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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 java.util.ArrayList;
import java.util.List;

import org.treetank.data.AtomicValue;

/**
 * ItemList
 * 
 * Data structure to store XPath items.
 * 
 * 
 * This structure is used for atomic values that are needed for the evaluation of a query. They can be results
 * of a query expression or be specified directly in the query e.g. as literals perform an arithmetic
 * operation or a comparison.
 * 
 * 
 * Since these items have to be distinguishable from nodes their key will be a negative long value (node key
 * is always a positive long value). This value is retrieved by negate their index in the internal data
 * structure.
 * 
 */
public final class ItemList {

    /**
     * Internal storage of items.
     */
    private final List mList;

    /**
     * Constructor. Initializes the list.
     */
    public ItemList() {
        mList = new ArrayList();
    }

    /**
     * Adding to this list.
     * 
     * @param pItem
     *            setting and item to this list
     */
    public int addItem(final AtomicValue pItem) {
        final int key = mList.size();
        pItem.setNodeKey(key);
        // TODO: +2 is necessary, because key -1 is the NULLDATA
        final int itemKey = (key + 2) * (-1);
        pItem.setNodeKey(itemKey);

        mList.add(pItem);
        return itemKey;
    }

    /**
     * Getting an {@link AtomicValue} from the list.
     * 
     * @param pKey
     *            for the value
     * @return an {@link AtomicValue}
     */
    public AtomicValue getItem(final long pKey) {
        assert pKey <= Integer.MAX_VALUE;

        int index = (int)pKey; // cast to integer, because the list only
                               // accepts int

        if (index < 0) {
            index = index * (-1);
        }

        // TODO: This is necessary, because key -1 is the NULLDATA
        index = index - 2;

        return mList.get(index);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString() {
        return new StringBuilder("ItemList: ").append(mList.toString()).toString();
    }

}