-module(gwr@parser@binary_reader).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([create/1, bytes_read/1, is_empty/1, can_read/1, read/2, advance/2, get_remaining/1, read_remaining/1]).
-export_type([binary_reader/0]).

-type binary_reader() :: {binary_reader, bitstring(), integer()}.

-spec create(bitstring()) -> binary_reader().
create(Data) ->
    {binary_reader, Data, 0}.

-spec bytes_read(binary_reader()) -> integer().
bytes_read(Reader) ->
    erlang:element(3, Reader).

-spec is_empty(binary_reader()) -> boolean().
is_empty(Reader) ->
    erlang:element(2, Reader) =:= <<>>.

-spec can_read(binary_reader()) -> boolean().
can_read(Reader) ->
    erlang:element(3, Reader) < erlang:byte_size(erlang:element(2, Reader)).

-spec read(binary_reader(), integer()) -> {ok, {binary_reader(), bitstring()}} |
    {error, binary()}.
read(Reader, Count) ->
    gleam@bool:guard(
        (erlang:element(3, Reader) + Count) > erlang:byte_size(
            erlang:element(2, Reader)
        ),
        {error, <<"no enough bytes"/utf8>>},
        fun() ->
            case gleam_stdlib:bit_array_slice(
                erlang:element(2, Reader),
                erlang:element(3, Reader),
                Count
            ) of
                {ok, Data_read} ->
                    {ok,
                        {{binary_reader,
                                erlang:element(2, Reader),
                                erlang:element(3, Reader) + Count},
                            Data_read}};

                _ ->
                    {error, <<""/utf8>>}
            end
        end
    ).

-spec advance(binary_reader(), integer()) -> binary_reader().
advance(Reader, Count) ->
    erlang:setelement(3, Reader, erlang:element(3, Reader) + Count).

-spec get_remaining(binary_reader()) -> {ok, bitstring()} | {error, binary()}.
get_remaining(Reader) ->
    case gleam_stdlib:bit_array_slice(
        erlang:element(2, Reader),
        erlang:element(3, Reader),
        erlang:byte_size(erlang:element(2, Reader)) - erlang:element(3, Reader)
    ) of
        {ok, Remaining_data} ->
            {ok, Remaining_data};

        _ ->
            {error, <<""/utf8>>}
    end.

-spec read_remaining(binary_reader()) -> {ok, {binary_reader(), bitstring()}} |
    {error, binary()}.
read_remaining(Reader) ->
    read(
        Reader,
        erlang:byte_size(erlang:element(2, Reader)) - erlang:element(3, Reader)
    ).