// Copyright 2014 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 SERVICES_WINDOW_MANAGER_FOCUS_CONTROLLER_H_
#define SERVICES_WINDOW_MANAGER_FOCUS_CONTROLLER_H_

#include "base/compiler_specific.h"
#include "base/memory/scoped_ptr.h"
#include "base/observer_list.h"
#include "base/scoped_observer.h"
#include "mojo/services/public/cpp/view_manager/view_observer.h"
#include "ui/events/event_handler.h"

namespace mojo {

class FocusControllerObserver;
class FocusRules;

// FocusController handles focus and activation changes in a mojo window
// manager. Within the window manager, there can only be one focused and one
// active window at a time. When focus or activation changes, notifications are
// sent using the FocusControllerObserver interface.
class FocusController : public ui::EventHandler,
                        public ViewObserver {
 public:
  // |rules| cannot be null.
  explicit FocusController(scoped_ptr<FocusRules> rules);
  virtual ~FocusController();

  void AddObserver(FocusControllerObserver* observer);
  void RemoveObserver(FocusControllerObserver* observer);

  void ActivateView(View* view);
  void DeactivateView(View* view);
  View* GetActiveView();
  View* GetActivatableView(View* view);
  View* GetToplevelView(View* view);
  bool CanActivateView(View* view) const;

  void FocusView(View* view);

  void ResetFocusWithinActiveView(View* view);
  View* GetFocusedView();

  // Overridden from ui::EventHandler:
  void OnKeyEvent(ui::KeyEvent* event) override;
  void OnMouseEvent(ui::MouseEvent* event) override;
  void OnScrollEvent(ui::ScrollEvent* event) override;
  void OnTouchEvent(ui::TouchEvent* event) override;
  void OnGestureEvent(ui::GestureEvent* event) override;

  // Overridden from ViewObserver:
  void OnTreeChanging(const TreeChangeParams& params) override;
  void OnTreeChanged(const TreeChangeParams& params) override;
  void OnViewVisibilityChanged(View* view) override;
  void OnViewDestroying(View* view) override;

 private:
  // Internal implementation that sets the focused view, fires events etc.
  // This function must be called with a valid focusable view.
  void SetFocusedView(View* view);

  // Internal implementation that sets the active window, fires events etc.
  // This function must be called with a valid |activatable_window|.
  // |requested window| refers to the window that was passed in to an external
  // request (e.g. FocusWindow or ActivateWindow). It may be null, e.g. if
  // SetActiveWindow was not called by an external request. |activatable_window|
  // refers to the actual window to be activated, which may be different.
  void SetActiveView(View* requested_view,
                     View* activatable_view);

  // Called when a window's disposition changed such that it and its hierarchy
  // are no longer focusable/activatable. |next| is a valid window that is used
  // as a starting point for finding a window to focus next based on rules.
  void ViewLostFocusFromDispositionChange(View* view, View* next);

  // Called when an attempt is made to focus or activate a window via an input
  // event targeted at that window. Rules determine the best focusable window
  // for the input window.
  void ViewFocusedFromInputEvent(View* view);

  View* active_view_;
  View* focused_view_;

  bool updating_focus_;
  bool updating_activation_;

  scoped_ptr<FocusRules> rules_;

  ObserverList<FocusControllerObserver> focus_controller_observers_;

  ScopedObserver<View, ViewObserver> observer_manager_;

  DISALLOW_COPY_AND_ASSIGN(FocusController);
};

// Sets/Gets the focus controller for a root view.
void SetFocusController(View* view, FocusController* focus_controller);
FocusController* GetFocusController(View* view);

}  // namespace mojo

#endif  // SERVICES_WINDOW_MANAGER_FOCUS_CONTROLLER_H_