chaosbot/ChaosBot/Services/Timer.cs

using System;
using System.Collections.Generic;
using System.Threading;

namespace ChaosBot.Services
{
    public static class Timer
    {
        private static Dictionary<int, System.Threading.Timer> _timers = new Dictionary<int, System.Threading.Timer>();

        private static int _nextTimerIndex = 0;
        private static int NextTimerIndex
        {
            get
            {
                _nextTimerIndex++;
                return _nextTimerIndex;
            }
        }
        
        public static int RunAt(Action toRun, DateTime deadlineTime)
        {
            DateTime current = DateTime.Now;
            TimeSpan timeToGo = deadlineTime - current;
            if (timeToGo < TimeSpan.Zero)
            {
                return -1; //time already passed
            }

            int timerIndex = NextTimerIndex;
            _timers.Add(timerIndex, new System.Threading.Timer(x =>
            {
                toRun();
                _timers.Remove(timerIndex);
            }, null, timeToGo, Timeout.InfiniteTimeSpan));

            return timerIndex;
        }

        public static int RunIn(Action toRun, TimeSpan dueTime)
        {
            DateTime current = DateTime.Now;
            if (dueTime < TimeSpan.Zero)
            {
                return -1; //time already passed
            }

            int timerIndex = NextTimerIndex;
            _timers.Add(timerIndex, new System.Threading.Timer(x =>
            {
                toRun();
                _timers.Remove(timerIndex);
            }, null, dueTime, Timeout.InfiniteTimeSpan));

            return timerIndex;
        }

        public static int RunTimer(Action toRun, TimeSpan interval)
        {
            return RunTimer(toRun, interval, TimeSpan.Zero);
        }

        public static int RunTimer(Action toRun, TimeSpan interval, TimeSpan offset)
        {
            DateTime current = DateTime.Now;
            if (offset < TimeSpan.Zero)
            {
                return -1; //time already passed
            }

            int timerIndex = NextTimerIndex;

            void Callback()
            {
                toRun();

                if (_timers.ContainsKey(timerIndex))
                    _timers.Remove(timerIndex);
                _timers.Add(timerIndex, new System.Threading.Timer(x => { Callback(); }, null, interval, Timeout.InfiniteTimeSpan));
            }

            if (offset > TimeSpan.Zero)
            {
                _timers.Add(timerIndex, new System.Threading.Timer(x => { Callback(); }, null, offset, Timeout.InfiniteTimeSpan));
            }
            else
            {
                Callback();
            }

            return timerIndex;
        }

        public static void CancelTimer(int id)
        {
            if (id < 0) return;

            if (!_timers.ContainsKey(id)) return;

            _timers.GetValueOrDefault(id)?.Dispose();

            if (_timers.ContainsKey(id))
                _timers.Remove(id);
        }

        public static void Join(int id)
        {
            if (id < 0) return;
            
            while (_timers.ContainsKey(id))
            {
                Thread.Sleep(500);
            }
        }
    }
}