LunaWin/LunaWin/LunaWin/LunaCalc.cs

using System;
using System.Collections.Generic;

namespace LunaWin
{
    class LunaCalc
    {
		/// <summary>
		/// get array of lunar phases
		/// </summary>
		public static List<LunaPhase> Phases
        {
			get { return _phases; }
		}

		/// <summary>
		/// array of lunar phases
		/// </summary>
		private static List<LunaPhase> _phases = new List<LunaPhase>
		{
			new LunaPhase() {
				Id = "new",
				Name = "New Moon",
				Start = 0,
				End = 1,
				Icon = "🌑",
				Utf = "1F311"
			},
			new LunaPhase() {
				Id = "waxc",
				Name = "Waxing Crescent",
				Start = 1,
				End = 6.38264692644,
				Icon = "🌒",
				Utf = "1F312"
			},
			new LunaPhase() {
				Id = "firstq",
				Name = "First Quarter",
				Start = 6.38264692644,
				End = 8.38264692644,
				Icon = "🌓",
				Utf = "1F313"
			},
			new LunaPhase() {
				Id = "waxg",
				Name = "Waxing Gibbous",
				Start = 8.38264692644,
				End = 13.76529385288,
				Icon = "🌔",
				Utf = "1F314"
			},
			new LunaPhase() {
				Id = "full",
				Name = "Full Moon",
				Start = 13.76529385288,
				End = 15.76529385288,
				Icon = "🌕",
				Utf = "1F315"
			},
			new LunaPhase() {
				Id = "wang",
				Name = "Waning Gibbous",
				Start = 15.76529385288,
				End = 21.14794077932,
				Icon = "🌖",
				Utf = "1F316"
			},
			new LunaPhase() {
				Id = "lastq",
				Name = "Last Quarter",
				Start = 21.14794077932,
				End = 23.14794077932,
				Icon = "🌗",
				Utf = "1F317"
			},
			new LunaPhase() {
				Id = "wanc",
				Name = "Waning Crescent",
				Start = 23.14794077932,
				End = 28.53058770576,
				Icon = "🌘",
				Utf = "1F318"
			},
			new LunaPhase() {
				Id = "new2",
				Name = "New Moon",
				Start = 28.53058770576,
				End = 29.53058770576,
				Icon = "🌑",
				Utf = "1F311"
			},
			new LunaPhase() {
				Id = "default",
				Name = "Failed to calculate.",
				Icon = "🌙",
				Utf = "1F319"
			}
		};

		/// <summary>
		/// get lunar constant (total days in a lunar phase)
		/// </summary>
		public static double LunarDays
        {
			get { return _lunarDays; }
        }

		/// <summary>
		/// lunar constant (total days in a lunar phase)
		/// </summary>
		private static double _lunarDays = 29.53058770576;

		/// <summary>
		/// get total seconds in a lunar phase
		/// </summary>
		public static double LunarSecs
        {
			get { return _lunarSecs; }
        }

		/// <summary>
		/// total seconds in a lunar phase
		/// </summary>
		private static double _lunarSecs = LunarDays * (24 * 60 * 60);

		/// <summary>
		/// get datetime of first full moon in 2000
		/// </summary>
		public static DateTime BaseDate
		{
			get { return _baseDate; }
		}

		/// <summary>
		/// datetime of first full moon in 2000
		/// </summary>
		// private static DateTime _baseDate = DateTime.Parse("2000-01-6 18:14:00Z");
		private static DateTime _baseDate = new DateTime(2000, 01, 6, 18, 14, 00, DateTimeKind.Utc);

		public LunaPhase CurrentPhase(DateTime inputDate = default)
        {
			LunaPhase currPhase = new LunaPhase();

			DateTime currDate = inputDate == default ? DateTime.UtcNow : inputDate.ToUniversalTime();

			// get total seconds between current and base datetime
			double totalSecs = (currDate - BaseDate).TotalSeconds;

			// make sure TotalSecs is positive
			totalSecs = totalSecs < 0 ? totalSecs * -1 : totalSecs;

			// calculate total seconds into current lunar cycle
			double CurrSecs = totalSecs % LunarSecs;

			// current position in lunar cycle
			double CurrFrac = CurrSecs / LunarSecs;

			// days into current cycle
			double CurrDays = CurrFrac * LunarDays;

			// search phase array for CurrDays value to fall between start and finish doubles
			currPhase = Phases.Find(p => CurrDays >= p.Start && CurrDays <= p.End);

			return currPhase;
        }
}

	/// <summary>
	/// creates a single lunar phase
	/// </summary>
    class LunaPhase
    {
		/// <summary>
		/// lunar phase shortname
		/// </summary>
        public string Id;

		/// <summary>
		/// lunar phase friendly name
		/// </summary>
        public string Name;

		/// <summary>
		/// start of lunar phase
		/// </summary>
        public double Start;

		/// <summary>
		/// end of lunar phase
		/// </summary>
        public double End;

		/// <summary>
		/// emoji icon
		/// </summary>
        public string Icon;

		/// <summary>
		/// unicode value
		/// </summary>
        public string Utf;
    }
}