/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2003 Sun
 * Microsystems, Inc. All Rights Reserved.
 */
package org.netbeans.modules.refactoring.api;

import java.util.Collection;
import org.netbeans.modules.refactoring.RefactoringSupportImpl;
import org.netbeans.modules.refactoring.api.Problem;
import org.netbeans.modules.javacore.internalapi.ProgressListener;
import org.netbeans.modules.javacore.internalapi.ProgressListener;

/** Singleton class used to invoke refactorings.
 *
 * @author Martin Matula, Daniel Prusa
 */
public abstract class RefactoringSupport {

    private static RefactoringSupport defaultInstance = null;
    
    /** Returns the default instance of RefactoringSupport.
     *
     * @return Default instance.
     */
    public static synchronized RefactoringSupport getDefault() {
        if (defaultInstance == null)
            defaultInstance = new RefactoringSupportImpl();
        return defaultInstance;
    }
    
    /** Performs refactoring based on the passed collection of refactoring elements.
     * @param elements Collection of refactoring elements previously returned from
     * {@link org.netbeans.modules.refactoring.api.AbstractRefactoring#prepare} method.
     * @return Chain of problems or null if no problem was encountered.
     */
    public abstract Problem doRefactoring(Collection elements, String description, ProgressListener l);
}