%%%-------------------------------------------------------------------
%%% @author Eric Merritt <ericbmerritt@gmail.com>
%%% @copyright 2011 Erlware, LLC.
%%% @doc
%%%  A module that provides config parsing and support to the system
%%% @end
%%%-------------------------------------------------------------------
-module(rcl_prv_config).

-behaviour(rcl_provider).

%% API
-export([init/1,
         do/1,
         format_error/1]).


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

%% @doc Required by the system, but not used in this provider
-spec init(rcl_state:t()) -> {ok, rcl_state:t()} | {error, Reason::term()}.
init(State) ->
    {ok, State}.

%% @doc parse all the configs currently specified in the state,
%% populating the state as a result.
-spec do(rcl_state:t()) ->{ok,  rcl_state:t()} | {error, Reason::term()}.
do(State) ->
    ConfigFiles = rcl_state:config_files(State),
    lists:foldl(fun load_config/2, {ok, State}, ConfigFiles).

-spec format_error({error, Reason::term()}) -> iolist().
format_error({error, {consult, Reason}}) ->
    file:format_error(Reason);
format_error({error, {invalid_term, Term}}) ->
    io_lib:format("Invalid term in config file: ~p", [Term]).

%%%===================================================================
%%% Internal Functions
%%%===================================================================
load_config(_, Err = {error, _}) ->
    Err;
load_config(ConfigFile, {ok, State}) ->
    {ok, CurrentCwd} = file:get_cwd(),
    ok = file:set_cwd(filename:dirname(ConfigFile)),
    Result = case file:consult(ConfigFile) of
                 {error, Reason} ->
                     {error, {consult, Reason}};
                 {ok, Terms} ->
                     lists:foldl(fun load_terms/2, {ok, State}, Terms)
             end,
    ok = file:set_cwd(CurrentCwd),
    Result.

load_terms({default_release, RelName, RelVsn}, {ok, State}) ->
    {ok, rcl_state:default_release(State, RelName, RelVsn)};
load_terms({paths, Paths}, {ok, State}) ->
    code:add_pathsa([filename:absname(Path) || Path <- Paths]),
    {ok, State};
load_terms({providers, Providers0}, {ok, State0}) ->
    Providers1 = gen_providers(Providers0, State0),
    case Providers1 of
        {error, _} ->
            Providers1;
        {Providers3, {ok, State3}} ->
            {ok, rcl_state:providers(State3, Providers3)}
    end;
load_terms({add_providers, Providers0}, {ok, State0}) ->
    Providers1 = gen_providers(Providers0, State0),
    case Providers1 of
        {error, _} ->
            Providers1;
        {Providers3, {ok, State1}} ->
            ExistingProviders = rcl_state:providers(State1),
            {ok, rcl_state:providers(State1, ExistingProviders ++ Providers3)}
    end;

load_terms({release, {RelName, Vsn}, Applications}, {ok, State0}) ->
    Release0 = rcl_release:new(RelName, Vsn),
    case rcl_release:goals(Release0, Applications) of
        E = {error, _} ->
            E;
        {ok, Release1} ->
            {ok, rcl_state:add_release(State0, Release1)}
        end;
load_terms({release, {RelName, Vsn}, {erts, ErtsVsn},
            Applications}, {ok, State}) ->
    Release0 = rcl_release:erts(rcl_release:new(RelName, Vsn), ErtsVsn),
    case rcl_release:goals(Release0, Applications) of
        E = {error, _} ->
            E;
        {ok, Release1} ->
            {ok, rcl_state:add_release(State, Release1)}
    end;
load_terms({Name, Value}, {ok, State})
  when erlang:is_atom(Name) ->
    {ok, rcl_state:put(State, Name, Value)};
load_terms(InvalidTerm, _) ->
    {error, {invalid_term, InvalidTerm}}.


gen_providers(Providers, State) ->
    lists:foldl(fun(ProviderName, {Providers1, {ok, State1}}) ->
                        {Provider, State2} = rcl_provider:new(ProviderName, State1),
                        {[Provider | Providers1], State2};
                   (_, E={error, _}) ->
                        E
                end, {[], {ok, State}}, Providers).