#pragma once

#include <string>

#include <vector>

#include "envoy/api/api.h"

#include "envoy/common/optref.h"

#include "envoy/config/subscription.h"

#include "envoy/config/typed_config.h"

#include "envoy/protobuf/message_validator.h"

#include "envoy/stats/scope.h"

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

#include "google/rpc/status.pb.h"

namespace Envoy {

namespace Config {

/**

 * An interface for hooking into xDS update events to provide the ablility to use some external

 * processor in xDS update. This tracker provides the process point when the discovery response

 * is received, when the resources are successfully processed and applied, and when there is any

 * failure.

 *

 * Instance of this interface get invoked on the main Envoy thread. Thus, it is important

 * for implementations of this interface to not execute any blocking operations on the same

 * thread.

 */

class XdsConfigTracker {

public:

  /**

   * Invoked when SotW xDS configuration updates have been successfully parsed, applied on

   * the Envoy instance, and are about to be ACK'ed.

   *

   * For SotW, the passed resources contain all the received resources except for the heart-beat

   * ones in the original message. The call of this method means there is a subscriber for this

   * type_url and the type of resource is same as the message's type_url.

   *

   * Note: this method is called when *all* the resources in a response are accepted.

   *

   * @param type_url The type url of xDS message.

   * @param resources A list of decoded resources to add to the current state.

   */

  virtual void onConfigAccepted(const absl::string_view type_url,

                                const std::vector<DecodedResourcePtr>& resources) PURE;

  /**

   * Invoked when Delta xDS configuration updates have been successfully accepted, applied on

   * the Envoy instance, and are about to be ACK'ed.

   *

   * For Delta, added_resources contains all the received added resources except for the heart-beat

   * ones in the original message, and the removed resources are the same in the xDS message.

   *

   * Note: this method is called when *all* the resources in a response are accepted.

   *

   * @param type_url The type url of xDS message.

   * @param added_resources A list of decoded resources to add to the current state.

   * @param removed_resources A list of resources to remove from the current state.

   */

  virtual void

  onConfigAccepted(const absl::string_view type_url,

                   absl::Span<const envoy::service::discovery::v3::Resource* const> added_resources,

                   const Protobuf::RepeatedPtrField<std::string>& removed_resources) PURE;

  /**

   * Invoked when xds configs are rejected during xDS ingestion.

   *

   * @param message The SotW discovery response message body.

   * @param details The process state and error details.

   */

  virtual void onConfigRejected(const envoy::service::discovery::v3::DiscoveryResponse& message,

                                const absl::string_view error_detail) PURE;

  /**

   * Invoked when xds configs are rejected during xDS ingestion.

   *

   * @param message The Delta discovery response message body.

   * @param details The process state and error details.

   */

  virtual void

  onConfigRejected(const envoy::service::discovery::v3::DeltaDiscoveryResponse& message,

                   const absl::string_view error_detail) PURE;

};

using XdsConfigTrackerPtr = std::unique_ptr<XdsConfigTracker>;

using XdsConfigTrackerOptRef = OptRef<XdsConfigTracker>;

/**

 * A factory abstract class for creating instances of XdsConfigTracker.

 */

class XdsConfigTrackerFactory : public Config::TypedFactory {

public:

  /**

   * Creates an XdsConfigTracker using the given config.

   */

  virtual XdsConfigTrackerPtr

  createXdsConfigTracker(const Protobuf::Any& config,

                         ProtobufMessage::ValidationVisitor& validation_visitor, Api::Api& api,

                         Event::Dispatcher& dispatcher) PURE;

};

} // namespace Config

} // namespace Envoy