#include "common/http/utility.h"

#include <http_parser.h>

#include <cstdint>
#include <string>
#include <vector>

#include "envoy/config/core/v3/http_uri.pb.h"
#include "envoy/config/core/v3/protocol.pb.h"
#include "envoy/http/header_map.h"

#include "common/buffer/buffer_impl.h"
#include "common/common/assert.h"
#include "common/common/empty_string.h"
#include "common/common/enum_to_int.h"
#include "common/common/fmt.h"
#include "common/common/utility.h"
#include "common/grpc/status.h"
#include "common/http/exception.h"
#include "common/http/header_map_impl.h"
#include "common/http/headers.h"
#include "common/http/message_impl.h"
#include "common/network/utility.h"
#include "common/protobuf/utility.h"
#include "common/runtime/runtime_features.h"

#include "absl/container/node_hash_set.h"
#include "absl/strings/match.h"
#include "absl/strings/numbers.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_split.h"
#include "absl/strings/string_view.h"
#include "nghttp2/nghttp2.h"

namespace Envoy {
namespace Http {
namespace Utility {
Http::Status exceptionToStatus(std::function<Http::Status(Buffer::Instance&)> dispatch,
                               Buffer::Instance& data) {
  Http::Status status;
  try {
    status = dispatch(data);
    // TODO(#10878): Remove this when exception removal is complete. It is currently in migration,
    // so dispatch may either return an error status or throw an exception. Soon we won't need to
    // catch these exceptions, as all codec errors will be migrated to using error statuses that are
    // returned from dispatch.
  } catch (FrameFloodException& e) {
    status = bufferFloodError(e.what());
  } catch (CodecProtocolException& e) {
    status = codecProtocolError(e.what());
  } catch (PrematureResponseException& e) {
    status = prematureResponseError(e.what(), e.responseCode());
  }
  return status;
}
} // namespace Utility
} // namespace Http
namespace Http2 {
namespace Utility {

namespace {

void validateCustomSettingsParameters(
    const envoy::config::core::v3::Http2ProtocolOptions& options) {
  std::vector<std::string> parameter_collisions, custom_parameter_collisions;
  absl::node_hash_set<nghttp2_settings_entry, SettingsEntryHash, SettingsEntryEquals>
      custom_parameters;
  // User defined and named parameters with the same SETTINGS identifier can not both be set.
  for (const auto& it : options.custom_settings_parameters()) {
    ASSERT(it.identifier().value() <= std::numeric_limits<uint16_t>::max());
    // Check for custom parameter inconsistencies.
    const auto result = custom_parameters.insert(
        {static_cast<int32_t>(it.identifier().value()), it.value().value()});
    if (!result.second) {
      if (result.first->value != it.value().value()) {
        custom_parameter_collisions.push_back(
            absl::StrCat("0x", absl::Hex(it.identifier().value(), absl::kZeroPad2)));
        // Fall through to allow unbatched exceptions to throw first.
      }
    }
    switch (it.identifier().value()) {
    case NGHTTP2_SETTINGS_ENABLE_PUSH:
      if (it.value().value() == 1) {
        throw EnvoyException("server push is not supported by Envoy and can not be enabled via a "
                             "SETTINGS parameter.");
      }
      break;
    case NGHTTP2_SETTINGS_ENABLE_CONNECT_PROTOCOL:
      // An exception is made for `allow_connect` which can't be checked for presence due to the
      // use of a primitive type (bool).
      throw EnvoyException("the \"allow_connect\" SETTINGS parameter must only be configured "
                           "through the named field");
    case NGHTTP2_SETTINGS_HEADER_TABLE_SIZE:
      if (options.has_hpack_table_size()) {
        parameter_collisions.push_back("hpack_table_size");
      }
      break;
    case NGHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS:
      if (options.has_max_concurrent_streams()) {
        parameter_collisions.push_back("max_concurrent_streams");
      }
      break;
    case NGHTTP2_SETTINGS_INITIAL_WINDOW_SIZE:
      if (options.has_initial_stream_window_size()) {
        parameter_collisions.push_back("initial_stream_window_size");
      }
      break;
    default:
      // Ignore unknown parameters.
      break;
    }
  }

  if (!custom_parameter_collisions.empty()) {
    throw EnvoyException(fmt::format(
        "inconsistent HTTP/2 custom SETTINGS parameter(s) detected; identifiers = {{{}}}",
        absl::StrJoin(custom_parameter_collisions, ",")));
  }
  if (!parameter_collisions.empty()) {
    throw EnvoyException(fmt::format(
        "the {{{}}} HTTP/2 SETTINGS parameter(s) can not be configured through both named and "
        "custom parameters",
        absl::StrJoin(parameter_collisions, ",")));
  }
}

