#pragma once

#include <memory>

#include "envoy/common/pure.h"

#include "envoy/init/watcher.h"

#include "absl/strings/string_view.h"

namespace Envoy {

namespace Init {

/**

 * A TargetHandle functions as a weak reference to a Target. It is how an implementation of

 * Init::Manager would safely tell a target to `initialize` with no guarantees about the

 * target's lifetime. Typical usage (outside of Init::ManagerImpl) does not require touching

 * TargetHandles at all.

 */

struct TargetHandle {

  /**

   * Tell the target to begin initialization, if it is still available.

   * @param watcher A Watcher for the target to notify when it has initialized.

   * @return true if the target received this call, false if the target was already destroyed.

   */

  virtual bool initialize(const Watcher& watcher) const PURE;

  /**

   * @return a human-readable target name, for logging / debugging / tracking target names.

   * The target name has to be unique.

   */

  virtual absl::string_view name() const PURE;

};

using TargetHandlePtr = std::unique_ptr<TargetHandle>;

/**

 * An initialization Target is an entity that can be registered with a Manager for initialization.

 * It can only be invoked through a TargetHandle.

 */

struct Target {

  /**

   * @return a human-readable target name, for logging / debugging.

   */

  virtual absl::string_view name() const PURE;

  /**

   * Create a new handle that can initialize this target.

   * @param name a human readable handle name, for logging / debugging.

   * @return a new handle that can initialize this target.

   */

  virtual TargetHandlePtr createHandle(absl::string_view name) const PURE;

};

} // namespace Init

} // namespace Envoy