// Copyright 2017 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "cobalt/layout/topmost_event_target.h"

#include "base/debug/trace_event.h"
#include "base/optional.h"
#include "cobalt/base/token.h"
#include "cobalt/base/tokens.h"
#include "cobalt/cssom/keyword_value.h"
#include "cobalt/dom/document.h"
#include "cobalt/dom/event.h"
#include "cobalt/dom/html_element.h"
#include "cobalt/dom/html_html_element.h"
#include "cobalt/dom/mouse_event.h"
#include "cobalt/dom/mouse_event_init.h"
#include "cobalt/dom/pointer_event.h"
#include "cobalt/dom/pointer_event_init.h"
#include "cobalt/dom/pointer_state.h"
#include "cobalt/dom/ui_event.h"
#include "cobalt/dom/wheel_event.h"
#include "cobalt/math/vector2d.h"
#include "cobalt/math/vector2d_f.h"

namespace cobalt {
namespace layout {

scoped_refptr<dom::HTMLElement> TopmostEventTarget::FindTopmostEventTarget(
    const scoped_refptr<dom::Document>& document,
    const math::Vector2dF& coordinate) {
  TRACE_EVENT0("cobalt::layout",
               "TopmostEventTarget::FindTopmostEventTarget()");
  DCHECK(document);
  DCHECK(!box_);
  DCHECK(render_sequence_.empty());

  // Make sure the document's layout box tree is up-to-date.
  document->DoSynchronousLayout();

  html_element_ = document->html();
  ConsiderElement(html_element_, coordinate);
  box_ = NULL;
  render_sequence_.clear();
  document->SetIndicatedElement(html_element_);
  scoped_refptr<dom::HTMLElement> topmost_element;
  topmost_element.swap(html_element_);
  DCHECK(!html_element_);
  return topmost_element;
}

namespace {

LayoutBoxes* GetLayoutBoxesIfNotEmpty(dom::Element* element) {
  dom::HTMLElement* html_element = element->AsHTMLElement();
  if (html_element && html_element->computed_style()) {
    dom::LayoutBoxes* dom_layout_boxes = html_element->layout_boxes();
    if (dom_layout_boxes &&
        dom_layout_boxes->type() == dom::LayoutBoxes::kLayoutLayoutBoxes) {
      LayoutBoxes* layout_boxes =
          base::polymorphic_downcast<LayoutBoxes*>(dom_layout_boxes);
      if (!layout_boxes->boxes().empty()) {
        return layout_boxes;
      }
    }
  }
  return NULL;
}

}  // namespace
void TopmostEventTarget::ConsiderElement(dom::Element* element,
                                         const math::Vector2dF& coordinate) {
  if (!element) return;
  math::Vector2dF element_coordinate(coordinate);
  LayoutBoxes* layout_boxes = GetLayoutBoxesIfNotEmpty(element);
  if (layout_boxes) {
    const Box* box = layout_boxes->boxes().front();
    if (box->computed_style() && box->IsTransformed()) {
      // Early out if the transform cannot be applied. This can occur if the
      // transform matrix is not invertible.
      if (!box->ApplyTransformActionToCoordinate(Box::kEnterTransform,
                                                 &element_coordinate)) {
        return;
      }
    }

    scoped_refptr<dom::HTMLElement> html_element = element->AsHTMLElement();
    if (html_element && html_element->CanbeDesignatedByPointerIfDisplayed()) {
      ConsiderBoxes(html_element, layout_boxes, element_coordinate);
    }
  }

  for (dom::Element* child_element = element->first_element_child();
       child_element; child_element = child_element->next_element_sibling()) {
    ConsiderElement(child_element, element_coordinate);
  }
}

