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beencode

1.0.0
🐝 bencode in Gleam
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beencode src beencode.erl
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src/beencode.erl

-module(beencode).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([encode/1, decode/1]).
-export_type([b_value/0, b_decode_error/0]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

-type b_value() :: {b_string, bitstring()} |
    {b_int, integer()} |
    {b_list, list(b_value())} |
    {b_dict, gleam@dict:dict(bitstring(), b_value())}.

-type b_decode_error() :: expecting_eof |
    unexpected_eof |
    {unexpected_char, integer()} |
    {empty_number, integer()} |
    {negative_zero, integer()} |
    {leading_zero, integer()} |
    {invalid_dict_key, integer()} |
    {string_shorter_than_expected, integer()}.

-file("/Users/giacomocavalieri/Documents/progetti/bvalue/src/beencode.gleam", 225).
-spec decode_string(bitstring(), integer(), integer()) -> {ok,
        {b_value(), bitstring(), integer()}} |
    {error, b_decode_error()}.
decode_string(String, Acc, Byte_index) ->
    case String of
        <<"0"/utf8, Rest/bitstring>> ->
            decode_string(Rest, Acc * 10, Byte_index + 1);

        <<"1"/utf8, Rest@1/bitstring>> ->
            decode_string(Rest@1, (Acc * 10) + 1, Byte_index + 1);

        <<"2"/utf8, Rest@2/bitstring>> ->
            decode_string(Rest@2, (Acc * 10) + 2, Byte_index + 1);

        <<"3"/utf8, Rest@3/bitstring>> ->
            decode_string(Rest@3, (Acc * 10) + 3, Byte_index + 1);

        <<"4"/utf8, Rest@4/bitstring>> ->
            decode_string(Rest@4, (Acc * 10) + 4, Byte_index + 1);

        <<"5"/utf8, Rest@5/bitstring>> ->
            decode_string(Rest@5, (Acc * 10) + 5, Byte_index + 1);

        <<"6"/utf8, Rest@6/bitstring>> ->
            decode_string(Rest@6, (Acc * 10) + 6, Byte_index + 1);

        <<"7"/utf8, Rest@7/bitstring>> ->
            decode_string(Rest@7, (Acc * 10) + 7, Byte_index + 1);

        <<"8"/utf8, Rest@8/bitstring>> ->
            decode_string(Rest@8, (Acc * 10) + 8, Byte_index + 1);

        <<"9"/utf8, Rest@9/bitstring>> ->
            decode_string(Rest@9, (Acc * 10) + 9, Byte_index + 1);

        <<":"/utf8, Rest@10/bitstring>> ->
            case Rest@10 of
                <<String@1:Acc/binary, Rest@11/bitstring>> ->
                    {ok,
                        {{b_string, String@1}, Rest@11, (Byte_index + 1) + Acc}};

                _ ->
                    {error, {string_shorter_than_expected, Byte_index}}
            end;

        <<>> ->
            {error, unexpected_eof};

        _ ->
            {error, {unexpected_char, Byte_index}}
    end.

-file("/Users/giacomocavalieri/Documents/progetti/bvalue/src/beencode.gleam", 278).
-spec decode_int(bitstring(), integer(), boolean(), integer()) -> {ok,
        {b_value(), bitstring(), integer()}} |
    {error, b_decode_error()}.
decode_int(String, Acc, Negative, Byte_index) ->
    case String of
        <<"e"/utf8, Rest/bitstring>> when Negative ->
            {ok, {{b_int, - Acc}, Rest, Byte_index + 1}};

        <<"e"/utf8, Rest@1/bitstring>> ->
            {ok, {{b_int, Acc}, Rest@1, Byte_index + 1}};

        <<"0"/utf8, Rest@2/bitstring>> ->
            decode_int(Rest@2, Acc * 10, Negative, Byte_index + 1);

        <<"1"/utf8, Rest@3/bitstring>> ->
            decode_int(Rest@3, (Acc * 10) + 1, Negative, Byte_index + 1);

        <<"2"/utf8, Rest@4/bitstring>> ->
            decode_int(Rest@4, (Acc * 10) + 2, Negative, Byte_index + 1);

        <<"3"/utf8, Rest@5/bitstring>> ->
            decode_int(Rest@5, (Acc * 10) + 3, Negative, Byte_index + 1);

        <<"4"/utf8, Rest@6/bitstring>> ->
            decode_int(Rest@6, (Acc * 10) + 4, Negative, Byte_index + 1);

