// Copyright (c) 2011 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 UI_VIEWS_FOCUS_EXTERNAL_FOCUS_TRACKER_H_
#define UI_VIEWS_FOCUS_EXTERNAL_FOCUS_TRACKER_H_

#include "base/compiler_specific.h"
#include "base/macros.h"
#include "ui/views/focus/focus_manager.h"

namespace views {

class View;
class ViewTracker;

// ExternalFocusTracker tracks the last focused view which belongs to the
// provided focus manager and is not either the provided parent view or one of
// its descendants. This is generally used if the parent view want to return
// focus to some other view once it is dismissed. The parent view and the focus
// manager must exist for the duration of the tracking. If the focus manager
// must be deleted before this object is deleted, make sure to call
// SetFocusManager(NULL) first.
//
// Typical use: When a view is added to the view hierarchy, it instantiates an
// ExternalFocusTracker and passes in itself and its focus manager. Then,
// when that view wants to return focus to the last focused view which is not
// itself and not a descandant of itself, (usually when it is being closed)
// it calls FocusLastFocusedExternalView.
class VIEWS_EXPORT ExternalFocusTracker : public FocusChangeListener {
 public:
  ExternalFocusTracker(View* parent_view, FocusManager* focus_manager);
  ~ExternalFocusTracker() override;

  // FocusChangeListener:
  void OnWillChangeFocus(View* focused_before, View* focused_now) override;
  void OnDidChangeFocus(View* focused_before, View* focused_now) override;

  // Focuses last focused view which is not a child of parent view and is not
  // parent view itself. Returns true if focus for a view was requested, false
  // otherwise.
  void FocusLastFocusedExternalView();

  // Sets the focus manager whose focus we are tracking. |focus_manager| can
  // be NULL, but no focus changes will be tracked. This is useful if the focus
  // manager went away, but you might later want to start tracking with a new
  // manager later, or call FocusLastFocusedExternalView to focus the previous
  // view.
  void SetFocusManager(FocusManager* focus_manager);

 private:
  // Store the provided view. This view will be focused when
  // FocusLastFocusedExternalView is called.
  void StoreLastFocusedView(View* view);

  // Store the currently focused view for our view manager and register as a
  // listener for future focus changes.
  void StartTracking();

  // Focus manager which we are a listener for.
  FocusManager* focus_manager_;

  // The parent view of views which we should not track focus changes to. We
  // also do not track changes to parent_view_ itself.
  View* parent_view_;

  // Holds the last focused view.
  std::unique_ptr<ViewTracker> last_focused_view_tracker_;

  DISALLOW_COPY_AND_ASSIGN(ExternalFocusTracker);
};

}  // namespace views

#endif  // UI_VIEWS_FOCUS_EXTERNAL_FOCUS_TRACKER_H_