} // namespace

const uint32_t OptionsLimits::MIN_HPACK_TABLE_SIZE;
const uint32_t OptionsLimits::DEFAULT_HPACK_TABLE_SIZE;
const uint32_t OptionsLimits::MAX_HPACK_TABLE_SIZE;
const uint32_t OptionsLimits::MIN_MAX_CONCURRENT_STREAMS;
const uint32_t OptionsLimits::DEFAULT_MAX_CONCURRENT_STREAMS;
const uint32_t OptionsLimits::MAX_MAX_CONCURRENT_STREAMS;
const uint32_t OptionsLimits::MIN_INITIAL_STREAM_WINDOW_SIZE;
const uint32_t OptionsLimits::DEFAULT_INITIAL_STREAM_WINDOW_SIZE;
const uint32_t OptionsLimits::MAX_INITIAL_STREAM_WINDOW_SIZE;
const uint32_t OptionsLimits::MIN_INITIAL_CONNECTION_WINDOW_SIZE;
const uint32_t OptionsLimits::DEFAULT_INITIAL_CONNECTION_WINDOW_SIZE;
const uint32_t OptionsLimits::MAX_INITIAL_CONNECTION_WINDOW_SIZE;
const uint32_t OptionsLimits::DEFAULT_MAX_OUTBOUND_FRAMES;
const uint32_t OptionsLimits::DEFAULT_MAX_OUTBOUND_CONTROL_FRAMES;
const uint32_t OptionsLimits::DEFAULT_MAX_CONSECUTIVE_INBOUND_FRAMES_WITH_EMPTY_PAYLOAD;
const uint32_t OptionsLimits::DEFAULT_MAX_INBOUND_PRIORITY_FRAMES_PER_STREAM;
const uint32_t OptionsLimits::DEFAULT_MAX_INBOUND_WINDOW_UPDATE_FRAMES_PER_DATA_FRAME_SENT;

envoy::config::core::v3::Http2ProtocolOptions
initializeAndValidateOptions(const envoy::config::core::v3::Http2ProtocolOptions& options,
                             bool hcm_stream_error_set,
                             const Protobuf::BoolValue& hcm_stream_error) {
  auto ret = initializeAndValidateOptions(options);
  if (Runtime::runtimeFeatureEnabled(
          "envoy.reloadable_features.hcm_stream_error_on_invalid_message") &&
      !options.has_override_stream_error_on_invalid_http_message() && hcm_stream_error_set) {
    ret.mutable_override_stream_error_on_invalid_http_message()->set_value(
        hcm_stream_error.value());
  }
  return ret;
}

envoy::config::core::v3::Http2ProtocolOptions
initializeAndValidateOptions(const envoy::config::core::v3::Http2ProtocolOptions& options) {
  envoy::config::core::v3::Http2ProtocolOptions options_clone(options);
  // This will throw an exception when a custom parameter and a named parameter collide.
  validateCustomSettingsParameters(options);

  if (!options.has_override_stream_error_on_invalid_http_message()) {
    options_clone.mutable_override_stream_error_on_invalid_http_message()->set_value(
        options.stream_error_on_invalid_http_messaging());
  }

  if (!options_clone.has_hpack_table_size()) {
    options_clone.mutable_hpack_table_size()->set_value(OptionsLimits::DEFAULT_HPACK_TABLE_SIZE);
  }
  ASSERT(options_clone.hpack_table_size().value() <= OptionsLimits::MAX_HPACK_TABLE_SIZE);
  if (!options_clone.has_max_concurrent_streams()) {
    options_clone.mutable_max_concurrent_streams()->set_value(
        OptionsLimits::DEFAULT_MAX_CONCURRENT_STREAMS);
  }
  ASSERT(
      options_clone.max_concurrent_streams().value() >= OptionsLimits::MIN_MAX_CONCURRENT_STREAMS &&
      options_clone.max_concurrent_streams().value() <= OptionsLimits::MAX_MAX_CONCURRENT_STREAMS);
  if (!options_clone.has_initial_stream_window_size()) {
    options_clone.mutable_initial_stream_window_size()->set_value(
        OptionsLimits::DEFAULT_INITIAL_STREAM_WINDOW_SIZE);
  }
  ASSERT(options_clone.initial_stream_window_size().value() >=
             OptionsLimits::MIN_INITIAL_STREAM_WINDOW_SIZE &&
         options_clone.initial_stream_window_size().value() <=
             OptionsLimits::MAX_INITIAL_STREAM_WINDOW_SIZE);
  if (!options_clone.has_initial_connection_window_size()) {
    options_clone.mutable_initial_connection_window_size()->set_value(
        OptionsLimits::DEFAULT_INITIAL_CONNECTION_WINDOW_SIZE);
  }
  ASSERT(options_clone.initial_connection_window_size().value() >=
             OptionsLimits::MIN_INITIAL_CONNECTION_WINDOW_SIZE &&
         options_clone.initial_connection_window_size().value() <=
             OptionsLimits::MAX_INITIAL_CONNECTION_WINDOW_SIZE);
  if (!options_clone.has_max_outbound_frames()) {
    options_clone.mutable_max_outbound_frames()->set_value(
        OptionsLimits::DEFAULT_MAX_OUTBOUND_FRAMES);
  }
  if (!options_clone.has_max_outbound_control_frames()) {
    options_clone.mutable_max_outbound_control_frames()->set_value(
        OptionsLimits::DEFAULT_MAX_OUTBOUND_CONTROL_FRAMES);
  }
  if (!options_clone.has_max_consecutive_inbound_frames_with_empty_payload()) {
    options_clone.mutable_max_consecutive_inbound_frames_with_empty_payload()->set_value(
        OptionsLimits::DEFAULT_MAX_CONSECUTIVE_INBOUND_FRAMES_WITH_EMPTY_PAYLOAD);
  }
  if (!options_clone.has_max_inbound_priority_frames_per_stream()) {
    options_clone.mutable_max_inbound_priority_frames_per_stream()->set_value(
        OptionsLimits::DEFAULT_MAX_INBOUND_PRIORITY_FRAMES_PER_STREAM);
  }
  if (!options_clone.has_max_inbound_window_update_frames_per_data_frame_sent()) {
    options_clone.mutable_max_inbound_window_update_frames_per_data_frame_sent()->set_value(
        OptionsLimits::DEFAULT_MAX_INBOUND_WINDOW_UPDATE_FRAMES_PER_DATA_FRAME_SENT);
  }

  return options_clone;
}

} // namespace Utility
} // namespace Http2

namespace Http {

static const char kDefaultPath[] = "/";

