#pragma once

#include "envoy/config/typed_config.h"

#include "envoy/network/socket.h"

#include "envoy/server/factory_context.h"

#include "quiche/quic/core/connection_id_generator.h"

#include "quiche/quic/load_balancer/load_balancer_encoder.h"

namespace Envoy {

namespace Quic {

using QuicConnectionIdGeneratorPtr = std::unique_ptr<quic::ConnectionIdGeneratorInterface>;

// A function similar to the BPF program from createCompatibleLinuxBpfSocketOption, it takes

// a QUIC packet and returns the appropriate worker_index.

using QuicConnectionIdWorkerSelector =

    std::function<uint32_t(const Buffer::Instance& packet, uint32_t default_value)>;

/**

 * A factory interface to provide QUIC connection IDs and compatible BPF code for stable packet

 * routing.

 */

class EnvoyQuicConnectionIdGeneratorFactory {

public:

  /**

   * Create a connection ID generator object.

   * @param worker_index an index to be encoded to QUIC connection ID for routing packets to the

   * current listener.

   */

  virtual QuicConnectionIdGeneratorPtr createQuicConnectionIdGenerator(uint32_t worker_index) PURE;

  /**

   * Create a socket option with BPF program to consistently route QUIC packets to the right listen

   * socket. Linux only.

   * @param concurrency the total number of worker threads.

   */

  virtual Network::Socket::OptionConstSharedPtr

  createCompatibleLinuxBpfSocketOption(uint32_t concurrency) PURE;

  /**

   * Returns a function to retrieve the worker index associated with a QUIC packet; the same

   * principle as the BPF program above, but for contexts where BPF is unavailable.

   */

  virtual QuicConnectionIdWorkerSelector

  getCompatibleConnectionIdWorkerSelector(uint32_t concurrency) PURE;

};

using EnvoyQuicConnectionIdGeneratorFactoryPtr =

    std::unique_ptr<EnvoyQuicConnectionIdGeneratorFactory>;

class EnvoyQuicConnectionIdGeneratorConfigFactory : public Config::TypedFactory {

public:

  /**

   * Returns a connection ID factory based on the given config.

   */

  virtual EnvoyQuicConnectionIdGeneratorFactoryPtr

  createQuicConnectionIdGeneratorFactory(const Protobuf::Message& config,

                                         ProtobufMessage::ValidationVisitor& validation_visitor,

                                         Server::Configuration::FactoryContext& context) PURE;

};

} // namespace Quic

} // namespace Envoy