using System;

namespace Neo.Afx.Services
{
    /// <remarks>
    /// The poll time is specified as d.hh:mm:ss where seconds are always ignored.
    /// Hours and minutes are used to specify the time of day for all frequencies.
    /// If the poll frequency is <see cref="PollFrequencyEnum.Weekly"/> then 
    /// days refers to the day of week and must be a number between zero (Sun) and 6 (Sat).
    /// If the poll frequency is <see cref="PollFrequencyEnum.Monthly"/> then 
    /// days refers to the day of month. Otherwise days are ignored.
    /// </remarks>
    public class ServiceSchedule
    {
        readonly int _pollDays;
        readonly int _pollHours;
        readonly int _pollMinutes;
        readonly int _pollSeconds;

        #region Initialization

        /// <summary>
        ///  Initializes a new instance of the <see cref="ServiceSchedule"/> class.
        /// </summary>
        /// <param name="pollFrequency">The poll frequency.</param>
        /// <param name="pollTime">The poll time specified as d.hh:mm:ss</param>
        public ServiceSchedule(PollFrequencyEnum pollFrequency, TimeSpan pollTime)
        {
            PollFrequency = pollFrequency;
            _pollDays = pollTime.Days;
            _pollHours = pollTime.Hours;
            _pollMinutes = pollTime.Minutes;
            _pollSeconds = pollTime.Seconds;

            switch (pollFrequency)
            {
                case PollFrequencyEnum.Weekly:
                    if(_pollDays < (int)DayOfWeek.Sunday)
                    {
                        _pollDays = (int)DayOfWeek.Sunday;
                    }
                    else if(_pollDays > (int)DayOfWeek.Saturday)
                    {
                        _pollDays = (int)DayOfWeek.Saturday;
                    }
                    break;

                case PollFrequencyEnum.Monthly:
                    if(_pollDays < 1)
                    {
                        _pollDays = 1;
                    }
                    else if(_pollDays > 31)
                    {
                        _pollDays = 31;
                    }
                    break;
            }
        }

        #endregion

        #region PollFrequency

        /// <summary>
        /// Gets the poll frequency.
        /// </summary>
        public PollFrequencyEnum PollFrequency
        {
            get;
            private set;
        }

        #endregion

        #region LastRunTime

        /// <summary>
        /// Gets or sets the last run time.
        /// </summary>
        public DateTime LastRunTime
        {
            get;
            set;
        }

        #endregion

        #region NextRunTime

        /// <summary>
        /// Calculates the next run time based on the <see cref="LastRunTime"/>.
        /// </summary>
        /// <param name="signalTime">The signal time.</param>
        /// <returns>The next run time.</returns>
        public DateTime NextRunTime(DateTime signalTime)
        {
            double offset;
            var nextTime = signalTime;

            switch(PollFrequency)
            {
                case PollFrequencyEnum.Seconds:
                    nextTime = new DateTime(LastRunTime.Year, LastRunTime.Month, LastRunTime.Day, LastRunTime.Hour, LastRunTime.Minute, LastRunTime.Second);
                    break;
                case PollFrequencyEnum.Minutes:
                    nextTime = new DateTime(LastRunTime.Year, LastRunTime.Month, LastRunTime.Day, LastRunTime.Hour, LastRunTime.Minute, 0);
                    break;
                case PollFrequencyEnum.Hourly:
                    nextTime = new DateTime(LastRunTime.Year, LastRunTime.Month, LastRunTime.Day, LastRunTime.Hour, _pollMinutes, 0);
                    break;
                case PollFrequencyEnum.Daily:
                    nextTime = new DateTime(LastRunTime.Year, LastRunTime.Month, LastRunTime.Day, _pollHours, _pollMinutes, 0);
                    break;
                case PollFrequencyEnum.Weekly:
                    nextTime = new DateTime(LastRunTime.Year, LastRunTime.Month, LastRunTime.Day, _pollHours, _pollMinutes, 0);
                    offset = (int)nextTime.DayOfWeek - _pollDays;
                    nextTime = nextTime.AddDays(-offset);
                    break;
                case PollFrequencyEnum.Monthly:
                    nextTime = new DateTime(LastRunTime.Year, LastRunTime.Month, 1, _pollHours, _pollMinutes, 0);
                    var maxDays = DateTime.DaysInMonth(nextTime.Year, nextTime.Month);
                    offset = Math.Min(_pollDays, maxDays);
                    nextTime = nextTime.AddDays(offset - 1);
                    break;
            }

            if(nextTime == signalTime)
            {
                return signalTime;
            }
            if(nextTime > signalTime)
            {
                return nextTime;
            }

            // next < signalTime   i.e.
            // next run time has already elapsed
            // so increment to the next interval 
            switch(PollFrequency)
            {
                case PollFrequencyEnum.Seconds:
                    return nextTime.AddSeconds(_pollSeconds);
                case PollFrequencyEnum.Minutes:
                    return nextTime.AddMinutes(_pollMinutes);
                case PollFrequencyEnum.Hourly:
                    return nextTime.AddHours(1);
                case PollFrequencyEnum.Daily:
                    return nextTime.AddDays(1);
                case PollFrequencyEnum.Weekly:
                    return nextTime.AddDays(7);
                case PollFrequencyEnum.Monthly:
                    return nextTime.AddMonths(1);
            }
            return signalTime;
        }

        #endregion

        #region IsDue

        /// <summary>
        /// Determines if the schedule is due in the given time frame.
        /// </summary>
        /// <param name="begin">The begin time.</param>
        /// <param name="end">The end time.</param>
        /// <returns><code>true</code> if the schedule is due; <code>false</code> otherwise.</returns>
        public bool IsDue(DateTime begin, DateTime end)
        {
            var next = NextRunTime(begin);
            return next <= end;
        }

        #endregion

    }
}