using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace Aitex.DataAnalysis.Core
{
    public class PeriodicJob
    {
        Thread _thread;
        int _interval;
        int _tick = 0;
        Func<bool> _func;
        
        CancellationTokenSource _cancelFlag = new CancellationTokenSource();        //for quit thread 
        ManualResetEvent _waitFlag = new ManualResetEvent(true);                    //for pause purpose
        ManualResetEvent _sleepFlag = new ManualResetEvent(false);                //for sleep time

        public PeriodicJob(int interval, Func<bool> func, string name, bool isStartNow=false, bool isBackground=true)
        {
            _thread = new Thread(new ParameterizedThreadStart(ThreadFunction));
            _thread.Name = name;
            _thread.IsBackground = true;

            _interval = interval;
            _func = func;

            if (isStartNow)
                Start();
        }

        public void Start()
        {
            if (_thread == null)
                return;
            
            _waitFlag.Set();

            if (_thread.IsAlive)
                return;

            _thread.Start(this);
        }

        public void Pause()
        {
            _waitFlag.Reset();
        }

        public void Stop()
        {
            _sleepFlag.Set(); //do not sleep

            _waitFlag.Set();    //do not pause

            _cancelFlag.Cancel();   //quit

            _thread.Abort();

            _thread.Join();

            _thread = null;
        }

        void ThreadFunction(object param)
        {
            PeriodicJob t = (PeriodicJob)param;
            t.Run();
        }

        void Run()
        {
            while (!_cancelFlag.IsCancellationRequested)
            {
                _tick = Environment.TickCount;

                _waitFlag.WaitOne();
                                
                if (!_func())
                    break;

                _sleepFlag.WaitOne(Math.Max(_interval - (Environment.TickCount - _tick), 30));
            }
        }
    }
}