/*******************************************************************************
 * Copyright (c) 2006, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Matthew Hall - bug 208858
 *******************************************************************************/

module org.eclipse.core.databinding.observable.list.ListDiff;

import java.lang.all;

import org.eclipse.core.internal.databinding.Util;

/**
 * Object describing a diff between two lists.
 * 
 * @since 1.0
 */
public abstract class ListDiff {

    /**
     * Returns a ListDiffEntry array representing the differences in the list,
     * in the order they are to be processed.
     * 
     * @return a ListDiffEntry array representing the differences in the list,
     *         in the order they are to be processed.
     */
    public abstract ListDiffEntry[] getDifferences();

    /**
     * Traverses the {@link #getDifferences()} array, calling the appropriate
     * method in <code>visitor</code> for each difference.
     * <ol>
     * <li>{@link ListDiffVisitor#handleReplace(int, Object, Object)} is called
     * whenever a remove entry is immediately followed by an add entry which
     * shares the same list index.
     * <li>{@link ListDiffVisitor#handleMove(int, int, Object)} is called
     * whenever a remove entry is immediately followed by an add entry with an
     * equivalent element.
     * <li>{@link ListDiffVisitor#handleRemove(int, Object)} is called whenever
     * a remove entry does not match conditions 1 or 2.
     * <li>{@link ListDiffVisitor#handleAdd(int, Object)} is called whenever an
     * add entry does not match conditions in 1 or 2.
     * </ol>
     * 
     * @param visitor
     *            the visitor to receive callbacks.
     * @see ListDiffVisitor
     * @since 1.1
     */
    public void accept(ListDiffVisitor visitor) {
        ListDiffEntry[] differences = getDifferences();
        for (int i = 0; i < differences.length; i++) {
            ListDiffEntry entry = differences[i];
            int position = entry.getPosition();
            Object element = entry.getElement();
            bool addition = entry.isAddition();

            if (!addition && i + 1 < differences.length) {
                ListDiffEntry entry2 = differences[i + 1];
                if (entry2.isAddition()) {
                    int position2 = entry2.getPosition();
                    Object element2 = entry2.getElement();
                    if (position is position2) {
                        visitor.handleReplace(position, element, element2);
                        i++;
                        continue;
                    }
                    if (Util.equals(element, element2)) {
                        visitor.handleMove(position, position2, element);
                        i++;
                        continue;
                    }
                }
            }
            if (addition)
                visitor.handleAdd(position, element);
            else
                visitor.handleRemove(position, element);
        }
    }

    /**
     * @see java.lang.Object#toString()
     */
    public String toString() {
        ListDiffEntry[] differences = getDifferences();
        StringBuffer buffer = new StringBuffer();
        buffer.append(getClass().getName());
        
        if (differences is null || differences.length is 0) {
            buffer
                .append("{}"); //$NON-NLS-1$
        } else {
            buffer
                .append("{"); //$NON-NLS-1$
            
            for (int i = 0; i < differences.length; i++) {
                if (i > 0)
                    buffer.append(", "); //$NON-NLS-1$
                
                buffer
                    .append("difference[") //$NON-NLS-1$
                    .append(i)
                    .append("] [") //$NON-NLS-1$
                    .append(differences[i] !is null ? differences[i].toString() : "null") //$NON-NLS-1$
                    .append("]"); //$NON-NLS-1$
            }
            buffer.append("}"); //$NON-NLS-1$
        }
        
        return buffer.toString();
    }
}