#ifndef TIME_KEEPER_H_
#define TIME_KEEPER_H_

class GlfwApiInterface;

class TimeKeeper {
  public:
    explicit TimeKeeper(GlfwApiInterface *glfw_api);
    virtual ~TimeKeeper();
    void calculate();
    void reset();
    double getDelta() const;
  protected:
    GlfwApiInterface *glfw_api_;
    double frame_time_;
    double delta_;
};

#endif


///////////////////

#include "time_keeper.h"
#include "api/glfw_api_interface.h"

TimeKeeper::TimeKeeper(GlfwApiInterface* glfw_api)
    : glfw_api_(glfw_api), frame_time_(0), delta_(0) {
}

TimeKeeper::~TimeKeeper() {
}

void TimeKeeper::calculate() {
  double time = glfw_api_->glfwGetTime();

  delta_ = time - frame_time_;
  frame_time_ = time;
}

void TimeKeeper::reset() {
  delta_ = 0;
  frame_time_ = glfw_api_->glfwGetTime();
}

double TimeKeeper::getDelta() const {
  return delta_;
}