-module(prequel@internals@token).
-compile([no_auto_import, nowarn_unused_vars]).

-export([to_string/1, scan/1]).
-export_type([token/0]).

-type token() :: open_bracket |
    close_bracket |
    open_parens |
    close_parens |
    colon |
    circle_lollipop |
    star_lollipop |
    arrow_lollipop |
    minus |
    ampersand |
    {simple_comment, binary()} |
    {number, binary()} |
    {word, binary()}.

-spec to_string(token()) -> binary().
to_string(Token) ->
    case Token of
        open_bracket ->
            <<"{"/utf8>>;

        close_bracket ->
            <<"}"/utf8>>;

        open_parens ->
            <<"("/utf8>>;

        close_parens ->
            <<")"/utf8>>;

        colon ->
            <<":"/utf8>>;

        circle_lollipop ->
            <<"-o"/utf8>>;

        star_lollipop ->
            <<"-*"/utf8>>;

        arrow_lollipop ->
            <<"->"/utf8>>;

        minus ->
            <<"-"/utf8>>;

        ampersand ->
            <<"&"/utf8>>;

        {simple_comment, Comment} ->
            <<"//"/utf8, Comment/binary>>;

        {number, Number} ->
            Number;

        {word, Word} ->
            Word
    end.

-spec scan_comment_body(
    gleam@string_builder:string_builder(),
    integer(),
    binary()
) -> {binary(), integer(), binary()}.
scan_comment_body(Acc, Size, Source) ->
    case Source of
        <<"\r\n"/utf8, Rest/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Rest};

        <<"\n"/utf8, Rest/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Rest};

        Rest@1 ->
            case gleam@string:pop_grapheme(Rest@1) of
                {error, nil} ->
                    {gleam@string_builder:to_string(Acc), Size, Rest@1};

                {ok, {Grapheme, Rest@2}} ->
                    scan_comment_body(
                        gleam@string_builder:append(Acc, Grapheme),
                        Size + 1,
                        Rest@2
                    )
            end
    end.

-spec scan_word(gleam@string_builder:string_builder(), integer(), binary()) -> {binary(),
    integer(),
    binary()}.
scan_word(Acc, Size, Source) ->
    case Source of
        <<"//"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<"///"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<"////"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<":"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<"("/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<")"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<"{"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<"}"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<" "/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<"\n"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<"\r"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        <<"\t"/utf8, _/binary>> ->
            {gleam@string_builder:to_string(Acc), Size, Source};

        Rest ->
            case gleam@string:pop_grapheme(Rest) of
                {error, nil} ->
                    {gleam@string_builder:to_string(Acc), Size, Rest};

                {ok, {Grapheme, Rest@1}} ->
                    scan_word(
                        gleam@string_builder:append(Acc, Grapheme),
                        Size + 1,
                        Rest@1
                    )
            end
    end.

-spec do_scan(
    binary(),
    integer(),
    integer(),
    list({token(), prequel@span:span()})
) -> list({token(), prequel@span:span()}).
do_scan(Source, Line, Column, Acc) ->
    case Source of
        <<""/utf8>> ->
            gleam@list:reverse(Acc);

        <<"\n"/utf8, Rest/binary>> ->
            do_scan(Rest, Line + 1, 1, Acc);

        <<" "/utf8, Rest@1/binary>> ->
            do_scan(Rest@1, Line, Column + 1, Acc);

        <<"\t"/utf8, Rest@1/binary>> ->
            do_scan(Rest@1, Line, Column + 1, Acc);

        <<"\r"/utf8, Rest@1/binary>> ->
            do_scan(Rest@1, Line, Column + 1, Acc);

        <<"{"/utf8, Rest@2/binary>> ->
            Lexeme = {open_bracket, prequel@span:point(Line, Column)},
            do_scan(Rest@2, Line, Column + 1, [Lexeme | Acc]);

        <<"}"/utf8, Rest@3/binary>> ->
            Lexeme@1 = {close_bracket, prequel@span:point(Line, Column)},
            do_scan(Rest@3, Line, Column + 1, [Lexeme@1 | Acc]);

        <<"("/utf8, Rest@4/binary>> ->
            Lexeme@2 = {open_parens, prequel@span:point(Line, Column)},
            do_scan(Rest@4, Line, Column + 1, [Lexeme@2 | Acc]);

        <<")"/utf8, Rest@5/binary>> ->
            Lexeme@3 = {close_parens, prequel@span:point(Line, Column)},
            do_scan(Rest@5, Line, Column + 1, [Lexeme@3 | Acc]);

