// Copyright 2016 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 "third_party/blink/renderer/core/page/scrolling/root_scroller_controller.h"

#include "third_party/blink/renderer/core/css/style_change_reason.h"
#include "third_party/blink/renderer/core/dom/document.h"
#include "third_party/blink/renderer/core/dom/element.h"
#include "third_party/blink/renderer/core/frame/browser_controls.h"
#include "third_party/blink/renderer/core/frame/local_frame_view.h"
#include "third_party/blink/renderer/core/fullscreen/document_fullscreen.h"
#include "third_party/blink/renderer/core/html/html_frame_owner_element.h"
#include "third_party/blink/renderer/core/layout/layout_box.h"
#include "third_party/blink/renderer/core/layout/layout_embedded_content.h"
#include "third_party/blink/renderer/core/layout/layout_view.h"
#include "third_party/blink/renderer/core/page/chrome_client.h"
#include "third_party/blink/renderer/core/page/page.h"
#include "third_party/blink/renderer/core/page/scrolling/root_scroller_util.h"
#include "third_party/blink/renderer/core/page/scrolling/top_document_root_scroller_controller.h"
#include "third_party/blink/renderer/core/paint/compositing/paint_layer_compositor.h"
#include "third_party/blink/renderer/core/paint/paint_layer.h"
#include "third_party/blink/renderer/core/paint/paint_layer_scrollable_area.h"
#include "third_party/blink/renderer/core/scroll/scrollable_area.h"
#include "third_party/blink/renderer/platform/graphics/graphics_layer.h"
#include "third_party/blink/renderer/platform/instrumentation/tracing/trace_event.h"
#include "third_party/blink/renderer/platform/instrumentation/use_counter.h"

namespace blink {

class RootFrameViewport;

namespace {

bool FillsViewport(const Element& element) {
  if (!element.GetLayoutObject())
    return false;

  DCHECK(element.GetLayoutObject()->IsBox());

  LayoutBox* layout_box = ToLayoutBox(element.GetLayoutObject());

  // TODO(bokan): Broken for OOPIF. crbug.com/642378.
  Document& top_document = element.GetDocument().TopDocument();
  if (!top_document.GetLayoutView())
    return false;

  // We need to be more strict for iframes and use the content box since the
  // iframe will use the parent's layout size. Using the padding box would mean
  // the content would relayout on promotion/demotion. The layout size matching
  // the parent is done to ensure consistent semantics with respect to how the
  // mobile URL bar affects layout, which isn't a concern for non-iframe
  // elements because those semantics will already be applied to the element.
  PhysicalRect rect = layout_box->IsLayoutIFrame()
                          ? layout_box->PhysicalContentBoxRect()
                          : layout_box->PhysicalPaddingBoxRect();

  FloatQuad quad = layout_box->LocalRectToAbsoluteQuad(rect);

  if (!quad.IsRectilinear())
    return false;

  IntRect bounding_box = EnclosingIntRect(quad.BoundingBox());

  IntSize icb_size = top_document.GetLayoutView()->GetLayoutSize();

  float zoom = top_document.GetFrame()->PageZoomFactor();
  IntSize controls_hidden_size = ExpandedIntSize(
      top_document.View()->ViewportSizeForViewportUnits().ScaledBy(zoom));

  if (bounding_box.Size() != icb_size &&
      bounding_box.Size() != controls_hidden_size)
    return false;

  return bounding_box.Location() == IntPoint::Zero();
}

// If the element is an iframe this grabs the ScrollableArea for the owned
// LayoutView.
PaintLayerScrollableArea* GetScrollableArea(const Element& element) {
  if (const auto* frame_owner = DynamicTo<HTMLFrameOwnerElement>(element)) {
    EmbeddedContentView* content_view = frame_owner->OwnedEmbeddedContentView();
    if (!content_view)
      return nullptr;

    auto* frame_view = DynamicTo<LocalFrameView>(content_view);
    if (!frame_view)
      return nullptr;

    return frame_view->LayoutViewport();
  }

  DCHECK(element.GetLayoutObject()->IsBox());
  return ToLayoutBox(element.GetLayoutObject())->GetScrollableArea();
}