void TopmostEventTarget::ConsiderBoxes(
    const scoped_refptr<dom::HTMLElement>& html_element,
    LayoutBoxes* layout_boxes, const math::Vector2dF& coordinate) {
  const Boxes& boxes = layout_boxes->boxes();
  Vector2dLayoutUnit layout_coordinate(LayoutUnit(coordinate.x()),
                                       LayoutUnit(coordinate.y()));
  for (Boxes::const_iterator box_iterator = boxes.begin();
       box_iterator != boxes.end(); ++box_iterator) {
    Box* box = *box_iterator;
    do {
      if (box->IsUnderCoordinate(layout_coordinate)) {
        Box::RenderSequence render_sequence = box->GetRenderSequence();
        if (Box::IsRenderedLater(render_sequence, render_sequence_)) {
          html_element_ = html_element;
          box_ = box;
          render_sequence_.swap(render_sequence);
        }
      }
      box = box->GetSplitSibling();
    } while (box != NULL);
  }
}

namespace {
void SendStateChangeEvents(bool is_pointer_event,
                           scoped_refptr<dom::HTMLElement> previous_element,
                           scoped_refptr<dom::HTMLElement> target_element,
                           dom::PointerEventInit* event_init) {
  // Send enter/leave/over/out (status change) events when needed.
  if (previous_element != target_element) {
    const scoped_refptr<dom::Window>& view = event_init->view();

    // The enter/leave status change events apply to all ancestors up to the
    // nearest common ancestor between the previous and current element.
    scoped_refptr<dom::Element> nearest_common_ancestor;

    // Send out and leave events.
    if (previous_element) {
      event_init->set_related_target(target_element);
      if (is_pointer_event) {
        previous_element->DispatchEvent(new dom::PointerEvent(
            base::Tokens::pointerout(), view, *event_init));
      }
      previous_element->DispatchEvent(
          new dom::MouseEvent(base::Tokens::mouseout(), view, *event_init));

      // Find the nearest common ancestor, if there is any.
      dom::Document* previous_document = previous_element->node_document();
      if (previous_document) {
        if (target_element &&
            previous_document == target_element->node_document()) {
          // The nearest ancestor of the current element that is already
          // designated is the nearest common ancestor of it and the previous
          // element.
          nearest_common_ancestor = target_element;
          while (nearest_common_ancestor &&
                 nearest_common_ancestor->AsHTMLElement() &&
                 !nearest_common_ancestor->AsHTMLElement()->IsDesignated()) {
            nearest_common_ancestor = nearest_common_ancestor->parent_element();
          }
        }

        for (scoped_refptr<dom::Element> element = previous_element;
             element && element != nearest_common_ancestor;
             element = element->parent_element()) {
          if (is_pointer_event) {
            element->DispatchEvent(new dom::PointerEvent(
                base::Tokens::pointerleave(), dom::Event::kNotBubbles,
                dom::Event::kNotCancelable, view, *event_init));
          }
          element->DispatchEvent(new dom::MouseEvent(
              base::Tokens::mouseleave(), dom::Event::kNotBubbles,
              dom::Event::kNotCancelable, view, *event_init));
        }

        if (!target_element ||
            previous_document != target_element->node_document()) {
          previous_document->SetIndicatedElement(NULL);
        }
      }
    }

    // Send over and enter events.
    if (target_element) {
      event_init->set_related_target(previous_element);
      if (is_pointer_event) {
        target_element->DispatchEvent(new dom::PointerEvent(
            base::Tokens::pointerover(), view, *event_init));
      }
      target_element->DispatchEvent(
          new dom::MouseEvent(base::Tokens::mouseover(), view, *event_init));

      for (scoped_refptr<dom::Element> element = target_element;
           element != nearest_common_ancestor;
           element = element->parent_element()) {
        if (is_pointer_event) {
          element->DispatchEvent(new dom::PointerEvent(
              base::Tokens::pointerenter(), dom::Event::kNotBubbles,
              dom::Event::kNotCancelable, view, *event_init));
        }
        element->DispatchEvent(new dom::MouseEvent(
            base::Tokens::mouseenter(), dom::Event::kNotBubbles,
            dom::Event::kNotCancelable, view, *event_init));
      }
    }
  }
}