        <<":"/utf8, Rest@6/binary>> ->
            Lexeme@4 = {colon, prequel@span:point(Line, Column)},
            do_scan(Rest@6, Line, Column + 1, [Lexeme@4 | Acc]);

        <<"-o"/utf8, Rest@7/binary>> ->
            Lexeme@5 = {circle_lollipop,
                prequel@span:segment(Line, Column, Column + 1)},
            do_scan(Rest@7, Line, Column + 2, [Lexeme@5 | Acc]);

        <<"-*"/utf8, Rest@8/binary>> ->
            Lexeme@6 = {star_lollipop,
                prequel@span:segment(Line, Column, Column + 1)},
            do_scan(Rest@8, Line, Column + 2, [Lexeme@6 | Acc]);

        <<"->"/utf8, Rest@9/binary>> ->
            Lexeme@7 = {arrow_lollipop,
                prequel@span:segment(Line, Column, Column + 1)},
            do_scan(Rest@9, Line, Column + 2, [Lexeme@7 | Acc]);

        <<"-"/utf8, Rest@10/binary>> ->
            Lexeme@8 = {minus, prequel@span:point(Line, Column)},
            do_scan(Rest@10, Line, Column + 1, [Lexeme@8 | Acc]);

        <<"&"/utf8, Rest@11/binary>> ->
            Lexeme@9 = {ampersand, prequel@span:point(Line, Column)},
            do_scan(Rest@11, Line, Column + 1, [Lexeme@9 | Acc]);

        <<"//"/utf8, Rest@12/binary>> ->
            {Comment_body, Size, Rest@13} = scan_comment_body(
                gleam@string_builder:new(),
                2,
                Rest@12
            ),
            Span = prequel@span:segment(Line, Column, (Column + Size) - 1),
            Lexeme@10 = {{simple_comment, Comment_body}, Span},
            do_scan(Rest@13, Line + 1, 1, [Lexeme@10 | Acc]);

        <<"0"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"1"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"2"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"3"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"4"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"5"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"6"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"7"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"8"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        <<"9"/utf8, _/binary>> ->
            {Number, Size@1, Rest@14} = scan_number(
                gleam@string_builder:new(),
                0,
                Source
            ),
            Span@1 = prequel@span:segment(Line, Column, (Column + Size@1) - 1),
            Lexeme@11 = {{number, Number}, Span@1},
            do_scan(Rest@14, Line, Column + Size@1, [Lexeme@11 | Acc]);

        Rest@15 ->
            {Word, Size@2, Rest@16} = scan_word(
                gleam@string_builder:new(),
                0,
                Rest@15
            ),
            Lexeme@12 = {{word, Word},
                prequel@span:segment(Line, Column, (Column + Size@2) - 1)},
            do_scan(Rest@16, Line, Column + Size@2, [Lexeme@12 | Acc])
    end.

-spec scan(binary()) -> list({token(), prequel@span:span()}).
scan(Source) ->
    do_scan(Source, 1, 1, []).

-spec scan_number(gleam@string_builder:string_builder(), integer(), binary()) -> {binary(),
    integer(),
    binary()}.
scan_number(Acc, Size, Content) ->
    case Content of
        <<"0"/utf8, Rest/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"0"/utf8>>),
                Size + 1,
                Rest
            );

        <<"1"/utf8, Rest@1/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"1"/utf8>>),
                Size + 1,
                Rest@1
            );

        <<"2"/utf8, Rest@2/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"2"/utf8>>),
                Size + 1,
                Rest@2
            );

        <<"3"/utf8, Rest@3/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"3"/utf8>>),
                Size + 1,
                Rest@3
            );

        <<"4"/utf8, Rest@4/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"4"/utf8>>),
                Size + 1,
                Rest@4
            );

        <<"5"/utf8, Rest@5/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"5"/utf8>>),
                Size + 1,
                Rest@5
            );

        <<"6"/utf8, Rest@6/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"6"/utf8>>),
                Size + 1,
                Rest@6
            );

        <<"7"/utf8, Rest@7/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"7"/utf8>>),
                Size + 1,
                Rest@7
            );

        <<"8"/utf8, Rest@8/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"8"/utf8>>),
                Size + 1,
                Rest@8
            );

        <<"9"/utf8, Rest@9/binary>> ->
            scan_number(
                gleam@string_builder:append(Acc, <<"9"/utf8>>),
                Size + 1,
                Rest@9
            );

        Rest@10 ->
            {gleam@string_builder:to_string(Acc), Size, Rest@10}
    end.