%%% @doc Plugin provider for rebar3
-module(rebar3_format_prv).

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

%% @private
-spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
init(State) ->
    Provider =
        providers:create([{name, format},
                          {module, rebar3_format_prv},
                          {bare, true},
                          {deps, [app_discovery]},
                          {example, "rebar3 format"},
                          {opts,
                           [{files,
                             $f,
                             "files",
                             string,
                             "List of files and directories to be formatted"},
                            {verify, $v, "verify", boolean, "Just verify, don't format"},
                            {output,
                             $o,
                             "output",
                             string,
                             "Output directory for the formatted files"}]},
                          {short_desc, "A rebar plugin for code formatting"},
                          {desc, ""}]),
    {ok, rebar_state:add_provider(State, Provider)}.

%% @private
-spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, iodata()}.
do(State) ->
    {Args, _} = rebar_state:command_parsed_args(State),
    Apps =
        case rebar_state:current_app(State) of
            undefined ->
                rebar_state:project_apps(State);
            AppInfo ->
                [AppInfo]
        end,
    Cwd = rebar_state:dir(State),
    Dirs = [dir_for_app(AppInfo, Cwd) || AppInfo <- Apps],
    Action = get_action(Args),
    OutputDirOpt = get_output_dir(Action, Args),
    Opts = maps:put(action, Action, maps:put(output_dir, OutputDirOpt, get_opts(State))),
    rebar_api:debug("Formatter options: ~p", [Opts]),
    Formatter = get_formatter(State, Opts),
    IgnoredFiles = get_ignored_files(State),
    Files = get_files(Args, State, Dirs) -- IgnoredFiles,
    rebar_api:debug("Found ~p files: ~p", [length(Files), Files]),
    case format_files(Files, Formatter) of
        ok ->
            ignore(IgnoredFiles, Formatter),
            {ok, State};
        {error, Error} ->
            {error, format_error(Error)}
    end.

%% @private
-spec dir_for_app(rebar_app_info:t(), file:filename_all()) -> file:filename_all() | [].
dir_for_app(AppInfo, Cwd) ->
    {ok, Dir} =
        rebar_file_utils:path_from_ancestor(
            rebar_app_info:dir(AppInfo), Cwd),
    Dir.

%% @private
-spec format_error(any()) -> string().
format_error({unformatted_files, Files}) ->
    lists:foldr(fun(File, Acc) -> [Acc, File, $\n] end,
                "The following files are not properly formatted:\n",
                Files);
format_error(Reason) ->
    io_lib:format("Unknown Formatting Error: ~p", [Reason]).

-spec get_action(proplists:proplist()) -> format | verify.
get_action(Args) ->
    case lists:keyfind(verify, 1, Args) of
        {verify, true} ->
            verify;
        _ ->
            format
    end.

-spec get_files(proplists:proplist(), rebar_state:t(), [file:filename_all() | []]) ->
                   [file:filename_all()].
get_files(Args, State, Dirs) ->
    FilesFromArgs = [Value || {files, Value} <- Args],
    {Patterns, Dirs1} =
        case FilesFromArgs of
            [] ->
                FormatConfig = rebar_state:get(State, format, []),
                case proplists:get_value(files, FormatConfig, undefined) of
                    undefined ->
                        {["include/**/*.[he]rl",
                          "include/**/*.app.src",
                          "src/**/*.[he]rl",
                          "src/**/*.app.src",
                          "test/**/*.[he]rl",
                          "test/**/*.app.src",
                          "{rebar,elvis,sys}.config"],
                         Dirs};
                    Wildcards ->
                        {Wildcards, []}
                end;
            Files ->
                {Files, []}
        end,
    %% Special handling needed for "" (current directory)
    %% so that ignore-lists work in an expected way.
    [File || Pattern <- Patterns, File <- filelib:wildcard(Pattern)]
    ++ [filename:join(Dir, File)
        || Dir <- Dirs1, Dir =/= "", Pattern <- Patterns, File <- filelib:wildcard(Pattern, Dir)].

-spec get_ignored_files(rebar_state:t()) -> [file:filename_all()].
get_ignored_files(State) ->
    FormatConfig = rebar_state:get(State, format, []),
    Patterns = proplists:get_value(ignore, FormatConfig, []),
    [IgnoredFile || Pat <- Patterns, IgnoredFile <- filelib:wildcard(Pat)].

-spec get_output_dir(format | verify, proplists:proplist()) ->
                        none | current | file:filename_all().
get_output_dir(Action, Args) ->
    case {lists:keyfind(output, 1, Args), Action} of
        {{output, OutputDir}, _} ->
            OutputDir;
        {false, format} ->
            current;
        {false, verify} ->
            none
    end.

-spec get_formatter(rebar_state:t(), rebar3_formatter:opts()) -> rebar3_formatter:t().
get_formatter(State, Opts) ->
    Module =
        proplists:get_value(formatter, rebar_state:get(State, format, []), default_formatter),
    rebar3_formatter:new(Module, Opts, State).

-spec get_opts(rebar_state:t()) -> rebar3_formatter:opts().
get_opts(State) ->
    proplists:get_value(options, rebar_state:get(State, format, []), #{}).

-spec format_files([file:filename_all()], rebar3_formatter:t()) -> ok | {error, term()}.
format_files(Files, Formatter) ->
    try lists:filter(fun(File) ->
                        rebar_api:debug("Formatting ~p with ~p", [File, Formatter]),
                        changed == rebar3_formatter:format_file(File, Formatter)
                     end,
                     Files)
    of
        [] ->
            ok;
        ChangedFiles ->
            case rebar3_formatter:action(Formatter) of
                format ->
                    ok;
                verify ->
                    {error, {unformatted_files, ChangedFiles}}
            end
    catch
        _:Error:Stack ->
            rebar_api:warn("Error parsing files: ~p~nStack: ~p", [Error, Stack]),
            {error, Error}
    end.

%% @doc Process ignored files
ignore(IgnoredFiles, Formatter) ->
    lists:foreach(fun(File) -> ok = rebar3_formatter:ignore(File, Formatter) end,
                  IgnoredFiles).