Index: /applications/editors/josm/plugins/reltoolbox/src/relcontext/RelContextDialog.java
===================================================================
--- /applications/editors/josm/plugins/reltoolbox/src/relcontext/RelContextDialog.java	(revision 26881)
+++ /applications/editors/josm/plugins/reltoolbox/src/relcontext/RelContextDialog.java	(revision 26882)
@@ -456,4 +456,5 @@
             add(new DeleteChosenRelationAction(chosenRelation));
             add(new DownloadParentsAction(chosenRelation));
+            add(new ReconstructPolygonAction(chosenRelation));
             addSeparator();
             add(new SelectInRelationPanelAction(chosenRelation));
Index: /applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/ReconstructPolygonAction.java
===================================================================
--- /applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/ReconstructPolygonAction.java	(revision 26881)
+++ /applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/ReconstructPolygonAction.java	(revision 26882)
@@ -3,8 +3,12 @@
 import static org.openstreetmap.josm.tools.I18n.tr;
 import java.awt.event.ActionEvent;
+import java.util.*;
 import javax.swing.AbstractAction;
+import javax.swing.JOptionPane;
 import org.openstreetmap.josm.Main;
-import org.openstreetmap.josm.command.DeleteCommand;
-import org.openstreetmap.josm.data.osm.Relation;
+import org.openstreetmap.josm.command.*;
+import org.openstreetmap.josm.data.osm.*;
+import org.openstreetmap.josm.data.osm.MultipolygonCreate.JoinedPolygon;
+import org.openstreetmap.josm.gui.DefaultNameFormatter;
 import org.openstreetmap.josm.tools.ImageProvider;
 import relcontext.ChosenRelation;
@@ -17,22 +21,122 @@
 public class ReconstructPolygonAction extends AbstractAction implements ChosenRelationListener {
     private ChosenRelation rel;
+    
+    private static final List<String> IRRELEVANT_KEYS = Arrays.asList(new String[] {
+	"source", "created_by", "note"});
 
     public ReconstructPolygonAction( ChosenRelation rel ) {
         super(tr("Reconstruct polygon"));
-        putValue(SMALL_ICON, ImageProvider.get("dialogs", "delete"));
+        putValue(SMALL_ICON, ImageProvider.get("dialogs", "filter"));
 	putValue(LONG_DESCRIPTION, "Reconstruct polygon from multipolygon relation");
         this.rel = rel;
         rel.addChosenRelationListener(this);
-        setEnabled(rel.get() != null);
+        setEnabled(isSuitableRelation(rel.get()));
     }
 
     public void actionPerformed( ActionEvent e ) {
         Relation r = rel.get();
-        rel.clear();
-//        Main.main.undoRedo.add(new DeleteCommand(r));
+	List<Way> ways = new ArrayList<Way>();
+	boolean wont = false;
+	for( RelationMember m : r.getMembers() ) {
+	    if( m.isWay() )
+		ways.add(m.getWay());
+	    else
+		wont = true;
+	}
+	if( wont ) {
+	    JOptionPane.showMessageDialog(Main.parent, tr("Multipolygon must consist only of ways"), tr("Reconstruct polygon"), JOptionPane.ERROR_MESSAGE);
+	    return;
+	}
+	
+	MultipolygonCreate mpc = new MultipolygonCreate();
+	String error = mpc.makeFromWays(ways);
+	if( error != null ) {
+	    JOptionPane.showMessageDialog(Main.parent, error);
+	    return;
+	}
+	
+	if( !mpc.innerWays.isEmpty() ) {
+	    JOptionPane.showMessageDialog(Main.parent, tr("Reconstruction of polygons can be done only from outer ways"), tr("Reconstruct polygon"), JOptionPane.ERROR_MESSAGE);
+	    return;
+	}
+	
+	rel.clear();
+	List<Way> newSelection = new ArrayList<Way>();
+	List<Command> commands = new ArrayList<Command>();
+	commands.add(new DeleteCommand(r));
+	
+	for( JoinedPolygon p : mpc.outerWays ) {
+	    // move all tags from relation and common tags from ways
+	    Map<String, String> tags = p.ways.get(0).getKeys();
+	    List<OsmPrimitive> relations = p.ways.get(0).getReferrers();
+	    Set<String> noTags = new HashSet<String>(r.keySet());
+	    for( int i = 1; i < p.ways.size(); i++ ) {
+		Way w = p.ways.get(i);
+		for( String key : w.keySet() ) {
+		    String value = w.get(key);
+		    if( !noTags.contains(key) && tags.containsKey(key) && !tags.get(key).equals(value) ) {
+			tags.remove(key);
+			noTags.add(key);
+		    }
+		}
+		List<OsmPrimitive> referrers = w.getReferrers();
+		for( Iterator<OsmPrimitive> ref1 = relations.iterator(); ref1.hasNext(); )
+		    if( !referrers.contains(ref1.next()) )
+			ref1.remove();
+	    }
+	    tags.putAll(r.getKeys());
+	    tags.remove("type");
+	    
+	    // then delete ways that are not relevant (do not take part in other relations of have strange tags)
+	    Way candidateWay = null;
+	    for( Way w : p.ways ) {
+		if( w.getReferrers().equals(relations) ) {
+		    // check tags that remain
+		    Set<String> keys = new HashSet<String>(w.keySet());
+		    keys.removeAll(tags.keySet());
+		    keys.removeAll(IRRELEVANT_KEYS);
+		    if( keys.isEmpty() ) {
+			if( candidateWay == null )
+			    candidateWay = w;
+			else {
+			    if( candidateWay.isNew() && !w.isNew() ) {
+				// prefer ways that are already in the database
+				Way tmp = w;
+				w = candidateWay;
+				candidateWay = w;
+			    }
+			    commands.add(new DeleteCommand(w));
+			}
+		    }
+		}
+	    }
+	    
+	    // take the first way, put all nodes into it, making it a closed polygon
+	    Way result = candidateWay == null ? new Way() : new Way(candidateWay);
+	    result.setNodes(p.nodes);
+	    result.addNode(result.firstNode());
+	    result.setKeys(tags);
+	    newSelection.add(candidateWay == null ? result : candidateWay);
+	    commands.add(candidateWay == null ? new AddCommand(result) : new ChangeCommand(candidateWay, result));
+	}
+	
+        Main.main.undoRedo.add(new SequenceCommand(tr("Reconstruct polygons from relation {0}",
+		r.getDisplayName(DefaultNameFormatter.getInstance())), commands));
+	Main.main.getCurrentDataSet().setSelected(newSelection);
     }
 
     public void chosenRelationChanged( Relation oldRelation, Relation newRelation ) {
-        setEnabled(newRelation != null); //todo
+	setEnabled(isSuitableRelation(newRelation));
+    }
+    
+    private boolean isSuitableRelation( Relation newRelation ) {
+	if( newRelation == null || !"multipolygon".equals(newRelation.get("type")) || newRelation.getMembersCount() == 0 )
+	    return false;
+	else {
+	    for( RelationMember m : newRelation.getMembers() )
+		if( "inner".equals(m.getRole()) )
+		    return false;
+	    return true;
+	}
     }
 }