        <<"5"/utf8, Rest@7/bitstring>> ->
            decode_int(Rest@7, (Acc * 10) + 5, Negative, Byte_index + 1);

        <<"6"/utf8, Rest@8/bitstring>> ->
            decode_int(Rest@8, (Acc * 10) + 6, Negative, Byte_index + 1);

        <<"7"/utf8, Rest@9/bitstring>> ->
            decode_int(Rest@9, (Acc * 10) + 7, Negative, Byte_index + 1);

        <<"8"/utf8, Rest@10/bitstring>> ->
            decode_int(Rest@10, (Acc * 10) + 8, Negative, Byte_index + 1);

        <<"9"/utf8, Rest@11/bitstring>> ->
            decode_int(Rest@11, (Acc * 10) + 9, Negative, Byte_index + 1);

        <<>> ->
            {error, unexpected_eof};

        _ ->
            {error, {unexpected_char, Byte_index}}
    end.

-file("/Users/giacomocavalieri/Documents/progetti/bvalue/src/beencode.gleam", 400).
?DOC(
    " Encodes a `BValue` into a [bencoded](https://en.wikipedia.org/wiki/Bencode)\n"
    " `BitArray`.\n"
    "\n"
    " ## Examples\n"
    "\n"
    " ```gleam\n"
    " encode(BInt(1))\n"
    " // -> <<\"i1e\":utf8>>\n"
    "\n"
    " encode(BString(\"wibble\"))\n"
    " // -> <<\"6:wibble\":utf8>>\n"
    "\n"
    " encode(BList([BInt(1), BString(\"wibble\")]))\n"
    " // -> <<\"li1e6:wibblee\":utf8>>\n"
    "\n"
    " encode(BDict(dict.from_list([#(BString(\"wibble\"), BInt(1))])))\n"
    " // -> <<\"d6:wibblei1ee\">>\n"
    " ```\n"
).
-spec encode(b_value()) -> bitstring().
encode(Value) ->
    case Value of
        {b_int, N} ->
            <<"i"/utf8, (erlang:integer_to_binary(N))/binary, "e"/utf8>>;

        {b_string, Value@1} ->
            Bytes = erlang:byte_size(Value@1),
            <<(erlang:integer_to_binary(Bytes))/binary,
                ":"/utf8,
                Value@1/bitstring>>;

        {b_list, Values} ->
            Encoded_values = gleam@list:map(Values, fun encode/1),
            <<"l"/utf8,
                (gleam_stdlib:bit_array_concat(Encoded_values))/bitstring,
                "e"/utf8>>;

        {b_dict, Dict} ->
            Values@1 = begin
                _pipe = maps:to_list(Dict),
                _pipe@1 = gleam@list:sort(
                    _pipe,
                    fun(One, Other) ->
                        {One_key, _} = One,
                        {Other_key, _} = Other,
                        gleam@bit_array:compare(One_key, Other_key)
                    end
                ),
                gleam@list:map(
                    _pipe@1,
                    fun(Pair) ->
                        {Key, Value@2} = Pair,
                        <<(encode({b_string, Key}))/bitstring,
                            (encode(Value@2))/bitstring>>
                    end
                )
            end,
            <<"d"/utf8,
                (gleam_stdlib:bit_array_concat(Values@1))/bitstring,
                "e"/utf8>>
    end.

-file("/Users/giacomocavalieri/Documents/progetti/bvalue/src/beencode.gleam", 323).
-spec decode_list(bitstring(), list(b_value()), integer()) -> {ok,
        {b_value(), bitstring(), integer()}} |
    {error, b_decode_error()}.
decode_list(String, Acc, Byte_index) ->
    case String of
        <<"e"/utf8, Rest/bitstring>> ->
            {ok, {{b_list, lists:reverse(Acc)}, Rest, Byte_index + 1}};

        _ ->
            case decode_value(String, Byte_index) of
                {error, Error} ->
                    {error, Error};

                {ok, {Value, Rest@1, Byte_index@1}} ->
                    decode_list(Rest@1, [Value | Acc], Byte_index@1)
            end
    end.

