%%% Copyright (c) 2016, NORDUnet A/S.
%%% See LICENSE for licensing information.

-module(plop_compat).
-export([unpack_spki/1, timestamp/0, monotonic_time/1, start_timer/4, unique_integer/1, time_offset/1]).
-include_lib("public_key/include/public_key.hrl").

unpack_spki(SPKI) ->
    unpack_spki(erlang:system_info(otp_release), SPKI).
timestamp() ->
    timestamp(erlang:system_info(otp_release)).
monotonic_time(Unit) ->
    monotonic_time(erlang:system_info(otp_release), Unit).
start_timer(Time, Dest, Msg, Options) ->
    start_timer(erlang:system_info(otp_release), Time, Dest, Msg, Options).
unique_integer(Modifiers) ->
    unique_integer(erlang:system_info(otp_release), Modifiers).
time_offset(Unit) ->
    time_offset(erlang:system_info(otp_release), Unit).

unpack_spki("R16" ++ _, SPKI) ->
    #'SubjectPublicKeyInfo'{subjectPublicKey = {_, Octets},
                            algorithm = Algorithm} = SPKI,
    {Octets, Algorithm};
unpack_spki("17", SPKI) ->
    #'SubjectPublicKeyInfo'{subjectPublicKey = {_, Octets},
                            algorithm = Algorithm} = SPKI,
    {Octets, Algorithm};
unpack_spki("18", SPKI) ->
    #'SubjectPublicKeyInfo'{subjectPublicKey = Octets,
                            algorithm = Algorithm} = SPKI,
    {Octets, Algorithm};
unpack_spki("19", SPKI) ->
    #'SubjectPublicKeyInfo'{subjectPublicKey = Octets,
                            algorithm = Algorithm} = SPKI,
    {Octets, Algorithm}.

%% <=R17: now/0, >=R18 timestamp/0
timestamp("R16" ++ _) ->
    erlang:now();
timestamp("17") ->
    erlang:now();
timestamp("18") ->
    erlang:timestamp();
timestamp("19") ->
    erlang:timestamp().

monotonic_time("R16" ++ _, millisecond) ->
    {MeS, S, MiS} = timestamp(),
    (MeS * 1000000 + S) * 1000 + MiS div 1000;
monotonic_time("17", millisecond) ->
    {MeS, S, MiS} = timestamp(),
    (MeS * 1000000 + S) * 1000 + MiS div 1000;
monotonic_time("18", Unit) ->
    erlang:monotonic_time(Unit);
monotonic_time("19", Unit) ->
    erlang:monotonic_time(Unit).

unique_integer("R16", _Modifiers) ->
    {MeS, S, MiS} = erlang:now(),
    (MeS * 1000000 + S) * 1000000 + MiS;
unique_integer("17", _Modifiers) ->
    {MeS, S, MiS} = erlang:now(),
    (MeS * 1000000 + S) * 1000000 + MiS;
unique_integer("18", Modifiers) ->
    erlang:unique_integer(Modifiers);
unique_integer("19", Modifiers) ->
    erlang:unique_integer(Modifiers).

time_offset("R16", _Unit) ->
    0;
time_offset("17", _Unit) ->
    0;
time_offset("18", Unit) ->
    erlang:time_offset(Unit);
time_offset("19", Unit) ->
    erlang:time_offset(Unit).

start_timer("R16" ++ _, Time, Dest, Msg, [{abs, true}]) ->
    erlang:start_timer(max(0, Time - monotonic_time(millisecond)), Dest, Msg);
start_timer("17", Time, Dest, Msg, [{abs, true}]) ->
    erlang:start_timer(max(0, Time - monotonic_time(millisecond)), Dest, Msg);
start_timer("18", Time, Dest, Msg, Options) ->
    erlang:start_timer(Time, Dest, Msg, Options);
start_timer("19", Time, Dest, Msg, Options) ->
    erlang:start_timer(Time, Dest, Msg, Options).