/* Copyright (C) 2014 A.Vontobel  
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * The license is in LICENCE-GPL.txt.
 * If not, see http://www.gnu.org/licenses/old-licenses/gpl-2.0.html.
 */

package net.sf.drawj2d.cmd.geom;

import java.util.ArrayList;
import java.util.Arrays;
import org.hecl.*;
import no.geosoft.cc.geometry.Geometry;

/**
 * GeomCentroidCmd implements the "geom.centroid" command, which computes
 * the center of gravity of an area (surrounded by a polygon).
 */

public class GeomCentroidCmd implements Command {
    boolean debug = false;
    
    public GeomCentroidCmd () {
    }
    
    @Override
    public Thing cmdCode(Interp interp, Thing[] argv) throws HeclException {
        assert argv.length > 0;
        if (debug) System.out.println(argv[0].toString());
        
        ArrayList singleargv = splitArgv(argv);
        // Convert the arguments from thing to double.
        int nbsingleargs = singleargv.size(); // without command from argv[0]
        double[] argd = new double[nbsingleargs];
        for (int i = 0; i < nbsingleargs; i++) {
            argd[i] = NumberThing.asNumber(singleargv.get(i)).doubleValue();
        }
        
        if (argd.length < 6) throw new HeclException ("Illegal nb of arguments.");
        
        if (argd.length % 2 != 0) throw new HeclException ("Illegal nb of arguments.");
        
        assert argd.length % 2 == 0: "nb of arguments not even";
        int n = argd.length / 2;
        double[] x = new double[n];
        double[] y = new double[n];

        for (int i = 0; i < n; i++) {
            x[i] = argd[2*i];
            y[i] = argd[1 + 2*i];
        }
        
        double[] centroid = Geometry.computePolygonCentroid(x, y);
        String xstr = StringThing.get(DoubleThing.create(centroid[0]));
        String ystr = StringThing.get(DoubleThing.create(centroid[1]));
        String answer = xstr + " " + ystr;
        
	return new Thing(answer);
    }
    
    /** Make a list of arguments (without command in argv[0]). 
     * Split List arguments to single arguments. */
    private ArrayList splitArgv(Thing[] argv) throws HeclException {
        ArrayList singleargv = new ArrayList(argv.length);
        for (int i = 1; i < argv.length; i++) {
            Thing[] currentargv = ListThing.getArray(argv[i]);
            singleargv.addAll(Arrays.asList(currentargv));
        }
        return singleargv;
    }
}