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A version of the Rhino Javascript engine pulled diretly from the Mozialla repos.
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/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Steve Yegge
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.javascript.ast;

import org.mozilla.javascript.Token;

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

/**
 * AST node for an Object literal (also called an Object initialiser in
 * Ecma-262).  The elements list will always be non-{@code null}, although
 * the list will have no elements if the Object literal is empty.
 *
 * Node type is {@link Token#OBJECTLIT}.

 *
 * 
ObjectLiteral :
 *       {}
 *       { PropertyNameAndValueList }
 * PropertyNameAndValueList :
 *       PropertyName : AssignmentExpression
 *       PropertyNameAndValueList , PropertyName : AssignmentExpression
 * PropertyName :
 *       Identifier
 *       StringLiteral
 *       NumericLiteral
 */
public class ObjectLiteral extends AstNode implements DestructuringForm {

    private static final List NO_ELEMS =
        Collections.unmodifiableList(new ArrayList());

    private List elements;
    boolean isDestructuring;

    {
        type = Token.OBJECTLIT;
    }

    public ObjectLiteral() {
    }

    public ObjectLiteral(int pos) {
        super(pos);
    }

    public ObjectLiteral(int pos, int len) {
        super(pos, len);
    }

    /**
     * Returns the element list.  Returns an immutable empty list if there are
     * no elements.
     */
    public List getElements() {
        return elements != null ? elements : NO_ELEMS;
    }

    /**
     * Sets the element list, and updates the parent of each element.
     * Replaces any existing elements.
     * @param elements the element list.  Can be {@code null}.
     */
    public void setElements(List elements) {
        if (elements == null) {
            this.elements = null;
        } else {
            if (this.elements != null)
                this.elements.clear();
            for (ObjectProperty o : elements)
                addElement(o);
        }
    }

    /**
     * Adds an element to the list, and sets its parent to this node.
     * @param element the property node to append to the end of the list
     * @throws IllegalArgumentException} if element is {@code null}
     */
    public void addElement(ObjectProperty element) {
        assertNotNull(element);
        if (elements == null) {
            elements = new ArrayList();
        }
        elements.add(element);
        element.setParent(this);
    }

    /**
     * Marks this node as being a destructuring form - that is, appearing
     * in a context such as {@code for ([a, b] in ...)} where it's the
     * target of a destructuring assignment.
     */
    public void setIsDestructuring(boolean destructuring) {
        isDestructuring = destructuring;
    }

    /**
     * Returns true if this node is in a destructuring position:
     * a function parameter, the target of a variable initializer, the
     * iterator of a for..in loop, etc.
     */
    public boolean isDestructuring() {
        return isDestructuring;
    }

    @Override
    public String toSource(int depth) {
        StringBuilder sb = new StringBuilder();
        sb.append(makeIndent(depth));
        sb.append("{");
        if (elements != null) {
            printList(elements, sb);
        }
        sb.append("}");
        return sb.toString();
    }

    /**
     * Visits this node, then visits each child property node, in lexical
     * (source) order.
     */
    @Override
    public void visit(NodeVisitor v) {
        if (v.visit(this)) {
            for (ObjectProperty prop : getElements()) {
                prop.visit(v);
            }
        }
    }
}