#pragma once

#include <string>

#include <vector>

#include "envoy/common/exception.h"

#include "envoy/common/optref.h"

#include "envoy/common/pure.h"

#include "envoy/service/discovery/v3/discovery.pb.h"

#include "envoy/stats/stats_macros.h"

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

namespace Envoy {

namespace Config {

/**

 * Reason that a config update is failed.

 */

enum class ConfigUpdateFailureReason {

  // A connection failure took place and the update could not be fetched.

  ConnectionFailure,

  // Config fetch timed out.

  FetchTimedout,

  // Update rejected because there is a problem in applying the update.

  UpdateRejected

};

/**

 * A wrapper for xDS resources that have been deserialized from the wire.

 */

class DecodedResource {

public:

  /**

   * @return const std::string& resource name.

   */

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

  /**

   * @return const std::vector<std::string& resource aliases.

   */

  virtual const std::vector<std::string>& aliases() const PURE;

  /**

   * @return const std::string& resource version.

   */

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

  /**

   * @return const Protobuf::Message& resource message reference. If hasResource() is false, this

   *         will be the empty message.

   */

  virtual const Protobuf::Message& resource() const PURE;

  virtual absl::optional<std::chrono::milliseconds> ttl() const PURE;

  /**

   * @return bool does the xDS discovery response have a set resource payload?

   */

  virtual bool hasResource() const PURE;

  /**

   * @return optional ref<envoy::config::core::v3::Metadata> of a resource.

   */

  virtual const OptRef<const envoy::config::core::v3::Metadata> metadata() const PURE;

};

using DecodedResourcePtr = std::unique_ptr<DecodedResource>;

using DecodedResourceRef = std::reference_wrapper<DecodedResource>;

class OpaqueResourceDecoder {

public:

  /**

   * @param resource some opaque resource (Protobuf::Any).

   * @return ProtobufTypes::MessagePtr decoded protobuf message in the opaque resource, e.g. the

   *         RouteConfiguration for an Any containing envoy.config.route.v3.RouteConfiguration.

   */

  virtual ProtobufTypes::MessagePtr decodeResource(const Protobuf::Any& resource) PURE;

  /**

   * @param resource some opaque resource (Protobuf::Message).

   * @return std::String the resource name in a Protobuf::Message returned by decodeResource(), e.g.

   *         the route config name for a envoy.config.route.v3.RouteConfiguration message.

   */

  virtual std::string resourceName(const Protobuf::Message& resource) PURE;

};

using OpaqueResourceDecoderSharedPtr = std::shared_ptr<OpaqueResourceDecoder>;

/**

 * Subscription to DecodedResources.

 */

class SubscriptionCallbacks {

public:

  /**

   * Called when a state-of-the-world configuration update is received. (State-of-the-world is

   * everything other than delta gRPC - filesystem, HTTP, non-delta gRPC).

   * @param resources vector of fetched resources corresponding to the configuration update.

   * @param version_info supplies the version information as supplied by the xDS discovery response.

   * @return an absl status indicating if a non-exception-throwing error was encountered.

   * @throw EnvoyException with reason if the configuration is rejected for legacy reasons,

   *        Accepted configurations have their version_info reflected in subsequent requests.

   */

  virtual absl::Status onConfigUpdate(const std::vector<DecodedResourceRef>& resources,

                                      const std::string& version_info) PURE;

  /**

   * Called when a delta configuration update is received.

   * @param added_resources resources newly added since the previous fetch.

   * @param removed_resources names of resources that this fetch instructed to be removed.

   * @param system_version_info aggregate response data "version", for debugging.

   * @return an absl status indicating if a non-exception-throwing error was encountered.

   * @throw EnvoyException with reason if the configuration is rejected for legacy reasons,

   *        Accepted configurations have their version_info reflected in subsequent requests.

   */

  virtual absl::Status

  onConfigUpdate(const std::vector<DecodedResourceRef>& added_resources,

                 const Protobuf::RepeatedPtrField<std::string>& removed_resources,

                 const std::string& system_version_info) PURE;

  /**

   * Called when either the Subscription is unable to fetch a config update or when onConfigUpdate

   * returns a failure or invokes an exception.

   * @param reason supplies the update failure reason.

   * @param e supplies any exception data on why the fetch failed. May be nullptr.

   */

  virtual void onConfigUpdateFailed(ConfigUpdateFailureReason reason, const EnvoyException* e) PURE;

};

/**

 * Options associated with a Subscription.

