%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2010-2011. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%

%%
%% The diameter application callback module configured by server.erl.
%%

-module(server_cb).

-include_lib("diameter/include/diameter.hrl").
-include_lib("diameter/src/app/diameter_gen_base_rfc3588.hrl").

%% diameter callbacks
-export([peer_up/3,
         peer_down/3,
         pick_peer/4,
         prepare_request/3,
         prepare_retransmit/3,
         handle_answer/4,
         handle_error/4,
         handle_request/3]).

-define(UNEXPECTED, erlang:error({unexpected, ?MODULE, ?LINE})).

peer_up(_SvcName, {PeerRef, _}, State) ->
    io:format("up: ~p~n", [PeerRef]),
    State.

peer_down(_SvcName, {PeerRef, _}, State) ->
    io:format("down: ~p~n", [PeerRef]),
    State.

pick_peer(_, _, _SvcName, _State) ->
    ?UNEXPECTED.

prepare_request(_, _SvcName, _Peer) ->
    ?UNEXPECTED.

prepare_retransmit(_Packet, _SvcName, _Peer) ->
    ?UNEXPECTED.

handle_answer(_Packet, _Request, _SvcName, _Peer) ->
    ?UNEXPECTED.

handle_error(_Reason, _Request, _SvcName, _Peer) ->
    ?UNEXPECTED.

%% A request whose decode was successful ...
handle_request(#diameter_packet{msg = Req, errors = []}, _SvcName, {_, Caps})
  when is_record(Req, diameter_base_RAR) ->
    #diameter_caps{origin_host = {OH,_},
                   origin_realm = {OR,_}}
        = Caps,
    #diameter_base_RAR{'Session-Id' = Id,
                       'Re-Auth-Request-Type' = RT}
        = Req,

    {reply, answer(RT, Id, OH, OR)};

%% ... or one that wasn't. 3xxx errors are answered by diameter itself
%% but these are non-3xxx errors for which we must contruct a reply.
%% Returning a packet with the non-[] errors field will cause
%% diameter to add the appropriate result code and Failed-AVPs avps.
%% We just have to return the relevant answer record with any required
%% avps.
handle_request(#diameter_packet{msg = Req} = Pkt, _SvcName, {_, Caps})
  when is_record(Req, diameter_base_RAR) ->
    #diameter_caps{origin_host = {OH,_},
                   origin_realm = {OR,_}}
        = Caps,
    #diameter_base_RAR{'Session-Id' = Id}
        = Req,

    Ans = #diameter_base_RAA{'Origin-Host' = OH,
                             'Origin-Realm' = OR,
                             'Session-Id' = Id},

    {reply, Pkt#diameter_packet{msg = Ans}};

%% Should really reply to other base messages that we don't support
%% but simply discard them instead.
handle_request(#diameter_packet{}, _SvcName, {_,_}) ->
    discard.

%% ---------------------------------------------------------------------------

%% Answer using the record or list encoding depending on
%% Re-Auth-Request-Type. This is just as an example. You would
%% typically just choose one, and this has nothing to do with the how
%% client.erl sends.

answer(0, Id, OH, OR) ->
    #diameter_base_RAA{'Result-Code' = 2001, %% DIAMETER_SUCCESS
                       'Origin-Host' = OH,
                       'Origin-Realm' = OR,
                       'Session-Id' = Id};

answer(_, Id, OH, OR) ->
    ['RAA', {'Result-Code', 5012}, %% DIAMETER_UNABLE_TO_COMPLY
            {'Origin-Host', OH},
            {'Origin-Realm', OR},
            {'Session-Id', Id}].