#pragma once

#include <memory>

#include "envoy/common/pure.h"

#include "absl/strings/string_view.h"

namespace Envoy {

namespace Init {

/**

 * A WatcherHandle functions as a weak reference to a Watcher. It is how an implementation of

 * Init::Target would safely notify a Manager that it has initialized, and likewise it's how

 * an implementation of Init::Manager would safely tell its client that all registered targets

 * have initialized, with no guarantees about the lifetimes of the manager or client. Typical usage

 * (outside of Init::TargetImpl and ManagerImpl) does not require touching WatcherHandles at

 * all.

 */

struct WatcherHandle {

  /**

   * Tell the watcher that initialization has completed, if it is still available.

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

   */

  virtual bool ready() const PURE;

};

using WatcherHandlePtr = std::unique_ptr<WatcherHandle>;

/**

 * A Watcher is an entity that listens for notifications that either an initialization target or

 * all targets registered with a manager have initialized. It can only be invoked through a

 * WatcherHandle.

 */

struct Watcher {

  /**

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

   */

  virtual absl::string_view name() const PURE;

  /**

   * Create a new handle that can notify this watcher.

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

   * @return a new handle that can notify this watcher.

   */

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

};

} // namespace Init

} // namespace Envoy