%% -*- mode: erlang;erlang-indent-level: 4;indent-tabs-mode: nil -*-

%% https://github.com/basho/webmachine/commit/a907e90086b39dcddf602e09a9ea1dc57ba675e4

%% 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.

%% -- Add development only options if we are a top-level build  --
%%
%% If a file named `./.rebar/DEV_MODE' exists, we assume we are a
%% top-level build (not being built as a dep of another project). We
%% add the deps from dev_only_deps defined in rebar.config, add
%% concrete as a dep, and define the compiler macro DEV_ONLY.

%% This macro can be used to conditionally enable code (e.g. tests)
%% that depend on development only dependencies.
ErlOpts = {erl_opts, [ {d, 'DEV_ONLY'}
                     , debug_info
                     ]},

%% Development only dependencies can be specified in the main
%% rebar.config. This file should not need to be edited directly.
DevOnlyDeps = case lists:keyfind(dev_only_deps, 1, CONFIG) of
                  false ->
                      [];
                  {dev_only_deps, DOD} ->
                      DOD
              end,

Deps = {deps, DevOnlyDeps},

ConfigPath = filename:dirname(SCRIPT),
DevMarker = filename:join([ConfigPath, ".rebar", "DEV_MODE"]),
_ = filelib:ensure_dir(DevMarker),
case filelib:is_file(DevMarker) of
    true ->
        lists:foldl(fun(I, C) -> MergeConfig(I, C) end,
                    CONFIG, [Deps, ErlOpts]);
    false ->
        %% If the ./.rebar/DEV_MODE marker is not present, this script simply
        %% returns the config specified in rebar.config. This will be
        %% the behavior when the project is built as a dependency of
        %% another project.
        CONFIG
end.