/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.synapse.util.xpath;

import com.google.gson.JsonElement;
import org.apache.axiom.om.OMAttribute;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.OMFactory;
import org.apache.axiom.om.OMNamespace;
import org.apache.axiom.om.impl.builder.StAXOMBuilder;
import org.apache.axiom.om.impl.dom.DOOMAbstractFactory;
import org.apache.axiom.om.impl.llom.OMDocumentImpl;
import org.apache.axiom.om.impl.llom.OMElementImpl;
import org.apache.axiom.om.impl.llom.OMTextImpl;
import org.apache.axiom.om.impl.llom.util.AXIOMUtil;
import org.apache.axiom.soap.SOAP11Constants;
import org.apache.axiom.soap.SOAP12Constants;
import org.apache.axiom.soap.SOAPEnvelope;
import org.apache.axiom.soap.impl.dom.factory.DOMSOAPFactory;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.synapse.MessageContext;
import org.apache.synapse.SynapseConstants;
import org.apache.synapse.config.SynapsePropertiesLoader;
import org.apache.synapse.config.xml.OMElementUtils;
import org.apache.synapse.config.xml.SynapsePath;
import org.apache.synapse.config.xml.XMLConfigConstants;
import org.apache.synapse.core.axis2.Axis2MessageContext;
import org.apache.synapse.transport.passthru.PassThroughConstants;
import org.apache.synapse.transport.passthru.config.PassThroughConfiguration;
import org.apache.synapse.transport.passthru.util.RelayUtils;
import org.apache.synapse.util.streaming_xpath.StreamingXPATH;
import org.apache.synapse.util.streaming_xpath.compiler.exception.StreamingXPATHCompilerException;
import org.apache.synapse.util.streaming_xpath.custom.components.ParserComponent;
import org.apache.synapse.util.streaming_xpath.exception.StreamingXPATHException;
import org.jaxen.BaseXPath;
import org.jaxen.Context;
import org.jaxen.ContextSupport;
import org.jaxen.JaxenException;
import org.jaxen.UnresolvableException;
import org.jaxen.util.SingletonList;

import javax.xml.namespace.QName;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * <p>XPath that has been used inside Synapse xpath processing. This has a extension function named
 * <code>get-property</code> which is use to retrieve message context properties with the given
 * name from the function</p>
 *
 * <p>For example the following function <code>get-property('prop')</code> can be evaluatedd using
 * an XPath to retrieve the message context property value with the name <code>prop</code>.</p>
 *
 * <p>Apart from that this XPath has a certain set of XPath variables associated with it. They are
 * as follows;
 * <dl>
 *   <dt><tt>body</tt></dt>
 *   <dd>The SOAP 1.1 or 1.2 body element.</dd>
 *   <dt><tt>header</tt></dt>
 *   <dd>The SOAP 1.1 or 1.2 header element.</dd>
 * </dl>
 * </p>
 *
 * <p>Also there are some XPath prefixes defined in <code>SynapseXPath</code> to access various
 * properties using XPath variables, where the variable name represents the particular prefix and
 * the property name as the local part of the variable. Those variables are;
 * <dl>
 *   <dt><tt>ctx</tt></dt>
 *   <dd>Prefix for Synapse MessageContext properties</dd>
 *   <dt><tt>axis2</tt></dt>
 *   <dd>Prefix for Axis2 MessageContext properties</dd>
 *   <dt><tt>trp</tt></dt>
 *   <dd>Prefix for the transport headers</dd>
 * </dl>
 * </p>
 *
 * <p>This XPath is Thread Safe, and provides a special set of evaluate functions for the
 * <code>MessageContext</code> and <code>SOAPEnvelope</code> as well as a method to retrieve
 * string values of the evaluated XPaths</p>
 *
 * @see org.apache.axiom.om.xpath.AXIOMXPath
 * @see #getContext(Object)
 * @see org.apache.synapse.util.xpath.SynapseXPathFunctionContext
 * @see org.apache.synapse.util.xpath.SynapseXPathVariableContext
 */
public class SynapseXPath extends SynapsePath {
    private static final long serialVersionUID = 7639226137534334222L;

