%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2010-2016. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
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%% %CopyrightEnd%
%%

-module(relay_cb).

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

%% diameter callbacks
-export([peer_up/3,
         peer_down/3,
         pick_peer/5,
         prepare_request/4,
         prepare_retransmit/4,
         handle_answer/5,
         handle_error/5,
         handle_request/3]).

peer_up(_SvcName, _Peer, State) ->
    State.

peer_down(_SvcName, _Peer, State) ->
    State.

%% Returning 'relay' from handle_request causes diameter to resend the
%% incoming request, which leads to pick_peer and prepare_request
%% callbacks as if sending explicitly. The 'extra' argument is
%% appended to the argument list for callbacks following from
%% resending of the request.

handle_request(_Pkt, _SvcName, _Peer) ->
    {relay, [{timeout, 1000}, {extra, [relayed]}]}.

%% diameter will filter the sender in the Peers list.
pick_peer([Peer | _], _, _SvcName, _State, relayed) ->
    {ok, Peer}.

prepare_request(Pkt, _SvcName, _Peer, relayed) ->
    {send, Pkt}.

prepare_retransmit(Pkt, _SvcName, _Peer, relayed) ->
    {send, Pkt}.

%% diameter expects handle_answer to return the diameter_packet record
%% containing the answer when called for a relayed request.

handle_answer(Pkt, _Request, _SvcName, _Peer, relayed) ->
    Pkt.

handle_error(Reason, _Request, _SvcName, _Peer, relayed) ->
    {error, Reason}.