// If http_parser encounters an IP address [address] as the host it will set the offset and
// length to point to 'address' rather than '[address]'. Fix this by adjusting the offset
// and length to include the brackets.
// @param absolute_url the absolute URL. This is usually of the form // http://host/path
//        but may be host:port for CONNECT requests
// @param offset the offset for the first character of the host. For IPv6 hosts
//        this will point to the first character inside the brackets and will be
//        adjusted to point at the brackets
// @param len the length of the host-and-port field. For IPv6 hosts this will
//        not include the brackets and will be adjusted to do so.
bool maybeAdjustForIpv6(absl::string_view absolute_url, uint64_t& offset, uint64_t& len) {
  // According to https://tools.ietf.org/html/rfc3986#section-3.2.2 the only way a hostname
  // may begin with '[' is if it's an ipv6 address.
  if (offset == 0 || *(absolute_url.data() + offset - 1) != '[') {
    return false;
  }
  // Start one character sooner and end one character later.
  offset--;
  len += 2;
  // HTTP parser ensures that any [ has a closing ]
  ASSERT(absolute_url.length() >= offset + len);
  return true;
}

bool Utility::Url::initialize(absl::string_view absolute_url, bool is_connect) {
  struct http_parser_url u;
  http_parser_url_init(&u);
  const int result =
      http_parser_parse_url(absolute_url.data(), absolute_url.length(), is_connect, &u);

  if (result != 0) {
    return false;
  }
  if ((u.field_set & (1 << UF_HOST)) != (1 << UF_HOST) &&
      (u.field_set & (1 << UF_SCHEMA)) != (1 << UF_SCHEMA)) {
    return false;
  }
  scheme_ = absl::string_view(absolute_url.data() + u.field_data[UF_SCHEMA].off,
                              u.field_data[UF_SCHEMA].len);

  uint64_t authority_len = u.field_data[UF_HOST].len;
  if ((u.field_set & (1 << UF_PORT)) == (1 << UF_PORT)) {
    authority_len = authority_len + u.field_data[UF_PORT].len + 1;
  }

  uint64_t authority_beginning = u.field_data[UF_HOST].off;
  const bool is_ipv6 = maybeAdjustForIpv6(absolute_url, authority_beginning, authority_len);
  host_and_port_ = absl::string_view(absolute_url.data() + authority_beginning, authority_len);
  if (is_ipv6 && !parseAuthority(host_and_port_).is_ip_address_) {
    return false;
  }

  // RFC allows the absolute-uri to not end in /, but the absolute path form
  // must start with. Determine if there's a non-zero path, and if so determine
  // the length of the path, query params etc.
  uint64_t path_etc_len = absolute_url.length() - (authority_beginning + hostAndPort().length());
  if (path_etc_len > 0) {
    uint64_t path_beginning = authority_beginning + hostAndPort().length();
    path_and_query_params_ = absl::string_view(absolute_url.data() + path_beginning, path_etc_len);
  } else if (!is_connect) {
    ASSERT((u.field_set & (1 << UF_PATH)) == 0);
    path_and_query_params_ = absl::string_view(kDefaultPath, 1);
  }
  return true;
}

void Utility::appendXff(RequestHeaderMap& headers,
                        const Network::Address::Instance& remote_address) {
  if (remote_address.type() != Network::Address::Type::Ip) {
    return;
  }

  headers.appendForwardedFor(remote_address.ip()->addressAsString(), ",");
}

void Utility::appendVia(RequestOrResponseHeaderMap& headers, const std::string& via) {
  // TODO(asraa): Investigate whether it is necessary to append with whitespace here by:
  //     (a) Validating we do not expect whitespace in via headers
  //     (b) Add runtime guarding in case users have upstreams which expect it.
  headers.appendVia(via, ", ");
}

std::string Utility::createSslRedirectPath(const RequestHeaderMap& headers) {
  ASSERT(headers.Host());
  ASSERT(headers.Path());
  return fmt::format("https://{}{}", headers.getHostValue(), headers.getPathValue());
}

Utility::QueryParams Utility::parseQueryString(absl::string_view url) {
  size_t start = url.find('?');
  if (start == std::string::npos) {
    QueryParams params;
    return params;
  }

  start++;
  return parseParameters(url, start, /*decode_params=*/false);
}

Utility::QueryParams Utility::parseAndDecodeQueryString(absl::string_view url) {
  size_t start = url.find('?');
  if (start == std::string::npos) {
    QueryParams params;
    return params;
  }

  start++;
  return parseParameters(url, start, /*decode_params=*/true);
}

Utility::QueryParams Utility::parseFromBody(absl::string_view body) {
  return parseParameters(body, 0, /*decode_params=*/true);
}

