// Copyright 2018 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 ASH_MAGNIFIER_DOCKED_MAGNIFIER_CONTROLLER_H_
#define ASH_MAGNIFIER_DOCKED_MAGNIFIER_CONTROLLER_H_

#include <memory>

#include "ash/ash_export.h"
#include "ash/display/window_tree_host_manager.h"
#include "ash/public/interfaces/docked_magnifier_controller.mojom.h"
#include "ash/session/session_observer.h"
#include "mojo/public/cpp/bindings/binding.h"
#include "ui/base/ime/ime_bridge_observer.h"
#include "ui/base/ime/input_method_observer.h"
#include "ui/events/event_handler.h"
#include "ui/views/widget/widget_observer.h"

class PrefRegistrySimple;
class PrefService;
class PrefChangeRegistrar;

namespace aura {
class Window;
class WindowTreeHost;
}  // namespace aura

namespace ui {
class Reflector;
class Layer;
}  // namespace ui

namespace views {
class Widget;
}  // namespace views

namespace ash {

// Controls the Docked Magnifier (a.k.a. picture-in-picture magnifier) feature,
// which allocates the top portion of the currently active display as a
// magnified viewport of an area around the point of interest in the screen
// (which follows the cursor location, text input caret location, or focus
// changes). In a multiple display scenario, the magnifier viewport is located
// on the same display as that of the point of interest.
class ASH_EXPORT DockedMagnifierController
    : public mojom::DockedMagnifierController,
      public SessionObserver,
      public ui::EventHandler,
      public ui::IMEBridgeObserver,
      public ui::InputMethodObserver,
      public views::WidgetObserver,
      public WindowTreeHostManager::Observer {
 public:
  DockedMagnifierController();
  ~DockedMagnifierController() override;

  // The height of the black separator layer between the magnifier viewport and
  // the rest of the screen.
  static constexpr int kSeparatorHeight = 10;

  // The value by which the screen height is divided to calculate the height of
  // the magnifier viewport.
  static constexpr int kScreenHeightDivisor = 3;

  static void RegisterProfilePrefs(PrefRegistrySimple* registry, bool for_test);

  void BindRequest(mojom::DockedMagnifierControllerRequest request);

  // Get the Docked Magnifier settings for the current active user prefs.
  bool GetEnabled() const;
  float GetScale() const;

  // Set the Docked Magnifier settings in the current active user prefs.
  void SetEnabled(bool enabled);
  void SetScale(float scale);

  // Maps the current scale value to an index in the range between the minimum
  // and maximum scale values, and steps up or down the scale depending on the
  // value of |delta_index|.
  void StepToNextScaleValue(int delta_index);

  // ash::mojom::DockedMagnifierController:
  void CenterOnPoint(const gfx::Point& point_in_screen) override;

  // ash::SessionObserver:
  void OnActiveUserPrefServiceChanged(PrefService* pref_service) override;
  void OnSigninScreenPrefServiceInitialized(PrefService* prefs) override;

  // ui::EventHandler:
  void OnMouseEvent(ui::MouseEvent* event) override;
  void OnScrollEvent(ui::ScrollEvent* event) override;
  void OnTouchEvent(ui::TouchEvent* event) override;

  // ui::IMEBridgeObserver:
  void OnRequestSwitchEngine() override {}
  void OnInputContextHandlerChanged() override;

  // ui::InputMethodObserver:
  void OnFocus() override {}
  void OnBlur() override {}
  void OnTextInputStateChanged(const ui::TextInputClient* client) override {}
  void OnInputMethodDestroyed(const ui::InputMethod* input_method) override;
  void OnShowVirtualKeyboardIfEnabled() override {}
  void OnCaretBoundsChanged(const ui::TextInputClient* client) override;

  // views::WidgetObserver:
  void OnWidgetDestroying(views::Widget* widget) override;

  // ash::WindowTreeHostManager::Observer:
  void OnDisplayConfigurationChanged() override;

