%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
%% ex: ts=4 sw=4 et

-module(rebar_prv_help).

-behaviour(provider).

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

-include("rebar.hrl").

-define(PROVIDER, help).
-define(DEPS, []).

%% ===================================================================
%% Public API
%% ===================================================================

-spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
init(State) ->
    State1 = rebar_state:add_provider(State, providers:create([{name, ?PROVIDER},
                                                               {module, ?MODULE},
                                                               {bare, false},
                                                               {deps, ?DEPS},
                                                               {example, "rebar help <task>"},
                                                               {short_desc, "Display a list of tasks or help for a given task or subtask."},
                                                               {desc, "Display a list of tasks or help for a given task or subtask."},
                                                               {opts, [
                                                                      {help_task, undefined, undefined, string, "Task to print help for."}
                                                                      ]}])),
    {ok, State1}.

-spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, string()}.
do(State) ->
    {Args, _} = rebar_state:command_parsed_args(State),
    case proplists:get_value(help_task, Args, undefined) of
        undefined ->
            help(State),
            {ok, State};
        Name ->
            Providers = rebar_state:providers(State),
            case providers:get_provider(list_to_atom(Name), Providers) of
                not_found ->
                    {error, io_lib:format("Unknown task ~s", [Name])};
                Provider ->
                    providers:help(Provider),
                    {ok, State}
            end
    end.

%%
%% print help/usage string
%%
help(State) ->
    ?CONSOLE("Rebar is a tool for working with Erlang projects.~n~n", []),
    OptSpecList = rebar3:global_option_spec_list(),
    getopt:usage(OptSpecList, "rebar", "", []),
    ?CONSOLE("~nSeveral tasks are available:~n", []),

    providers:help(rebar_state:providers(State)),

    ?CONSOLE("~nRun 'rebar help <TASK>' for details.~n~n", []).