-module(bitty@num).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/bitty/num.gleam").
-export([u8/0, i8/0, u16/1, u32/1, i16/1, i32/1, u64/1, i64/1, f32/1, f64/1, var_u32/0, var_u64/0, uint_bytes/1, int_bytes_twos_complement/1]).
-export_type([endian/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.

?MODULEDOC(
    " Numeric parsers for fixed-width integers, floats, and variable-length\n"
    " encodings. Includes single-byte (`u8`, `i8`) and multi-byte types with\n"
    " endianness control.\n"
).

-type endian() :: big_endian | little_endian.

-file("src/bitty/num.gleam", 18).
?DOC(" Parse a single byte as an unsigned integer (0–255).\n").
-spec u8() -> bitty:parser(integer()).
u8() ->
    bitty:make_parser(fun(State) -> case bitty:read_n_bytes(State, 1) of
                {continue, <<Byte>>, New_state, Consumed} ->
                    {continue, Byte, New_state, Consumed};

                {continue, _, New_state@1, _} ->
                    bitty:stop_expected(New_state@1, <<"a byte"/utf8>>);

                {stop, Error, Consumed@1, Committed} ->
                    {stop, Error, Consumed@1, Committed}
            end end).

-file("src/bitty/num.gleam", 32).
?DOC(" Parse a single byte as a signed integer (-128–127).\n").
-spec i8() -> bitty:parser(integer()).
i8() ->
    _pipe = u8(),
    bitty:map(_pipe, fun(Unsigned) -> case Unsigned >= 128 of
                true ->
                    Unsigned - 256;

                false ->
                    Unsigned
            end end).

-file("src/bitty/num.gleam", 49).
?DOC(
    " Parse a 16-bit unsigned integer with the given endianness.\n"
    "\n"
    " ```gleam\n"
    " let assert Ok(val) =\n"
    "   bitty.run(num.u16(num.BigEndian), on: <<0x01, 0x00>>)\n"
    " assert val == 256\n"
    " ```\n"
).
-spec u16(endian()) -> bitty:parser(integer()).
u16(Endian) ->
    bitty:make_parser(fun(State) -> case bitty:read_n_bytes(State, 2) of
                {continue, <<B0, B1>>, New_state, Consumed} ->
                    Value = case Endian of
                        big_endian ->
                            (B0 * 256) + B1;

                        little_endian ->
                            (B1 * 256) + B0
                    end,
                    {continue, Value, New_state, Consumed};

                {continue, _, _, _} ->
                    bitty:stop_expected(State, <<"2 bytes"/utf8>>);

                {stop, Error, Consumed@1, Committed} ->
                    {stop, Error, Consumed@1, Committed}
            end end).

-file("src/bitty/num.gleam", 67).
?DOC(" Parse a 32-bit unsigned integer with the given endianness.\n").
-spec u32(endian()) -> bitty:parser(integer()).
u32(Endian) ->
    bitty:make_parser(fun(State) -> case bitty:read_n_bytes(State, 4) of
                {continue, <<B0, B1, B2, B3>>, New_state, Consumed} ->
                    Value = case Endian of
                        big_endian ->
                            (((B0 * 16777216) + (B1 * 65536)) + (B2 * 256)) + B3;

                        little_endian ->
                            (((B3 * 16777216) + (B2 * 65536)) + (B1 * 256)) + B0
                    end,
                    {continue, Value, New_state, Consumed};

                {continue, _, _, _} ->
                    bitty:stop_expected(State, <<"4 bytes"/utf8>>);

                {stop, Error, Consumed@1, Committed} ->
                    {stop, Error, Consumed@1, Committed}
            end end).

-file("src/bitty/num.gleam", 85).
?DOC(" Parse a 16-bit signed integer (two's complement) with the given endianness.\n").
-spec i16(endian()) -> bitty:parser(integer()).
i16(Endian) ->
    _pipe = u16(Endian),
    bitty:map(_pipe, fun(Unsigned) -> case Unsigned >= 32768 of
                true ->
                    Unsigned - 65536;

                false ->
                    Unsigned
            end end).

-file("src/bitty/num.gleam", 96).
?DOC(" Parse a 32-bit signed integer (two's complement) with the given endianness.\n").
-spec i32(endian()) -> bitty:parser(integer()).
i32(Endian) ->
    _pipe = u32(Endian),
    bitty:map(_pipe, fun(Unsigned) -> case Unsigned >= 2147483648 of
                true ->
                    Unsigned - 4294967296;

                false ->
                    Unsigned
            end end).

