// Copyright 2020 Google LLC. All Rights Reserved.

#include "benchmarking/measurements.h"

#include <algorithm>

#include "base/logging.h"

namespace widevine {
namespace {
size_t RoundUp(size_t num, size_t denum) {
  return (num + denum - 1) / denum;
}
}  // namespace

void Timer::Reset() {
  start_ = Clock::now();
}

Period Timer::Get() const {
  const auto now = Clock::now();
  return std::chrono::duration_cast<Period>(now - start_);
}

Throughput::Throughput() : bytes(0), microseconds(0), bits_per_second(0) {}

Throughput::Throughput(const Period& duration, size_t bytes) {
  this->bytes = bytes;
  microseconds = duration.count();

  bits_per_second = 0;

  if (microseconds > 0) {
    // Make sure to only do one division to ensure that we are not loosing too
    // much information as we are avoiding floating-point values.
    bits_per_second = (bytes * 8 * 1000 * 1000) / microseconds;
  }
}

const Period& Sampler::Percentile::Get(size_t percentile) const {
  // Nearest-rank method:
  // https://en.wikipedia.org/wiki/Percentile#The_nearest-rank_method
  const size_t index = RoundUp(samples_.size() * percentile, 100);

  // The index will be from 1 to N, but we need it to be 0 to N-1.
  return samples_[index - 1];
}

void Sampler::Push(const Period& period) {
  samples_.push_back(period);
}

void PrettyPrint(const std::string& title,
                 const Throughput& throughput,
                 size_t bytes_per_call) {
  LOG(INFO) << title;
  LOG(INFO) << "  bytes per call:  " << bytes_per_call;
  LOG(INFO) << "  bytes:           " << throughput.bytes;
  LOG(INFO) << "  microseconds:    " << throughput.microseconds;
  LOG(INFO) << "  bits per second: " << throughput.bits_per_second;
}

void PrettyPrint(const std::string& title,
                 const Sampler& samples,
                 size_t per_sample_size) {
  const auto& percentiles = samples.Percentiles();

  LOG(INFO) << title;
  LOG(INFO) << "  Sample Size:  " << samples.SampleSize() << " ("
            << per_sample_size << " bytes)";
  LOG(INFO) << "  Min (0%):     " << percentiles.Get(0).count() << " us";
  LOG(INFO) << "  25%:          " << percentiles.Get(25).count() << " us";
  LOG(INFO) << "  Median (50%): " << percentiles.Get(50).count() << " us";
  LOG(INFO) << "  75%:         " << percentiles.Get(75).count() << " us";
  LOG(INFO) << "  Max (100%):   " << percentiles.Get(100).count() << " us";
}

}  // namespace widevine