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

import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;

import javax.swing.tree.MutableTreeNode;

import org.openstreetmap.josm.data.osm.Node;
import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.data.osm.Segment;
import org.openstreetmap.josm.data.osm.Way;
import org.openstreetmap.josm.data.osm.visitor.Visitor;
import org.openstreetmap.josm.gui.layer.Layer;
import org.openstreetmap.josm.gui.layer.OsmDataLayer;


/**
 * Classes implementing Command modify a dataset in a specific way. A command is
 * one atomic action on a specific dataset, such as move or delete.
 *
 * Remember, that the command must be executable and undoable, even if the 
 * Main.ds has changed, so the command must save the dataset it operates on
 * if necessary.
 *
 * @author imi
 */
abstract public class Command {

	private static final class CloneVisitor implements Visitor {
		public Map<OsmPrimitive, OsmPrimitive> orig = new HashMap<OsmPrimitive, OsmPrimitive>();

		public void visit(Node n) {
			orig.put(n, new Node(n));
		}
		public void visit(Segment s) {
			orig.put(s, new Segment(s));
		}
		public void visit(Way w) {
			orig.put(w, new Way(w));
		}
	}

	private CloneVisitor orig; 

	/**
	 * Executes the command on the dataset. This implementation will remember all
	 * primitives returned by fillModifiedData for restoring them on undo.
	 */
	public void executeCommand() {
		orig = new CloneVisitor();
		Collection<OsmPrimitive> all = new HashSet<OsmPrimitive>();
		fillModifiedData(all, all, all);
		for (OsmPrimitive osm : all)
			osm.visit(orig);
	}

	/**
	 * Undoes the command. 
	 * It can be assumed, that all objects are in the same state they were before.
	 * It can also be assumed that executeCommand was called exactly once before.
	 * 
	 * This implementation undoes all objects stored by a former call to executeCommand.
	 */
	public void undoCommand() {
		for (Entry<OsmPrimitive, OsmPrimitive> e : orig.orig.entrySet())
			e.getKey().cloneFrom(e.getValue());
	}


	/**
	 * Called, when a layer has been removed to have the command remove itself from
	 * any buffer if it is not longer applicable to the dataset (e.g. it was part of
	 * the removed layer)
	 */
	public boolean invalidBecauselayerRemoved(Layer oldLayer) {
		if (!(oldLayer instanceof OsmDataLayer))
			return false;
		HashSet<OsmPrimitive> modified = new HashSet<OsmPrimitive>();
		fillModifiedData(modified, modified, modified);
		if (modified.isEmpty())
			return false;

		HashSet<OsmPrimitive> all = new HashSet<OsmPrimitive>(((OsmDataLayer)oldLayer).data.allPrimitives());
		for (OsmPrimitive osm : all)
			if (all.contains(osm))
				return true;

		return false;
	}

	/**
	 * Fill in the changed data this command operates on.
	 * Add to the lists, don't clear them.
	 * 
	 * @param modified  The modified primitives
	 * @param deleted   The deleted primitives
	 * @param added		The added primitives
	 */
	abstract public void fillModifiedData(Collection<OsmPrimitive> modified,
			Collection<OsmPrimitive> deleted,
			Collection<OsmPrimitive> added);

	abstract public MutableTreeNode description();
}
