// Copyright 2013 The Flutter 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 "flutter/flow/instrumentation.h"

#include <algorithm>
#include <limits>

#include "third_party/skia/include/core/SkPath.h"
#include "third_party/skia/include/core/SkSurface.h"

namespace flutter {

static const size_t kMaxSamples = 120;
static const size_t kMaxFrameMarkers = 8;

Stopwatch::Stopwatch(fml::Milliseconds frame_budget)
    : start_(fml::TimePoint::Now()), current_sample_(0) {
  const fml::TimeDelta delta = fml::TimeDelta::Zero();
  laps_.resize(kMaxSamples, delta);
  cache_dirty_ = true;
  prev_drawn_sample_index_ = 0;
  frame_budget_ = frame_budget;
}

Stopwatch::~Stopwatch() = default;

void Stopwatch::Start() {
  start_ = fml::TimePoint::Now();
  current_sample_ = (current_sample_ + 1) % kMaxSamples;
}

void Stopwatch::Stop() {
  laps_[current_sample_] = fml::TimePoint::Now() - start_;
}

void Stopwatch::SetLapTime(const fml::TimeDelta& delta) {
  current_sample_ = (current_sample_ + 1) % kMaxSamples;
  laps_[current_sample_] = delta;
}

const fml::TimeDelta& Stopwatch::LastLap() const {
  return laps_[(current_sample_ - 1) % kMaxSamples];
}

double Stopwatch::UnitFrameInterval(double raster_time_ms) const {
  return raster_time_ms / frame_budget_.count();
}

double Stopwatch::UnitHeight(double raster_time_ms,
                             double max_unit_interval) const {
  double unitHeight = UnitFrameInterval(raster_time_ms) / max_unit_interval;
  if (unitHeight > 1.0) {
    unitHeight = 1.0;
  }
  return unitHeight;
}

fml::TimeDelta Stopwatch::MaxDelta() const {
  fml::TimeDelta max_delta;
  for (size_t i = 0; i < kMaxSamples; i++) {
    if (laps_[i] > max_delta) {
      max_delta = laps_[i];
    }
  }
  return max_delta;
}

fml::TimeDelta Stopwatch::AverageDelta() const {
  fml::TimeDelta sum;  // default to 0
  for (size_t i = 0; i < kMaxSamples; i++) {
    sum = sum + laps_[i];
  }
  return sum / kMaxSamples;
}

// Initialize the SkSurface for drawing into. Draws the base background and any
// timing data from before the initial Visualize() call.
void Stopwatch::InitVisualizeSurface(const SkRect& rect) const {
  if (!cache_dirty_) {
    return;
  }
  cache_dirty_ = false;

  // TODO(garyq): Use a GPU surface instead of a CPU surface.
  visualize_cache_surface_ =
      SkSurface::MakeRasterN32Premul(rect.width(), rect.height());

  SkCanvas* cache_canvas = visualize_cache_surface_->getCanvas();

  // Establish the graph position.
  const SkScalar x = 0;
  const SkScalar y = 0;
  const SkScalar width = rect.width();
  const SkScalar height = rect.height();

  SkPaint paint;
  paint.setColor(0x99FFFFFF);
  cache_canvas->drawRect(SkRect::MakeXYWH(x, y, width, height), paint);

  // Scale the graph to show frame times up to those that are 3 times the frame
  // time.
  const double one_frame_ms = frame_budget_.count();
  const double max_interval = one_frame_ms * 3.0;
  const double max_unit_interval = UnitFrameInterval(max_interval);

  // Draw the old data to initially populate the graph.
  // Prepare a path for the data. We start at the height of the last point, so
  // it looks like we wrap around
  SkPath path;
  path.setIsVolatile(true);
  path.moveTo(x, height);
  path.lineTo(x, y + height * (1.0 - UnitHeight(laps_[0].ToMillisecondsF(),
                                                max_unit_interval)));
  double unit_x;
  double unit_next_x = 0.0;
  for (size_t i = 0; i < kMaxSamples; i += 1) {
    unit_x = unit_next_x;
    unit_next_x = (static_cast<double>(i + 1) / kMaxSamples);
    const double sample_y =
        y + height * (1.0 - UnitHeight(laps_[i].ToMillisecondsF(),
                                       max_unit_interval));
    path.lineTo(x + width * unit_x, sample_y);
    path.lineTo(x + width * unit_next_x, sample_y);
  }
  path.lineTo(
      width,
      y + height * (1.0 - UnitHeight(laps_[kMaxSamples - 1].ToMillisecondsF(),
                                     max_unit_interval)));
  path.lineTo(width, height);
  path.close();

  // Draw the graph.
  paint.setColor(0xAA0000FF);
  cache_canvas->drawPath(path, paint);
}

void Stopwatch::Visualize(SkCanvas* canvas, const SkRect& rect) const {
  // Initialize visualize cache if it has not yet been initialized.
  InitVisualizeSurface(rect);

  SkCanvas* cache_canvas = visualize_cache_surface_->getCanvas();
  SkPaint paint;

  // Establish the graph position.
  const SkScalar x = 0;
  const SkScalar y = 0;
  const SkScalar width = rect.width();
  const SkScalar height = rect.height();

  // Scale the graph to show frame times up to those that are 3 times the frame
  // time.
  const double one_frame_ms = frame_budget_.count();
  const double max_interval = one_frame_ms * 3.0;
  const double max_unit_interval = UnitFrameInterval(max_interval);

  const double sample_unit_width = (1.0 / kMaxSamples);