Utility::QueryParams Utility::parseParameters(absl::string_view data, size_t start,
                                              bool decode_params) {
  QueryParams params;

  while (start < data.size()) {
    size_t end = data.find('&', start);
    if (end == std::string::npos) {
      end = data.size();
    }
    absl::string_view param(data.data() + start, end - start);

    const size_t equal = param.find('=');
    if (equal != std::string::npos) {
      const auto param_name = StringUtil::subspan(data, start, start + equal);
      const auto param_value = StringUtil::subspan(data, start + equal + 1, end);
      params.emplace(decode_params ? PercentEncoding::decode(param_name) : param_name,
                     decode_params ? PercentEncoding::decode(param_value) : param_value);
    } else {
      params.emplace(StringUtil::subspan(data, start, end), "");
    }

    start = end + 1;
  }

  return params;
}

absl::string_view Utility::findQueryStringStart(const HeaderString& path) {
  absl::string_view path_str = path.getStringView();
  size_t query_offset = path_str.find('?');
  if (query_offset == absl::string_view::npos) {
    query_offset = path_str.length();
  }
  path_str.remove_prefix(query_offset);
  return path_str;
}

std::string Utility::parseCookieValue(const HeaderMap& headers, const std::string& key) {

  std::string ret;

  headers.iterateReverse([&key, &ret](const HeaderEntry& header) -> HeaderMap::Iterate {
    // Find the cookie headers in the request (typically, there's only one).
    if (header.key() == Http::Headers::get().Cookie.get()) {

      // Split the cookie header into individual cookies.
      for (const auto& s : StringUtil::splitToken(header.value().getStringView(), ";")) {
        // Find the key part of the cookie (i.e. the name of the cookie).
        size_t first_non_space = s.find_first_not_of(" ");
        size_t equals_index = s.find('=');
        if (equals_index == absl::string_view::npos) {
          // The cookie is malformed if it does not have an `=`. Continue
          // checking other cookies in this header.
          continue;
        }
        const absl::string_view k = s.substr(first_non_space, equals_index - first_non_space);
        // If the key matches, parse the value from the rest of the cookie string.
        if (k == key) {
          absl::string_view v = s.substr(equals_index + 1, s.size() - 1);

          // Cookie values may be wrapped in double quotes.
          // https://tools.ietf.org/html/rfc6265#section-4.1.1
          if (v.size() >= 2 && v.back() == '"' && v[0] == '"') {
            v = v.substr(1, v.size() - 2);
          }
          ret = std::string{v};
          return HeaderMap::Iterate::Break;
        }
      }
    }
    return HeaderMap::Iterate::Continue;
  });

  return ret;
}

std::string Utility::makeSetCookieValue(const std::string& key, const std::string& value,
                                        const std::string& path, const std::chrono::seconds max_age,
                                        bool httponly) {
  std::string cookie_value;
  // Best effort attempt to avoid numerous string copies.
  cookie_value.reserve(value.size() + path.size() + 30);

  cookie_value = absl::StrCat(key, "=\"", value, "\"");
  if (max_age != std::chrono::seconds::zero()) {
    absl::StrAppend(&cookie_value, "; Max-Age=", max_age.count());
  }
  if (!path.empty()) {
    absl::StrAppend(&cookie_value, "; Path=", path);
  }
  if (httponly) {
    absl::StrAppend(&cookie_value, "; HttpOnly");
  }
  return cookie_value;
}

uint64_t Utility::getResponseStatus(const ResponseHeaderMap& headers) {
  const HeaderEntry* header = headers.Status();
  uint64_t response_code;
  if (!header || !absl::SimpleAtoi(headers.getStatusValue(), &response_code)) {
    throw CodecClientException(":status must be specified and a valid unsigned long");
  }
  return response_code;
}

bool Utility::isUpgrade(const RequestOrResponseHeaderMap& headers) {
  // In firefox the "Connection" request header value is "keep-alive, Upgrade",
  // we should check if it contains the "Upgrade" token.
  return (headers.Upgrade() &&
          Envoy::StringUtil::caseFindToken(headers.getConnectionValue(), ",",
                                           Http::Headers::get().ConnectionValues.Upgrade.c_str()));
}

bool Utility::isH2UpgradeRequest(const RequestHeaderMap& headers) {
  return headers.getMethodValue() == Http::Headers::get().MethodValues.Connect &&
         headers.Protocol() && !headers.Protocol()->value().empty() &&
         headers.Protocol()->value() != Headers::get().ProtocolValues.Bytestream;
}

bool Utility::isWebSocketUpgradeRequest(const RequestHeaderMap& headers) {
  return (isUpgrade(headers) &&
          absl::EqualsIgnoreCase(headers.getUpgradeValue(),
                                 Http::Headers::get().UpgradeValues.WebSocket));
}

Http1Settings
Utility::parseHttp1Settings(const envoy::config::core::v3::Http1ProtocolOptions& config) {
  Http1Settings ret;
  ret.allow_absolute_url_ = PROTOBUF_GET_WRAPPED_OR_DEFAULT(config, allow_absolute_url, true);
  ret.accept_http_10_ = config.accept_http_10();
  ret.default_host_for_http_10_ = config.default_host_for_http_10();
  ret.enable_trailers_ = config.enable_trailers();
  ret.allow_chunked_length_ = config.allow_chunked_length();

  if (config.header_key_format().has_proper_case_words()) {
    ret.header_key_format_ = Http1Settings::HeaderKeyFormat::ProperCase;
  } else {
    ret.header_key_format_ = Http1Settings::HeaderKeyFormat::Default;
  }

  return ret;
}

Http1Settings
Utility::parseHttp1Settings(const envoy::config::core::v3::Http1ProtocolOptions& config,
                            const Protobuf::BoolValue& hcm_stream_error) {
  Http1Settings ret = parseHttp1Settings(config);