void SendCompatibilityMappingMouseEvent(
    const scoped_refptr<dom::HTMLElement>& target_element,
    const scoped_refptr<dom::Event>& event,
    const dom::PointerEvent* pointer_event,
    const dom::PointerEventInit& event_init,
    std::set<std::string>* mouse_event_prevent_flags) {
  // Send compatibility mapping mouse event if needed.
  //   https://www.w3.org/TR/2015/REC-pointerevents-20150224/#compatibility-mapping-with-mouse-events
  bool has_compatibility_mouse_event = true;
  base::Token type = pointer_event->type();
  if (type == base::Tokens::pointerdown()) {
    // If the pointer event dispatched was pointerdown and the event was
    // canceled, then set the PREVENT MOUSE EVENT flag for this pointerType.
    if (event->default_prevented()) {
      mouse_event_prevent_flags->insert(pointer_event->pointer_type());
      has_compatibility_mouse_event = false;
    } else {
      type = base::Tokens::mousedown();
    }
  } else {
    has_compatibility_mouse_event =
        mouse_event_prevent_flags->find(pointer_event->pointer_type()) ==
        mouse_event_prevent_flags->end();
    if (type == base::Tokens::pointerup()) {
      // If the pointer event dispatched was pointerup, clear the PREVENT
      // MOUSE EVENT flag for this pointerType.
      mouse_event_prevent_flags->erase(pointer_event->pointer_type());
      type = base::Tokens::mouseup();
    } else if (type == base::Tokens::pointermove()) {
      type = base::Tokens::mousemove();
    } else {
      has_compatibility_mouse_event = false;
    }
  }
  if (has_compatibility_mouse_event) {
    target_element->DispatchEvent(
        new dom::MouseEvent(type, event_init.view(), event_init));
  }
}

void InitializePointerEventInitFromEvent(
    const dom::MouseEvent* const mouse_event,
    const dom::PointerEvent* pointer_event, dom::PointerEventInit* event_init) {
  // For EventInit
  event_init->set_bubbles(mouse_event->bubbles());
  event_init->set_cancelable(mouse_event->cancelable());

  // For UIEventInit
  event_init->set_view(mouse_event->view());
  event_init->set_detail(mouse_event->detail());
  event_init->set_which(mouse_event->which());

  // For EventModifierInit
  event_init->set_ctrl_key(mouse_event->ctrl_key());
  event_init->set_shift_key(mouse_event->shift_key());
  event_init->set_alt_key(mouse_event->alt_key());
  event_init->set_meta_key(mouse_event->meta_key());

  // For MouseEventInit
  event_init->set_screen_x(mouse_event->screen_x());
  event_init->set_screen_y(mouse_event->screen_y());
  event_init->set_client_x(mouse_event->screen_x());
  event_init->set_client_y(mouse_event->screen_y());
  event_init->set_button(mouse_event->button());
  event_init->set_buttons(mouse_event->buttons());
  event_init->set_related_target(mouse_event->related_target());
  if (pointer_event) {
    // For PointerEventInit
    event_init->set_pointer_id(pointer_event->pointer_id());
    event_init->set_width(pointer_event->width());
    event_init->set_height(pointer_event->height());
    event_init->set_pressure(pointer_event->pressure());
    event_init->set_tilt_x(pointer_event->tilt_x());
    event_init->set_tilt_y(pointer_event->tilt_y());
    event_init->set_pointer_type(pointer_event->pointer_type());
    event_init->set_is_primary(pointer_event->is_primary());
  }
}
}  // namespace

void TopmostEventTarget::MaybeSendPointerEvents(
    const scoped_refptr<dom::Event>& event) {
  TRACE_EVENT0("cobalt::layout",
               "TopmostEventTarget::MaybeSendPointerEvents()");

  const dom::MouseEvent* const mouse_event =
      base::polymorphic_downcast<const dom::MouseEvent* const>(event.get());
  DCHECK(mouse_event);
  DCHECK(!html_element_);
  const dom::PointerEvent* pointer_event =
      (event->GetWrappableType() == base::GetTypeId<dom::PointerEvent>())
          ? base::polymorphic_downcast<const dom::PointerEvent* const>(
                event.get())
          : NULL;
  bool is_touchpad_event = false;

