// 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 "ui/events/gestures/blink/web_gesture_curve_impl.h"

#include <limits.h>

#include <utility>

#include "base/metrics/histogram_macros.h"
#include "build/build_config.h"
#include "ui/base/ui_base_features.h"
#include "ui/events/gestures/fixed_velocity_curve.h"
#include "ui/events/gestures/fling_curve.h"
#include "ui/events/gestures/physics_based_fling_curve.h"
#include "ui/events/mobile_scroller.h"

#if defined(OS_WIN)
#include "ui/display/win/screen_win.h"
#endif  // defined(OS_WIN)

using blink::WebGestureCurve;

namespace ui {
namespace {

constexpr float kDefaultPixelsPerInch = 96.0f;
std::unique_ptr<GestureCurve> CreateDefaultPlatformCurve(
    blink::WebGestureDevice device_source,
    const gfx::Vector2dF& initial_velocity,
    bool use_mobile_fling_curve,
    const gfx::PointF& position_in_screen,
    const float boost_multiplier,
    const gfx::Size& bounding_size) {
  if (device_source == blink::WebGestureDevice::kSyntheticAutoscroll) {
    return std::make_unique<FixedVelocityCurve>(initial_velocity,
                                                base::TimeTicks());
  }

#ifdef USE_MOBILE_FLING_CURVE
  use_mobile_fling_curve = true;
#endif

  if (use_mobile_fling_curve) {
    MobileScroller::Config config;
#ifdef USE_MOBILE_FLING_CURVE
    config.chromecast_optimized = true;
#endif
    auto scroller = std::make_unique<MobileScroller>(config);
    scroller->Fling(0, 0, initial_velocity.x(), initial_velocity.y(), INT_MIN,
                    INT_MAX, INT_MIN, INT_MAX, base::TimeTicks());
    return std::move(scroller);
  }

  if (base::FeatureList::IsEnabled(features::kExperimentalFlingAnimation)) {
    gfx::Vector2dF pixels_per_inch(kDefaultPixelsPerInch,
                                   kDefaultPixelsPerInch);
#if defined(OS_WIN)
    pixels_per_inch =
        display::win::ScreenWin::GetPixelsPerInch(position_in_screen);
#endif  // define(OS_WIN)
    return std::make_unique<PhysicsBasedFlingCurve>(
        initial_velocity, base::TimeTicks(), pixels_per_inch, boost_multiplier,
        bounding_size);
  }

  return std::make_unique<FlingCurve>(initial_velocity, base::TimeTicks());
}

}  // namespace

// static
std::unique_ptr<WebGestureCurve>
WebGestureCurveImpl::CreateFromDefaultPlatformCurve(
    blink::WebGestureDevice device_source,
    const gfx::Vector2dF& initial_velocity,
    const gfx::Vector2dF& initial_offset,
    bool on_main_thread,
    bool use_mobile_fling_curve,
    const gfx::PointF& position_in_screen,
    const float boost_multiplier,
    const gfx::Size& viewport_size) {
  return std::unique_ptr<WebGestureCurve>(new WebGestureCurveImpl(
      CreateDefaultPlatformCurve(device_source, initial_velocity,
                                 use_mobile_fling_curve, position_in_screen,
                                 boost_multiplier, viewport_size),
      initial_offset, on_main_thread ? ThreadType::MAIN : ThreadType::IMPL));
}

// static
std::unique_ptr<WebGestureCurve>
WebGestureCurveImpl::CreateFromUICurveForTesting(
    std::unique_ptr<GestureCurve> curve,
    const gfx::Vector2dF& initial_offset) {
  return std::unique_ptr<WebGestureCurve>(new WebGestureCurveImpl(
      std::move(curve), initial_offset, ThreadType::TEST));
}

WebGestureCurveImpl::WebGestureCurveImpl(std::unique_ptr<GestureCurve> curve,
                                         const gfx::Vector2dF& initial_offset,
                                         ThreadType animating_thread_type)
    : curve_(std::move(curve)),
      last_offset_(initial_offset),
      ticks_since_first_animate_(0),
      first_animate_time_(0),
      last_animate_time_(0) {}

WebGestureCurveImpl::~WebGestureCurveImpl() {}

bool WebGestureCurveImpl::Advance(double time,
                                  gfx::Vector2dF& out_current_velocity,
                                  gfx::Vector2dF& out_delta_to_scroll) {
  // If the fling has yet to start, simply return and report true to prevent
  // fling termination.
  if (time <= 0)
    return true;

  if (!first_animate_time_) {
    first_animate_time_ = last_animate_time_ = time;
  } else if (time != last_animate_time_) {
    // Animation can occur multiple times a frame, but with the same timestamp.
    // Suppress recording of such redundant animate calls, avoiding artificially
    // inflated FPS computation.
    last_animate_time_ = time;
    ++ticks_since_first_animate_;
  }

  const base::TimeTicks time_ticks =
      base::TimeTicks() + base::TimeDelta::FromSecondsD(time);
  gfx::Vector2dF offset;
  bool still_active =
      curve_->ComputeScrollOffset(time_ticks, &offset, &out_current_velocity);

  out_delta_to_scroll = offset - last_offset_;
  last_offset_ = offset;

  return still_active;
}

}  // namespace ui
