//
// this is a header-only library
// in one cpp:
//   #define TIMER_IMPLEMENTATION
//   #include <timer.h>
//
// to use:
//   Timer timer;
//   timer.Start();
//   do_some_work();
//   timer.Update();
//   float deltaTime = timer.deltaTime;
//   std::string timeSinceStartString = timer.ToStdString();
//

#ifndef TIMER_H_
#define TIMER_H_

#ifdef _MSC_VER
#include <Windows.h>
#elif __APPLE__
#include <sys/time.h>
#endif

#include <string>
#include <cstdio>

class Timer
{	
public:
	Timer(void);
	void Start(long initMktime = 0);
	void Update(void);
	float DeltaTime(void);
	float timeScale;
	float TimeSinceStart(void);
	std::string ToStdString(void);
private:
	long totalMktime;
	float deltaTime;
#ifdef _MSC_VER
	float frequency;
	__int64 lastUpdate;
#elif __APPLE__
	long lastUpdate;
#else
	no_timer_implementation_available_in_this_environment
#endif
};

#endif // TIMER_H

#ifdef TIMER_IMPLEMENTATION

Timer::Timer(void) :
	timeScale(1.0f)
{	
	Start(0);
}

void Timer::Start(long initMktime)
{
	totalMktime = initMktime;
	deltaTime = 0.0f;
#ifdef _MSC_VER
	LARGE_INTEGER f;
	QueryPerformanceFrequency(&f);
	frequency = float(f.QuadPart) / 1000.0f;
	QueryPerformanceCounter(&f);
	lastUpdate = f.QuadPart;
#elif __APPLE__
	timeval time;
	gettimeofday(&time, NULL);
	lastUpdate = time.tv_sec * 1000 + time.tv_usec / 1000;
#endif
}

void Timer::Update(void)
{
#ifdef _MSC_VER
	LARGE_INTEGER t;
	QueryPerformanceCounter(&t);
	deltaTime =  (t.QuadPart - lastUpdate) / frequency * timeScale;
	totalMktime += long(deltaTime);
	deltaTime /= 1000.0f;
	lastUpdate = t.QuadPart;
#elif __APPLE__
	timeval time;
	gettimeofday(&time, NULL);
	long current = time.tv_sec * 1000 + time.tv_usec / 1000;
	deltaTime = (current - lastUpdate) * timeScale;
	totalMktime += long(deltaTime);
	deltaTime /= 1000.0f;
	lastUpdate = current;
#endif
}

std::string Timer::ToStdString(void)
{
	char buffer[18];
#ifdef _MSC_VER
	sprintf_s(buffer, "%02d:%02d:%02d'%03d",
#else
	sprintf(buffer, "%02d:%02d:%02d'%03d",
#endif
		totalMktime / 3600000 % 24,
		totalMktime / 60000 % 60,
		totalMktime / 1000 % 60,
		totalMktime % 1000);
	return buffer; // implicitly cast char* to std::string
}

float Timer::DeltaTime(void)
{
	return deltaTime;
}

float Timer::TimeSinceStart(void)
{
	return totalMktime / 1000.0f;
}

#endif //  TIMER_IMPLEMENTATION