// Copyright 2020 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 "components/exo/extended_drag_source.h"

#include <memory>
#include <string>

#include "ash/shell.h"
#include "ash/wm/toplevel_window_event_handler.h"
#include "base/check.h"
#include "base/check_op.h"
#include "base/logging.h"
#include "base/notreached.h"
#include "base/optional.h"
#include "components/exo/data_source.h"
#include "components/exo/surface.h"
#include "ui/aura/client/aura_constants.h"
#include "ui/aura/window_observer.h"
#include "ui/base/dragdrop/drag_drop_types.h"
#include "ui/base/dragdrop/mojom/drag_drop_types.mojom-shared.h"
#include "ui/base/hit_test.h"
#include "ui/events/event.h"
#include "ui/events/event_target.h"
#include "ui/events/types/event_type.h"
#include "ui/gfx/geometry/point.h"
#include "ui/gfx/geometry/point_conversions.h"
#include "ui/gfx/geometry/point_f.h"
#include "ui/gfx/geometry/vector2d.h"
#include "ui/wm/core/coordinate_conversion.h"
#include "ui/wm/public/window_move_client.h"

namespace exo {

// static
ExtendedDragSource* ExtendedDragSource::instance_ = nullptr;

// Internal representation of a toplevel window, backed by an Exo shell surface,
// which is being dragged. It supports both already mapped/visible windows as
// well as newly created ones (i.e: not added to a root window yet), in which
// case OnDraggedWindowVisibilityChanging callback is called to notify when it
// is about to get visible.
class ExtendedDragSource::DraggedWindowHolder : public aura::WindowObserver {
 public:
  DraggedWindowHolder(Surface* surface,
                      const gfx::Vector2d& drag_offset,
                      ExtendedDragSource* source)
      : surface_(surface), drag_offset_(drag_offset), source_(source) {
    DCHECK(surface_);
    DCHECK(surface_->window());
    if (!FindToplevelWindow()) {
      DVLOG(1) << "Dragged window not added to root window yet.";
      surface_->window()->AddObserver(this);
    }
  }

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

  ~DraggedWindowHolder() override {
    if (toplevel_window_) {
      toplevel_window_->RemoveObserver(this);
      toplevel_window_ = nullptr;
    } else {
      surface_->window()->RemoveObserver(this);
    }
  }

  aura::Window* toplevel_window() { return toplevel_window_; }
  const gfx::Vector2d& offset() const { return drag_offset_; }

 private:
  // aura::WindowObserver:
  void OnWindowAddedToRootWindow(aura::Window* window) override {
    DCHECK_EQ(window, surface_->window());
    FindToplevelWindow();
    DCHECK(toplevel_window_);
    surface_->window()->RemoveObserver(this);
  }

  void OnWindowVisibilityChanging(aura::Window* window, bool visible) override {
    DCHECK(window);
    if (window == toplevel_window_)
      source_->OnDraggedWindowVisibilityChanging(visible);
  }

  bool FindToplevelWindow() {
    if (!surface_->window()->GetRootWindow())
      return false;

    toplevel_window_ = surface_->window()->GetToplevelWindow();
    toplevel_window_->AddObserver(this);
    return true;
  }

  Surface* const surface_;
  gfx::Vector2d drag_offset_;
  ExtendedDragSource* const source_;
  aura::Window* toplevel_window_ = nullptr;
};

// static
ExtendedDragSource* ExtendedDragSource::Get() {
  return instance_;
}

ExtendedDragSource::ExtendedDragSource(DataSource* source, Delegate* delegate)
    : source_(source), delegate_(delegate) {
  DCHECK(source_);
  DCHECK(delegate_);

  source_->AddObserver(this);

  DCHECK(!instance_);
  instance_ = this;
}

ExtendedDragSource::~ExtendedDragSource() {
  delegate_->OnDataSourceDestroying();
  for (auto& observer : observers_)
    observer.OnExtendedDragSourceDestroying(this);

  if (source_)
    source_->RemoveObserver(this);

  DCHECK_EQ(instance_, this);
  instance_ = nullptr;
}

void ExtendedDragSource::AddObserver(Observer* observer) {
  DCHECK(observer);
  observers_.AddObserver(observer);
}

void ExtendedDragSource::RemoveObserver(Observer* observer) {
  DCHECK(observer);
  observers_.RemoveObserver(observer);
}

void ExtendedDragSource::Drag(Surface* dragged_surface,
                              const gfx::Vector2d& drag_offset) {
  // Associated data source already destroyed.
  if (!source_)
    return;

  if (!dragged_surface) {
    DVLOG(1) << "Unsetting dragged surface.";
    dragged_window_holder_.reset();
    return;
  }

  DVLOG(1) << "Dragged surface changed:"
           << " surface=" << dragged_surface
           << " offset=" << drag_offset.ToString();

  // Ensure that the surface already has a "role" assigned.
  DCHECK(dragged_surface->HasSurfaceDelegate());
  dragged_window_holder_ =
      std::make_unique<DraggedWindowHolder>(dragged_surface, drag_offset, this);

