% Internal SS7 route database keeping

% (C) 2011 by Harald Welte <laforge@gnumonks.org>
%
% All Rights Reserved
%
% This program is free software; you can redistribute it and/or modify
% it under the terms of the GNU Affero General Public License as
% published by the Free Software Foundation; either version 3 of the
% License, or (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU Affero General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.


% this module is keeping the point code routing table for the MTP3 layer
% of the Omsocom SS7 protocol stack.  Routes are created and deleted
% with create_route() and delete_route(), the arguments are
% 	* destination point code
% 	* point code mask
% 	* name of the linkset
%
% there is one function to actually make a routing decision: route_dpc/1
% with a single argument: the destination point code.

-module(ss7_routes).
-behaviour(gen_server).

-include_lib("osmo_ss7/include/mtp3.hrl").

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

% our published API
-export([start_link/0]).

% client functions, may internally talk to our sccp_user server
-export([create_route/3, delete_route/3]).
-export([dump/0]).
-export([route_dpc/1]).

-record(ss7route, {
	remote_pc_mask,		% {remote_pc, remote_pc_mask}
	linkset_name
}).

-record(sr_state, {
	route_tbl
}).

% initialization code

start_link() ->
	gen_server:start_link({local, ?MODULE}, ?MODULE, [], [{debug, [trace]}]).

init(_Arg) ->
	RouteTbl = ets:new(ss7_routes, [ordered_set, named_table,
			     {keypos, #ss7route.remote_pc_mask}]),
	process_flag(trap_exit, true),
	{ok, #sr_state{route_tbl = RouteTbl}}.

% client side API

% all write operations go through gen_server:call(), as only the ?MODULE
% process has permission to modify the table content

create_route(RemotePcIn, RemoteMask, LinksetName) ->
	RemotePc = osmo_util:pointcode2int(RemotePcIn),
	gen_server:call(?MODULE, {create_route, {RemotePc, RemoteMask, LinksetName}}).

delete_route(RemotePcIn, RemoteMask, LinksetName) ->
	RemotePc = osmo_util:pointcode2int(RemotePcIn),
	gen_server:call(?MODULE, {delete_route, {RemotePc, RemoteMask, LinksetName}}).

% the lookup functions can directly use the ets named_table from within
% the client process, no need to go through a synchronous IPC

route_dpc(DpcIn) ->
	Dpc = osmo_util:pointcode2int(DpcIn),
	% this was generated by ets:fun2ms() on the shell
	Match = [{#ss7route{remote_pc_mask={'$1','$2'},linkset_name='$3'},
			  [{'==',{'band',Dpc,'$2'},'$1'}],
			    ['$3']}],
	case ets:select(ss7_routes, Match) of
	    [Name|_] ->
		{ok, Name};
	    _ ->
		{error, no_route}
	end.

dump() ->
	List = ets:tab2list(ss7_routes),
	dump_routes(List).

dump_routes([]) ->
	ok;
dump_routes([Head|Tail]) when is_record(Head, ss7route) ->
	dump_single_route(Head),
	dump_routes(Tail).

dump_single_route(#ss7route{remote_pc_mask = {Pc, Mask},
			    linkset_name = Name}) ->
	PcTuple = osmo_util:pointcode_fmt(itu, Pc),
	MaskTuple = osmo_util:pointcode_fmt(itu, Mask),
	io:format("Dest PC ~p/~p -> Linkset ~p~n",
		  [PcTuple, MaskTuple, Name]).

% server side code

handle_call({create_route, {RemotePc, RemoteMask, Name}},
				{_FromPid, _FromRef}, S) ->
	#sr_state{route_tbl = Tbl} = S,
	R = #ss7route{remote_pc_mask = {RemotePc, RemoteMask},
		      linkset_name = Name},
	case ets:insert_new(Tbl, R) of
	    false ->
		{reply, {error, ets_insert}, S};
	    _ ->
		{reply, ok, S}
	end;

handle_call({delete_route, {RemotePc, RemoteMask, _Name}},
				{_FromPid, _FromRef}, S) ->
	#sr_state{route_tbl = Tbl} = S,
	ets:delete(Tbl, {RemotePc, RemoteMask}),
	{reply, ok, S}.

handle_info(Info, S) ->
	error_logger:error_report(["unknown handle_info",
				  {module, ?MODULE},
				  {info, Info}, {state, S}]),
	{noreply, S}.

terminate(Reason, _S) ->
	io:format("terminating ~p with reason ~p", [?MODULE, Reason]),
	ok.

code_change(_OldVsn, State, _Extra) ->
	{ok, State}.