
namespace simdutf {
std::string_view to_string(encoding_type bom) {
  switch (bom) {
  case UTF16_LE:
    return "UTF16 little-endian";
  case UTF16_BE:
    return "UTF16 big-endian";
  case UTF32_LE:
    return "UTF32 little-endian";
  case UTF32_BE:
    return "UTF32 big-endian";
  case UTF8:
    return "UTF8";
  case unspecified:
    return "unknown";
  default:
    return "error";
  }
}

namespace BOM {
// Note that BOM for UTF8 is discouraged.
encoding_type check_bom(const uint8_t *byte, size_t length) {
  if (length >= 2 && byte[0] == 0xff and byte[1] == 0xfe) {
    if (length >= 4 && byte[2] == 0x00 and byte[3] == 0x0) {
      return encoding_type::UTF32_LE;
    } else {
      return encoding_type::UTF16_LE;
    }
  } else if (length >= 2 && byte[0] == 0xfe and byte[1] == 0xff) {
    return encoding_type::UTF16_BE;
  } else if (length >= 4 && byte[0] == 0x00 and byte[1] == 0x00 and
             byte[2] == 0xfe and byte[3] == 0xff) {
    return encoding_type::UTF32_BE;
  } else if (length >= 3 && byte[0] == 0xef and byte[1] == 0xbb and
             byte[2] == 0xbf) {
    return encoding_type::UTF8;
  }
  return encoding_type::unspecified;
}

encoding_type check_bom(const char *byte, size_t length) {
  return check_bom(reinterpret_cast<const uint8_t *>(byte), length);
}

size_t bom_byte_size(encoding_type bom) {
  switch (bom) {
  case UTF16_LE:
    return 2;
  case UTF16_BE:
    return 2;
  case UTF32_LE:
    return 4;
  case UTF32_BE:
    return 4;
  case UTF8:
    return 3;
  case unspecified:
    return 0;
  default:
    return 0;
  }
}

} // namespace BOM
} // namespace simdutf
