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/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.javascript.ast;

/**
 * Base class for E4X XML attribute-access or property-get expressions. Such expressions can take a
 * variety of forms. The general syntax has three parts:
 *
 * 
 *   optional: an {@code @} (specifying an attribute access)
 *   
optional: a namespace (a {@code Name}) and double-colon
 *   
required: either a {@code Name} or a bracketed [expression]
 * 
 *
 * The property-name expressions (examples: {@code ns::name}, {@code @name}) are represented as
 * {@link XmlPropRef} nodes. The bracketed-expression versions (examples: {@code ns::[name]},
 * {@code @[name]}) become {@link XmlElemRef} nodes.
 *
 * This node type (or more specifically, its subclasses) will sometimes be the right-hand child
 * of a {@link PropertyGet} node or an {@link XmlMemberGet} node. The {@code XmlRef} node may also
 * be a standalone primary expression with no explicit target, which is valid in certain expression
 * contexts such as {@code company..employee.(@id < 100)} - in this case, the {@code @id} is an
 * {@code XmlRef} that is part of an infix '<' expression whose parent is an {@code XmlDotQuery}
 * node.
 */
public abstract class XmlRef extends AstNode {

    protected Name namespace;
    protected int atPos = -1;
    protected int colonPos = -1;

    public XmlRef() {}

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

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

    /** Return the namespace. May be {@code @null}. */
    public Name getNamespace() {
        return namespace;
    }

    /** Sets namespace, and sets its parent to this node. Can be {@code null}. */
    public void setNamespace(Name namespace) {
        this.namespace = namespace;
        if (namespace != null) namespace.setParent(this);
    }

    /** Returns {@code true} if this expression began with an {@code @}-token. */
    public boolean isAttributeAccess() {
        return atPos >= 0;
    }

    /** Returns position of {@code @}-token, or -1 if this is not an attribute-access expression. */
    public int getAtPos() {
        return atPos;
    }

    /** Sets position of {@code @}-token, or -1 */
    public void setAtPos(int atPos) {
        this.atPos = atPos;
    }

    /**
     * Returns position of {@code ::} token, or -1 if not present. It will only be present if the
     * namespace node is non-{@code null}.
     */
    public int getColonPos() {
        return colonPos;
    }

    /** Sets position of {@code ::} token, or -1 if not present */
    public void setColonPos(int colonPos) {
        this.colonPos = colonPos;
    }
}