/* 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 net.sf.drawj2d.cmd.API;

/**
 * GeomAngleRadCmd implements the "geom.anglerad" command, which
 * computes the angle (in radians) between three points. P0 is center point, clockwise.
 */

public class GeomAngleRadCmd implements Command {
    API api;
    boolean debug = false;
    
    public GeomAngleRadCmd (API api) {
        this.api = api;
    }
    
    @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();
        }
        
        String answer;
        switch (argd.length) {
            case 6: // xA yA xP yP xQ yQ
                double dir2 = Math.atan2(argd[5]-argd[1], argd[4]-argd[0]);
                double dir1 = Math.atan2(argd[3]-argd[1], argd[2]-argd[0]);
                double anglerad = dir2 - dir1;
                if (anglerad < 0) anglerad += 2. * Math.PI;
                answer = StringThing.get(DoubleThing.create(anglerad));
                break;
            case 4: // xP yP xQ yQ
                double[] here = api.here();
                double dirrel2 = Math.atan2(argd[3]-here[1], argd[2]-here[0]);
                double dirrel1 = Math.atan2(argd[1]-here[1], argd[0]-here[0]);
                double anglerelrad = dirrel2 - dirrel1;
                if (anglerelrad < 0) anglerelrad += 2. * Math.PI;
                answer = StringThing.get(DoubleThing.create(anglerelrad));
                break;
            case 2: // dx dy
                double dirrad = Math.atan2(argd[1], argd[0]);
                answer = StringThing.get(DoubleThing.create(dirrad));
                break;
            default:
                throw new HeclException ("Illegal nb of arguments.");
        }
        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;
    }
}