible
%% state name. Whenever a gen_fsm receives an event sent using
%% gen_fsm:send_event/2, the instance of this function with the same name as
%% the current state name StateName is called to handle the event. It is also 
%% called if a timeout occurs. 
%%--------------------------------------------------------------------

forwarding({out, N, Val},
	   State = #state{arity=Arity, vals=Vals, receiver=Receiver})
  when N > 0, N =< Arity ->
    Vals2 = ?DICT:store(N, Val, Vals),
    State2 = State#state{vals=Vals2},
    ebb_event:in(Receiver, N, Val),
    case is_done(State2) of
	true  -> {stop, normal, State2};
	false -> {next_state, forwarding, State2}
    end.

%%--------------------------------------------------------------------
%% Function:
%% state_name(Event, From, State) -> {next_state, NextStateName, NextState} |
%%                                   {next_state, NextStateName, 
%%                                     NextState, Timeout} |
%%                                   {reply, Reply, NextStateName, NextState}|
%%                                   {reply, Reply, NextStateName, 
%%                                    NextState, Timeout} |
%%                                   {stop, Reason, NewState}|
%%                                   {stop, Reason, Reply, NewState}
%% Description: There should be one instance of this function for each
%% possible state name. Whenever a gen_fsm receives an event sent using
%% gen_fsm:sync_send_event/2,3, the instance of this function with the same
%% name as the current state name StateName is called to handle the event.
%%--------------------------------------------------------------------


%%--------------------------------------------------------------------
%% Function: 
%% handle_event(Event, StateName, State) -> {next_state, NextStateName, 
%%						  NextState} |
%%                                          {next_state, NextStateName, 
%%					          NextState, Timeout} |
%%                                          {stop, Reason, NewState}
%% Description: Whenever a gen_fsm receives an event sent using
%% gen_fsm:send_all_state_event/2, this function is called to handle
%% the event.
%%--------------------------------------------------------------------
handle_event(_Event, StateName, State) ->
    {next_state, StateName, State}.

%%--------------------------------------------------------------------
%% Function: 
%% handle_sync_event(Event, From, StateName, 
%%                   State) -> {next_state, NextStateName, NextState} |
%%                             {next_state, NextStateName, NextState, 
%%                              Timeout} |
%%                             {reply, Reply, NextStateName, NextState}|
%%                             {reply, Reply, NextStateName, NextState, 
%%                              Timeout} |
%%                             {stop, Reason, NewState} |
%%                             {stop, Reason, Reply, NewState}
%% Description: Whenever a gen_fsm receives an event sent using
%% gen_fsm:sync_send_all_state_event/2,3, this function is called to handle
%% the event.
%%--------------------------------------------------------------------
handle_sync_event(_Event, _From, StateName, State) ->
    Reply = ok,
    {reply, Reply, StateName, State}.

%%--------------------------------------------------------------------
%% Function: 
%% handle_info(Info,StateName,State)-> {next_state, NextStateName, NextState}|
%%                                     {next_state, NextStateName, NextState, 
%%                                       Timeout} |
%%                                     {stop, Reason, NewState}
%% Description: This function is called by a gen_fsm when it receives any
%% other message than a synchronous or asynchronous event
%% (or a system message).
%%--------------------------------------------------------------------
handle_info(_Info, StateName, State) ->
    {next_state, StateName, State}.

%%--------------------------------------------------------------------
%% Function: terminate(Reason, StateName, State) -> void()
%% Description:This function is called by a gen_fsm 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_fsm terminates with
%% Reason. The return value is ignored.
%%--------------------------------------------------------------------
terminate(_Reason, _StateName, _State) ->
    ok.

%%--------------------------------------------------------------------
%% Function:
%% code_change(OldVsn, StateName, State, Extra) -> {ok, StateName, NewState}
%% Description: Convert process state when code is changed
%%--------------------------------------------------------------------
code_change(_OldVsn, StateName, State, _Extra) ->
    {ok, StateName, State}.

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

is_done(#state{arity=Arity, vals=Vals}) ->
  ?DICT:size(Vals) == Arity.