package org.madore.ephem;

import java.util.List;
import java.util.ArrayList;
import java.util.EnumMap;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.BufferedReader;

public final class Nutation {

    public static enum Variable {
	PSI("psi"), EPSILON("epsilon"), EQORG("eqorg");
	final String name;
	Variable(String name) { this.name = name; }
    }

    // The argument is in Julian centuries (value is in radians).
    public static Comput.Polynomial[] lambdas = new Comput.Polynomial[] {
	new Comput.Polynomial(134.96340251*Comput.degree, 1717915923.2178*Comput.arcsecond, 31.8792*Comput.arcsecond +0.051635*Comput.arcsecond, -0.00024470*Comput.arcsecond), // Delaunay l
	new Comput.Polynomial(357.52910918*Comput.degree, 129596581.0481*Comput.arcsecond, -0.5532*Comput.arcsecond +0.000136*Comput.arcsecond, -0.00001149*Comput.arcsecond), // Delaunay l′
	new Comput.Polynomial(93.27209062*Comput.degree, 1739527262.8478*Comput.arcsecond, -12.7512*Comput.arcsecond -0.001037*Comput.arcsecond, 0.00000417*Comput.arcsecond), // Delaunay F
	new Comput.Polynomial(297.85019547*Comput.degree, 1602961601.2090*Comput.arcsecond, -6.3706*Comput.arcsecond +0.006593*Comput.arcsecond, -0.00003169*Comput.arcsecond), // Delaunay D
	new Comput.Polynomial(125.04455501*Comput.degree, -6962890.5431*Comput.arcsecond, 7.4722*Comput.arcsecond +0.007702*Comput.arcsecond, -0.00005939*Comput.arcsecond), // Delaunay Ω
	new Comput.Polynomial(4.402608842, 2608.7903141574), // L(Mercury)
	new Comput.Polynomial(3.176146697, 1021.3285546211), // L(Venus)
	new Comput.Polynomial(1.753470314, 628.3075849991), // L(Earth)
	new Comput.Polynomial(6.203480913, 334.0612426700), // L(Mars)
	new Comput.Polynomial(0.599546497, 52.9690962641), // L(Jupiter)
	new Comput.Polynomial(0.874016757, 21.3299104960), // L(Saturn)
	new Comput.Polynomial(5.481293872, 7.4781598567), // L(Uranus)
	new Comput.Polynomial(5.311886287, 3.8133035638), // L(Neptune)
	new Comput.Polynomial(0, 0.02438175, 0.00000538691) // General precession
    };

    private static EnumMap<Variable, Comput.SumPoisson2Terms> data = new EnumMap<Variable, Comput.SumPoisson2Terms>(Variable.class);

    public static Comput.SumPoisson2Terms getFunc(Variable v) {
	if ( ! data.containsKey(v) ) {
	    List<Comput.Poisson2Term> series = new ArrayList<Comput.Poisson2Term>();
	    try {
		InputStream str = Nutation.class.getResourceAsStream("nutation.dat");
		BufferedReader in = new BufferedReader(new InputStreamReader(str, "utf-8"));
		String s;
		while ( ( s = in.readLine() ) != null ) {
		    String[] fields = s.split("\t");
		    if ( ! fields[1].equals(v.name) )
			continue;
		    int deg = Integer.parseInt(fields[2]);
		    String[] subfields = fields[3].split(",");
		    double[] om = new double[14];
		    for ( int j=0 ; j<14 ; j++ )
			om[j] = Double.parseDouble(subfields[j]);
		    double b = Double.parseDouble(fields[4]);
		    double a = Double.parseDouble(fields[5]);
		    series.add(Comput.Poisson2Term.ab(deg, a, b, om, lambdas));
		}
	    } catch ( Exception e ) {
		throw new RuntimeException(e);
	    }
	    data.put(v, new Comput.SumPoisson2Terms(series));
	}
	return data.get(v);
    }

    public static Frames.Rotation matrix(double t) {
	// Transform mean equatorial coordinates of date to true equatorial coordinates of date.
	Frames.Rotation mat1 = Frames.Rotation.rotx(Precession.epsilon.v(t)*Comput.arcsecond);
	Frames.Rotation mat2 = Frames.Rotation.rotz(-getFunc(Variable.PSI).v(t)*Comput.arcsecond).apply(mat1);
	Frames.Rotation mat3 = Frames.Rotation.rotx(-(Precession.epsilon.v(t)+getFunc(Variable.EPSILON).v(t))*Comput.arcsecond).apply(mat2);
	return mat3;
    }

    public static double eqeqnx(double t) { // Equation of the equinoxes (=GAST-GMST, in arc seconds)
	return getFunc(Variable.PSI).v(t)*Math.cos(Precession.epsilon.v(t)) + getFunc(Variable.EQORG).v(t);
    }

    public static double eqorg(double t) {
	return Precession.eqorg.v(t) + eqeqnx(t);
    }

}