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

namespace Aitex.DataAnalysis.Core
{
	/// <summary>
	/// DeviceTimer类  
	/// 
	/// 设计目的：
	/// 1. 进行ms级别的定时；
	/// 2. 弥补使用Windows系统时间作为定时，如果系统时间被更改，定时器面临误判风险（Alpha机台已有多次发生类似事件）；
	/// 
	/// 使用场合：
	/// 系统中凡是需要定时完成的事件，建议采用该定时器完成定时功能；
	/// </summary>
	public class DeviceTimer
	{
		//引入高性能计数器API，通过对CPU计数完成计时
		[DllImport("Kernel32.dll")]
		private static extern bool QueryPerformanceCounter(out long lpPerformanceCount);

		//获取当前CPU的工作频率
		[DllImport("Kernel32.dll")]
		private static extern bool QueryPerformanceFrequency(out long lpFrequency);

		/// <summary>
		/// 定时器内部状态定义
		/// </summary>
		private enum DeviceTimerState
		{
			TM_ST_IDLE = 0,
			TM_ST_BUSY = 1,
			TM_ST_TIMEOUT = 2,
		}

		/// <summary>
		/// 定时器内部状态
		/// </summary>
		DeviceTimerState _state;

		/// <summary>
		/// 定时器开始计时时刻的相对时间点
		/// </summary>
		long _startTime;

		/// <summary>
		/// 定时器超时时刻的相对时间点
		/// </summary>
		long _timeOut;

		/// <summary>
		/// CPU运行的时钟频率
		/// </summary>
		double _freq;

		/// <summary>
		/// 定时时间（单位：ms）
		/// </summary>
		double _duration;

		/// <summary>
		/// class constructure
		/// </summary>
		public DeviceTimer()
		{
			long freq;
			if (QueryPerformanceFrequency(out freq) == false)
				throw new Exception("本计算机不支持高性能计数器");
			//得到每1ms的CPU计时TickCount数目
			_freq = (double)freq / 1000.0;
			SetState(DeviceTimerState.TM_ST_IDLE);
			QueryPerformanceCounter(out _startTime);
			_timeOut = _startTime;
			_duration = 0;
		}

		/// <summary>
		/// 内部调用：设置定时器当前状态
		/// </summary>
		/// <param name="state"></param>
		private void SetState(DeviceTimerState state)
		{
			_state = state;
		}

		/// <summary>
		/// 内部调用：返回定时器当前状态
		/// </summary>
		/// <returns></returns>
		private DeviceTimerState GetState()
		{
			return _state;
		}

		/// <summary>
		/// 定时器开始计时到现在已流逝的时间（单位：毫秒）
		/// </summary>
		/// <returns></returns>
		public double GetElapseTime()
		{
			long curCount;
			QueryPerformanceCounter(out curCount);
			return (double)(curCount - _startTime) / (double)_freq;
		}

		/// <summary>
		/// 获取定时总时间
		/// </summary>
		/// <returns></returns>
		public double GetTotalTime()
		{
			return _duration;
		}

		/// <summary>
		/// 停止计时器计时
		/// </summary>
		public void Stop()
		{
			SetState(DeviceTimerState.TM_ST_IDLE);
			QueryPerformanceCounter(out _startTime);
			_timeOut = _startTime;
			_duration = 0;
		}

		/// <summary>
		/// 启动定时器
		/// </summary>
		/// <param name="delay_ms">定时时间（单位：毫秒）</param>
		public void Start(double delay_ms)
		{
			QueryPerformanceCounter(out _startTime);
			_timeOut = Convert.ToInt64(_startTime + delay_ms * _freq);
			SetState(DeviceTimerState.TM_ST_BUSY);
			_duration = delay_ms;
		}

		/// <summary>
		/// 重新开始定时器
		/// 开始的计时时间以上一次Start的时间为准
		/// </summary>
		/// <param name="delay_ms">定时时间（单位：毫秒）</param>
		public void Restart(double delay_ms)
		{
			_timeOut = Convert.ToInt64(_startTime + delay_ms * _freq);
			SetState(DeviceTimerState.TM_ST_BUSY);
			_duration = delay_ms;
		}

		/// <summary>
		/// 返回定时器是否超时
		/// </summary>
		/// <returns></returns>
        public bool IsTimeout()
        {
            long curCount;
            QueryPerformanceCounter(out curCount);
            if (_state == DeviceTimerState.TM_ST_BUSY && (curCount >= _timeOut))
            {
                SetState(DeviceTimerState.TM_ST_TIMEOUT);
                return true;
            }
            else if (_state == DeviceTimerState.TM_ST_TIMEOUT)
            {
                return true;
            }
            return false;
        }

		/// <summary>
		/// 定时器是否在工作中
		/// </summary>
		/// <returns></returns>
		public bool IsIdle()
		{
			return (_state == DeviceTimerState.TM_ST_IDLE);
		}
	}
}