    private static final Log log = LogFactory.getLog(SynapseXPath.class);

    private javax.xml.xpath.XPath domXpath = XPathFactory.newInstance().newXPath();
    private String domXpathConfig = SynapsePropertiesLoader.loadSynapseProperties().
            getProperty(SynapseConstants.FAIL_OVER_DOM_XPATH_PROCESSING);

    //Required to force stream XPath disable for some mediators, since the stream XPath 
    //has a limitation of extracting only the first element after its iterating a list so 
    //cases like PayloadMediators though the stream xPath enables we should use the old jaxen
    //way of extracting variable.
    private boolean forceDisableStreamXpath=false;

    private String enableStreamingXpath = SynapsePropertiesLoader.loadSynapseProperties().
            getProperty(SynapseConstants.STREAMING_XPATH_PROCESSING);
    private StreamingXPATH streamingXPATH =null;

    /** If the expression is identified as a XPath 2.0 expression in the compile time, we can make this property TRUE
     * Then it will not try to evaluate the expression in Jaxen (XPath 1) parser but directly evaluate with XPath 2.0*/
    private Boolean forceFailoverEvaluation = Boolean.FALSE;

    public String getEvaluator() {
        return evaluator;
    }

    public void setEvaluator(String evaluator) {
        this.evaluator = evaluator;
    }

    private String evaluator="null";




    /**
     * <p>Initializes the <code>SynapseXPath</code> with the given <code>xpathString</code> as the
     * XPath</p>
     *
     * @param xpathString xpath in its string format
     * @throws JaxenException in case of an initialization failure
     */
    public SynapseXPath(String xpathString) throws JaxenException {
        super(xpathString, log);
        this.setPathType(SynapsePath.X_PATH);

        this.expression = xpathString;

        PassThroughConfiguration conf = PassThroughConfiguration.getInstance();
        bufferSizeSupport =conf.getIOBufferSize();

        // TODO: Improve this
        if (xpathString.contains("/")) {
            contentAware = true;
        } else if (//xpathString.contains("get-property('To')") ||
                xpathString.contains("get-property('From'") ||
                xpathString.contains("get-property('FAULT')")) {
            contentAware = true;
        } else {
            contentAware = false;
        }
        
	 String propertyScope = getPropertyScope(xpathString);
	 // skip message building for scope registry, system and transport scopes
	 // for get-property() method
	 if (XMLConfigConstants.SCOPE_REGISTRY.equals(propertyScope)
			|| XMLConfigConstants.SCOPE_SYSTEM.equals(propertyScope)
             || XMLConfigConstants.SCOPE_TRANSPORT.equals(propertyScope)
             || XMLConfigConstants.SCOPE_ENVIRONMENT.equals(propertyScope)
             || XMLConfigConstants.SCOPE_FILE.equals(propertyScope)) {
         contentAware = false;
         return;
	 }

        if(xpathString.contains("$trp") || xpathString.contains("$ctx") || xpathString.contains("$axis2")){
            contentAware = false;
            return;
        }

        if("true".equals(enableStreamingXpath)){
            try {
                this.streamingXPATH = new StreamingXPATH(xpathString);
                contentAware = false;
            } catch (StreamingXPATHException e) {
                if (log.isDebugEnabled()) {
                    log.debug("Provided XPATH expression " + xpathString + " cant be evaluated custom.");
                }
                contentAware = true;
            } catch (StreamingXPATHCompilerException exception) {
                if (log.isDebugEnabled()) {
                    log.debug("Provided XPATH expression " + xpathString + " cant be evaluated custom.");
                }
                contentAware = true;
            } catch (Exception e) {
                if (log.isDebugEnabled()) {
                    log.debug("Provided XPATH expression " + xpathString + " cant be evaluated custom.");
                }
                contentAware = true;
            }
        }
    }

