source: josm/trunk/src/org/openstreetmap/josm/actions/CreateCircleAction.java@ 1640

// License: GPL. Copyright 2007 by Immanuel Scholz and others
package org.openstreetmap.josm.actions;

import static org.openstreetmap.josm.tools.I18n.tr;

import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.util.Collection;
import java.util.LinkedList;

import javax.swing.JOptionPane;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.command.Command;
import org.openstreetmap.josm.command.AddCommand;
import org.openstreetmap.josm.command.ChangeCommand;
import org.openstreetmap.josm.command.SequenceCommand;
import org.openstreetmap.josm.data.coor.EastNorth;
import org.openstreetmap.josm.data.osm.Node;
import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.data.osm.Way;
import org.openstreetmap.josm.tools.Shortcut;

/**
 * Create a new circle from three selected nodes--or a way with 3 nodes. (Useful for roundabouts)
 *
 * Note: If a way is selected, it is changed. If nodes are selected a new way is created.
 *       So if you've got a way with 3 nodes it makes a difference between running this on the way or the nodes!
 *
 * BTW: Someone might want to implement projection corrections for this...
 *
 * @author Henry Loenwind, based on much copy&Paste from other Actions.
 */
public final class CreateCircleAction extends JosmAction {

    public CreateCircleAction() {
        super(tr("Create Circle"), "createcircle", tr("Create a circle from three selected nodes."),
        Shortcut.registerShortcut("tools:createcircle", tr("Tool: {0}", tr("Create Circle")), KeyEvent.VK_O, Shortcut.GROUP_EDIT, Shortcut.SHIFT_DEFAULT), true);
    }

    private double calcang(double xc, double yc, double x, double y) {
        // calculate the angle from xc|yc to x|y
        if (xc == x && yc == y) {
            return 0; // actually invalid, but we won't have this case in this context
        }
        double yd = Math.abs(y - yc);
        if (yd == 0 && xc < x) {
            return 0;
        }
        if (yd == 0 && xc > x) {
            return Math.PI;
        }
        double xd = Math.abs(x - xc);
        double a = Math.atan2(xd, yd);
        if (y > yc) {
            a = Math.PI - a;
        }
        if (x < xc) {
            a = -a;
        }
        a = 1.5*Math.PI + a;
        if (a < 0) {
            a += 2*Math.PI;
        }
        if (a >= 2*Math.PI) {
            a -= 2*Math.PI;
        }
        return a;
    }

    public void actionPerformed(ActionEvent e) {
        int numberOfNodesInCircle = Main.pref.getInteger("createcircle.nodecount", 8);
        if (numberOfNodesInCircle < 1) {
            numberOfNodesInCircle = 1;
        } else if (numberOfNodesInCircle > 100) {
            numberOfNodesInCircle = 100;
        }

        Collection<OsmPrimitive> sel = Main.ds.getSelected();
        Collection<Node> nodes = new LinkedList<Node>();
        Way existingWay = null;

        for (OsmPrimitive osm : sel)
            if (osm instanceof Node)
                nodes.add((Node)osm);

        // special case if no single nodes are selected and exactly one way is:
        // then use the way's nodes
        if ((nodes.size() == 0) && (sel.size() == 1))
            for (OsmPrimitive osm : sel)
                if (osm instanceof Way) {
                    existingWay = ((Way)osm);
                    for (Node n : ((Way)osm).nodes)
                    {
                        if(!nodes.contains(n))
                            nodes.add(n);
                    }
                }

        if (nodes.size() != 3) {
            JOptionPane.showMessageDialog(Main.parent, tr("Please select exactly three nodes or one way with exactly three nodes."));
            return;
        }

        // let's get some shorter names
        Node   n1 = ((Node)nodes.toArray()[0]);
        double x1 = n1.getEastNorth().east();
        double y1 = n1.getEastNorth().north();
        Node   n2 = ((Node)nodes.toArray()[1]);
        double x2 = n2.getEastNorth().east();
        double y2 = n2.getEastNorth().north();
        Node   n3 = ((Node)nodes.toArray()[2]);
        double x3 = n3.getEastNorth().east();
        double y3 = n3.getEastNorth().north();

        // calculate the center (xc/yc)
        double s = 0.5*((x2 - x3)*(x1 - x3) - (y2 - y3)*(y3 - y1));
        double sUnder = (x1 - x2)*(y3 - y1) - (y2 - y1)*(x1 - x3);

        if (sUnder == 0) {
            JOptionPane.showMessageDialog(Main.parent, tr("Those nodes are not in a circle."));
            return;
        }

        s /= sUnder;

        double xc = 0.5*(x1 + x2) + s*(y2 - y1);
        double yc = 0.5*(y1 + y2) + s*(x1 - x2);

        // calculate the radius (r)
        double r = Math.sqrt(Math.pow(xc-x1,2) + Math.pow(yc-y1,2));

        // find where to put the existing nodes
        double a1 = calcang(xc, yc, x1, y1);
        double a2 = calcang(xc, yc, x2, y2);
        double a3 = calcang(xc, yc, x3, y3);
        if (a1 < a2) { double at = a1; Node nt = n1; a1 = a2; n1 = n2; a2 = at; n2 = nt; }
        if (a2 < a3) { double at = a2; Node nt = n2; a2 = a3; n2 = n3; a3 = at; n3 = nt; }
        if (a1 < a2) { double at = a1; Node nt = n1; a1 = a2; n1 = n2; a2 = at; n2 = nt; }

        // now we can start doing thigs to OSM data
        Collection<Command> cmds = new LinkedList<Command>();

        // build a way for the circle
        Way wayToAdd;
        if (existingWay == null) {
            wayToAdd = new Way();
        } else {
            // re-use existing way if it was selected
            wayToAdd = new Way(existingWay);
            wayToAdd.nodes.clear();
        }
        for (int i = 1; i <= numberOfNodesInCircle; i++) {
            double a = 2*Math.PI*(1.0 - i/(double)numberOfNodesInCircle); // "1-" to get it clock-wise
            // insert existing nodes if they fit before this new node (999 means "already added this node")
            if (a1 < 999 && a1 > a) {
                wayToAdd.nodes.add(n1);
                a1 = 999;
            }
            if (a2 < 999 && a2 > a) {
                wayToAdd.nodes.add(n2);
                a2 = 999;
            }
            if (a3 < 999 && a3 > a) {
                wayToAdd.nodes.add(n3);
                a3 = 999;
            }
            // get the position of the new node and insert it
            double x = xc + r*Math.cos(a);
            double y = yc + r*Math.sin(a);
            Node n = new Node(Main.proj.eastNorth2latlon(new EastNorth(x,y)));
            wayToAdd.nodes.add(n);
            cmds.add(new AddCommand(n));
        }
        wayToAdd.nodes.add(wayToAdd.nodes.get(0)); // close the circle
        if (existingWay == null) {
            cmds.add(new AddCommand(wayToAdd));
        } else {
            cmds.add(new ChangeCommand(existingWay, wayToAdd));
        }

        Main.main.undoRedo.add(new SequenceCommand(tr("Create Circle"), cmds));
        Main.map.repaint();
    }
}