-module(rebar3_lint_prv).

-export([init/1, do/1]).
-export([default_config/0]).

-define(PROVIDER, lint).
-define(DEPS, [compile, app_discovery]).

%% ===================================================================
%% Public API
%% ===================================================================
-spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
init(State) ->
    Provider =
        providers:create([{name, ?PROVIDER},
                          {module, ?MODULE},
                          {bare, true},
                          {deps, ?DEPS},
                          {example, "rebar3 lint"},
                          {opts, []},
                          {short_desc, "A rebar plugin for elvis"},
                          {desc, "A rebar linter plugin based on elvis"}]),
    {ok, rebar_state:add_provider(State, Provider)}.

-spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, {string(), any()}}.
do(State) ->
    Elvis = get_elvis_config(State),
    _ = rebar_log:log(info, "elvis analysis starting, this may take a while...", []),
    try elvis_core:rock(Elvis) of
        ok ->
            {ok, State};
        {fail, [{throw, Error} | _]} ->
            rebar_api:abort("elvis_core threw an exception: ~p", [Error]);
        {fail, _} ->
            {error, "Linting failed"}
    catch
        Error ->
            rebar_api:abort("elvis_core threw an exception: ~p", [Error])
    end.

-spec get_elvis_config(rebar_state:t()) -> elvis_config:configs().
get_elvis_config(State) ->
    try_elvis_config_rebar(State).

-spec try_elvis_config_rebar(rebar_state:t()) -> elvis_config:configs().
try_elvis_config_rebar(State) ->
    rebar_api:debug("Looking for Elvis in rebar.config", []),
    handle_output_format(State),
    case rebar_state:get(State, elvis, no_config) of
        no_config ->
            try_elvis_config_file(State);
        Config ->
            Config
    end.

-spec handle_output_format(rebar_state:t()) -> ok.
handle_output_format(State) ->
    case rebar_state:get(State, elvis_output_format, no_config) of
        no_config ->
            ok;
        plain ->
            application:set_env(elvis_core, output_format, plain);
        colors ->
            application:set_env(elvis_core, output_format, colors);
        parsable ->
            application:set_env(elvis_core, output_format, parsable);
        Other ->
            rebar_api:abort("~p is not a valid elvis output format. Must be either plain, colors or"
                            "parsable",
                            [Other])
    end.

-spec try_elvis_config_file(rebar_state:t()) -> elvis_config:configs().
try_elvis_config_file(State) ->
    Filename =
        filename:join(
            rebar_dir:root_dir(State), "elvis.config"),
    rebar_api:debug("Looking for Elvis in ~s", [Filename]),
    try elvis_config:from_file(Filename) of
        [] ->
            rebar_api:debug("Using default Elvis configuration", []),
            default_config();
        Config ->
            Config
    catch
        Error ->
            rebar_api:abort("Error reading Elvis config from ~s: ~p", [Filename, Error])
    end.

-spec default_config() -> elvis_config:configs().
default_config() ->
    [#{dirs => ["apps/*/src/**", "src/**"],
       filter => "*.erl",
       ruleset => erl_files},
     #{dirs => ["."],
       filter => "rebar.config",
       ruleset => rebar_config},
     #{dirs => ["."],
       filter => "elvis.config",
       ruleset => elvis_config}].