  // Getters and setters of the enabled status of the Fullscreen Magnifier.
  // We need these so that we can guarantee that both magnifiers are mutually
  // exclusive (i.e. only one can be on at the same time).
  // Note: We can't use the ash::MagnificationController since it's not hooked
  // to the associated user-prefs except when Chrome is running (via
  // chromeos::MagnificationManager), so we can't assert this behavior in
  // ash_unittests. Keep them public for now.
  // TODO(afakhry): Refactor the Fullscreen Magnifier and remove these
  // functions. https://crbug.com/817157.
  bool GetFullscreenMagnifierEnabled() const;
  void SetFullscreenMagnifierEnabled(bool enabled);

  const views::Widget* GetViewportWidgetForTesting() const;

  const ui::Layer* GetViewportMagnifierLayerForTesting() const;

  float GetMinimumPointOfInterestHeightForTesting() const;

 private:
  // Switches the current source root window to |new_root_window| if it's
  // different than |current_source_root_window_|, destroys (if any) old
  // viewport layers and widgets, and recreates them if |new_root_window| is not
  // |nullptr|.
  // In the event of a display removal in which the magnifier viewport was
  // resident, use |update_old_root_workarea = true| to avoid updating the
  // workarea of a removed display which involves re-layout of the shelf which
  // may have been destroyed.
  void SwitchCurrentSourceRootWindowIfNeeded(aura::Window* new_root_window,
                                             bool update_old_root_workarea);

  void InitFromUserPrefs();

  // Handlers of prefs changes.
  void OnEnabledPrefChanged();
  void OnScalePrefChanged();
  void OnFullscreenMagnifierEnabledPrefChanged();
  void OnHighContrastEnabledPrefChanged();

  void Refresh();

  void NotifyClientWithStatusChanged();

  void CreateMagnifierViewport();

  // Whenever there's a change that affects the screen size, rotation, the
  // current root window or the scale of the magnified view, this function is
  // used to recalculate (if needed) minimum height of the point of interest,
  // which is used to avoid translating the magnifier layer such that magnifier
  // viewport shows a magnified version of itself.
  void MaybeCachePointOfInterestMinimumHeight(aura::WindowTreeHost* host);

  // Prevents the mouse cursor from being able to enter inside the magnifier
  // viewport.
  void ConfineMouseCursorOutsideViewport();

  // The current root window of the source display from which we are reflecting
  // and magnifying into the viewport. It is set to |nullptr| when the magnifier
  // is disabled. The viewport is placed on the same display.
  aura::Window* current_source_root_window_ = nullptr;

  // The height below which the point of interest is not allowed to go. This is
  // so that we can avoid mirroring the magnifier viewport into itself.
  float minimum_point_of_interest_height_ = 0.0f;

  // Indicates the the above value is valid and doesn't need to be recalculated.
  bool is_minimum_point_of_interest_height_valid_ = false;

  // The viewport widget which occupies the top 1/4th of the current display on
  // which it is shown. It contains all the magnifier related layer.
  views::Widget* viewport_widget_ = nullptr;

  // A solid color layer that shows a dark gray background behind the magnifier
  // layer.
  std::unique_ptr<ui::Layer> viewport_background_layer_;

  // The layer into which the current display's compositor is reflected and
  // magnified. It is transformed such that only the area around the point of
  // interest shows up in the viewport.
  std::unique_ptr<ui::Layer> viewport_magnifier_layer_;

  // A solid color layer that shows a black line separating the magnifier
  // viewport from the rest of the display contents.
  std::unique_ptr<ui::Layer> separator_layer_;

  // Reflects the contents of the current display's compositor into the
  // viewport's magnifier layer.
  std::unique_ptr<ui::Reflector> reflector_;

  // The pref service of the currently active user. Can be null in
  // ash_unittests.
  PrefService* active_user_pref_service_ = nullptr;

  // The currently active input method, observed for caret bounds changes.
  ui::InputMethod* input_method_ = nullptr;

  std::unique_ptr<PrefChangeRegistrar> pref_change_registrar_;

  mojo::Binding<mojom::DockedMagnifierController> binding_;

  DISALLOW_COPY_AND_ASSIGN(DockedMagnifierController);
};

}  // namespace ash

#endif  // ASH_MAGNIFIER_DOCKED_MAGNIFIER_CONTROLLER_H_