/*
 * Copyright 1999-2004 The Apache Software Foundation
 *
 * 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.apache.commons.jxpath;

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

/**
 * A simple implementation of NodeSet that behaves as a collection of pointers. 
 * @author Dmitri Plotnikov
 * @version $Revision: 1.3 $ $Date: 2004/02/29 14:17:42 $
 */
public class BasicNodeSet implements NodeSet {
    private List pointers = new ArrayList();
    private List readOnlyPointers;
    private List nodes;
    private List values;

    public void add(Pointer pointer) {
        pointers.add(pointer);
        readOnlyPointers = null;
    }
    
    public void remove(Pointer pointer) {
        pointers.remove(pointer);
        readOnlyPointers = null;
    }
    
    public List getPointers() {
        if (readOnlyPointers == null) {
            readOnlyPointers = Collections.unmodifiableList(pointers);
        }
        return readOnlyPointers;
    }

    public List getNodes() {
        if (nodes == null) {
            nodes = new ArrayList();
            for (int i = 0; i < pointers.size(); i++) {
                Pointer pointer = (Pointer) pointers.get(i);
                nodes.add(pointer.getValue());
            }
            nodes = Collections.unmodifiableList(nodes);
        }
        return nodes;
    }

    public List getValues() {
        if (values == null) {
            values = new ArrayList();
            for (int i = 0; i < pointers.size(); i++) {
                Pointer pointer = (Pointer) pointers.get(i);
                values.add(pointer.getValue());
            }
            values = Collections.unmodifiableList(values);
        }
        return values;
    }
    
    public String toString() {
        return pointers.toString();
    }
}