#pragma once

#include <string>

#include "envoy/buffer/buffer.h"

#include "envoy/common/pure.h"

#include "source/common/common/macros.h"

#include "source/extensions/filters/network/thrift_proxy/binary_protocol_impl.h"

#include "absl/types/optional.h"

namespace Envoy {

namespace Extensions {

namespace NetworkFilters {

namespace ThriftProxy {

/**

 * TwitterProtocolImpl implements the Twitter-upgraded (AKA "TTwitter") Thrift protocol.

 * See https://twitter.github.io/finagle/docs/com/twitter/finagle/Thrift$ and

 * https://github.com/twitter/finagle/blob/master/finagle-thrift/src/main/thrift/tracing.thrift

 */

class TwitterProtocolImpl : public BinaryProtocolImpl {

public:

  // Protocol

  const std::string& name() const override { return ProtocolNames::get().TWITTER; }

  ProtocolType type() const override { return ProtocolType::Twitter; }

  bool readMessageBegin(Buffer::Instance& buffer, MessageMetadata& metadata) override;

  void writeMessageBegin(Buffer::Instance& buffer, const MessageMetadata& metadata) override;

  bool supportsUpgrade() override { return true; }

  DecoderEventHandlerSharedPtr upgradeRequestDecoder() override;

  DirectResponsePtr upgradeResponse(const DecoderEventHandler& decoder) override;

  ThriftObjectPtr attemptUpgrade(Transport& transport, ThriftConnectionState& state,

                                 Buffer::Instance& buffer) override;

  void completeUpgrade(ThriftConnectionState& state, ThriftObject& response) override;

  /**

   * @return true if the protocol upgrade was success, false if not, no value if the result is not

   *         yet known

   */

  absl::optional<bool> upgraded() { return upgraded_; }

  /**

   * @return std::string containing the "improbably-named method" used for Twitter protocol upgrade.

   */

  static const std::string& upgradeMethodName() {

    // https://github.com/twitter/finagle/blob/master/finagle-thrift/src/main/scala/com/twitter/finagle/thrift/ThriftTracing.scala

    CONSTRUCT_ON_FIRST_USE(std::string, "__can__finagle__trace__v3__");

  }

  /**

   * @return true if the buffer (minimum 12 bytes) appears to start with a Twitter protocol

   *         upgrade message, false otherwise

   */

  static bool isUpgradePrefix(Buffer::Instance& buffer);

protected:

  static void updateMetadataWithRequestHeader(const ThriftObject& header_object,

                                              MessageMetadata& metadata);

  static void updateMetadataWithResponseHeader(const ThriftObject& header_object,

                                               MessageMetadata& metadata);

  static void writeRequestHeader(Buffer::Instance& buffer, const MessageMetadata& metadata);

  static void writeResponseHeader(Buffer::Instance& buffer, const MessageMetadata& metadata);

  static ThriftObjectPtr newHeader();

private:

  ThriftObjectPtr header_;

  bool header_complete_{false};

  absl::optional<bool> upgraded_;

};

} // namespace ThriftProxy

} // namespace NetworkFilters

} // namespace Extensions

} // namespace Envoy