  // Draw vertical replacement bar to erase old/stale pixels.
  paint.setColor(0x99FFFFFF);
  paint.setStyle(SkPaint::Style::kFill_Style);
  paint.setBlendMode(SkBlendMode::kSrc);
  double sample_x =
      x + width * (static_cast<double>(prev_drawn_sample_index_) / kMaxSamples);
  const auto eraser_rect = SkRect::MakeLTRB(
      sample_x, y, sample_x + width * sample_unit_width, height);
  cache_canvas->drawRect(eraser_rect, paint);

  // Draws blue timing bar for new data.
  paint.setColor(0xAA0000FF);
  paint.setBlendMode(SkBlendMode::kSrcOver);
  const auto bar_rect = SkRect::MakeLTRB(
      sample_x,
      y + height * (1.0 -
                    UnitHeight(laps_[current_sample_ == 0 ? kMaxSamples - 1
                                                          : current_sample_ - 1]
                                   .ToMillisecondsF(),
                               max_unit_interval)),
      sample_x + width * sample_unit_width, height);
  cache_canvas->drawRect(bar_rect, paint);

  // Draw horizontal frame markers.
  paint.setStrokeWidth(0);  // hairline
  paint.setStyle(SkPaint::Style::kStroke_Style);
  paint.setColor(0xCC000000);

  if (max_interval > one_frame_ms) {
    // Paint the horizontal markers
    size_t frame_marker_count =
        static_cast<size_t>(max_interval / one_frame_ms);

    // Limit the number of markers displayed. After a certain point, the graph
    // becomes crowded
    if (frame_marker_count > kMaxFrameMarkers) {
      frame_marker_count = 1;
    }

    for (size_t frame_index = 0; frame_index < frame_marker_count;
         frame_index++) {
      const double frame_height =
          height * (1.0 - (UnitFrameInterval((frame_index + 1) * one_frame_ms) /
                           max_unit_interval));
      cache_canvas->drawLine(x, y + frame_height, width, y + frame_height,
                             paint);
    }
  }

  // Paint the vertical marker for the current frame.
  // We paint it over the current frame, not after it, because when we
  // paint this we don't yet have all the times for the current frame.
  paint.setStyle(SkPaint::Style::kFill_Style);
  paint.setBlendMode(SkBlendMode::kSrcOver);
  if (UnitFrameInterval(LastLap().ToMillisecondsF()) > 1.0) {
    // budget exceeded
    paint.setColor(SK_ColorRED);
  } else {
    // within budget
    paint.setColor(SK_ColorGREEN);
  }
  sample_x = x + width * (static_cast<double>(current_sample_) / kMaxSamples);
  const auto marker_rect = SkRect::MakeLTRB(
      sample_x, y, sample_x + width * sample_unit_width, height);
  cache_canvas->drawRect(marker_rect, paint);
  prev_drawn_sample_index_ = current_sample_;

  // Draw the cached surface onto the output canvas.
  visualize_cache_surface_->draw(canvas, rect.x(), rect.y());
}

CounterValues::CounterValues() : current_sample_(kMaxSamples - 1) {
  values_.resize(kMaxSamples, 0);
}

CounterValues::~CounterValues() = default;

void CounterValues::Add(int64_t value) {
  current_sample_ = (current_sample_ + 1) % kMaxSamples;
  values_[current_sample_] = value;
}

void CounterValues::Visualize(SkCanvas* canvas, const SkRect& rect) const {
  size_t max_bytes = GetMaxValue();

  if (max_bytes == 0) {
    // The backend for this counter probably did not fill in any values.
    return;
  }

  size_t min_bytes = GetMinValue();

  SkPaint paint;

  // Paint the background.
  paint.setColor(0x99FFFFFF);
  canvas->drawRect(rect, paint);

  // Establish the graph position.
  const SkScalar x = rect.x();
  const SkScalar y = rect.y();
  const SkScalar width = rect.width();
  const SkScalar height = rect.height();
  const SkScalar bottom = y + height;
  const SkScalar right = x + width;

  // Prepare a path for the data.
  SkPath path;
  path.moveTo(x, bottom);

  for (size_t i = 0; i < kMaxSamples; ++i) {
    int64_t current_bytes = values_[i];
    double ratio = static_cast<double>(current_bytes - min_bytes) /
                   static_cast<double>(max_bytes - min_bytes);
    path.lineTo(
        x + ((static_cast<double>(i) / static_cast<double>(kMaxSamples)) *
             width),
        y + ((1.0 - ratio) * height));
  }

  path.rLineTo(100, 0);
  path.lineTo(right, bottom);
  path.close();

  // Draw the graph.
  paint.setColor(0xAA0000FF);
  canvas->drawPath(path, paint);

  // Paint the vertical marker for the current frame.
  const double sample_unit_width = (1.0 / kMaxSamples);
  const double sample_margin_unit_width = sample_unit_width / 6.0;
  const double sample_margin_width = width * sample_margin_unit_width;
  paint.setStyle(SkPaint::Style::kFill_Style);
  paint.setColor(SK_ColorGRAY);
  double sample_x =
      x + width * (static_cast<double>(current_sample_) / kMaxSamples) -
      sample_margin_width;
  const auto marker_rect = SkRect::MakeLTRB(
      sample_x, y,
      sample_x + width * sample_unit_width + sample_margin_width * 2, bottom);
  canvas->drawRect(marker_rect, paint);
}

int64_t CounterValues::GetCurrentValue() const {
  return values_[current_sample_];
}

int64_t CounterValues::GetMaxValue() const {
  auto max = std::numeric_limits<int64_t>::min();
  for (size_t i = 0; i < kMaxSamples; ++i) {
    max = std::max<int64_t>(max, values_[i]);
  }
  return max;
}

int64_t CounterValues::GetMinValue() const {
  auto min = std::numeric_limits<int64_t>::max();
  for (size_t i = 0; i < kMaxSamples; ++i) {
    min = std::min<int64_t>(min, values_[i]);
  }
  return min;
}

}  // namespace flutter