erlarg

-module(erlarg).

-export([parse/2, parse/3]).
-export([opt/2, opt/3]).

-record(opt, { name, short, long, syntax, doc }).
-record(state, { depth = 0, aliases = #{} }).

-define(MAX_DEPTH_RECURSION, 1024).
-define(REV(List), lists:reverse(List)).

-type args() :: [string()].
-type base_type() :: int | float | number | bool | string | binary | atom.
-type custom_type() :: fun((args()) -> {ok, any(), args()} | any()).
-type type() :: base_type() | custom_type().
-type option_name() :: {string() | undefined, string() | undefined} | string().

-opaque opt() :: #opt{}.
-opaque syntax() :: [syntax()] | {any | first, [syntax()]}
                  | type() | {any(), type()}.

-export_type([opt/0, syntax/0, args/0, option_name/0]).


% @doc
% Retuns the specification for an option `Name' that doesn't have parameter.
%
% Example:
% ```
% --help % also -h
% erlarg:opt({"-h", "--help"}, help).
% '''
% @end
-spec opt(Option, Name) -> Return when
      Option :: option_name() | undefined,
      Name :: atom(),
      Return :: opt() | {atom(), syntax()}.

opt(Option, Name) ->
    opt(Option, Name, undefined).


% @doc
% Return the specification for an option `Name' that
% must be parsed with `Syntax'.
%
% Example:
% ```
% date -d 'now'
% erlarg:opt({"-d", "--date"}, date, string()).
% '''
% @end
-spec opt(Option, Name, Syntax) -> Return when
      Option :: option_name() | undefined,
      Name :: atom(),
      Syntax :: syntax() | undefined,
      Return :: opt() | {atom(), syntax()}.

opt({undefined, undefined}, Name, Syntax) ->
    {Name, Syntax};
opt({Short, Long}, Name, Syntax) ->
    #opt{ name = Name,
          short = Short, long = Long,
          syntax = Syntax };
opt(Short, Name, Syntax) ->
    opt({Short, undefined}, Name, Syntax).


% @doc
% Parses arguments into a structured data according to a given `syntax'
% @end
-spec parse(Args, Syntax) -> Options | Error when
      Args :: args(),
      Syntax :: syntax(),
      Options :: {ok, {any(), args()}},
      Error :: error.

parse(Args, Syntax) ->
    parse(Args, Syntax, #{}).


% @doc
% Parses arguments into a structured data according to a given `syntax' and 
% `aliases'
% @end
-spec parse(Args, Syntax, Aliases) -> Options | Error when
      Args :: args(),
      Syntax :: syntax(),
      Aliases :: map(),
      Options :: {ok, {any(), args()}},
      Error :: error.

parse(Args, Syntax, Aliases) ->
    try parse(#state{ aliases = Aliases }, Syntax, Args, []) of
        {Acc, RemainingArgs} ->
            {ok, {?REV(Acc), RemainingArgs}}
    catch
        error:Error ->
            {error, Error}
    end.

