//	Spludlow Software
//	Copyright © Samuel P. Ludlow 2020 All Rights Reserved
//	Distributed under the terms of the GNU General Public License version 3
//	Distributed WITHOUT ANY WARRANTY; without implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE
//	https://www.spludlow.co.uk/LICENCE.TXT
//	The Spludlow logo is a registered trademark of Samuel P. Ludlow and may not be used without permission
//	v1.14

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

using System.Data;

namespace Spludlow
{
	/// <summary>
	/// Put dates into periods of different sizes
	/// </summary>
	public class Periods
	{
		public enum PeriodSize
		{
			Minute, //	N
			Hour,
			Day,
			Week,
			Month,
			Quarter,
			Year
		};

		public static DateTime[] Range(PeriodSize periodSize, DateTime firstDate, DateTime lastDate)
		{
			firstDate = RoundDown(periodSize, firstDate);
			lastDate = RoundDown(periodSize, lastDate);

			List<DateTime> range = new List<DateTime>();

			for (DateTime dateTime = firstDate; dateTime <= lastDate; dateTime = AddPeriod(periodSize, dateTime))
				range.Add(dateTime);

			return range.ToArray();
		}

		public static string PeriodName(PeriodSize periodSize, DateTime date)
		{
			return PeriodNameRaw(periodSize, RoundDown(periodSize, date));
		}

		/// <summary>
		/// Date must already be rounded
		/// </summary>
		public static string PeriodNameRaw(PeriodSize periodSize, DateTime date)
		{
			StringBuilder text = new StringBuilder();

			switch (periodSize)
			{
				case PeriodSize.Minute:
					text.Append("N");
					text.Append(date.ToString("mm-HH-dd"));
					break;

				case PeriodSize.Hour:
					text.Append("H");
					text.Append(date.ToString("HH-dd"));
					break;

				case PeriodSize.Day:
					text.Append("D");
					text.Append(date.ToString("dd-MM-yyyy"));
					break;

				case PeriodSize.Week:
					date = RoundToMonday(date);
					text.Append("W");
					text.Append(date.ToString("dd-MM-yyyy"));
					break;

				case PeriodSize.Month:
					text.Append("M");
					text.Append(date.ToString("MM-yyyy"));
					break;

				case PeriodSize.Quarter:
					text.Append("Q");
					int quarter = ((date.Month - 1) / 3) + 1;
					text.Append(quarter.ToString());
					text.Append("-");
					text.Append(date.ToString("yyyy"));
					break;

				case PeriodSize.Year:
					text.Append("Y");
					text.Append(date.ToString("yyyy"));
					break;

				default:
					throw new ApplicationException("PeriodSize not supported: " + periodSize.ToString());

			}

			return text.ToString();
		}

		public static DateTime RoundDown(PeriodSize periodSize, DateTime dateTime)
		{

			switch (periodSize)
			{
				case PeriodSize.Minute:
					return new DateTime(dateTime.Year, dateTime.Month, dateTime.Day, dateTime.Hour, dateTime.Minute, 0);

				case PeriodSize.Hour:
					return new DateTime(dateTime.Year, dateTime.Month, dateTime.Day, dateTime.Hour, 0, 0);

				case PeriodSize.Day:
					return dateTime.Date;

				case PeriodSize.Week:
					return RoundToMonday(dateTime.Date);

				case PeriodSize.Month:
					return new DateTime(dateTime.Year, dateTime.Month, 1);

				case PeriodSize.Quarter:
					return RoundToQuarter(dateTime);

				case PeriodSize.Year:
					return new DateTime(dateTime.Year, 1, 1);

				default:
					throw new ApplicationException("PeriodSize not supported: " + periodSize.ToString());

			}
		}

		private static DateTime RoundToMonday(DateTime date)
		{
			date = date.Date;

			while (date.DayOfWeek != DayOfWeek.Monday)
				date = date.AddDays(-1);

			return date;
		}

		private static DateTime RoundToQuarter(DateTime date)
		{
			//01 / 01   2   3
			//01 / 04   5   6
			//01 / 07   8   9
			//01 / 10   11  12

			date = new DateTime(date.Year, date.Month, 1);

			while ((date.Month % 3) != 1)
				date = date.AddMonths(-1);

			return date;
		}

		private static DateTime AddPeriod(PeriodSize periodSize, DateTime dateTime)  // must already be rounded
		{

			switch (periodSize) //	"yyyy-MM-dd-HH-mm-ss-fff"
			{
				case PeriodSize.Minute:
					return dateTime.AddMinutes(1);

				case PeriodSize.Hour:
					return dateTime.AddHours(1);

				case PeriodSize.Day:
					return dateTime.AddDays(1);

				case PeriodSize.Week:
					return dateTime.AddDays(7);

				case PeriodSize.Month:
					return dateTime.AddMonths(1);

				case PeriodSize.Quarter:
					return dateTime.AddMonths(3);

				case PeriodSize.Year:
					return dateTime.AddYears(1);

				default:
					throw new ApplicationException("PeriodSize not supported: " + periodSize.ToString());

			}
		}
	}
}