// high-resolution timing
#ifndef Timer_hpp
#define Timer_hpp

//////////////////////////////////////////////////////////////////////
// Timer class using C++11 chrono
#if __cplusplus >= 201100L || defined(__GXX_EXPERIMENTAL_CXX0X__)

#include <chrono>

class Timer {
	// raw timer tick value for last query
	std::chrono::time_point<std::chrono::high_resolution_clock> tick;

public:
    Timer() {			  // find time scale factor and set first tick
		tick = std::chrono::high_resolution_clock::now();
	}
    double time() {		  // return time in seconds since last tick
		std::chrono::time_point<std::chrono::high_resolution_clock> last = tick;
        tick = std::chrono::high_resolution_clock::now();
        return std::chrono::duration<double>(tick - last).count();
	}
};

//////////////////////////////////////////////////////////////////////
// Timer class using Windows QueryPerformanceCounter
#elif defined(_WIN32)

#include <Windows.h>

class Timer {
    double scale;               // scale factor from ticks to seconds
    LARGE_INTEGER tick;			// raw timer tick value for last query

public:
	Timer() {			  // find time scale factor and set first tick
		LARGE_INTEGER frequency;
		QueryPerformanceFrequency(&frequency);
		scale = 1e3 / double(frequency.QuadPart);
		QueryPerformanceCounter(&tick);
	}
	double time() {		  // return time in seconds since last tick
		LARGE_INTEGER last = tick;
		QueryPerformanceCounter(&tick);
		return scale * (tick.QuadPart - last.QuadPart);
	}
};

//////////////////////////////////////////////////////////////////////
// Timer class using Linux clock_gettime
#elif defined(__unix__)

#include <time.h>

class Timer {
    struct timespec tick;		// raw timer tick value for last query

public:
    Timer() {			  // find time scale factor and set first tick
		clock_gettime(CLOCK_REALTIME, &tick);
	}
    double time() {		  // return time in seconds since last tick
		struct timespec last = tick;
		clock_gettime(CLOCK_REALTIME, &tick);
		return double(tick.tv_sec - last.tv_sec)
			+ double(tick.tv_nsec - last.tv_nsec)*1e-9;
	}
};

//////////////////////////////////////////////////////////////////////
// Timer class using Mac 
#elif defined(__APPLE__)

#include <mach/mach_time.h>

class Timer {
    double scale;               // scale factor from ticks to seconds
    uint64_t tick;              // raw timer tick value for last query

public:
    Timer() {			  // find time scale factor and set first tick
		mach_timebase_info_data_t mtb;
		mach_timebase_info(&mtb);
		scale = 1e-9 * double(mtb.numer) / double(mtb.denom);
		tick = mach_absolute_time();
	}
	double time() {		  // return time in seconds since last tick
		uint64_t last = tick;
		tick = mach_absolute_time();
		return scale * (tick - last);
	}
};

#endif

#endif