}  // namespace

RootScrollerController::RootScrollerController(Document& document)
    : document_(&document), effective_root_scroller_(&document) {}

void RootScrollerController::Trace(blink::Visitor* visitor) {
  visitor->Trace(document_);
  visitor->Trace(root_scroller_);
  visitor->Trace(effective_root_scroller_);
  visitor->Trace(implicit_candidates_);
  visitor->Trace(implicit_root_scroller_);
}

void RootScrollerController::Set(Element* new_root_scroller) {
  if (root_scroller_ == new_root_scroller)
    return;

  root_scroller_ = new_root_scroller;

  if (LocalFrame* frame = document_->GetFrame())
    frame->ScheduleVisualUpdateUnlessThrottled();
}

Element* RootScrollerController::Get() const {
  return root_scroller_;
}

Node& RootScrollerController::EffectiveRootScroller() const {
  DCHECK(effective_root_scroller_);
  return *effective_root_scroller_;
}

void RootScrollerController::DidResizeFrameView() {
  DCHECK(document_);

  Page* page = document_->GetPage();
  if (document_->GetFrame() && document_->GetFrame()->IsMainFrame() && page)
    page->GlobalRootScrollerController().DidResizeViewport();

  // If the effective root scroller in this Document is a Frame, it'll match
  // its parent's frame rect. We can't rely on layout to kick it to update its
  // geometry so we do so explicitly here.
  if (auto* frame_owner =
          DynamicTo<HTMLFrameOwnerElement>(EffectiveRootScroller())) {
    UpdateIFrameGeometryAndLayoutSize(*frame_owner);
  }
}

void RootScrollerController::DidUpdateIFrameFrameView(
    HTMLFrameOwnerElement& element) {
  if (&element != root_scroller_.Get() && &element != implicit_root_scroller_)
    return;

  // Ensure properties are re-applied even if the effective root scroller
  // doesn't change since the FrameView might have been swapped out and the new
  // one should have the properties reapplied.
  if (element.OwnedEmbeddedContentView())
    ApplyRootScrollerProperties(element);

  // Schedule a frame so we can reevaluate whether the iframe should be the
  // effective root scroller (e.g.  demote it if it became remote).
  if (LocalFrame* frame = document_->GetFrame())
    frame->ScheduleVisualUpdateUnlessThrottled();
}

void RootScrollerController::RecomputeEffectiveRootScroller() {
  ProcessImplicitCandidates();

  Node* new_effective_root_scroller = document_;

  if (!DocumentFullscreen::fullscreenElement(*document_)) {
    bool root_scroller_valid =
        root_scroller_ && IsValidRootScroller(*root_scroller_);
    if (root_scroller_valid) {
      new_effective_root_scroller = root_scroller_;
    } else if (implicit_root_scroller_) {
      new_effective_root_scroller = implicit_root_scroller_;
      UseCounter::Count(document_, WebFeature::kActivatedImplicitRootScroller);
    }
  }

  if (effective_root_scroller_ == new_effective_root_scroller)
    return;

  Node* old_effective_root_scroller = effective_root_scroller_;
  effective_root_scroller_ = new_effective_root_scroller;

  DCHECK(new_effective_root_scroller);
  if (LayoutBoxModelObject* new_obj =
          new_effective_root_scroller->GetLayoutBoxModelObject()) {
    if (new_obj->Layer()) {
      new_effective_root_scroller->GetLayoutBoxModelObject()
          ->Layer()
          ->SetNeedsCompositingInputsUpdate();
    }
  }

  DCHECK(old_effective_root_scroller);
  if (LayoutBoxModelObject* old_obj =
          old_effective_root_scroller->GetLayoutBoxModelObject()) {
    if (old_obj->Layer()) {
      old_effective_root_scroller->GetLayoutBoxModelObject()
          ->Layer()
          ->SetNeedsCompositingInputsUpdate();
    }
  }

  if (auto* object = old_effective_root_scroller->GetLayoutObject())
    object->SetIsEffectiveRootScroller(false);

  if (auto* object = new_effective_root_scroller->GetLayoutObject())
    object->SetIsEffectiveRootScroller(true);