  // Drag process will be started once OnDragStarted gets called.
}

bool ExtendedDragSource::IsActive() const {
  return !!source_;
}

void ExtendedDragSource::OnToplevelWindowDragStarted(
    const gfx::PointF& start_location,
    ui::mojom::DragEventSource source) {
  pointer_location_ = start_location;
  drag_event_source_ = source;
  MaybeLockCursor();

  if (dragged_window_holder_ && dragged_window_holder_->toplevel_window())
    StartDrag(dragged_window_holder_->toplevel_window(), start_location);
}

int ExtendedDragSource::OnToplevelWindowDragDropped() {
  DVLOG(1) << "OnDragDropped()";
  Cleanup();
  return delegate_->ShouldAllowDropAnywhere() ? ui::DragDropTypes::DRAG_MOVE
                                              : ui::DragDropTypes::DRAG_NONE;
}

void ExtendedDragSource::OnToplevelWindowDragCancelled() {
  DVLOG(1) << "OnDragCancelled()";
  // TODO(crbug.com/1099418): Handle cancellation/revert.
  Cleanup();
}

void ExtendedDragSource::OnToplevelWindowDragEvent(ui::LocatedEvent* event) {
  DCHECK(event);
  pointer_location_ = event->root_location_f();

  if (!dragged_window_holder_)
    return;

  auto* handler = ash::Shell::Get()->toplevel_window_event_handler();
  if (event->IsMouseEvent()) {
    handler->OnMouseEvent(event->AsMouseEvent());
    return;
  }

  // TODO(crbug.com/1099418): Support touch move source.
  NOTIMPLEMENTED() << "Non-mouse window dragging not supported yet.";
}

void ExtendedDragSource::OnDataSourceDestroying(DataSource* source) {
  DCHECK_EQ(source, source_);
  source_->RemoveObserver(this);
  source_ = nullptr;
}

void ExtendedDragSource::MaybeLockCursor() {
  if (delegate_->ShouldLockCursor()) {
    ash::Shell::Get()->cursor_manager()->LockCursor();
    cursor_locked_ = true;
  }
}

void ExtendedDragSource::UnlockCursor() {
  if (cursor_locked_) {
    ash::Shell::Get()->cursor_manager()->UnlockCursor();
    cursor_locked_ = false;
  }
}

void ExtendedDragSource::StartDrag(aura::Window* toplevel,
                                   const gfx::PointF& pointer_location) {
  // Ensure |toplevel| window does skip events while it's being dragged.
  event_blocker_ =
      std::make_unique<aura::ScopedWindowEventTargetingBlocker>(toplevel);

  // Disable visibility change animations on the dragged window.
  toplevel->SetProperty(aura::client::kAnimationsDisabledKey, true);

  DVLOG(1) << "Starting drag. pointer_loc=" << pointer_location.ToString();
  auto* toplevel_handler = ash::Shell::Get()->toplevel_window_event_handler();
  auto move_source = drag_event_source_ == ui::mojom::DragEventSource::kTouch
                         ? ::wm::WINDOW_MOVE_SOURCE_TOUCH
                         : ::wm::WINDOW_MOVE_SOURCE_MOUSE;
  toplevel_handler->AttemptToStartDrag(
      toplevel, pointer_location, HTCAPTION, move_source,
      ash::ToplevelWindowEventHandler::EndClosure(),
      /*update_gesture_target=*/true, /*grab_capture=*/false);
}

void ExtendedDragSource::OnDraggedWindowVisibilityChanging(bool visible) {
  DCHECK(dragged_window_holder_);
  DVLOG(1) << "Dragged window visibility changed. visible=" << visible;

  if (!visible) {
    dragged_window_holder_.reset();
    return;
  }

  aura::Window* toplevel = dragged_window_holder_->toplevel_window();
  DCHECK(toplevel);

  // The |toplevel| window for the dragged surface has just been created and
  // it's about to be mapped. Calculate and set its position based on
  // |drag_offset_| and |pointer_location_| before starting the actual drag.
  auto screen_location = CalculateOrigin(toplevel);
  toplevel->SetBounds({screen_location, toplevel->bounds().size()});

  DVLOG(1) << "Dragged window mapped. toplevel=" << toplevel
           << " origin=" << screen_location.ToString();

  gfx::PointF pointer_location(screen_location +
                               dragged_window_holder_->offset());
  StartDrag(toplevel, pointer_location);
}

gfx::Point ExtendedDragSource::CalculateOrigin(aura::Window* target) const {
  DCHECK(dragged_window_holder_);
  gfx::Point screen_location = gfx::ToRoundedPoint(pointer_location_);
  wm::ConvertPointToScreen(target->GetRootWindow(), &screen_location);
  return screen_location - dragged_window_holder_->offset();
}

void ExtendedDragSource::Cleanup() {
  if (dragged_window_holder_ && dragged_window_holder_->toplevel_window()) {
    dragged_window_holder_->toplevel_window()->ClearProperty(
        aura::client::kAnimationsDisabledKey);
  }
  event_blocker_.reset();
  dragged_window_holder_.reset();
  UnlockCursor();
}

aura::Window* ExtendedDragSource::GetDraggedWindowForTesting() {
  return dragged_window_holder_ ? dragged_window_holder_->toplevel_window()
                                : nullptr;
}

base::Optional<gfx::Vector2d> ExtendedDragSource::GetDragOffsetForTesting()
    const {
  return dragged_window_holder_
             ? base::Optional<gfx::Vector2d>(dragged_window_holder_->offset())
             : base::nullopt;
}

}  // namespace exo