// Copyright 2019 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.

#include "ash/home_screen/home_screen_controller.h"

#include "ash/home_screen/home_launcher_gesture_handler.h"
#include "ash/home_screen/home_screen_delegate.h"
#include "ash/public/cpp/shell_window_ids.h"
#include "ash/session/session_controller_impl.h"
#include "ash/shelf/shelf.h"
#include "ash/shell.h"
#include "ash/wallpaper/wallpaper_controller.h"
#include "ash/wm/mru_window_tracker.h"
#include "ash/wm/overview/overview_controller.h"
#include "ash/wm/overview/overview_session.h"
#include "ash/wm/splitview/split_view_controller.h"
#include "ash/wm/tablet_mode/tablet_mode_controller.h"
#include "ash/wm/window_state.h"
#include "base/logging.h"
#include "ui/aura/window.h"
#include "ui/display/manager/display_manager.h"

namespace ash {
namespace {

// Minimizes all windows that aren't in the home screen container. Done in
// reverse order to preserve the mru ordering.
// Returns true if any windows are minimized.
bool MinimizeAllWindows() {
  bool handled = false;
  aura::Window* container = Shell::Get()->GetPrimaryRootWindow()->GetChildById(
      kShellWindowId_HomeScreenContainer);
  aura::Window::Windows windows =
      Shell::Get()->mru_window_tracker()->BuildWindowForCycleList();
  for (auto it = windows.rbegin(); it != windows.rend(); it++) {
    if (!container->Contains(*it) && !wm::GetWindowState(*it)->IsMinimized()) {
      wm::GetWindowState(*it)->Minimize();
      handled = true;
    }
  }
  return handled;
}

}  // namespace

HomeScreenController::HomeScreenController()
    : home_launcher_gesture_handler_(
          std::make_unique<HomeLauncherGestureHandler>()) {
  Shell::Get()->overview_controller()->AddObserver(this);
  Shell::Get()->wallpaper_controller()->AddObserver(this);
}

HomeScreenController::~HomeScreenController() {
  Shell::Get()->wallpaper_controller()->RemoveObserver(this);
  Shell::Get()->overview_controller()->RemoveObserver(this);
}

bool HomeScreenController::IsHomeScreenAvailable() {
  return Shell::Get()
      ->tablet_mode_controller()
      ->IsTabletModeWindowManagerEnabled();
}

void HomeScreenController::Show() {
  DCHECK(IsHomeScreenAvailable());

  if (!Shell::Get()->session_controller()->IsActiveUserSessionStarted())
    return;

  delegate_->ShowHomeScreenView();
  UpdateVisibility();

  aura::Window* window = delegate_->GetHomeScreenWindow();
  if (window)
    Shelf::ForWindow(window)->MaybeUpdateShelfBackground();
}

bool HomeScreenController::GoHome(int64_t display_id) {
  DCHECK(IsHomeScreenAvailable());

  if (home_launcher_gesture_handler_->ShowHomeLauncher(
          Shell::Get()->display_manager()->GetDisplayForId(display_id))) {
    return true;
  }

  if (Shell::Get()->overview_controller()->InOverviewSession()) {
    // End overview mode.
    Shell::Get()->overview_controller()->ToggleOverview(
        OverviewSession::EnterExitOverviewType::kWindowsMinimized);
    return true;
  }

  if (Shell::Get()->split_view_controller()->InSplitViewMode()) {
    // End split view mode.
    Shell::Get()->split_view_controller()->EndSplitView(
        SplitViewController::EndReason::kHomeLauncherPressed);
    return true;
  }

  if (MinimizeAllWindows())
    return true;

  return false;
}

void HomeScreenController::SetDelegate(HomeScreenDelegate* delegate) {
  delegate_ = delegate;
}

void HomeScreenController::OnWindowDragStarted() {
  in_window_dragging_ = true;
  UpdateVisibility();
}

void HomeScreenController::OnWindowDragEnded() {
  in_window_dragging_ = false;
  UpdateVisibility();
}

void HomeScreenController::OnOverviewModeStarting() {
  // Only animate the home screen when overview mode is using slide animation.
  bool animate = Shell::Get()
                     ->overview_controller()
                     ->overview_session()
                     ->enter_exit_overview_type() ==
                 OverviewSession::EnterExitOverviewType::kWindowsMinimized;
  home_screen_presenter_.ScheduleOverviewModeAnimation(true /* start */,
                                                       animate);
}

void HomeScreenController::OnOverviewModeEnding(
    OverviewSession* overview_session) {
  // Animate the launcher if overview mode is sliding out. Let
  // OnOverviewModeEndingAnimationComplete handle showing the launcher after
  // overview mode finishes animating. Overview however is nullptr by the
  // time the animations are finished, so we need to check the animation type
  // here.
  use_slide_to_exit_overview_ =
      overview_session->enter_exit_overview_type() ==
      OverviewSession::EnterExitOverviewType::kWindowsMinimized;
}

void HomeScreenController::OnOverviewModeEndingAnimationComplete(
    bool canceled) {
  if (canceled)
    return;
  home_screen_presenter_.ScheduleOverviewModeAnimation(
      false /* start */, use_slide_to_exit_overview_);
}

void HomeScreenController::OnWallpaperPreviewStarted() {
  in_wallpaper_preview_ = true;
  UpdateVisibility();
}

void HomeScreenController::OnWallpaperPreviewEnded() {
  in_wallpaper_preview_ = false;
  UpdateVisibility();
}

void HomeScreenController::UpdateVisibility() {
  if (!IsHomeScreenAvailable())
    return;

  aura::Window* window = delegate_->GetHomeScreenWindow();
  if (!window)
    return;

  const bool in_overview =
      Shell::Get()->overview_controller()->InOverviewSession();
  if (in_overview || in_wallpaper_preview_ || in_window_dragging_)
    window->Hide();
  else
    window->Show();
}

}  // namespace ash