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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 org.treetank.api.INodeReadTrx;

/**
 * ChainedAxis
 * 
 * 
 * Chains two axis operations.
 * 
 */
public class NestedAxis extends AbsAxis {

    /** Parent axis. */
    private final AbsAxis mParentAxis;

    /** Child axis to apply to each node found with parent axis. */
    private final AbsAxis mChildAxis;

    /** Is it the first run of parent axis? */
    private boolean mIsFirst;

    /**
     * Constructor initializing internal state.
     * 
     * @param parentAxis
     *            Inner nested axis.
     * @param mChildAxis
     *            Outer nested axis.
     */
    public NestedAxis(final AbsAxis parentAxis, final AbsAxis mChildAxis, final INodeReadTrx pRtx) {
        super(pRtx);
        this.mParentAxis = parentAxis;
        this.mChildAxis = mChildAxis;
        this.mIsFirst = true;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public final void reset(final long mNodeKey) {
        super.reset(mNodeKey);
        if (mParentAxis != null) {
            mParentAxis.reset(mNodeKey);
        }
        if (mChildAxis != null) {
            mChildAxis.reset(mNodeKey);
        }
        mIsFirst = true;
    }

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

        // Make sure that parent axis is moved for the first time.
        if (mIsFirst) {
            mIsFirst = false;
            if (mParentAxis.hasNext()) {
                mChildAxis.reset(mParentAxis.next());
            } else {
                resetToStartKey();
                return false;
            }
        }

        // Execute child axis for each node found with parent axis.
        boolean hasNext = false;
        while (!(hasNext = mChildAxis.hasNext())) {
            if (mParentAxis.hasNext()) {
                mChildAxis.reset(mParentAxis.next());
            } else {
                break;
            }
        }
        if (hasNext) {
            mChildAxis.next();
            return true;
        }

        resetToStartKey();
        return false;
    }

}