  ApplyRootScrollerProperties(*old_effective_root_scroller);
  ApplyRootScrollerProperties(*effective_root_scroller_);

  if (Page* page = document_->GetPage())
    page->GlobalRootScrollerController().DidChangeRootScroller();
}

bool RootScrollerController::IsValidRootScroller(const Element& element) const {
  if (!element.IsInTreeScope())
    return false;

  if (!element.GetLayoutObject())
    return false;

  if (!element.GetLayoutObject()->IsBox())
    return false;

  // Ignore anything inside a FlowThread (multi-col, paginated, etc.).
  if (element.GetLayoutObject()->IsInsideFlowThread())
    return false;

  if (!element.GetLayoutObject()->HasOverflowClip() &&
      !element.IsFrameOwnerElement())
    return false;

  if (const auto* frame_owner = DynamicTo<HTMLFrameOwnerElement>(element)) {
    if (!frame_owner->OwnedEmbeddedContentView())
      return false;

    // TODO(bokan): Make work with OOPIF. crbug.com/642378.
    if (!frame_owner->OwnedEmbeddedContentView()->IsLocalFrameView())
      return false;
  }

  if (!FillsViewport(element))
    return false;

  return true;
}

bool RootScrollerController::IsValidImplicitCandidate(
    const Element& element) const {
  if (!element.IsInTreeScope())
    return false;

  if (!element.GetLayoutObject())
    return false;

  if (!element.GetLayoutObject()->IsBox())
    return false;

  // Ignore anything inside a FlowThread (multi-col, paginated, etc.).
  if (element.GetLayoutObject()->IsInsideFlowThread())
    return false;

  PaintLayerScrollableArea* scrollable_area = GetScrollableArea(element);
  if (!scrollable_area || !scrollable_area->ScrollsOverflow())
    return false;

  return true;
}

bool RootScrollerController::IsValidImplicit(const Element& element) const {
  // Valid implicit root scroller are a subset of valid root scrollers.
  if (!IsValidRootScroller(element))
    return false;

  const ComputedStyle* style = element.GetLayoutObject()->Style();
  if (!style)
    return false;

  // Do not implicitly promote things that are partially or fully invisible.
  if (style->HasOpacity() || style->Visibility() != EVisibility::kVisible)
    return false;

  PaintLayerScrollableArea* scrollable_area = GetScrollableArea(element);
  if (!scrollable_area)
    return false;

  if (!scrollable_area->ScrollsOverflow())
    return false;

  // If any of the ancestors clip overflow, don't promote. Promoting a
  // descendant of an overflow clip means it may not resize when the URL bar
  // hides so we'd leave a portion of the page hidden/unreachable.
  for (LayoutBox* ancestor = element.GetLayoutObject()->ContainingBlock();
       ancestor; ancestor = ancestor->ContainingBlock()) {
    // The LayoutView is allowed to have a clip (since its clip is resized by
    // the URL bar movement). Test it for scrolling so that we only promote if
    // we know we won't block scrolling the main document.
    if (ancestor->IsLayoutView()) {
      const ComputedStyle* ancestor_style = ancestor->Style();
      DCHECK(ancestor_style);

      PaintLayerScrollableArea* area = ancestor->GetScrollableArea();
      DCHECK(area);

      if (ancestor_style->ScrollsOverflowY() && area->HasVerticalOverflow())
        return false;
    } else {
      if (ancestor->ShouldClipOverflow() || ancestor->HasMask() ||
          ancestor->HasClip() || ancestor->HasClipPath()) {
        return false;
      }
    }
  }

  return true;
}

void RootScrollerController::ApplyRootScrollerProperties(Node& node) {
  DCHECK(document_->GetFrame());
  DCHECK(document_->GetFrame()->View());

  // If the node has been removed from the Document, we shouldn't be touching
  // anything related to the Frame- or Layout- hierarchies.
  if (!node.IsInTreeScope())
    return;

  auto* frame_owner = DynamicTo<HTMLFrameOwnerElement>(node);
  if (!frame_owner)
    return;

  // The current effective root scroller may have lost its ContentFrame. If
  // that's the case, there's nothing to be done. https://crbug.com/805317 for
  // an example of how we get here.
  if (!frame_owner->ContentFrame())
    return;

  if (IsA<LocalFrame>(frame_owner->ContentFrame())) {
    LocalFrameView* frame_view =
        DynamicTo<LocalFrameView>(frame_owner->OwnedEmbeddedContentView());

    bool is_root_scroller = &EffectiveRootScroller() == &node;

