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/**
 * Copyright (c) 2011, University of Konstanz, Distributed Systems Group
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * * Neither the name of the University of Konstanz nor the
 * names of its contributors may be used to endorse or promote products
 * derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL  BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.treetank.axis;

import static org.treetank.data.IConstants.NULL_NODE;

import java.util.Stack;

import org.treetank.api.INodeReadTrx;
import org.treetank.data.interfaces.ITreeStructData;

/**
 * DescendantAxis
 * 
 * 
 * Iterate over all descendants of kind ELEMENT or TEXT starting at a given node. Self is not included.
 * 
 */
public final class DescendantAxis extends AbsAxis {

    /** Stack for remembering next nodeKey in document order. */
    private Stack mRightSiblingKeyStack;

    /** The nodeKey of the next node to visit. */
    private long mNextKey;

    /**
     * Constructor initializing internal state.
     * 
     * @param rtx
     *            Exclusive (immutable) trx to iterate with.
     */
    public DescendantAxis(final INodeReadTrx rtx) {
        super(rtx);
    }

    /**
     * Constructor initializing internal state.
     * 
     * @param rtx
     *            Exclusive (immutable) trx to iterate with.
     * @param mIncludeSelf
     *            Is self included?
     */
    public DescendantAxis(final INodeReadTrx rtx, final boolean mIncludeSelf) {
        super(rtx, mIncludeSelf);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void reset(final long mNodeKey) {
        super.reset(mNodeKey);
        mRightSiblingKeyStack = new Stack();
        if (isSelfIncluded()) {
            mNextKey = getNode().getDataKey();
        } else {
            mNextKey = ((ITreeStructData)getNode()).getFirstChildKey();
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean hasNext() {
        resetToLastKey();

        // Fail if there is no node anymore.
        if (mNextKey == NULL_NODE) {
            resetToStartKey();
            return false;
        }

        moveTo(mNextKey);

        // Fail if the subtree is finished.
        if (((ITreeStructData)getNode()).getLeftSiblingKey() == getStartKey()) {
            resetToStartKey();
            return false;
        }

        // Always follow first child if there is one.
        if (((ITreeStructData)getNode()).hasFirstChild()) {
            mNextKey = ((ITreeStructData)getNode()).getFirstChildKey();
            if (((ITreeStructData)getNode()).hasRightSibling()) {
                mRightSiblingKeyStack.push(((ITreeStructData)getNode()).getRightSiblingKey());
            }
            return true;
        }

        // Then follow right sibling if there is one.
        if (((ITreeStructData)getNode()).hasRightSibling()) {
            mNextKey = ((ITreeStructData)getNode()).getRightSiblingKey();
            return true;
        }

        // Then follow right sibling on stack.
        if (mRightSiblingKeyStack.size() > 0) {
            mNextKey = mRightSiblingKeyStack.pop();
            return true;
        }

        // Then end.
        mNextKey = NULL_NODE;
        return true;
    }

}