-file("/Users/giacomocavalieri/Documents/progetti/bvalue/src/beencode.gleam", 146).
-spec decode_value(bitstring(), integer()) -> {ok,
        {b_value(), bitstring(), integer()}} |
    {error, b_decode_error()}.
decode_value(String, Byte_index) ->
    case String of
        <<"ie"/utf8, _/bitstring>> ->
            {error, {empty_number, Byte_index}};

        <<"i0e"/utf8, Rest/bitstring>> ->
            {ok, {{b_int, 0}, Rest, Byte_index + 1}};

        <<"i-0e"/utf8, _/bitstring>> ->
            {error, {negative_zero, Byte_index}};

        <<"i0"/utf8, _/bitstring>> ->
            {error, {leading_zero, Byte_index}};

        <<"i-0"/utf8, _/bitstring>> ->
            {error, {leading_zero, Byte_index}};

        <<"i-"/utf8, Rest@1/bitstring>> ->
            decode_int(Rest@1, 0, true, Byte_index);

        <<"i"/utf8, Rest@2/bitstring>> ->
            decode_int(Rest@2, 0, false, Byte_index);

        <<"l"/utf8, Rest@3/bitstring>> ->
            decode_list(Rest@3, [], Byte_index);

        <<"d"/utf8, Rest@4/bitstring>> ->
            decode_dict(Rest@4, maps:new(), Byte_index);

        <<"0:"/utf8, Rest@5/bitstring>> ->
            {ok, {{b_string, <<>>}, Rest@5, Byte_index + 2}};

        <<"0"/utf8, _/bitstring>> ->
            {error, {unexpected_char, Byte_index}};

        <<"1"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<"2"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<"3"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<"4"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<"5"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<"6"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<"7"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<"8"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<"9"/utf8, _/bitstring>> ->
            decode_string(String, 0, Byte_index + 1);

        <<>> ->
            {error, unexpected_eof};

        _ ->
            {error, {unexpected_char, Byte_index}}
    end.

-file("/Users/giacomocavalieri/Documents/progetti/bvalue/src/beencode.gleam", 123).
?DOC(
    " Decodes a [bencoded](https://en.wikipedia.org/wiki/Bencode) `BitArray` into\n"
    " a `BValue`.\n"
    "\n"
    " > ⚠️ According to the bencode specification the keys of a dictionary should\n"
    " > always be sorted lexicographically. This decoder is a bit more permissive\n"
    " > and will successfully decode a dictionary even if its keys appear in a\n"
    " > different order.\n"
    "\n"
    " ## Examples\n"
    "\n"
    " ```gleam\n"
    " decode(<<\"i1e\":utf8>>)\n"
    " // -> BInt(1)\n"
    "\n"
    " decode(<<\"6:wibble\":utf8>>)\n"
    " // -> BString(\"wibble\")\n"
    "\n"
    " decode(<<\"li1e6:wibblee\":utf8>>)\n"
    " // -> BList([BInt(1), BString(\"wibble\")])\n"
    "\n"
    " decode(<<\"d6:wibblei1ee\">>)\n"
    " // -> BDict(dict.from_list([#(BString(\"wibble\"), BInt(1))]))\n"
    " ```\n"
).
-spec decode(bitstring()) -> {ok, b_value()} | {error, b_decode_error()}.
decode(Input) ->
    case decode_value(Input, 0) of
        {ok, {Value, <<>>, _}} ->
            {ok, Value};

        {ok, {_, _, _}} ->
            {error, expecting_eof};

        {error, Reason} ->
            {error, Reason}
    end.

-file("/Users/giacomocavalieri/Documents/progetti/bvalue/src/beencode.gleam", 349).
-spec decode_dict(
    bitstring(),
    gleam@dict:dict(bitstring(), b_value()),
    integer()
) -> {ok, {b_value(), bitstring(), integer()}} | {error, b_decode_error()}.
decode_dict(String, Acc, Byte_index) ->
    case String of
        <<"e"/utf8, Rest/bitstring>> ->
            {ok, {{b_dict, Acc}, Rest, Byte_index + 1}};

        _ ->
            case decode_value(String, Byte_index) of
                {error, Error} ->
                    {error, Error};

                {ok, {{b_string, Key}, Rest@1, Byte_index@1}} ->
                    case decode_value(Rest@1, Byte_index@1) of
                        {error, Error@1} ->
                            {error, Error@1};

                        {ok, {Value, Rest@2, Byte_index@2}} ->
                            decode_dict(
                                Rest@2,
                                gleam@dict:insert(Acc, Key, Value),
                                Byte_index@2
                            )
                    end;

                {ok, {_, _, Byte_index@3}} ->
                    {error, {invalid_dict_key, Byte_index@3}}
            end
    end.
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