zkoss/zk

/* Node.java

    Purpose:
        
    Description:
        
    History:
        Sat Sep 17 13:53:14     2005, Created by tomyeh

Copyright (C) 2004 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
    This program is distributed under LGPL Version 2.1 in the hope that
    it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.web.servlet.dsp.impl;

import java.io.IOException;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;

import org.zkoss.web.servlet.dsp.DspException;

/**
 * Represents a node in an {@link org.zkoss.web.servlet.dsp.Interpretation}.
 *
 * @author tomyeh
 */
abstract class Node {
    protected List<Node> _children;

    /** Interprets the node to generate the result to the output
     * specified in the interpret context.
     */
    abstract void interpret(InterpretContext ic) throws DspException, IOException;

    /** Adds a child. */
    void addChild(Node node) {
        if (node == null)
            throw new IllegalArgumentException("null");
        if (_children == null)
            _children = new LinkedList<Node>();
        _children.add(node);
    }

    /** Adds a child to the specified position. */
    void addChild(int pos, Node node) {
        if (node == null)
            throw new IllegalArgumentException("null");
        if (_children == null)
            _children = new LinkedList<Node>();
        _children.add(pos, node);
    }

    /** Returns the list of child nodes ({@link Node}).
     * @since 3.0.0
     */
    public List<Node> getChildren() {
        if (_children != null)
            return _children;
        return Collections.emptyList();
    }
}