计算任务的下一次运行时间

Question

我有以下任务的数据结构：

Task{
    Start: 17:00:00
    End:   20:00:00
    Interval: 5
    Days: [1, 2, 3, 6, 7]
}

所以这有点像某些任务的计划设置。我有一个 Windows 服务，它每 5 秒打勾，如果是时候运行任务，它会做一些计算。检查它很简单。例如，我正在检查当前时间的日期是否在Days 数组中，当前时间是否在Start 和End 等之间。所以这个任务将在17:05:04、17:10:01 等处执行（近似值为 5 秒）。所以它当前时间接近17:00 + N*5 seconds 它执行一些代码。那工作正常。

我现在正在努力计算未来执行此任务的时间。例如，如果现在是Monday 16:58:30，那么下一次将执行它是Monday 17:05。如果是Friday 18:00，它将在Saturday 17:05 处执行。如果是Monday 18:33，下一次运行是Monday 18:35。当您意识到 Start 可以是 Start: 17:03:00 等运行时间现在发生变化时，困难就来了 17:08、17:13 等。

Answer 1

/// <summary>
/// Calculates the next run for the task.
/// </summary>
/// <param name="task"></param>
/// <returns></returns>
public static string GetNextRun(TaskBase task)
{
    var now = DateTime.Now;
    var currentDay = now.DayOfWeek == DayOfWeek.Sunday ? 7.ToString() : ((int)now.DayOfWeek).ToString();
    var currentTime = now.TimeOfDay;

    var startAt = task.StartAt;

    //If Days is empty the task will never execute.
    if (task.Days.Length == 0)
    {
        return "Never";
    }
    //If the current day is allowed.
    else if (task.Days.Contains(currentDay))
    {
        //If current time is allowed
        if (currentTime >= task.StartAt && currentTime <= task.StopAt)
        {
            //Start from beginning and add interval till we get a time greater than current day.
            while (startAt < currentTime)
            {
                startAt = startAt.Add(TimeSpan.FromMinutes(task.IntervalInMinutes));
            }

            //If we are still in the allowed range return this time.
            if (startAt >= task.StartAt && startAt <= task.StopAt)
            {
                return now.Date.Add(startAt).ToString();
            }
        }
        //If we are before starting point just return the first tick.
        else if (currentTime < task.StartAt)
        {
            startAt = startAt.Add(TimeSpan.FromMinutes(task.IntervalInMinutes));

            return now.Date.Add(startAt).ToString();
        }
    }

    startAt = task.StartAt;

    //If the current day is not allowed or the day is allowed but currentTime > task.StopAt.
    //Add days until we get next allowed day and return the first tick.
    while (true)
    {
        now = now.AddDays(1);
        currentDay = now.DayOfWeek == DayOfWeek.Sunday ? 7.ToString() : ((int)now.DayOfWeek).ToString();

        if (task.Days.Contains(currentDay))
        {
            startAt = startAt.Add(TimeSpan.FromMinutes(task.IntervalInMinutes));

            return now.Date.Add(startAt).ToString();
        }
    }
}