/**
 * Moon<p>
 *
 * Compute the times of moonrise and moonset for a specified date and location.
 *
 * Algorithms from "Astronomy on the Personal Computer" by Oliver Montenbruck
 * and Thomas Pfleger. Springer Verlag 1994. ISBN 3-540-57700-9.
 *
 * Copyright &copy; 1996-1998 Martin Minow. All Rights Reserved.<p>
 *
 * Permission to use, copy, modify, and redistribute this software and its
 * documentation for personal, non-commercial use is hereby granted provided that
 * this copyright notice and appropriate documentation appears in all copies. This
 * software may not be distributed for fee or as part of commercial, "shareware,"
 * and/or not-for-profit endevors including, but not limited to, CD-ROM collections,
 * online databases, and subscription services without specific license.<p>
 *
 * @author <a href="mailto:minow@merrymeet.com">Martin Minow</a>
 * @version 1.0
 * Set tabs every 4 characters.
 */
// package Classes;

import java.util.*;

public class Moon implements Constants
{
	/*
	 * Example (from United States Naval Observatory):
	 *	For 1996.11.02 (San Francisco), Moonset 12:33, Moonrise 23:26
	 */
	public static final double	MOONRISE				= Astro.sin(+8.0 / 60.0);

	/**
	 * Compute the times of sunrise and sunset for a specific date and location.
	 * @param	date			Java date
	 * @param	timezoneOffset	Observer's timezone (msec East of Greenwich)
	 * @param	latitude		Observer's latitude (North is positive).
	 * @param	longitude		Observer's longitude (East is positive).
	 * @return	double[]		double[RISE] is the local civil time of sunrise
	 *							double[SET] is the local civil time of sunset
	 * Note the following special result values:
	 *	ABOVE_HORIZON		The moon does not set
	 *	BELOW_HORIZON		The moon does not rise
	 * Note that these are independent: there are days each month when the
	 * moon rises and does not set (and vice-versa).
	 */
	public static double[] riseSet(
			Date			javaDate,
			long			timezoneOffset,
			double			latitude,
			double			longitude
		)
	{
		double DATE				= Astro.midnightMJD(javaDate);
		double ZONE				= ((double) timezoneOffset) / 86400000.0;
		if (false) {
			System.out.println("Moon rise/set for " + javaDate.toString());
			Format.log("DATE",		DATE);
			Format.log("ZONE",		ZONE);
			Format.log("latitude",	latitude);
			Format.log("longitude",	longitude);
		}
		DATE					-= ZONE;
		double sinLatitude		= Astro.sin(latitude);
		double cosLatitude		= Astro.cos(latitude);
		double yMinus			= sinAltitude(
					DATE, 0.0, longitude, cosLatitude, sinLatitude
				) - MOONRISE;
		boolean aboveHorizon	= (yMinus > 0.0);
		double rise				= BELOW_HORIZON;
		double set				= BELOW_HORIZON;;
		if (aboveHorizon) {
			rise				= ABOVE_HORIZON;
			set					= ABOVE_HORIZON;
		}
		for (double hour = 1.0; hour <= 24.0; hour += 2.0) {
			double yThis		= sinAltitude(
					DATE, hour, longitude, cosLatitude, sinLatitude
				) - MOONRISE;
			double yPlus		= sinAltitude(
					DATE, hour + 1.0, longitude, cosLatitude, sinLatitude
				) - MOONRISE;
			/* .________________________________________________________________.
			 * | Quadratic interpolation through the three points:				|
			 * | [-1, yMinus], [0, yThis], [+1, yNext]							|
			 * | (These must not lie on a straight line.)						|
			 * | Note: I've in-lined this as it returns several values.			|
			 * .________________________________________________________________.
			 */
			double root1		= 0.0;
			double root2		= 0.0;
			int nRoots			= 0;
			double A			= (0.5 * (yMinus + yPlus)) - yThis;
			double B			= (0.5 * (yPlus - yMinus));
			double C			= yThis;
			double xExtreme		= -B / (2.0 * A);
			double yExtreme		= (A * xExtreme + B) * xExtreme + C;
			double discriminant	= (B * B) - 4.0 * A * C;
			if (discriminant >= 0.0) {	/* Intersects x-axis? */
				double DX = 0.5 * Math.sqrt(discriminant) / Math.abs(A);
				root1 = xExtreme - DX;
				root2 = xExtreme + DX;
				if (Math.abs(root1) <= +1.0)	nRoots++;
				if (Math.abs(root2) <= +1.0)	nRoots++;
				if (root1 < -1.0)
					root1 = root2;
			}
			/* .________________________________________________________________.
			 * | Quadratic interpolation result:									|
			 * | nRoots		Number of roots found (0, 1, or 2)						|
			 * |			If nRoots == zero, there is no event in this range.	|
			 * | root1		First root (nRoots >= 1)								|
			 * | root2		Second root (nRoots == 2)								|
			 * | yMinus		Y-value at interpolation start. If < 0, root1 is		|
			 * |			a moonrise event.										|
			 * | yExtreme	Maximum value of y (nRoots == 2) -- this determines	|
			 * |			whether a 2-root event is a rise-set or a set-rise.	|
			 * .________________________________________________________________.
			 */
			switch (nRoots) {
			case 0:				/* No root at this hour			*/
				break;
			case 1:				/* Found either a rise or a set	*/
				if (yMinus < 0.0) {
					rise = hour + root1;
				}
				else {
					set = hour + root1;
				}
				break;
			case 2:				/* Found both a rise and a set	*/
				if (yExtreme < 0.0) {
					rise = hour + root2;
					set = hour + root1;
				}
				else {
					rise = hour + root1;
					set = hour + root2;
				}
				break;
			}
			yMinus = yPlus;
			if (Astro.isEvent(rise) && Astro.isEvent(set))
				break;
		}
		double result[] = new double[2];
		result[RISE] = rise;
		result[SET] = set;
		return (result);
	}