    private String getPropertyScope(String xPathString) {
        String xpath = null;
        String scope = "";
        if (xPathString.contains("get-property")) {
            // extract property args
            Matcher matcher = Pattern.compile("get-property\\(([^)]+)\\)").matcher(xPathString);
            if (matcher.find()) {
                xpath = matcher.group(1);
            }
            if (xpath != null) {
                String[] args = xpath.split(",");
                if (args.length == 2) {
                    // remove leading and trailing quotes
                    scope = args[0].trim().replaceAll("^\'|\'$", "").trim();
                }
            }
        }
        return scope;
    }

    /**
     * Evaluate if the expression is compilable in XPath 2.0 format. This will only be used when its failing to
     * compile in Jaxen
     *
     * @param xpathExpr XPath expression
     * @param elem Expression Configurations
     * @throws JaxenException will be thrown if the expression is malformed
     */
    public SynapseXPath(String xpathExpr, OMElement elem) throws JaxenException {
        super(xpathExpr, SynapsePath.X_PATH, log);

        /* Setting namespaces */
        OMElementUtils.addNameSpaces(this, elem, log);
        this.addNamespacesForFallbackProcessing(elem);
        domXpath.setNamespaceContext(domNamespaceMap);

        /* Setting Path type */
        this.setPathType(SynapseXPath.X_PATH);

        /* Compile and see if the expression is valid */
        try {
            XPathExpression expr = domXpath.compile(xpathExpr);
        } catch (XPathExpressionException e) {
            throw new JaxenException(e);
        }

        /* Make evaluation of this expression forced to XPath 2.0 */
        this.forceFailoverEvaluation = Boolean.TRUE;

        PassThroughConfiguration conf = PassThroughConfiguration.getInstance();
        bufferSizeSupport =conf.getIOBufferSize();

        /* Handle special cases of content aware/unaware scenarios */
        if (xpathExpr.contains("/") || xpathExpr.contains("get-property('From'") || xpathExpr
                .contains("get-property('FAULT')")) {
            contentAware = true;
        } else {
            contentAware = false;
        }

        if (xpathExpr.contains("$trp") || xpathExpr.contains("$ctx") || xpathExpr.contains("$axis2")) {
            contentAware = false;
        }
    }

    /**
     * Construct an XPath expression from a given string and initialize its
     * namespace context based on a given element.
     *
     * @param element The element that determines the namespace context of the
     *                XPath expression. See {@link #addNamespaces(OMElement)}
     *                for more details.
     * @param xpathExpr the string representation of the XPath expression.
     * @throws JaxenException if there is a syntax error while parsing the expression
     *                        or if the namespace context could not be set up
     */
    public SynapseXPath(OMElement element, String xpathExpr) throws JaxenException {
        super(element, xpathExpr, log);
        this.expression = xpathExpr;
        this.setPathType(SynapsePath.X_PATH);
    }

    /**
     * Construct an XPath expression from a given attribute.
     * The string representation of the expression is taken from the attribute
     * value, while the attribute's owner element is used to determine the
     * namespace context of the expression.
     *
     * @param attribute the attribute to construct the expression from
     * @throws JaxenException if there is a syntax error while parsing the expression
     *                        or if the namespace context could not be set up
     */
    public SynapseXPath(OMAttribute attribute) throws JaxenException {
        super(attribute, log);
        this.expression = attribute.getAttributeValue();
        this.setPathType(SynapsePath.X_PATH);
    }

    public static SynapseXPath parseXPathString(String xPathStr) throws JaxenException {
        if (xPathStr.indexOf('{') == -1) {
            return new SynapseXPath(xPathStr);
        }

        int count = 0;
        StringBuffer newXPath = new StringBuffer();

