#pragma once

#include "envoy/buffer/buffer.h"

#include "envoy/extensions/filters/network/tcp_proxy/v3/tcp_proxy.pb.h"

#include "envoy/http/filter.h"

#include "envoy/http/header_evaluator.h"

#include "envoy/stream_info/stream_info.h"

#include "envoy/tcp/conn_pool.h"

#include "envoy/upstream/upstream.h"

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

namespace Envoy {

namespace Upstream {

class LoadBalancerContext;

class ThreadLocalCluster;

} // namespace Upstream

namespace TcpProxy {

class GenericConnectionPoolCallbacks;

class GenericUpstream;

/**

 * A configuration for an individual tunneling TCP over HTTP protocols.

 */

class TunnelingConfigHelper {

public:

  virtual ~TunnelingConfigHelper() = default;

  // The host name of the tunneling upstream HTTP request.

  // This function evaluates command operators if specified. Otherwise it returns host name as is.

  virtual std::string host(const StreamInfo::StreamInfo& stream_info) const PURE;

  // The method of the upstream HTTP request. True if using POST method, CONNECT otherwise.

  virtual bool usePost() const PURE;

  // The path used for POST method.

  virtual const std::string& postPath() const PURE;

  // The evaluator to add additional HTTP request headers to the upstream request.

  virtual Envoy::Http::HeaderEvaluator& headerEvaluator() const PURE;

  // Save HTTP response headers to the downstream filter state.

  virtual void

  propagateResponseHeaders(Http::ResponseHeaderMapPtr&& headers,

                           const StreamInfo::FilterStateSharedPtr& filter_state) const PURE;

  // Save HTTP response trailers to the downstream filter state.

  virtual void

  propagateResponseTrailers(Http::ResponseTrailerMapPtr&& trailers,

                            const StreamInfo::FilterStateSharedPtr& filter_state) const PURE;

  virtual const Envoy::Router::FilterConfig& routerFilterConfig() const PURE;

  virtual Server::Configuration::ServerFactoryContext& serverFactoryContext() const PURE;

};

using TunnelingConfigHelperOptConstRef = OptRef<const TunnelingConfigHelper>;

// An API for wrapping either a TCP or an HTTP connection pool.

class GenericConnPool : public Event::DeferredDeletable,

                        public Logger::Loggable<Logger::Id::router> {

public:

  ~GenericConnPool() override = default;

  /**

   * Called to create a TCP connection or HTTP stream for "CONNECT" streams.

   *

   * The implementation is then responsible for calling either onGenericPoolReady or

   * onGenericPoolFailure on the supplied GenericConnectionPoolCallbacks.

   *

   * @param callbacks callbacks to communicate stream failure or creation on.

   */

  virtual void newStream(GenericConnectionPoolCallbacks& callbacks) PURE;

};

// An API for the UpstreamRequest to get callbacks from either an HTTP or TCP

// connection pool.

class GenericConnectionPoolCallbacks {

public:

  virtual ~GenericConnectionPoolCallbacks() = default;

  /**

   * Called when GenericConnPool::newStream has established a new stream.

   *

   * @param info supplies the stream info object associated with the upstream connection.

   * @param upstream supplies the generic upstream for the stream.

   * @param host supplies the description of the host that will carry the request.

   * @param address_provider supplies the address provider of the upstream connection.

   * @param ssl_info supplies the ssl information of the upstream connection.

   */

  virtual void onGenericPoolReady(StreamInfo::StreamInfo* info,

                                  std::unique_ptr<GenericUpstream>&& upstream,

                                  Upstream::HostDescriptionConstSharedPtr& host,

                                  const Network::ConnectionInfoProvider& address_provider,

                                  Ssl::ConnectionInfoConstSharedPtr ssl_info) PURE;

  /**

   * Called to indicate a failure for GenericConnPool::newStream to establish a stream.

   *

   * @param reason supplies the failure reason.

   * @param failure_reason failure reason string (Note: it is expected that the caller will provide

   * matching `reason` and `failure_reason`).

   * @param host supplies the description of the host that caused the failure. This may be nullptr

   *             if no host was involved in the failure (for example overflow).

   */

  virtual void onGenericPoolFailure(ConnectionPool::PoolFailureReason reason,

                                    absl::string_view failure_reason,

                                    Upstream::HostDescriptionConstSharedPtr host) PURE;

};

// Interface for a generic Upstream, which can communicate with a TCP or HTTP

// upstream.

class GenericUpstream : public Event::DeferredDeletable {

public:

  ~GenericUpstream() override = default;

  /**

   * Enable/disable further data from this stream.

   *

   * @param disable true if the stream should be read disabled, false otherwise.

   * @return returns true if the disable is performed, false otherwise

   *         (e.g. if the connection is closed)

   */

  virtual bool readDisable(bool disable) PURE;

  /**

   * Encodes data upstream.

   * @param data supplies the data to encode. The data may be moved by the encoder.

   * @param end_stream supplies whether this is the last data to encode.

   */

  virtual void encodeData(Buffer::Instance& data, bool end_stream) PURE;

  /**

   * Adds a callback to be called when the data is sent to the kernel.

   * @param cb supplies the callback to be called

   */

  virtual void addBytesSentCallback(Network::Connection::BytesSentCb cb) PURE;

  /**

   * Called when an event is received on the downstream connection

   * @param event supplies the event which occurred.

   * @return the underlying ConnectionData if the event is not "Connected" and draining

             is supported for this upstream.

   */

  virtual Tcp::ConnectionPool::ConnectionData*

  onDownstreamEvent(Network::ConnectionEvent event) PURE;

  /* Called to convert underlying transport socket from non-secure mode

   * to secure mode. Implemented only by start_tls transport socket.

   */

  virtual bool startUpstreamSecureTransport() PURE;

  /**

   * Called when upstream starttls socket is converted to tls and upstream ssl info

   * needs to be set in the connection's stream_info.

   * @return the const SSL connection data of upstream.

   */

  virtual Ssl::ConnectionInfoConstSharedPtr getUpstreamConnectionSslInfo() PURE;

};

using GenericConnPoolPtr = std::unique_ptr<GenericConnPool>;

/*

 * A factory for creating generic connection pools.

 */

class GenericConnPoolFactory : public Envoy::Config::TypedFactory {

public:

  ~GenericConnPoolFactory() override = default;

  /*

   * @param thread_local_cluster the thread local cluster to use for conn pool creation.

   * @param config the tunneling config, if doing connect tunneling.

   * @param context the load balancing context for this connection.

   * @param upstream_callbacks the callbacks to provide to the connection if successfully created.

   * @param downstream_info is the downstream connection stream info.

   * @return may be null if there is no cluster with the given name.

   */

  virtual GenericConnPoolPtr

  createGenericConnPool(Upstream::ThreadLocalCluster& thread_local_cluster,

                        TunnelingConfigHelperOptConstRef config,

                        Upstream::LoadBalancerContext* context,

                        Tcp::ConnectionPool::UpstreamCallbacks& upstream_callbacks,

                        Http::StreamDecoderFilterCallbacks& stream_decoder_callbacks,

                        StreamInfo::StreamInfo& downstream_info) const PURE;

};

using GenericConnPoolFactoryPtr = std::unique_ptr<GenericConnPoolFactory>;

} // namespace TcpProxy

} // namespace Envoy