 */

struct SubscriptionOptions {

  /**

   * For legacy VHDS, should an xDS resource name be treated as <namespace>/<resource name>? This is

   * incompatible with the use of xdstp:// naming.

   */

  bool use_namespace_matching_{};

  /**

   * For xdstp:// resource names, should node context parameters be added at the transport layer?

   */

  bool add_xdstp_node_context_params_{};

};

/**

 * Invoked when raw config received from xDS wire.

 */

class UntypedConfigUpdateCallbacks {

public:

  // TODO (dmitri-d) remove this method when legacy sotw mux has been removed.

  /**

   * Called when a state-of-the-world configuration update is received. (State-of-the-world is

   * everything other than delta gRPC - filesystem, HTTP, non-delta gRPC).

   * @param resources vector of fetched resources corresponding to the configuration update.

   * @param version_info supplies the version information as supplied by the xDS discovery response.

   * @throw EnvoyException with reason if the configuration is rejected. Otherwise the configuration

   *        is accepted. Accepted configurations have their version_info reflected in subsequent

   *        requests.

   */

  virtual void onConfigUpdate(const Protobuf::RepeatedPtrField<Protobuf::Any>& resources,

                              const std::string& version_info) PURE;

  /**

   * Called when a non-delta gRPC configuration update is received.

   * @param resources vector of fetched resources corresponding to the configuration update.

   * @param version_info supplies the version information as supplied by the xDS discovery response.

   * @throw EnvoyException with reason if the configuration is rejected. Otherwise the configuration

   *        is accepted. Accepted configurations have their version_info reflected in subsequent

   *        requests.

   */

  virtual void onConfigUpdate(const std::vector<DecodedResourcePtr>& resources,

                              const std::string& version_info) PURE;

  /**

   * Called when a delta configuration update is received.

   * @param added_resources resources newly added since the previous fetch.

   * @param removed_resources names of resources that this fetch instructed to be removed.

   * @param system_version_info aggregate response data "version", for debugging.

   * @throw EnvoyException with reason if the config changes are rejected. Otherwise the changes

   * @param use_namespace_matching if the resources should me matched on their namespaces, rather

   * than unique names. This is used when a collection of resources (e.g. virtual hosts in VHDS) is

   * being updated. Accepted changes have their version_info reflected in subsequent

   * requests.

   */

  virtual void

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

                 const Protobuf::RepeatedPtrField<std::string>& removed_resources,

                 const std::string& system_version_info) PURE;

  /**

   * Called when either the Subscription is unable to fetch a config update or when onConfigUpdate

   * invokes an exception.

   * @param reason supplies the update failure reason.

   * @param e supplies any exception data on why the fetch failed. May be nullptr.

   */

  virtual void onConfigUpdateFailed(ConfigUpdateFailureReason reason, const EnvoyException* e) PURE;

};

/**

 * Common abstraction for subscribing to versioned config updates. This may be implemented via bidi

 * gRPC streams, periodic/long polling REST or inotify filesystem updates.

 */

class Subscription {

public:

  /**

   * Start a configuration subscription asynchronously. This should be called once and will continue

   * to fetch throughout the lifetime of the Subscription object.

   * @param resources set of resource names to fetch.

   */

  virtual void start(const absl::flat_hash_set<std::string>& resource_names) PURE;

  /**

   * Update the resources to fetch.

   * @param resources vector of resource names to fetch.

   */

  virtual void

  updateResourceInterest(const absl::flat_hash_set<std::string>& update_to_these_names) PURE;

  /**

   * Creates a discovery request for resources.

   * @param add_these_names resource ids for inclusion in the discovery request.

   */

  virtual void requestOnDemandUpdate(const absl::flat_hash_set<std::string>& add_these_names) PURE;

};

using SubscriptionPtr = std::unique_ptr<Subscription>;

/**

 * Per subscription stats. @see stats_macros.h

 */

#define ALL_SUBSCRIPTION_STATS(COUNTER, GAUGE, TEXT_READOUT, HISTOGRAM)                            \

/**

 * Struct definition for per subscription stats. @see stats_macros.h

 */

struct SubscriptionStats {

  ALL_SUBSCRIPTION_STATS(GENERATE_COUNTER_STRUCT, GENERATE_GAUGE_STRUCT,

                         GENERATE_TEXT_READOUT_STRUCT, GENERATE_HISTOGRAM_STRUCT)

};

} // namespace Config

} // namespace Envoy