	/**
	 * Compute the sine of the altitude of the object for this date, hour,
	 * and location. cosLatitude and sinLatitude pre-compute the observer's
	 * location.
	 * @param	MJD0		Modified Julian Date at midnight
	 * @param	hour		Hour past midnight.
	 * @param	longitude	Observer's longitude, East is positive.
	 * @param	cosLatitude	Cosine(observer's latitude)
	 * @param	sinLatitude	Sine(observer's latitude)
	 * @result				The sine of the object's altitude above the horizon.
	 *
	 * Note: this overrides Sun.sinAltitude and contains the moon orbital
	 * computation.
	 */
	protected static double sinAltitude(
			double				MJD0,
			double				hour,
			double				longitude,
			double				cosLatitude,
			double				sinLatitude
		)
	{
		double MJD		= MJD0 + (hour / 24.0);
		double[] moon	= Astro.lunarEphemeris(MJD);
		double TAU		= 15.0 * (Astro.LMST(MJD, longitude) - moon[Astro.RA]);
		double result	= sinLatitude * Astro.sin(moon[Astro.DEC])
						+ cosLatitude * Astro.cos(moon[Astro.DEC]) * Astro.cos(TAU);
		return (result);
	}
 	/**
 	 * Compute the time of moonrise and moonset for a specific time and location.
	 * @param	date			Java date
	 * @param	timezoneOffset	Observer's timezone (msec East of Greenwich)
	 * @param	latitude		Observer's latitude (North is positive).
	 * @param	longitude		Observer's longitude (East is positive).
	 * @return	a text string with the times.
	 * Note: this is a little messy - the problem is the moon takes slightly
	 * more than 24 hours to orbit the earth, hence there are days that have
	 * no moonrise or moonset. The U.S. Naval Observatory web page displays
	 * times for tomorrow or yesterday to fill in the blanks.
	 */
 	public static String riseSetString(
			Date			date,
			long			timezoneOffset,
			double			latitude,
			double			longitude
		)
	{
		double[] riseSet = Moon.riseSet(date, timezoneOffset, latitude, longitude);
		return (Moon.riseSetString(riseSet));
	} 	
	public static String riseSetString(
			double[]		riseSet
		)
	{
		return (Moon.riseSetString(riseSet[RISE], riseSet[SET]));
	}
	public static String riseSetString(
			double			moonrise,
			double			moonset
		)
	{
		if (Astro.isEvent(moonrise)) {
			if (Astro.isEvent(moonset)) {
				if (moonrise <= moonset) {
					return (
						getRiseSetString(moonrise, "Moonrise at ")
						+ getRiseSetString(moonset, "; moonset at ")
					);
				}
				else {
					return (
						getRiseSetString(moonset, "Moonset at ")
						+ getRiseSetString(moonrise, "; moonrise at ")
					);
				}
			}
			else {
				return (getRiseSetString(moonrise, "Moonrise at "));
			}
		}
		else if (Astro.isEvent(moonset)) {
			return (getRiseSetString(moonset, "Moonset at "));
		}
		else {
			return ("");
		}
  	}
	/**
	 * Compute the string corresponding to this Sunrise/Sunset.
	 * @param riseSetValue  the time of sunrise or sunset
	 * @param whichEvent	If there is an event, this will be prepended
	 *						to the time.
	 * @return				The proper string: null string if no event.
	 */
	public static String getRiseSetString(
			double		eventValue,
			String		whichEvent	/* "Moonrise" or "Moonset"	*/
		)
	{
		if (Astro.isEvent(eventValue)) {
			return (whichEvent + AstroFormat.hm(eventValue));
		}
		else {
			return ("");
		}
	}
}