%%%=============================================================================
%%% Copyright 2013-2017, Tobias Schlager <schlagert@github.com>
%%%
%%% Permission to use, copy, modify, and/or distribute this software for any
%%% purpose with or without fee is hereby granted, provided that the above
%%% copyright notice and this permission notice appear in all copies.
%%%
%%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
%%%
%%% @doc
%%% An RFC3164 compliant protocol backend for syslog messages.
%%% @end
%%%=============================================================================
-module(syslog_rfc3164).

-behaviour(syslog_logger).

%% API
-export([hdr/3, msg/2]).

-include("syslog.hrl").

%%%=============================================================================
%%% API
%%%=============================================================================

%%------------------------------------------------------------------------------
%% @doc
%% Format the HDR part of RFC 3164 excluding the PRI.
%% @end
%%------------------------------------------------------------------------------
-spec hdr(syslog:datetime(), binary(), #syslog_cfg{}) -> iodata().
hdr(Datetime, Pid, Cfg = #syslog_cfg{appname = A, beam_pid = B}) ->
    [
     syslog_lib:format_rfc3164_date(Datetime), $\s,
     get_hostname(Cfg), $\s,
     A, $[, B, $], $\s,
     Pid, $\s, $-, $\s
    ].

%%------------------------------------------------------------------------------
%% @doc
%% Format the MSG part of RFC 3164. Basically a noop.
%% @end
%%------------------------------------------------------------------------------
-spec msg(binary(), #syslog_cfg{}) -> binary().
msg(Msg, _Cfg) -> Msg.

%%%=============================================================================
%%% internal functions
%%%=============================================================================

%%------------------------------------------------------------------------------
%% @private
%%------------------------------------------------------------------------------
get_hostname(#syslog_cfg{hostname = H, domain = D}) ->
    get_hostname(H, string:rstr(H, [$. | D])).
get_hostname(Hostname, Occurence) when Occurence > 2 ->
    string:sub_string(Hostname, 1, Occurence - 1);
get_hostname(Hostname, _) ->
    Hostname.

%%%=============================================================================
%%% Tests
%%%=============================================================================

-ifdef(TEST).

-include_lib("eunit/include/eunit.hrl").

get_hostname_test() ->
    R1 = #syslog_cfg{hostname = "host.domain.com", domain = "domain.com"},
    ?assertEqual("host", get_hostname(R1)),
    R2 = #syslog_cfg{hostname = "host", domain = ""},
    ?assertEqual("host", get_hostname(R2)).

hdr_test() ->
    Datetime = {{{2013,4,6},{21,20,56}},908235},
    Pid = "init",
    Cfg = #syslog_cfg{hostname = "host.domain.com",
                      domain = "domain.com",
                      appname = "beam",
                      beam_pid = "12345"},
    Rx = <<"Apr  6 \\d\\d:20:56 host beam\\[12345\\] init - ">>,
    Actual = iolist_to_binary(hdr(Datetime, Pid, Cfg)),
    ?assertMatch({match, _}, re:run(Actual, Rx)).

msg_test() -> ?assertEqual(<<"info">>, msg(<<"info">>, #syslog_cfg{})).

-endif.