%% Merge the list values in `ToAdd' into the list found at key `Key'
%% in proplist `C'. Don't duplicate items. New Items are added to the
%% front of existing items. It is an error if the value at `Key' is
%% not a list in `C'.
MergeConfig = fun({Key, ToAdd}, C) ->
                      case lists:keyfind(Key, 1, C) of
                          false ->
                              lists:keystore(Key, 1, C, {Key, ToAdd});
                          {Key, List} when is_list(List) ->
                              %% remove items in ToAdd already in List
                              ToAdd1 = [ I || I <- ToAdd, not lists:member(I, List) ],
                              lists:keystore(Key, 1, C, {Key, ToAdd1 ++ List })
                      end
              end.

{match, [ErtsNumber]} = re:run(erlang:system_info(otp_release), "(\\d+)", [{capture, [0], list}]),
ErtsVsn = erlang:list_to_integer(ErtsNumber),
AddErlOpts = if
                 ErtsVsn >= 15 ->
                     [{d, have_callback_support}];
                 true ->
                     []
             end,

DevOnlyDeps = [{neotoma, "",
                {git, "https://github.com/seancribbs/neotoma.git", {branch, master}}},
               {proper, "",
                {git, "https://github.com/bkearns/proper.git", {branch, master}}}],

Config1 = MergeConfig({erl_opts, AddErlOpts}, CONFIG),

ConfigPath = filename:dirname(SCRIPT),
DevMarker = filename:join([ConfigPath, ".DEV_MODE"]),
case filelib:is_file(DevMarker) of
    true ->
        lists:foldl(MergeConfig, Config1,
                    [{deps, DevOnlyDeps},
                     {erl_opts, [{d, 'DEV_ONLY'}]}]);
    false ->
        Config1
end.