  // The target override element for the pointer event. This may not be the same
  // as the hit test target, and it also may not be set.
  scoped_refptr<dom::HTMLElement> target_override_element;

  // Store the data for the status change and pointer capture event(s).
  dom::PointerEventInit event_init;
  InitializePointerEventInitFromEvent(mouse_event, pointer_event, &event_init);
  const scoped_refptr<dom::Window>& view = event_init.view();
  if (!view) {
    return;
  }
  dom::PointerState* pointer_state = view->document()->pointer_state();
  if (pointer_event) {
    pointer_state->SetActiveButtonsState(pointer_event->pointer_id(),
                                         pointer_event->buttons());
    is_touchpad_event = pointer_event->pointer_type() == "touchpad";
    if (is_touchpad_event) {
      if (pointer_event->type() == base::Tokens::pointerdown()) {
        pointer_state->SetActive(pointer_event->pointer_id());
        // Implicitly capture the pointer to the active element.
        //   https://www.w3.org/TR/pointerevents/#implicit-pointer-capture
        scoped_refptr<dom::HTMLElement> html_element =
            view->document()->active_element()->AsHTMLElement();
        if (html_element) {
          pointer_state->SetPendingPointerCaptureTargetOverride(
              pointer_event->pointer_id(), html_element);
        }
      }
    } else {
      pointer_state->SetActive(pointer_event->pointer_id());
    }
    target_override_element = pointer_state->GetPointerCaptureOverrideElement(
        pointer_event->pointer_id(), &event_init);
  }

  scoped_refptr<dom::HTMLElement> target_element;
  if (target_override_element) {
    target_element = target_override_element;
  } else {
    // Do a hit test if there is no target override element.
    math::Vector2dF coordinate(static_cast<float>(event_init.client_x()),
                               static_cast<float>(event_init.client_y()));
    target_element = FindTopmostEventTarget(view->document(), coordinate);
  }

  if (target_element) {
    target_element->DispatchEvent(event);
  }

  if (pointer_event) {
    if (pointer_event->type() == base::Tokens::pointerup()) {
      if (is_touchpad_event) {
        // A touchpad becomes inactive after a pointerup.
        pointer_state->ClearActive(pointer_event->pointer_id());
      }
      // Implicit release of pointer capture.
      //   https://www.w3.org/TR/pointerevents/#implicit-release-of-pointer-capture
      pointer_state->ClearPendingPointerCaptureTargetOverride(
          pointer_event->pointer_id());
    }
    if (target_element && !is_touchpad_event) {
      SendCompatibilityMappingMouseEvent(target_element, event, pointer_event,
                                         event_init,
                                         &mouse_event_prevent_flags_);
    }
  }

  if (target_element && !is_touchpad_event) {
    // Send the click event if needed, which is not prevented by canceling the
    // pointerdown event.
    //   https://www.w3.org/TR/uievents/#event-type-click
    //   https://www.w3.org/TR/pointerevents/#compatibility-mapping-with-mouse-events
    if (event_init.button() == 0 &&
        ((mouse_event->type() == base::Tokens::pointerup()) ||
         (mouse_event->type() == base::Tokens::mouseup()))) {
      target_element->DispatchEvent(
          new dom::MouseEvent(base::Tokens::click(), view, event_init));
    }
  }

  scoped_refptr<dom::HTMLElement> previous_html_element(
      previous_html_element_weak_);

  SendStateChangeEvents(pointer_event, previous_html_element, target_element,
                        &event_init);

  if (target_element) {
    previous_html_element_weak_ = base::AsWeakPtr(target_element.get());
  } else {
    previous_html_element_weak_.reset();
  }
  DCHECK(!html_element_);
}

}  // namespace layout
}  // namespace cobalt