org.databene.commons.tree.TreeIterator Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of databene-commons Show documentation
'databene commons' is an open source Java library by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.
The newest version!
/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.databene.commons.tree;

import org.databene.commons.NullSafeComparator;
import org.databene.commons.TreeModel;
import org.databene.commons.iterator.BidirectionalIterator;

/**
 * Iterates a tree forward and backward.
 * Created: 08.05.2007 18:05:24
 * @param  the type of object to iterate
 * @author Volker Bergmann
 */
public class TreeIterator implements BidirectionalIterator {

    private TreeModel treeModel;
    private E cursor;

    private Boolean hasNext;
    private E next;
    private Boolean hasPrevious;
    private E previous;
    
    // constructors ----------------------------------------------------------------------------------------------------

    public TreeIterator(TreeModel treeModel) {
        this.treeModel = treeModel;
        this.cursor = treeModel.getRoot();
        this.hasNext = true;
        this.next = cursor;
        this.hasPrevious = null;
        this.previous = null;
    }
    
    // BidirectionalIterator interface implementation ------------------------------------------------------------------

    @Override
	public E first() {
        this.cursor = treeModel.getRoot();
        this.hasNext = null;
        this.next = null;
        this.hasPrevious = null;
        this.previous = null;
        return this.cursor;
    }

    @Override
	public boolean hasPrevious() {
        if (hasPrevious == null) {
            previous = nodeBefore(cursor, treeModel);
            hasPrevious = (previous != null);
        }
        return hasPrevious;
    }

    @Override
	public E previous() {
        if (!hasPrevious())
            throw new IllegalStateException("No object available for previous()");
        hasNext = true;
        next = cursor;
        cursor = previous;
        hasPrevious = null;
        previous = null;
        return cursor;
    }

    @Override
	public E last() {
        hasNext = false;
        next = null;
        hasPrevious = null;
        previous = null;
        E tmp = lastChild(treeModel.getRoot(), treeModel);
        while (treeModel.getChildCount(tmp) > 0) {
            E candidate = lastChild(tmp, treeModel);
            if (candidate == null) {// empty directory
                cursor = tmp;
                return cursor;
            }
            tmp = candidate;
        }
        cursor = tmp;
        return cursor;
    }

    @Override
	public boolean hasNext() {
        if (hasNext == null) {
            next = nodeAfter(cursor, treeModel);
            hasNext = (next != null);
        }
        return hasNext;
    }

    @Override
	public E next() {
        if (!hasNext())
            throw new IllegalStateException("No object available for next()");
        hasPrevious = true;
        previous = cursor;
        cursor = next;
        hasNext = null;
        next = null;
        return cursor;
    }

    @Override
	public void remove() {
        throw new UnsupportedOperationException("remove() is not supported on " + getClass());
    }
    
    // private helpers -------------------------------------------------------------------------------------------------
    
    private static  T nodeBefore(T cursor, TreeModel treeModel) {
        // root is the very first node
        if (cursor == treeModel.getRoot())
            return null;
        // check previous siblings
        T parent = treeModel.getParent(cursor);
        for (int i = treeModel.getIndexOfChild(parent, cursor); i > 0; i--) {
            T tmp = treeModel.getChild(parent, i - 1);
            if (treeModel.getChildCount(tmp) == 0)
                return tmp;
            else {
                T candidate = lastSubNode(tmp, treeModel);
                if (candidate != null)
                    return candidate;
            }
        }
        /*
        // check sibling of parent
        if (!treeModel.getRoot().equals(parent))
            return nodeBefore(parent, treeModel);
        else // return root
        	return treeModel.getRoot();
        */
        return parent;
    }

    private static  T lastChild(T node, TreeModel treeModel) {
        int childCount = treeModel.getChildCount(node);
        if (childCount > 0)
            return treeModel.getChild(node, childCount - 1);
        else
            return null;
    }

    private static  T lastSubNode(T node, TreeModel treeModel) {
        T candidate = lastChild(node, treeModel);
        while (candidate != null) {
            if (treeModel.getChildCount(candidate) == 0)
                return candidate;
            else
                candidate = lastChild(candidate, treeModel);
        }
        return null;
    }

    private static  T nodeAfter(T cursor, TreeModel treeModel) {
        // find next
        T tmp = null;
        if (treeModel.getChildCount(cursor) > 0)
                tmp = treeModel.getChild(cursor, 0);
        T parent = treeModel.getParent(cursor);
        if (tmp == null && parent != null) {
            int cursorIndex = treeModel.getIndexOfChild(parent, cursor);
            if (cursorIndex < treeModel.getChildCount(parent) - 1)
                tmp = treeModel.getChild(parent, cursorIndex + 1);
        }
        while (tmp == null && parent != null && !NullSafeComparator.equals(parent, treeModel.getRoot())) {
            T parentsParent = treeModel.getParent(parent);
            int parentsIndex = treeModel.getIndexOfChild(parentsParent, parent);
            int parentLevelCount = treeModel.getChildCount(parentsParent);
            if (parentsIndex < parentLevelCount - 1)
                tmp = treeModel.getChild(parentsParent, parentsIndex + 1);
            parent = parentsParent;
        }
        return tmp;
    }

}