  if (config.has_override_stream_error_on_invalid_http_message()) {
    // override_stream_error_on_invalid_http_message, if set, takes precedence over any HCM
    // stream_error_on_invalid_http_message
    ret.stream_error_on_invalid_http_message_ =
        config.override_stream_error_on_invalid_http_message().value();
  } else {
    // fallback to HCM value
    ret.stream_error_on_invalid_http_message_ = hcm_stream_error.value();
  }

  return ret;
}

void Utility::sendLocalReply(const bool& is_reset, StreamDecoderFilterCallbacks& callbacks,
                             const LocalReplyData& local_reply_data) {
  absl::string_view details;
  if (callbacks.streamInfo().responseCodeDetails().has_value()) {
    details = callbacks.streamInfo().responseCodeDetails().value();
  };

  sendLocalReply(
      is_reset,
      Utility::EncodeFunctions{nullptr, nullptr,
                               [&](ResponseHeaderMapPtr&& headers, bool end_stream) -> void {
                                 callbacks.encodeHeaders(std::move(headers), end_stream, details);
                               },
                               [&](Buffer::Instance& data, bool end_stream) -> void {
                                 callbacks.encodeData(data, end_stream);
                               }},
      local_reply_data);
}

void Utility::sendLocalReply(const bool& is_reset, const EncodeFunctions& encode_functions,
                             const LocalReplyData& local_reply_data) {
  // encode_headers() may reset the stream, so the stream must not be reset before calling it.
  ASSERT(!is_reset);

  // rewrite_response will rewrite response code and body text.
  Code response_code = local_reply_data.response_code_;
  std::string body_text(local_reply_data.body_text_);
  absl::string_view content_type(Headers::get().ContentTypeValues.Text);

  ResponseHeaderMapPtr response_headers{createHeaderMap<ResponseHeaderMapImpl>(
      {{Headers::get().Status, std::to_string(enumToInt(response_code))}})};

  if (encode_functions.modify_headers_) {
    encode_functions.modify_headers_(*response_headers);
  }
  if (encode_functions.rewrite_) {
    encode_functions.rewrite_(*response_headers, response_code, body_text, content_type);
  }

  // Respond with a gRPC trailers-only response if the request is gRPC
  if (local_reply_data.is_grpc_) {
    response_headers->setStatus(std::to_string(enumToInt(Code::OK)));
    response_headers->setReferenceContentType(Headers::get().ContentTypeValues.Grpc);
    response_headers->setGrpcStatus(
        std::to_string(enumToInt(local_reply_data.grpc_status_
                                     ? local_reply_data.grpc_status_.value()
                                     : Grpc::Utility::httpToGrpcStatus(enumToInt(response_code)))));
    if (!body_text.empty() && !local_reply_data.is_head_request_) {
      // TODO(dio): Probably it is worth to consider caching the encoded message based on gRPC
      // status.
      // JsonFormatter adds a '\n' at the end. For header value, it should be removed.
      // https://github.com/envoyproxy/envoy/blob/master/source/common/formatter/substitution_formatter.cc#L129
      if (body_text[body_text.length() - 1] == '\n') {
        body_text = body_text.substr(0, body_text.length() - 1);
      }
      response_headers->setGrpcMessage(PercentEncoding::encode(body_text));
    }
    // The `modify_headers` function may have added content-length, remove it.
    response_headers->removeContentLength();
    encode_functions.encode_headers_(std::move(response_headers), true); // Trailers only response
    return;
  }

  if (!body_text.empty()) {
    response_headers->setContentLength(body_text.size());
    // If the `rewrite` function has changed body_text or content-type is not set, set it.
    // This allows `modify_headers` function to set content-type for the body. For example,
    // router.direct_response is calling sendLocalReply and may need to set content-type for
    // the body.
    if (body_text != local_reply_data.body_text_ || response_headers->ContentType() == nullptr) {
      response_headers->setReferenceContentType(content_type);
    }
  } else {
    response_headers->removeContentLength();
    response_headers->removeContentType();
  }

  if (local_reply_data.is_head_request_) {
    encode_functions.encode_headers_(std::move(response_headers), true);
    return;
  }

  encode_functions.encode_headers_(std::move(response_headers), body_text.empty());
  // encode_headers() may have changed the referenced is_reset so we need to test it
  if (!body_text.empty() && !is_reset) {
    Buffer::OwnedImpl buffer(body_text);
    encode_functions.encode_data_(buffer, true);
  }
}

Utility::GetLastAddressFromXffInfo
Utility::getLastAddressFromXFF(const Http::RequestHeaderMap& request_headers,
                               uint32_t num_to_skip) {
  const auto xff_header = request_headers.ForwardedFor();
  if (xff_header == nullptr) {
    return {nullptr, false};
  }

  absl::string_view xff_string(xff_header->value().getStringView());
  static const std::string separator(",");
  // Ignore the last num_to_skip addresses at the end of XFF.
  for (uint32_t i = 0; i < num_to_skip; i++) {
    const std::string::size_type last_comma = xff_string.rfind(separator);
    if (last_comma == std::string::npos) {
      return {nullptr, false};
    }
    xff_string = xff_string.substr(0, last_comma);
  }
  // The text after the last remaining comma, or the entirety of the string if there
  // is no comma, is the requested IP address.
  const std::string::size_type last_comma = xff_string.rfind(separator);
  if (last_comma != std::string::npos && last_comma + separator.size() < xff_string.size()) {
    xff_string = xff_string.substr(last_comma + separator.size());
  }

