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/*
Copyright 2006 Jerry Huxtable

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

/*
 * This file was semi-automatically converted from the public-domain USGS PROJ source.
 */
package org.osgeo.proj4j.proj;

import org.osgeo.proj4j.*;
import org.osgeo.proj4j.util.ProjectionMath;

public class CassiniProjection extends Projection {

	private double m0;
	private double n;
	private double t;
	private double a1;
	private double c;
	private double r;
	private double dd;
	private double d2;
	private double a2;
	private double tn;
	private double[] en;

	private final static double EPS10 = 1e-10;
	private final static double C1 = .16666666666666666666;
	private final static double C2 = .00833333333333333333;
	private final static double C3 = .04166666666666666666;
	private final static double C4 = .33333333333333333333;
	private final static double C5 = .06666666666666666666;

	public CassiniProjection() {
		projectionLatitude = Math.toRadians(0);
		projectionLongitude = Math.toRadians(0);
		minLongitude = Math.toRadians(-90);
		maxLongitude = Math.toRadians(90);
		initialize();
	}

	public ProjCoordinate project(double lplam, double lpphi, ProjCoordinate xy) {
		if (spherical) {
			xy.x = Math.asin(Math.cos(lpphi) * Math.sin(lplam));
			xy.y = Math.atan2(Math.tan(lpphi) , Math.cos(lplam)) - projectionLatitude;
		} else {
			xy.y = ProjectionMath.mlfn(lpphi, n = Math.sin(lpphi), c = Math.cos(lpphi), en);
			n = 1./Math.sqrt(1. - es * n * n);
			tn = Math.tan(lpphi); t = tn * tn;
			a1 = lplam * c;
			c *= es * c / (1 - es);
			a2 = a1 * a1;
			xy.x = n * a1 * (1. - a2 * t *
				(C1 - (8. - t + 8. * c) * a2 * C2));
			xy.y -= m0 - n * tn * a2 *
				(.5 + (5. - t + 6. * c) * a2 * C3);
		}
		return xy;
	}

	public ProjCoordinate projectInverse(double xyx, double xyy, ProjCoordinate out) {
		if (spherical) {
			out.y = Math.asin(Math.sin(dd = xyy + projectionLatitude) * Math.cos(xyx));
			out.x = Math.atan2(Math.tan(xyx), Math.cos(dd));
		} else {
			double ph1;

			ph1 = ProjectionMath.inv_mlfn(m0 + xyy, es, en);
			tn = Math.tan(ph1); t = tn * tn;
			n = Math.sin(ph1);
			r = 1. / (1. - es * n * n);
			n = Math.sqrt(r);
			r *= (1. - es) * n;
			dd = xyx / n;
			d2 = dd * dd;
			out.y = ph1 - (n * tn / r) * d2 *
				(.5 - (1. + 3. * t) * d2 * C3);
			out.x = dd * (1. + t * d2 *
				(-C4 + (1. + 3. * t) * d2 * C5)) / Math.cos(ph1);
		}
		return out;
	}

	public void initialize() {
		super.initialize();
		if (!spherical) {
			if ((en = ProjectionMath.enfn(es)) == null)
				throw new ProjectionException();
			m0 = ProjectionMath.mlfn(projectionLatitude, Math.sin(projectionLatitude), Math.cos(projectionLatitude), en);
		}
	}

	public boolean hasInverse() {
		return true;
	}

	/**
	 * Returns the ESPG code for this projection, or 0 if unknown.
	 */
	public int getEPSGCode() {
		return 9806;
	}

	public String toString() {
		return "Cassini";
	}

}