        Map<String, String> nameSpaces = new HashMap<String, String>();
        String curSegment = null;
        boolean xPath = false;

        StringTokenizer st = new StringTokenizer(xPathStr, "{}", true);
        while (st.hasMoreTokens()) {
            String s = st.nextToken();
            if ("{".equals(s)) {
                xPath = true;
            } else if ("}".equals(s)) {
                xPath = false;
                String prefix = "rp" + count++;
                nameSpaces.put(prefix, curSegment);
                newXPath.append(prefix).append(":");
            } else {
                if (xPath) {
                    curSegment = s;
                } else {
                    newXPath.append(s);
                }
            }
        }

        SynapseXPath synXPath = new SynapseXPath(newXPath.toString());
        for (Map.Entry<String,String> entry : nameSpaces.entrySet()) {
            synXPath.addNamespace(entry.getKey(), entry.getValue());
        }

        return synXPath;
    }

    /**
     * <P>Evaluates the XPath expression against the MessageContext of the current message and
     * returns a String representation of the result</p>
     *
     * @param synCtx the source message which holds the MessageContext against full context
     * @return a String representation of the result of evaluation
     */
    public String stringValueOf(MessageContext synCtx) {

        try {
            if(forceFailoverEvaluation) {
                if(log.isDebugEnabled()){
                    log.debug("Forced evaluation of the expression with the DOM parser by bypassing the Jaxen: "
                            + getExpression());
                }
                throw new UnresolvableException("Forced to evaluate with DOM parser bypassing Jaxen");
            }
            InputStream inputStream = null;
            Object result = null;
            org.apache.axis2.context.MessageContext axis2MC =null;

            if (!forceDisableStreamXpath && "true".equals(enableStreamingXpath) && streamingXPATH != null &&
                    (((Axis2MessageContext) synCtx).getEnvelope() == null ||
                            ((Axis2MessageContext) synCtx).getEnvelope().getBody().getFirstElement() == null)) {
                try {
                    axis2MC = ((Axis2MessageContext) synCtx).getAxis2MessageContext();
                    String contentType = (String) axis2MC.getProperty(SynapseConstants.AXIS2_PROPERTY_CONTENT_TYPE);
                    if (!isStreamingXpathSupportedContentType(contentType) &&
                            !Boolean.TRUE.equals(PassThroughConstants.MESSAGE_BUILDER_INVOKED)) {
                        RelayUtils.buildMessage(axis2MC);
                    } else {
                        inputStream = getMessageInputStreamPT(axis2MC);
                    }
                } catch (XMLStreamException e) {
                    handleException("Error occurred while building the message from the message context", e);
                } catch (IOException e) {
                    log.error("Error occurred while obtaining input stream from the message context", e);
                }
                if (inputStream != null) {
                    try {
                        result = streamingXPATH.getStringValue(inputStream);
                    } catch (XMLStreamException e) {
                        handleException("Error occurred while parsing the XPATH String", e);
                    } catch (StreamingXPATHException e) {
                        handleException("Error occurred while parsing the XPATH String", e);
                    }
                } else {
                    try {
                        result = streamingXPATH.getStringValue(synCtx.getEnvelope());
                    } catch (XMLStreamException e) {
                        handleException("Error occurred while parsing the XPATH String", e);
                    } catch (StreamingXPATHException e) {
                        handleException("Error occurred while parsing the XPATH String", e);
                    }
                }
            } else {
                result = evaluate(synCtx);
            }

            if (result == null) {
                return null;
            }

            StringBuffer textValue = new StringBuffer();
            if (result instanceof List) {

                List list = (List) result;
                for (Object o : list) {

                    if (o == null && list.size() == 1) {
                        return null;
                    }

                    if (o instanceof OMTextImpl) {
                        textValue.append(((OMTextImpl) o).getText());
                    } else if (o instanceof OMElementImpl) {
                        if (list.size() == 1) {
                            String s = ((OMElementImpl) o).getText();

