%% -*- mode: erlang; indent-tabs-mode: nil -*-

Conf0 = CONFIG,                                 %The original config

%% Do a deep set stepping down a list of keys replacing/adding last
%% with value. Named funs would be nicer but not always available.

SetConf = fun ([K], Val, Ps, _F) ->
                  %% Replace the whole K field with Val.
                  [Val|proplists:delete(K, Ps)];
              ([K|Ks], Val, Ps, F) ->
                  %% Step down and build coming up.
                  case lists:keyfind(K, 1, Ps) of
                      {K,Kps} ->
                          lists:keyreplace(K, 1, Ps, {K,F(Ks, Val, Kps, F)});
                      false -> Ps ++ [{K,F(Ks, Val, [], F)}]
                  end
          end,

%% Get the release number.
%% We have stolen the idea and most of the code from rebar3.

Version = case erlang:system_info(otp_release) of
              [$R,N1|Rest] when is_integer(N1) ->
                  %% If OTP <= R16, take the digits.
                  [N1|Rest];
              Rel ->
                  File = filename:join([code:root_dir(),"releases",Rel,"OTP_VERSION"]),
                  case file:read_file(File) of
                      {error, _} -> Rel;
                      {ok, Vsn} ->
                          Size = byte_size(Vsn),
                          %% The shortest vsn string consists of at least
                          %% two digits followed by "\n". Therefore, it's
                          %% safe to assume Size >= 3.
                          case binary:part(Vsn, {Size, -3}) of
                              <<"**\n">> ->
                                  binary:bin_to_list(Vsn, {0, Size - 3});
                              _ ->
                                  binary:bin_to_list(Vsn, {0, Size - 1})
                          end
                  end
          end,

%% Collect the macro definitions we will add to the compiler options.

%% Erlc macro definitions.
HasOpt = {d,'HAS_MAPS',true},
FullOpt = {d,'HAS_FULL_KEYS',true},
RecOpt = {d,'NEW_REC_CORE',true},
RandOpt = {d,'NEW_RAND',true},

Copts0 = [{d,'ERLANG_VERSION',Version}],
Copts1 = if Version >= "17" -> Copts0 ++ [HasOpt];
            true -> Copts0
         end,
Copts2 = if Version >= "18" -> Copts1 ++ [FullOpt];
            true -> Copts1
         end,
Copts3 = if Version >= "19" -> Copts2 ++ [RecOpt,RandOpt];
            true -> Copts2
         end,
Copts = Copts3,                                 %This is it

%% Ensure they are in erl_opts.

Conf1 = case lists:keyfind(erl_opts, 1, Conf0) of
            {erl_opts,Opts} ->                  %Existing erl_opts
                NewOpts = {erl_opts,Opts ++ Copts},
                lists:keyreplace(erl_opts, 1, Conf0, NewOpts);
            false ->                            %No erl_opts
                Conf0 ++ [{erl_opts,Copts}]
        end,

Conf1.