using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace Aiwaz.Common
{
    public static class HiPerfTimer
    {
        [DllImport("Kernel32.dll")]
        private static extern bool QueryPerformanceCounter(out long performanceCount);
        [DllImport("Kernel32.dll")]
        private static extern bool QueryPerformanceFrequency(out long frequency);
        private static double? startTime;
        private static double lastTime;

        public static double LastDeltaTime
        {
            get;
            private set;
        }

        public static double ElapsedTime
        {
            get
            {
                long frequency, performanceCount;
                QueryPerformanceFrequency(out frequency);
                QueryPerformanceCounter(out performanceCount);
                double thisTime = performanceCount / (double)frequency;
                if (!startTime.HasValue)
                {
                    startTime = thisTime;
                    lastTime = thisTime;
                    return 0.0;
                }
                LastDeltaTime = thisTime - lastTime;
                lastTime = thisTime;
                return thisTime - startTime.Value;
            }
        }
    }
}