parse(#state{ depth = Depth }, _, _, _)
  when Depth >= ?MAX_DEPTH_RECURSION ->
    error(max_recursion);
parse(_, undefined, _, _) ->
    error({bad_syntax, undefined});
parse(_, [], Args, Acc) ->
    {Acc, Args};
parse(_, Syntax, [], Acc) ->
    case Syntax of
        {any, _} -> {Acc, []};
        _ -> error({missing, Syntax})
    end;
parse(State, {any, Syntax}, Args, Acc) when is_list(Syntax) ->
    case parse(State, {first, Syntax}, Args, Acc) of
        {Acc, Args} -> {Acc, Args};
        {Acc2, Args2} -> parse(State, {any, Syntax}, Args2, Acc2)
    end;
parse(State, {any, Syntax}, Args, Acc) ->
    parse(State, {any, [Syntax]}, Args, Acc);
parse(_, {first, []}, Args, Acc) ->
    {Acc, Args};
parse(State, {first, [Item | Syntax]}, Args, Acc) ->
    try parse(State, Item, Args, Acc) of
        {Acc2, Args2} -> {Acc2, Args2}
    catch
        error:{bad_opt, _, _} = Error ->
            error(Error);
        error:_ ->
            parse(State, {first, Syntax}, Args, Acc)
    end;
parse(State, [Item | Syntax], Args, Acc) ->
    {Acc2, Args2} = parse(State, Item, Args, Acc),
    parse(State, Syntax, Args2, Acc2);
parse(State, {Name, Syntax}, Args, Acc) ->
    {Value, Args2} = parse(State, Syntax, Args, []),
    {[commit_value(Syntax, Name, Value) | Acc], Args2};
parse(_, BaseType, [Arg | Args], Acc)
  when BaseType =:= int; BaseType =:= float; BaseType =:= number;
       BaseType =:= bool; BaseType =:= string; BaseType =:= binary;
       BaseType =:= atom ->
    {[consume(BaseType, Arg) | Acc], Args};
parse(#state{ depth = Depth, aliases = Aliases } = State, Alias, Args, Acc)
  when is_atom(Alias) ->
    case maps:find(Alias, Aliases) of
        {ok, #opt{} = Option} ->
            parse(State#state{ depth = Depth + 1 }, Option, Args, Acc);
        {ok, Fun} when is_function(Fun, 1) ->
            parse(State, Fun, Args, Acc);
        {ok, Syntax} ->
            parse(State#state{ depth = Depth + 1 }, Syntax, Args, Acc);
        error ->
            error({unknown_alias, Alias})
    end;
parse(_, #opt{ syntax = undefined } = Option, [Arg | _] = Args, Acc) ->
    case argument_matches_option(Option, Args) of
        {true, Args2} ->
            {[Option#opt.name | Acc], Args2};
        _ ->
            error({not_opt, Option, Arg})
    end;
parse(#state{ depth = Depth } = State,
      #opt{ syntax = Syntax } = Option,
      [Arg | _] = Args,
      Acc) ->
    case argument_matches_option(Option, Args) of
        {true, Args2} ->
            try parse(State#state{ depth = Depth + 1 }, Syntax, Args2, []) of
                {Acc2, Args3} ->
                    Acc3 = [commit_value(Syntax, Option#opt.name, Acc2) | Acc],
                    {Acc3, Args3}
            catch
                error:Error ->
                    error({bad_opt, Option, Error})
            end;
        _ ->
            error({not_opt, Option, Arg})
    end;
parse(_, Fun, Args, Acc)
  when is_function(Fun, 1) ->
    case Fun(Args) of
        {ok, Value, Args2} ->
            {[Value | Acc], Args2};
        Error ->
            error(Error)
    end.


-spec argument_matches_option(Option, Args) -> IsMatching when
      Option :: opt(),
      Args :: args(),
      IsMatching :: false | {true, args()}.

argument_matches_option(#opt{ short = Short, long = Long }, [Arg | Args])
  when Arg =:= Short; Arg =:= Long ->
    {true, Args};
argument_matches_option(#opt{ short = [$-, Short], syntax = undefined},
                        [[$-, Short | Arg] | Args]) ->
    {true, [[$- | Arg] | Args]};
argument_matches_option(#opt{ short = [$-, Short]},
                        [[$-, Short | Arg] | Args]) ->
    {true, [Arg | Args]};
argument_matches_option(#opt{ long = Long }, [Arg | Args]) ->
    case string:split(Arg, "=") of
        [Long, Value] ->
            {true, [Value | Args]};
        _ -> false
    end.

commit_value(Syntax, Name, [Value])
  when not is_list(Syntax) ->
    {Name, Value};
commit_value(_, Name, Values)
  when is_list(Values) ->
    {Name, ?REV(Values)}.

consume(int, Arg) ->
    to_int(Arg);
consume(float, Arg) ->
    to_float(Arg);
consume(number, Arg) ->
    to_number(Arg);
consume(bool, String) ->
    to_bool(string:lowercase(String));
consume(atom, String) ->
    list_to_atom(String);
consume(binary, String) ->
    unicode:characters_to_binary(String);
consume(string, String) ->
    String.


-spec to_int(String) -> Result when
      String :: string(),
      Result :: integer().

to_int(String) ->
    try list_to_integer(String) of
        Int -> Int
    catch
        error:_ -> error({not_int, String})
    end.


-spec to_float(String) -> Result when
      String :: string(),
      Result :: float().

to_float(String) ->
    try to_number(String) of
        Int when is_integer(Int) -> float(Int);
        Float when is_float(Float) -> Float
    catch
        error:_ -> error({not_float, String})
    end.


-spec to_number(String) -> Result when
      String :: string(),
      Result :: integer() | float().

to_number(String) ->
    to_number(String, [int, float]).

to_number(String, []) ->
    error({not_number, String});
to_number(String, [int | Tail]) ->
    try list_to_integer(String) of
        Int -> Int
    catch
        error:_ -> to_number(String, Tail)
    end;
to_number(String, [float | Tail]) ->
    try list_to_float(String) of
        Float -> Float
    catch
        error:_ -> to_number(String, Tail)
    end.


-spec to_bool(Argument :: string()) -> Result :: boolean().

to_bool("") -> false;
to_bool("0") -> false;
to_bool("disabled") -> false;
to_bool("f") -> false;
to_bool("false") -> false;
to_bool("n") -> false;
to_bool("no") -> false;
to_bool(Arg) ->
    try to_number(Arg) of
        Float when is_float(Float) -> Float =/= +0.0;
        Int when is_integer(Int) -> Int =/= 0
    catch
        error:_ -> true
    end.