// Copyright 2014 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 "cc/input/scroll_elasticity_helper.h"

#include "cc/layers/layer_impl.h"
#include "cc/trees/layer_tree_host_impl.h"
#include "cc/trees/layer_tree_impl.h"

namespace cc {

class ScrollElasticityHelperImpl : public ScrollElasticityHelper {
 public:
  explicit ScrollElasticityHelperImpl(LayerTreeHostImpl* layer_tree_host_impl);
  ~ScrollElasticityHelperImpl() override;

  bool IsUserScrollable() const override;
  gfx::Vector2dF StretchAmount() const override;
  void SetStretchAmount(const gfx::Vector2dF& stretch_amount) override;
  gfx::ScrollOffset ScrollOffset() const override;
  gfx::ScrollOffset MaxScrollOffset() const override;
  void ScrollBy(const gfx::Vector2dF& delta) override;
  void RequestOneBeginFrame() override;

 private:
  LayerTreeHostImpl* layer_tree_host_impl_;
};

ScrollElasticityHelperImpl::ScrollElasticityHelperImpl(
    LayerTreeHostImpl* layer_tree)
    : layer_tree_host_impl_(layer_tree) {
}

ScrollElasticityHelperImpl::~ScrollElasticityHelperImpl() {
}

bool ScrollElasticityHelperImpl::IsUserScrollable() const {
  LayerImpl* layer = layer_tree_host_impl_->OuterViewportScrollLayer();
  if (!layer)
    return false;
  return layer->user_scrollable_horizontal() ||
         layer->user_scrollable_vertical();
}

gfx::Vector2dF ScrollElasticityHelperImpl::StretchAmount() const {
  return layer_tree_host_impl_->active_tree()->elastic_overscroll()->Current(
      true);
}

void ScrollElasticityHelperImpl::SetStretchAmount(
    const gfx::Vector2dF& stretch_amount) {
  if (stretch_amount == StretchAmount())
    return;

  layer_tree_host_impl_->active_tree()->elastic_overscroll()->SetCurrent(
      stretch_amount);
  layer_tree_host_impl_->active_tree()->set_needs_update_draw_properties();
  layer_tree_host_impl_->SetNeedsCommit();
  layer_tree_host_impl_->SetNeedsRedraw();
  layer_tree_host_impl_->SetFullViewportDamage();
}

gfx::ScrollOffset ScrollElasticityHelperImpl::ScrollOffset() const {
  return layer_tree_host_impl_->active_tree()->TotalScrollOffset();
}

gfx::ScrollOffset ScrollElasticityHelperImpl::MaxScrollOffset() const {
  return layer_tree_host_impl_->active_tree()->TotalMaxScrollOffset();
}

void ScrollElasticityHelperImpl::ScrollBy(const gfx::Vector2dF& delta) {
  LayerImpl* root_scroll_layer =
      layer_tree_host_impl_->OuterViewportScrollLayer()
          ? layer_tree_host_impl_->OuterViewportScrollLayer()
          : layer_tree_host_impl_->InnerViewportScrollLayer();
  if (root_scroll_layer)
    root_scroll_layer->ScrollBy(delta);
}

void ScrollElasticityHelperImpl::RequestOneBeginFrame() {
  layer_tree_host_impl_->SetNeedsOneBeginImplFrame();
}

// static
ScrollElasticityHelper* ScrollElasticityHelper::CreateForLayerTreeHostImpl(
    LayerTreeHostImpl* layer_tree_host_impl) {
  return new ScrollElasticityHelperImpl(layer_tree_host_impl);
}

}  // namespace cc