-file("src/bitty/num.gleam", 109).
?DOC(
    " Parse a 64-bit unsigned integer with the given endianness.\n"
    " On the JavaScript target, values above 2^53 - 1 (9,007,199,254,740,991)\n"
    " may lose precision due to IEEE 754 double-precision limitations.\n"
).
-spec u64(endian()) -> bitty:parser(integer()).
u64(Endian) ->
    bitty:make_parser(fun(State) -> case bitty:read_n_bytes(State, 8) of
                {continue,
                    <<B0, B1, B2, B3, B4, B5, B6, B7>>,
                    New_state,
                    Consumed} ->
                    {Hi, Lo} = case Endian of
                        big_endian ->
                            {(((B0 * 16777216) + (B1 * 65536)) + (B2 * 256)) + B3,
                                (((B4 * 16777216) + (B5 * 65536)) + (B6 * 256))
                                + B7};

                        little_endian ->
                            {(((B7 * 16777216) + (B6 * 65536)) + (B5 * 256)) + B4,
                                (((B3 * 16777216) + (B2 * 65536)) + (B1 * 256))
                                + B0}
                    end,
                    {continue, (Hi * 4294967296) + Lo, New_state, Consumed};

                {continue, _, _, _} ->
                    bitty:stop_expected(State, <<"8 bytes"/utf8>>);

                {stop, Error, Consumed@1, Committed} ->
                    {stop, Error, Consumed@1, Committed}
            end end).

-file("src/bitty/num.gleam", 135).
?DOC(
    " Parse a 64-bit signed integer (two's complement) with the given endianness.\n"
    " On the JavaScript target, values outside the safe integer range\n"
    " (-2^53 + 1 to 2^53 - 1) may lose precision.\n"
).
-spec i64(endian()) -> bitty:parser(integer()).
i64(Endian) ->
    _pipe = u64(Endian),
    bitty:map(_pipe, fun(Unsigned) -> case Unsigned >= 9223372036854775808 of
                true ->
                    Unsigned - 18446744073709551616;

                false ->
                    Unsigned
            end end).

-file("src/bitty/num.gleam", 146).
?DOC(" Parse a 32-bit IEEE 754 float with the given endianness.\n").
-spec f32(endian()) -> bitty:parser(float()).
f32(Endian) ->
    bitty:make_parser(fun(State) -> case bitty:read_n_bytes(State, 4) of
                {continue, <<B0, B1, B2, B3>>, New_state, Consumed} ->
                    Ordered = case Endian of
                        big_endian ->
                            <<B0, B1, B2, B3>>;

                        little_endian ->
                            <<B3, B2, B1, B0>>
                    end,
                    case Ordered of
                        <<Value:32/float>> ->
                            {continue, Value, New_state, Consumed};

                        _ ->
                            bitty:stop_expected(State, <<"valid f32"/utf8>>)
                    end;

                {continue, _, _, _} ->
                    bitty:stop_expected(State, <<"4 bytes"/utf8>>);

                {stop, Error, Consumed@1, Committed} ->
                    {stop, Error, Consumed@1, Committed}
            end end).

-file("src/bitty/num.gleam", 167).
?DOC(" Parse a 64-bit IEEE 754 double with the given endianness.\n").
-spec f64(endian()) -> bitty:parser(float()).
f64(Endian) ->
    bitty:make_parser(fun(State) -> case bitty:read_n_bytes(State, 8) of
                {continue,
                    <<B0, B1, B2, B3, B4, B5, B6, B7>>,
                    New_state,
                    Consumed} ->
                    Ordered = case Endian of
                        big_endian ->
                            <<B0, B1, B2, B3, B4, B5, B6, B7>>;

                        little_endian ->
                            <<B7, B6, B5, B4, B3, B2, B1, B0>>
                    end,
                    case Ordered of
                        <<Value/float>> ->
                            {continue, Value, New_state, Consumed};

                        _ ->
                            bitty:stop_expected(State, <<"valid f64"/utf8>>)
                    end;

                {continue, _, _, _} ->
                    bitty:stop_expected(State, <<"8 bytes"/utf8>>);

                {stop, Error, Consumed@1, Committed} ->
                    {stop, Error, Consumed@1, Committed}
            end end).

-file("src/bitty/num.gleam", 255).
-spec varint_overflow(bitty:state(), binary()) -> bitty:step(any()).
varint_overflow(State, Expected) ->
    {stop,
        {bitty_error,
            {location, erlang:element(3, State), erlang:element(4, State)},
            [Expected],
            [],
            none},
        true,
        erlang:element(5, State)}.