  // Ignore the whitespace, since they are allowed in HTTP lists (see RFC7239#section-7.1).
  xff_string = StringUtil::ltrim(xff_string);
  xff_string = StringUtil::rtrim(xff_string);

  try {
    // This technically requires a copy because inet_pton takes a null terminated string. In
    // practice, we are working with a view at the end of the owning string, and could pass the
    // raw pointer.
    // TODO(mattklein123) PERF: Avoid the copy here.
    return {
        Network::Utility::parseInternetAddress(std::string(xff_string.data(), xff_string.size())),
        last_comma == std::string::npos && num_to_skip == 0};
  } catch (const EnvoyException&) {
    return {nullptr, false};
  }
}

bool Utility::sanitizeConnectionHeader(Http::RequestHeaderMap& headers) {
  static const size_t MAX_ALLOWED_NOMINATED_HEADERS = 10;
  static const size_t MAX_ALLOWED_TE_VALUE_SIZE = 256;

  // Remove any headers nominated by the Connection header. The TE header
  // is sanitized and removed only if it's empty after removing unsupported values
  // See https://github.com/envoyproxy/envoy/issues/8623
  const auto& cv = Http::Headers::get().ConnectionValues;
  const auto& connection_header_value = headers.Connection()->value();

  StringUtil::CaseUnorderedSet headers_to_remove{};
  std::vector<absl::string_view> connection_header_tokens =
      StringUtil::splitToken(connection_header_value.getStringView(), ",", false);

  // If we have 10 or more nominated headers, fail this request
  if (connection_header_tokens.size() >= MAX_ALLOWED_NOMINATED_HEADERS) {
    ENVOY_LOG_MISC(trace, "Too many nominated headers in request");
    return false;
  }

  // Split the connection header and evaluate each nominated header
  for (const auto& token : connection_header_tokens) {

    const auto token_sv = StringUtil::trim(token);

    // Build the LowerCaseString for header lookup
    const LowerCaseString lcs_header_to_remove{std::string(token_sv)};

    // If the Connection token value is not a nominated header, ignore it here since
    // the connection header is removed elsewhere when the H1 request is upgraded to H2
    if ((lcs_header_to_remove.get() == cv.Close) ||
        (lcs_header_to_remove.get() == cv.Http2Settings) ||
        (lcs_header_to_remove.get() == cv.KeepAlive) ||
        (lcs_header_to_remove.get() == cv.Upgrade)) {
      continue;
    }

    // By default we will remove any nominated headers
    bool keep_header = false;

    // Determine whether the nominated header contains invalid values
    HeaderMap::GetResult nominated_header;

    if (lcs_header_to_remove == Http::Headers::get().Connection) {
      // Remove the connection header from the nominated tokens if it's self nominated
      // The connection header itself is *not removed*
      ENVOY_LOG_MISC(trace, "Skipping self nominated header [{}]", token_sv);
      keep_header = true;
      headers_to_remove.emplace(token_sv);

    } else if ((lcs_header_to_remove == Http::Headers::get().ForwardedFor) ||
               (lcs_header_to_remove == Http::Headers::get().ForwardedHost) ||
               (lcs_header_to_remove == Http::Headers::get().ForwardedProto) ||
               !token_sv.find(':')) {

      // An attacker could nominate an X-Forwarded* header, and its removal may mask
      // the origin of the incoming request and potentially alter its handling.
      // Additionally, pseudo headers should never be nominated. In both cases, we
      // should fail the request.
      // See: https://nathandavison.com/blog/abusing-http-hop-by-hop-request-headers

      ENVOY_LOG_MISC(trace, "Invalid nomination of {} header", token_sv);
      return false;
    } else {
      // Examine the value of all other nominated headers
      nominated_header = headers.get(lcs_header_to_remove);
    }

    if (!nominated_header.empty()) {
      // NOTE: The TE header is an inline header, so by definition if we operate on it there can
      // only be a single value. In all other cases we remove the nominated header.
      auto nominated_header_value_sv = nominated_header[0]->value().getStringView();

      const bool is_te_header = (lcs_header_to_remove == Http::Headers::get().TE);

      // reject the request if the TE header is too large
      if (is_te_header && (nominated_header_value_sv.size() >= MAX_ALLOWED_TE_VALUE_SIZE)) {
        ENVOY_LOG_MISC(trace, "TE header contains a value that exceeds the allowable length");
        return false;
      }

      if (is_te_header) {
        ASSERT(nominated_header.size() == 1);
        for (const auto& header_value :
             StringUtil::splitToken(nominated_header_value_sv, ",", false)) {

          const absl::string_view header_sv = StringUtil::trim(header_value);

          // If trailers exist in the TE value tokens, keep the header, removing any other values
          // that may exist
          if (StringUtil::CaseInsensitiveCompare()(header_sv,
                                                   Http::Headers::get().TEValues.Trailers)) {
            keep_header = true;
            break;
          }
        }

        if (keep_header) {
          headers.setTE(Http::Headers::get().TEValues.Trailers);
        }
      }
    }

    if (!keep_header) {
      ENVOY_LOG_MISC(trace, "Removing nominated header [{}]", token_sv);
      headers.remove(lcs_header_to_remove);
      headers_to_remove.emplace(token_sv);
    }
  }

  // Lastly remove extra nominated headers from the Connection header
  if (!headers_to_remove.empty()) {
    const std::string new_value = StringUtil::removeTokens(connection_header_value.getStringView(),
                                                           ",", headers_to_remove, ",");

    if (new_value.empty()) {
      headers.removeConnection();
    } else {
      headers.setConnection(new_value);
    }
  }

  return true;
}

const std::string& Utility::getProtocolString(const Protocol protocol) {
  switch (protocol) {
  case Protocol::Http10:
    return Headers::get().ProtocolStrings.Http10String;
  case Protocol::Http11:
    return Headers::get().ProtocolStrings.Http11String;
  case Protocol::Http2:
    return Headers::get().ProtocolStrings.Http2String;
  case Protocol::Http3:
    return Headers::get().ProtocolStrings.Http3String;
  }

