TShock scheduler, made with Bukkit's scheduler in mind

Scheduler.cs

using TerrariaApi.Server;

public class Scheduler : IDisposable
{
    public const long TicksPerSecond = 60;
    public long TotalTicks { get; private set; }
    private readonly TerrariaPlugin _plugin;
    private readonly List<Task> _tasks = new();

    public Scheduler(TerrariaPlugin plugin)
    {
        _plugin = plugin;
        ServerApi.Hooks.GameUpdate.Register(plugin, OnGameUpdate);
    }

    private void OnGameUpdate(EventArgs args)
    {
        for (var i = 0; i < _tasks.Count; i++)
        {
            var t = _tasks[i];
            if (t.Expired)
            {
                t.Action();
                _tasks.RemoveAt(i);
                i--;
            }
        }

        TotalTicks++;
    }

    public void Dispose()
    {
        ServerApi.Hooks.GameUpdate.Deregister(_plugin, OnGameUpdate);
    }

    public Task ScheduleTaskLater(Action what, long howManyTicksLater)
    {
        var task = new Task(what, TotalTicks + howManyTicksLater, this);
        _tasks.Add(task);
        return task;
    }

    public class Task
    {
        public Action Action { get; }
        public long When { get; }
        public bool Expired => _owner.TotalTicks >= When;
        private readonly Scheduler _owner;

        public Task(Action action, long when, Scheduler owner)
        {
            When = when;
            Action = action;
            _owner = owner;
        }

        // FIXME: If a consumer cancels inside their own callback, nothing good can come out of it when iterating tasks!
        //        It is their fault, but we should throw an exception before it ruins everyone else's day.
        public void Cancel()
        {
            _owner._tasks.Remove(this);
        }
    }
}