-file("src/bitty/num.gleam", 206).
-spec varint_loop(
    bitty:state(),
    integer(),
    integer(),
    integer(),
    integer(),
    integer(),
    integer(),
    binary()
) -> bitty:step(integer()).
varint_loop(
    State,
    Acc,
    Shift,
    Bytes_read,
    Max_bytes,
    Last_byte_index,
    Last_byte_max,
    Label
) ->
    gleam@bool:guard(
        Bytes_read >= Max_bytes,
        varint_overflow(
            State,
            <<<<"varint within "/utf8,
                    (erlang:integer_to_binary(Max_bytes))/binary>>/binary,
                " bytes"/utf8>>
        ),
        fun() -> case bitty:read_n_bytes(State, 1) of
                {continue, <<Byte>>, Byte_state, _} ->
                    Value = erlang:'band'(Byte, 16#7F),
                    gleam@bool:guard(
                        (Bytes_read =:= Last_byte_index) andalso (Value > Last_byte_max),
                        varint_overflow(
                            Byte_state,
                            <<<<"varint within "/utf8, Label/binary>>/binary,
                                " range"/utf8>>
                        ),
                        fun() ->
                            New_acc = erlang:'bor'(
                                Acc,
                                erlang:'bsl'(Value, Shift)
                            ),
                            case erlang:'band'(Byte, 16#80) /= 0 of
                                true ->
                                    varint_loop(
                                        Byte_state,
                                        New_acc,
                                        Shift + 7,
                                        Bytes_read + 1,
                                        Max_bytes,
                                        Last_byte_index,
                                        Last_byte_max,
                                        Label
                                    );

                                false ->
                                    {continue, New_acc, Byte_state, true}
                            end
                        end
                    );

                {continue, _, _, _} ->
                    bitty:stop_expected(State, <<"varint byte"/utf8>>);

                {stop, Error, Consumed, Committed} ->
                    {stop, Error, Consumed, Committed}
            end end
    ).

-file("src/bitty/num.gleam", 194).
?DOC(
    " Parse an LEB128-encoded unsigned 32-bit variable-length integer.\n"
    " Consumes at most 5 bytes.\n"
    "\n"
    " ```gleam\n"
    " let assert Ok(val) = bitty.run(num.var_u32(), on: <<0xAC, 0x02>>)\n"
    " assert val == 300\n"
    " ```\n"
).
-spec var_u32() -> bitty:parser(integer()).
var_u32() ->
    bitty:make_parser(
        fun(_capture) ->
            varint_loop(_capture, 0, 0, 0, 5, 4, 16#0F, <<"u32"/utf8>>)
        end
    ).

-file("src/bitty/num.gleam", 202).
?DOC(
    " Parse an LEB128-encoded unsigned 64-bit variable-length integer.\n"
    " Consumes at most 10 bytes.\n"
    " On the JavaScript target, values above 2^53 - 1 (9,007,199,254,740,991)\n"
    " may lose precision due to IEEE 754 double-precision limitations.\n"
).
-spec var_u64() -> bitty:parser(integer()).
var_u64() ->
    bitty:make_parser(
        fun(_capture) ->
            varint_loop(_capture, 0, 0, 0, 10, 9, 16#01, <<"u64"/utf8>>)
        end
    ).

-file("src/bitty/num.gleam", 272).
?DOC(
    " Read `count` bytes as a raw `BitArray` representing an unsigned integer.\n"
    " Unlike `bytes.take`, this is intended for numeric byte sequences\n"
    " (e.g. ASN.1 DER integer encodings) where the bytes represent a single\n"
    " big-endian value.\n"
).
-spec uint_bytes(integer()) -> bitty:parser(bitstring()).
uint_bytes(Count) ->
    bitty:make_parser(fun(_capture) -> bitty:read_n_bytes(_capture, Count) end).

-file("src/bitty/num.gleam", 285).
-spec strip_leading_zeros(bitstring()) -> bitstring().
strip_leading_zeros(Bytes) ->
    case Bytes of
        <<16#00, Next, _/bitstring>> when Next >= 16#80 ->
            Bytes;

        <<16#00, _, _/bitstring>> ->
            case gleam_stdlib:bit_array_slice(
                Bytes,
                1,
                erlang:byte_size(Bytes) - 1
            ) of
                {ok, Rest} ->
                    strip_leading_zeros(Rest);

                _ ->
                    Bytes
            end;

        _ ->
            Bytes
    end.

-file("src/bitty/num.gleam", 280).
?DOC(
    " Read `count` bytes as a two's complement signed integer `BitArray`,\n"
    " stripping redundant leading zero bytes while preserving the sign bit.\n"
    " Returns the normalized raw bytes, not a decoded `Int`.\n"
    " Useful for ASN.1 DER integer encoding.\n"
).
-spec int_bytes_twos_complement(integer()) -> bitty:parser(bitstring()).
int_bytes_twos_complement(Count) ->
    _pipe = uint_bytes(Count),
    bitty:map(_pipe, fun strip_leading_zeros/1).