#pragma once

#include <cstddef>

#include <cstdint>

#include <memory>

#include "envoy/common/pure.h"

#include "envoy/common/resource.h"

namespace Envoy {

namespace Upstream {

/**

 * Resource priority classes. The parallel NumResourcePriorities constant allows defining fixed

 * arrays for each priority, but does not pollute the enum.

 */

enum class ResourcePriority : uint8_t { Default, High };

const size_t NumResourcePriorities = 2;

/**

 * RAII wrapper that increments a resource on construction and decrements it on destruction.

 */

class ResourceAutoIncDec {

public:

private:

  ResourceLimit& resource_;

};

using ResourceAutoIncDecPtr = std::unique_ptr<ResourceAutoIncDec>;

/**

 * Global resource manager that loosely synchronizes maximum connections, pending requests, etc.

 * NOTE: Currently this is used on a per cluster basis. In the future we may consider also chaining

 *       this with a global resource manager.

 */

class ResourceManager {

public:

  /**

   * @return ResourceLimit& active TCP connections and UDP sessions.

   */

  virtual ResourceLimit& connections() PURE;

  /**

   * @return ResourceLimit& active pending requests (requests that have not yet been attached to a

   *         connection pool connection).

   */

  virtual ResourceLimit& pendingRequests() PURE;

  /**

   * @return ResourceLimit& active requests (requests that are currently bound to a connection pool

   *         connection and are awaiting response).

   */

  virtual ResourceLimit& requests() PURE;

  /**

   * @return ResourceLimit& active retries.

   */

  virtual ResourceLimit& retries() PURE;

  /**

   * @return ResourceLimit& active connection pools.

   */

  virtual ResourceLimit& connectionPools() PURE;

  /**

   * @return uint64_t the max number of connections per host.

   */

  virtual uint64_t maxConnectionsPerHost() PURE;

};

} // namespace Upstream

} // namespace Envoy