  NOT_REACHED_GCOVR_EXCL_LINE;
}

void Utility::extractHostPathFromUri(const absl::string_view& uri, absl::string_view& host,
                                     absl::string_view& path) {
  /**
   *  URI RFC: https://www.ietf.org/rfc/rfc2396.txt
   *
   *  Example:
   *  uri  = "https://example.com:8443/certs"
   *  pos:         ^
   *  host_pos:       ^
   *  path_pos:                       ^
   *  host = "example.com:8443"
   *  path = "/certs"
   */
  const auto pos = uri.find("://");
  // Start position of the host
  const auto host_pos = (pos == std::string::npos) ? 0 : pos + 3;
  // Start position of the path
  const auto path_pos = uri.find("/", host_pos);
  if (path_pos == std::string::npos) {
    // If uri doesn't have "/", the whole string is treated as host.
    host = uri.substr(host_pos);
    path = "/";
  } else {
    host = uri.substr(host_pos, path_pos - host_pos);
    path = uri.substr(path_pos);
  }
}

std::string Utility::localPathFromFilePath(const absl::string_view& file_path) {
  if (file_path.size() >= 3 && file_path[1] == ':' && file_path[2] == '/' &&
      std::isalpha(file_path[0])) {
    return std::string(file_path);
  }
  return absl::StrCat("/", file_path);
}

RequestMessagePtr Utility::prepareHeaders(const envoy::config::core::v3::HttpUri& http_uri) {
  absl::string_view host, path;
  extractHostPathFromUri(http_uri.uri(), host, path);

  RequestMessagePtr message(new RequestMessageImpl());
  message->headers().setPath(path);
  message->headers().setHost(host);

  return message;
}

// TODO(jmarantz): make QueryParams a real class and put this serializer there,
// along with proper URL escaping of the name and value.
std::string Utility::queryParamsToString(const QueryParams& params) {
  std::string out;
  std::string delim = "?";
  for (const auto& p : params) {
    absl::StrAppend(&out, delim, p.first, "=", p.second);
    delim = "&";
  }
  return out;
}

const std::string Utility::resetReasonToString(const Http::StreamResetReason reset_reason) {
  switch (reset_reason) {
  case Http::StreamResetReason::ConnectionFailure:
    return "connection failure";
  case Http::StreamResetReason::ConnectionTermination:
    return "connection termination";
  case Http::StreamResetReason::LocalReset:
    return "local reset";
  case Http::StreamResetReason::LocalRefusedStreamReset:
    return "local refused stream reset";
  case Http::StreamResetReason::Overflow:
    return "overflow";
  case Http::StreamResetReason::RemoteReset:
    return "remote reset";
  case Http::StreamResetReason::RemoteRefusedStreamReset:
    return "remote refused stream reset";
  case Http::StreamResetReason::ConnectError:
    return "remote error with CONNECT request";
  }

  NOT_REACHED_GCOVR_EXCL_LINE;
}

void Utility::transformUpgradeRequestFromH1toH2(RequestHeaderMap& headers) {
  ASSERT(Utility::isUpgrade(headers));

  headers.setReferenceMethod(Http::Headers::get().MethodValues.Connect);
  headers.setProtocol(headers.getUpgradeValue());
  headers.removeUpgrade();
  headers.removeConnection();
  // nghttp2 rejects upgrade requests/responses with content length, so strip
  // any unnecessary content length header.
  if (headers.getContentLengthValue() == "0") {
    headers.removeContentLength();
  }
}

void Utility::transformUpgradeResponseFromH1toH2(ResponseHeaderMap& headers) {
  if (getResponseStatus(headers) == 101) {
    headers.setStatus(200);
  }
  headers.removeUpgrade();
  headers.removeConnection();
  if (headers.getContentLengthValue() == "0") {
    headers.removeContentLength();
  }
}

void Utility::transformUpgradeRequestFromH2toH1(RequestHeaderMap& headers) {
  ASSERT(Utility::isH2UpgradeRequest(headers));

  headers.setReferenceMethod(Http::Headers::get().MethodValues.Get);
  headers.setUpgrade(headers.getProtocolValue());
  headers.setReferenceConnection(Http::Headers::get().ConnectionValues.Upgrade);
  headers.removeProtocol();
}

void Utility::transformUpgradeResponseFromH2toH1(ResponseHeaderMap& headers,
                                                 absl::string_view upgrade) {
  if (getResponseStatus(headers) == 200) {
    headers.setUpgrade(upgrade);
    headers.setReferenceConnection(Http::Headers::get().ConnectionValues.Upgrade);
    headers.setStatus(101);
  }
}

const Router::RouteSpecificFilterConfig*
Utility::resolveMostSpecificPerFilterConfigGeneric(const std::string& filter_name,
                                                   const Router::RouteConstSharedPtr& route) {

  const Router::RouteSpecificFilterConfig* maybe_filter_config{};
  traversePerFilterConfigGeneric(
      filter_name, route, [&maybe_filter_config](const Router::RouteSpecificFilterConfig& cfg) {
        maybe_filter_config = &cfg;
      });
  return maybe_filter_config;
}

