%%%
%%%---------------------------------------------------------------------
%%% @copyright 2011 Harald Welte
%%% @author Harald Welte <laforge@gnumonks.org>
%%% @end
%%%
%%% Copyright (c) 2011 Harald Welte
%%% 
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%%%---------------------------------------------------------------------
%%%
%%% @doc TCAP application user SAP helper functions.
%%%
%%% @reference <a href="index.html">TCAP User's Guide</a>
%%%
%%% @private

-module(tcap_user).
-copyright('Copyright (c) 2011 Harald Welte').
-author('Harald Welte <laforge@gnumonks.org>').

-export([get_dialg_id/1, send_prim/2, start_sap/3]).

-include("tcap.hrl").

get_or_start_dha(TCO, DialgId) ->
	case ets:lookup(tcap_dha, DialgId) of
	    [] ->
		% ask TCO to start new transaction_sup, which will start
		% dialogue_sup, which will start dha_fsm
		gen_server:call(TCO, {local_new_trans, DialgId}),
		[{DialgId, DHA}] = ets:lookup(tcap_dha, DialgId),
		DHA;
	    [{DialgId, DHA}] ->
		DHA
	end.

get_dha(_TCO, DialgId) ->
	case ets:lookup(tcap_dha, DialgId) of
	    [{DialgId, DHA}] ->
		{ok, DHA};
	    _ ->
		{error, notfound}
	end.


get_dialg_id(#'TC-INVOKE'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-RESULT-L'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-RESULT-NL'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-BEGIN'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-CONTINUE'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-END'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-U-ERROR'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-U-REJECT'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-U-CANCEL'{dialogueID = DlgId}) ->
	DlgId;
get_dialg_id(#'TC-U-ABORT'{dialogueID = DlgId}) ->
	DlgId.

% the user (TCU) sends us a primitive.  We decide where to route it
send_prim(TCO, P={'TC', 'INVOKE', request, Param}) ->
	% component primitive establishing new dialogue
	DialgId = get_dialg_id(Param),
	DHA = get_or_start_dha(TCO, DialgId),
	CCO = tcap_dha_fsm:get_cco_pid(DHA),
	gen_server:cast(CCO, P);
send_prim(TCO, P={'TC', What, request, Param}) when
				What == 'RESULT-L';
				What == 'INVOKE';
				What == 'RESULT-NL';
				What == 'U-ERROR';
				What == 'U-CANCEL';
				What == 'U-REJECT'	->
	% component primitive relating to existing components
	DialgId = get_dialg_id(Param),
	{ok, DHA} = get_dha(TCO, DialgId),
	CCO = tcap_dha_fsm:get_cco_pid(DHA),
	gen_server:cast(CCO, P);
send_prim(TCO, P={'TC', 'BEGIN', request, Param}) when
				is_record(Param, 'TC-BEGIN') ->
	% dialogue primitives establishing new dialogue
	DialgId = Param#'TC-BEGIN'.dialogueID,
	DHA = get_or_start_dha(TCO, DialgId),
	gen_fsm:send_event(DHA, P);
send_prim(TCO, P={'TC', What, request, Param}) when
				What == 'CONTINUE';
				What == 'END';
				What == 'U-ABORT'	->
	% dialogue primitives for already-existing dialogues
	DialgId = get_dialg_id(Param),
	{ok, DHA} = get_dha(TCO, DialgId),
	gen_fsm:send_event(DHA, P);
send_prim(_TCO, P) ->
	{error, {unknown_prim, P}}.

% high-level user API to start the TCAP SAP supervisor + TCO server for a given SAP
start_sap(SccpModule, Args, Opts) ->
	% tcap_sup os simple_one_for_one and thus will start a tcap_sap_sup
	% process that will in turn start the TCO "Module" as a child.  The pid
	% we get is the tcap_sap_sup, not the TCO itself!
	case supervisor:start_child(tcap_sup, [SccpModule, Args, Opts]) of
		{ok, TcoSupPid} ->
			[{_, TCO, _, _}] = supervisor:which_children(TcoSupPid),
			{ok, TCO};
		Default ->
			Default
	end.

%% local functions

start_new_dha(TCO, LocalTID) ->
	Args = {self(), LocalTID, TCO},
	% this returns the _supervisor_ pid, not DHA
	{ok, Pid} = supervisor:start_link(tcap_dialogue_sup, Args),
	list_to_atom("tcap_dha_" ++ integer_to_list(LocalTID)).