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The Axiom API
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/*
 * Copyright 2005 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.axiom.om.util;

import org.apache.axiom.om.*;
import org.apache.axiom.om.impl.builder.StAXOMBuilder;

import javax.xml.namespace.QName;
import javax.xml.stream.XMLStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.Iterator;

/**
 * Helper class to provide extra utility stuff against elements.
 * The code is designed to work with any element implementation.
 */

public class ElementHelper {

    private OMElement element;

    /**
     * Constructs and binds to an element.
     *
     * @param element element to work with
     */
    public ElementHelper(OMElement element) {
        this.element = element;
    }

    /**
     * Turns a prefix:local qname string into a proper QName, evaluating it in the OMElement context.
     *
     * @param qname                    qname to resolve
     * @param defaultToParentNameSpace flag that controls behaviour when there is no namespace.
     * @return Returns null for any failure to extract a qname.
     */
    public QName resolveQName(String qname, boolean defaultToParentNameSpace) {
        int colon = qname.indexOf(':');
        if (colon < 0) {
            if (defaultToParentNameSpace) {
                //get the parent ns and use it for the child
                OMNamespace namespace = element.getNamespace();
                return new QName(namespace.getNamespaceURI(), qname, namespace.getPrefix());
            } else {
                //else things without no prefix are local.
                return new QName(qname);
            }
        }
        String prefix = qname.substring(0, colon);
        String local = qname.substring(colon + 1);
        if (local.length() == 0) {
            //empy local, exit accordingly
            return null;
        }

        OMNamespace namespace = element.findNamespaceURI(prefix);
        if (namespace == null) {
            return null;
        }
        return new QName(namespace.getNamespaceURI(), local, prefix);
    }

    /**
     * Turns a prefix:local qname string into a proper QName, evaluating it in the OMElement context.
     * Unprefixed qnames resolve to the local namespace.
     *
     * @param qname prefixed qname string to resolve
     * @return Returns null for any failure to extract a qname.
     */
    public QName resolveQName(String qname) {
        return resolveQName(qname, true);
    }

    public static void setNewElement(OMElement parent,
                                     OMElement myElement,
                                     OMElement newElement) {
        if (myElement != null) {
            myElement.discard();
        }
        parent.addChild(newElement);
        myElement = newElement;
    }

    public static OMElement getChildWithName(OMElement parent,
                                             String childName) {
        Iterator childrenIter = parent.getChildren();
        while (childrenIter.hasNext()) {
            OMNode node = (OMNode) childrenIter.next();
            if (node.getType() == OMNode.ELEMENT_NODE &&
                    childName.equals(((OMElement) node).getLocalName())) {
                return (OMElement) node;
            }
        }
        return null;
    }

    public static String getContentID(XMLStreamReader parser, String charsetEncoding) {
        String contentID;
        String contentIDName;
        if (parser.getAttributeCount() > 0) {
            contentID = parser.getAttributeValue(0);
            contentID = contentID.trim();
            contentIDName = parser.getAttributeLocalName(0);
            if (contentIDName.equalsIgnoreCase("href")
                    & contentID.substring(0, 3).equalsIgnoreCase("cid")) {
                contentID = contentID.substring(4);
                String charEnc = charsetEncoding == null || "".equals(charsetEncoding) ? "UTF-8" : charsetEncoding;
                try {
                    contentID = URLDecoder.decode(contentID, charEnc);
                } catch (UnsupportedEncodingException e) {
                    throw new OMException("Unsupported Character Encoding Found", e);
                }
            } else if (!(contentIDName.equalsIgnoreCase("href")
                    & (!contentID.equals("")))) {
                throw new OMException(
                        "contentID not Found in XOP:Include element");
            }
        } else {
            throw new OMException(
                    "Href attribute not found in XOP:Include element");
        }
        return contentID;
    }

    /**
     * Some times two OMElements needs to be added to the same object tree. But in Axiom, a single tree should always
     * contain object created from the same type of factory (eg: LinkedListImplFactory, DOMFactory, etc.,). If one OMElement
     * is created from a different factory than that of the factory which was used to create the object in the existing
     * tree, we need to convert the new OMElement to match to the factory of existing object tree.
     * This method will convert omElement to the given omFactory.
     *
     */
    public static OMElement importOMElement(OMElement omElement, OMFactory omFactory) {
        // first check whether the given OMElement has the same omFactory
        if (omElement.getOMFactory().getClass().isInstance(omFactory)) {
            return omElement;
        }else {
            OMElement documentElement = new StAXOMBuilder(omFactory, omElement.getXMLStreamReader()).getDocumentElement();
            documentElement.build();
            return documentElement;
        }

    }

}