#ifndef BENCHMARK_THREAD_TIMER_H
#define BENCHMARK_THREAD_TIMER_H

#include "check.h"
#include "timers.h"

namespace benchmark {
namespace internal {

class ThreadTimer {
 public:
  ThreadTimer() = default;

  // Called by each thread
  void StartTimer() {
    running_ = true;
    start_real_time_ = ChronoClockNow();
    start_cpu_time_ = ThreadCPUUsage();
  }

  // Called by each thread
  void StopTimer() {
    CHECK(running_);
    running_ = false;
    real_time_used_ += ChronoClockNow() - start_real_time_;
    // Floating point error can result in the subtraction producing a negative
    // time. Guard against that.
    cpu_time_used_ += std::max<double>(ThreadCPUUsage() - start_cpu_time_, 0);
  }

  // Called by each thread
  void SetIterationTime(double seconds) { manual_time_used_ += seconds; }

  bool running() const { return running_; }

  // REQUIRES: timer is not running
  double real_time_used() {
    CHECK(!running_);
    return real_time_used_;
  }

  // REQUIRES: timer is not running
  double cpu_time_used() {
    CHECK(!running_);
    return cpu_time_used_;
  }

  // REQUIRES: timer is not running
  double manual_time_used() {
    CHECK(!running_);
    return manual_time_used_;
  }

 private:
  bool running_ = false;        // Is the timer running
  double start_real_time_ = 0;  // If running_
  double start_cpu_time_ = 0;   // If running_

  // Accumulated time so far (does not contain current slice if running_)
  double real_time_used_ = 0;
  double cpu_time_used_ = 0;
  // Manually set iteration time. User sets this with SetIterationTime(seconds).
  double manual_time_used_ = 0;
};

}  // namespace internal
}  // namespace benchmark

#endif  // BENCHMARK_THREAD_TIMER_H