// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MOJO_CORE_WATCHER_SET_H_
#define MOJO_CORE_WATCHER_SET_H_

#include "base/containers/flat_map.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "mojo/core/handle_signals_state.h"
#include "mojo/core/watcher_dispatcher.h"
#include "third_party/abseil-cpp/absl/types/optional.h"

namespace mojo {
namespace core {

// A WatcherSet maintains a set of references to WatcherDispatchers to be
// notified when a handle changes state.
//
// Dispatchers which may be watched by a watcher should own a WatcherSet and
// notify it of all relevant state changes.
class WatcherSet {
 public:
  // |owner| is the Dispatcher who owns this WatcherSet.
  explicit WatcherSet(Dispatcher* owner);

  WatcherSet(const WatcherSet&) = delete;
  WatcherSet& operator=(const WatcherSet&) = delete;

  ~WatcherSet();

  // Notifies all watchers of the handle's current signals state.
  void NotifyState(const HandleSignalsState& state);

  // Notifies all watchers that this handle has been closed.
  void NotifyClosed();

  // Adds a new watcher+context.
  MojoResult Add(const scoped_refptr<WatcherDispatcher>& watcher,
                 uintptr_t context,
                 const HandleSignalsState& current_state);

  // Removes a watcher+context.
  MojoResult Remove(WatcherDispatcher* watcher, uintptr_t context);

 private:
  using ContextSet = std::set<uintptr_t>;

  struct Entry {
    Entry(const scoped_refptr<WatcherDispatcher>& dispatcher);

    Entry(const Entry&) = delete;
    Entry& operator=(const Entry&) = delete;

    Entry(Entry&& other);

    ~Entry();

    Entry& operator=(Entry&& other);

    scoped_refptr<WatcherDispatcher> dispatcher;
    ContextSet contexts;
  };

  Dispatcher* const owner_;
  base::flat_map<WatcherDispatcher*, Entry> watchers_;
  absl::optional<HandleSignalsState> last_known_state_;
};

}  // namespace core
}  // namespace mojo

#endif  // MOJO_CORE_WATCHER_SET_H_