void Utility::traversePerFilterConfigGeneric(
    const std::string& filter_name, const Router::RouteConstSharedPtr& route,
    std::function<void(const Router::RouteSpecificFilterConfig&)> cb) {
  if (!route) {
    return;
  }

  const Router::RouteEntry* routeEntry = route->routeEntry();

  if (routeEntry != nullptr) {
    auto maybe_vhost_config = routeEntry->virtualHost().perFilterConfig(filter_name);
    if (maybe_vhost_config != nullptr) {
      cb(*maybe_vhost_config);
    }
  }

  auto maybe_route_config = route->perFilterConfig(filter_name);
  if (maybe_route_config != nullptr) {
    cb(*maybe_route_config);
  }

  if (routeEntry != nullptr) {
    auto maybe_weighted_cluster_config = routeEntry->perFilterConfig(filter_name);
    if (maybe_weighted_cluster_config != nullptr) {
      cb(*maybe_weighted_cluster_config);
    }
  }
}

std::string Utility::PercentEncoding::encode(absl::string_view value,
                                             absl::string_view reserved_chars) {
  absl::flat_hash_set<char> reserved_char_set{reserved_chars.begin(), reserved_chars.end()};
  for (size_t i = 0; i < value.size(); ++i) {
    const char& ch = value[i];
    // The escaping characters are defined in
    // https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#responses.
    //
    // We do checking for each char in the string. If the current char is included in the defined
    // escaping characters, we jump to "the slow path" (append the char [encoded or not encoded]
    // to the returned string one by one) started from the current index.
    if (ch < ' ' || ch >= '~' || reserved_char_set.find(ch) != reserved_char_set.end()) {
      return PercentEncoding::encode(value, i, reserved_char_set);
    }
  }
  return std::string(value);
}

std::string Utility::PercentEncoding::encode(absl::string_view value, const size_t index,
                                             const absl::flat_hash_set<char>& reserved_char_set) {
  std::string encoded;
  if (index > 0) {
    absl::StrAppend(&encoded, value.substr(0, index));
  }

  for (size_t i = index; i < value.size(); ++i) {
    const char& ch = value[i];
    if (ch < ' ' || ch >= '~' || reserved_char_set.find(ch) != reserved_char_set.end()) {
      // For consistency, URI producers should use uppercase hexadecimal digits for all
      // percent-encodings. https://tools.ietf.org/html/rfc3986#section-2.1.
      absl::StrAppend(&encoded, fmt::format("%{:02X}", ch));
    } else {
      encoded.push_back(ch);
    }
  }
  return encoded;
}

std::string Utility::PercentEncoding::decode(absl::string_view encoded) {
  std::string decoded;
  decoded.reserve(encoded.size());
  for (size_t i = 0; i < encoded.size(); ++i) {
    char ch = encoded[i];
    if (ch == '%' && i + 2 < encoded.size()) {
      const char& hi = encoded[i + 1];
      const char& lo = encoded[i + 2];
      if (absl::ascii_isdigit(hi)) {
        ch = hi - '0';
      } else {
        ch = absl::ascii_toupper(hi) - 'A' + 10;
      }

      ch *= 16;
      if (absl::ascii_isdigit(lo)) {
        ch += lo - '0';
      } else {
        ch += absl::ascii_toupper(lo) - 'A' + 10;
      }
      i += 2;
    }
    decoded.push_back(ch);
  }
  return decoded;
}

Utility::AuthorityAttributes Utility::parseAuthority(absl::string_view host) {
  // First try to see if there is a port included. This also checks to see that there is not a ']'
  // as the last character which is indicative of an IPv6 address without a port. This is a best
  // effort attempt.
  const auto colon_pos = host.rfind(':');
  absl::string_view host_to_resolve = host;
  absl::optional<uint16_t> port;
  if (colon_pos != absl::string_view::npos && host_to_resolve.back() != ']') {
    const absl::string_view string_view_host = host;
    host_to_resolve = string_view_host.substr(0, colon_pos);
    const auto port_str = string_view_host.substr(colon_pos + 1);
    uint64_t port64;
    if (port_str.empty() || !absl::SimpleAtoi(port_str, &port64) || port64 > 65535) {
      // Just attempt to resolve whatever we were given. This will very likely fail.
      host_to_resolve = host;
    } else {
      port = static_cast<uint16_t>(port64);
    }
  }

  // Now see if this is an IP address. We need to know this because some things (such as setting
  // SNI) are special cased if this is an IP address. Either way, we still go through the normal
  // resolver flow. We could short-circuit the DNS resolver in this case, but the extra code to do
  // so is not worth it since the DNS resolver should handle it for us.
  bool is_ip_address = false;
  try {
    absl::string_view potential_ip_address = host_to_resolve;
    // TODO(mattklein123): Optimally we would support bracket parsing in parseInternetAddress(),
    // but we still need to trim the brackets to send the IPv6 address into the DNS resolver. For
    // now, just do all the trimming here, but in the future we should consider whether we can
    // have unified [] handling as low as possible in the stack.
    if (!potential_ip_address.empty() && potential_ip_address.front() == '[' &&
        potential_ip_address.back() == ']') {
      potential_ip_address.remove_prefix(1);
      potential_ip_address.remove_suffix(1);
    }
    Network::Utility::parseInternetAddress(std::string(potential_ip_address));
    is_ip_address = true;
    host_to_resolve = potential_ip_address;
  } catch (const EnvoyException&) {
  }

  return {is_ip_address, host_to_resolve, port};
}

} // namespace Http
} // namespace Envoy