#pragma once

#include <string>

#include <vector>

#include "envoy/common/optref.h"

#include "envoy/config/subscription.h"

#include "envoy/server/instance.h"

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

namespace Envoy {

namespace Config {

/**

 * The configuration validator interface. One can implement such validator

 * to add custom constraints to the fetched config, and reject a config

 * which violates these constraints.

 * The validators will be extensions that can be dynamically configured.

 *

 * A validator example: a validator that prevents removing all Clusters

 * from an Envoy (which may be caused by a bug in the config plane, and not

 * intentional change).

 */

class ConfigValidator {

public:

  /**

   * Validates a given set of resources matching a State-of-the-World update.

   * @param server A server instance to fetch the state before applying the config.

   * @param resources List of decoded resources that reflect the new state.

   * @throw EnvoyException if the config should be rejected.

   */

  virtual void validate(const Server::Instance& server,

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

  /**

   * Validates a given set of resources matching an Incremental update.

   * @param server A server instance to fetch the state before applying the config.

   * @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.

   * @throw EnvoyException if the config should be rejected.

   */

  virtual void validate(const Server::Instance& server,

                        const std::vector<DecodedResourcePtr>& added_resources,

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

};

using ConfigValidatorPtr = std::unique_ptr<ConfigValidator>;

/**

 * A factory abstract class for creating instances of ConfigValidators.

 */

class ConfigValidatorFactory : public Config::TypedFactory {

public:

  /**

   * Creates a ConfigValidator using the given config.

   */

  virtual ConfigValidatorPtr

  createConfigValidator(const Protobuf::Any& config,

                        ProtobufMessage::ValidationVisitor& validation_visitor) PURE;

  /**

   * Returns the xDS service type url that the config validator expects to receive.

   */

  virtual std::string typeUrl() const PURE;

};

} // namespace Config

} // namespace Envoy