    // If we're making the Frame the root scroller, it must have a FrameView
    // by now.
    DCHECK(frame_view || !is_root_scroller);
    if (frame_view) {
      frame_view->SetLayoutSizeFixedToFrameSize(!is_root_scroller);
      UpdateIFrameGeometryAndLayoutSize(*frame_owner);
    }
  } else {
    // TODO(bokan): Make work with OOPIF. crbug.com/642378.
  }
}

void RootScrollerController::UpdateIFrameGeometryAndLayoutSize(
    HTMLFrameOwnerElement& frame_owner) const {
  DCHECK(document_->GetFrame());
  DCHECK(document_->GetFrame()->View());

  LocalFrameView* child_view =
      To<LocalFrameView>(frame_owner.OwnedEmbeddedContentView());

  if (!child_view)
    return;

  child_view->UpdateGeometry();

  if (&EffectiveRootScroller() == frame_owner)
    child_view->SetLayoutSize(document_->GetFrame()->View()->GetLayoutSize());
}

void RootScrollerController::ProcessImplicitCandidates() {
  implicit_root_scroller_ = nullptr;

  if (!RuntimeEnabledFeatures::ImplicitRootScrollerEnabled())
    return;

  if (!document_->GetLayoutView())
    return;

  if (!document_->GetFrame()->IsMainFrame())
    return;

  bool multiple_matches = false;

  HeapHashSet<WeakMember<Element>> copy(implicit_candidates_);
  for (auto& element : copy) {
    if (!IsValidImplicit(*element)) {
      if (!IsValidImplicitCandidate(*element))
        implicit_candidates_.erase(element);
      continue;
    }

    if (implicit_root_scroller_)
      multiple_matches = true;

    implicit_root_scroller_ = element;
  }

  // Only promote an implicit root scroller if we have a unique match.
  if (multiple_matches)
    implicit_root_scroller_ = nullptr;
}

PaintLayer* RootScrollerController::RootScrollerPaintLayer() const {
  return root_scroller_util::PaintLayerForRootScroller(
      effective_root_scroller_);
}

void RootScrollerController::ElementRemoved(const Element& element) {
  if (element != effective_root_scroller_.Get())
    return;

  effective_root_scroller_ = document_;
  if (Page* page = document_->GetPage())
    page->GlobalRootScrollerController().DidChangeRootScroller();
}

void RootScrollerController::ConsiderForImplicit(Node& node) {
  DCHECK(RuntimeEnabledFeatures::ImplicitRootScrollerEnabled());
  if (!document_->GetFrame()->IsMainFrame())
    return;

  if (document_->GetPage()->GetChromeClient().IsPopup())
    return;

  auto* element = DynamicTo<Element>(node);
  if (!element)
    return;

  if (!IsValidImplicitCandidate(*element))
    return;

  implicit_candidates_.insert(element);
}

template <typename Function>
void RootScrollerController::ForAllNonThrottledLocalControllers(
    const Function& function) {
  if (!document_->View() || !document_->GetFrame())
    return;

  LocalFrameView* frame_view = document_->View();
  if (frame_view->ShouldThrottleRendering())
    return;

  LocalFrame* frame = document_->GetFrame();
  for (Frame* child = frame->Tree().FirstChild(); child;
       child = child->Tree().NextSibling()) {
    auto* child_local_frame = DynamicTo<LocalFrame>(child);
    if (!child_local_frame)
      continue;
    if (Document* child_document = child_local_frame->GetDocument()) {
      child_document->GetRootScrollerController()
          .ForAllNonThrottledLocalControllers(function);
    }
  }

  function(*this);
}

void RootScrollerController::PerformRootScrollerSelection() {
  TRACE_EVENT0("blink", "RootScrollerController::PerformRootScrollerSelection");

  // Printing can cause a lifecycle update on a detached frame. In that case,
  // don't make any changes.
  if (!document_->GetFrame() || !document_->GetFrame()->IsLocalRoot())
    return;

  DCHECK(document_->Lifecycle().GetState() >= DocumentLifecycle::kLayoutClean);

  ForAllNonThrottledLocalControllers([](RootScrollerController& controller) {
    controller.RecomputeEffectiveRootScroller();
  });
}

}  // namespace blink