// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_TIMING_LAYOUT_SHIFT_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_TIMING_LAYOUT_SHIFT_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/dom/dom_high_res_time_stamp.h"
#include "third_party/blink/renderer/core/timing/layout_shift_attribution.h"
#include "third_party/blink/renderer/core/timing/performance_entry.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_vector.h"
#include "third_party/blink/renderer/platform/wtf/casting.h"

namespace blink {

// Exposes the layout shift score of an animation frame, computed as described
// in http://bit.ly/lsm-explainer.
class CORE_EXPORT LayoutShift final : public PerformanceEntry {
  DEFINE_WRAPPERTYPEINFO();

 public:
  // Maximum number of attributions (shifted elements) to record in any single
  // animation frame.
  static constexpr int kMaxAttributions = 5;
  // AttributionList contains up to kMaxAttributions elements, sorted by
  // impact area in descending order (largest first). Impact area is the
  // union of previousRect and currentRect for each attribution.
  typedef HeapVector<Member<LayoutShiftAttribution>, kMaxAttributions>
      AttributionList;

  static LayoutShift* Create(double start_time,
                             double value,
                             bool input_detected,
                             double input_timestamp,
                             AttributionList sources,
                             DOMWindow* source,
                             uint64_t navigation_id);

  explicit LayoutShift(double start_time,
                       double value,
                       bool input_detected,
                       double input_timestamp,
                       AttributionList sources,
                       DOMWindow* source,
                       uint64_t navigation_id);

  ~LayoutShift() override;

  const AtomicString& entryType() const override;
  PerformanceEntryType EntryTypeEnum() const override;

  double value() const { return value_; }
  bool hadRecentInput() const { return had_recent_input_; }
  double lastInputTime() const { return most_recent_input_timestamp_; }

  const AttributionList& sources() const { return sources_; }

  void Trace(Visitor*) const override;

 private:
  void BuildJSONValue(V8ObjectBuilder&) const override;

  double value_;
  bool had_recent_input_;
  DOMHighResTimeStamp most_recent_input_timestamp_;
  AttributionList sources_;
};

template <>
struct DowncastTraits<LayoutShift> {
  static bool AllowFrom(const PerformanceEntry& entry) {
    return entry.EntryTypeEnum() == PerformanceEntry::EntryType::kLayoutShift;
  }
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_TIMING_LAYOUT_SHIFT_H_