-module(ewe_ffi).

-export([decode_packet/3, rescue/1, validate_field_value/1]).

decode_packet(Type, Packet, Options) ->
  case erlang:decode_packet(Type, Packet, Options) of
    {ok, {http_request, Method, Uri, Version}, Rest} ->
      {ok, {packet, {http_request, atom_to_binary(Method), Uri, Version}, Rest}};

    {ok, {http_header, Idx, _, Field, Value}, Rest} ->
      {ok, {packet, {http_header, Idx, Field, Value}, Rest}};

    {ok, Bin, Rest} ->
      {ok, {packet, Bin, Rest}};

    {more, undefined} ->
      {ok, {more, none}};
    {more, Length} ->
      {ok, {more, {some, Length}}};

    {error, Reason} ->
      {error, Reason}
  end.
rescue(Callable) ->
  try {ok, Callable()}
  catch
    error:Error -> {error, {errored, Error}};
    throw:Error -> {error, {thrown, Error}};
    exit:Error -> {error, {exited, Error}}
  end.

validate_field_value(Value) ->
  case do_validate_field_value(Value) of
    true -> {ok, Value};
    false -> {error, nil}
  end.

% HTTP field values can contain:
% - VCHAR: 0x21-0x7E (visible ASCII characters)
% - WSP: 0x20 (space), 0x09 (tab)
% - obs-text: 0x80-0xFF (for backward compatibility)
% Invalid: control characters 0x00-0x08, 0x0A-0x1F, 0x7F
do_validate_field_value(Value) ->
  case Value of
    <<>> -> true;
    <<C, Rest/bitstring>> when C =:= 16#09
    orelse (C >= 16#20 andalso C =< 16#7E)
    orelse (C >= 16#80 andalso C =< 16#FF)
    -> do_validate_field_value(Rest);
  _ -> false
  end.