                            // We use StringUtils.trim as String.trim does not remove U+00A0 (int 160) (No-break space)
                            if (s.replace(String.valueOf((char) 160), " ").trim().length() == 0) {
                                s = o.toString();
                            }
                            textValue.append(s);
                        } else {
                            String tmp = ((OMElementImpl) o).getText();
                            String trimmedText = tmp.replace(String.valueOf((char) 160), " ").trim();
                            String s = o.toString();
                            s = s.replace(tmp, trimmedText);
                            // We use StringUtils.trim as String.trim does not remove U+00A0 (int 160) (No-break space)
                            if (trimmedText.length() == 0) {
                                s = o.toString();
                            }
                            textValue.append(s);
                        }

                    } else if (o instanceof OMDocumentImpl) {

                        textValue.append(
                                ((OMDocumentImpl) o).getOMDocumentElement().toString());
                    } else if (o instanceof OMAttribute) {
                        textValue.append(
                                ((OMAttribute) o).getAttributeValue());
                    } else if (o instanceof SynapseXPath) {
                        textValue.append(
                                ((SynapseXPath) o).stringValueOf(synCtx));
                    } else if (o instanceof JsonElement) {
                        // Xpath evaluation can return a JSON Elements since property mediator
                        // can store JSON payloads
                        textValue.append(o.toString());
                    }
                }

            }else if("true".equals(enableStreamingXpath)&& streamingXPATH != null){
                if(!"".equals((String) result)){
                    OMElement re=AXIOMUtil.stringToOM((String) result);
                    if(re!=null){
                        textValue.append(re.getText());
                    }
                    else{
                        textValue.append(result.toString());
                    }
                }
            }
            else {
                textValue.append(result.toString());
            }

            return textValue.toString();

        } catch (UnresolvableException ex) {

            //if fail-over xpath processing is set to true in synapse properties, perform
            //xpath processing in DOM fashion which can support XPATH2.0 with supported XAPTH engine like SAXON
            if ("true".equals(domXpathConfig)) {

                if (log.isDebugEnabled()) {
                    log.debug("AXIOM xpath evaluation failed with UnresolvableException: "
                            + ex.getMessage()
                            + ". Trying to perform DOM based XPATH.");
                }

                try {
                    return evaluateDOMXPath(synCtx);
                } catch (Exception e) {
                    handleException("Evaluation of the XPath expression " + this.toString() +
                            " resulted in an error", e);
                }

            } else {
                handleException("Evaluation of the XPath expression " + this.toString() +
                        " resulted in an error", ex);
            }
        } catch (JaxenException je) {
            handleException("Evaluation of the XPath expression " + this.toString() +
                    " resulted in an error", je);
        } catch (XMLStreamException e) {
            handleException("Evaluation of the XPath expression " + this.toString() +
                    " resulted in an error", e);
        }

        return null;
    }

    /**
     * Specialized form of xpath evaluation function.An xpath evaluate() will be performed using two contexts
     * (ie:-soap-envelope and on Synapse Message Context). This is useful for evaluating xpath on a
     * nodeset for function contexts (we need both nodeset and synapse ctxts for evaluating function
     * scope expressions)
     * @param primaryContext  a context object ie:-  a soap envelope
     * @param secondaryContext  a context object ie:-synapse message ctxt
     * @return result
     */
    public Object evaluate(Object primaryContext, MessageContext secondaryContext) {
        Object result = null;
        //if result is still not found use second ctxt ie:-syn-ctxt with a wrapper to evaluate
        if (secondaryContext != null) {
            try {
                //wrapper Context is used to evaluate 'dynamic' function scope objects
                result = evaluate(new ContextWrapper((SOAPEnvelope) primaryContext,secondaryContext));
            } catch (Exception e) {
                handleException("Evaluation of the XPath expression " + this.toString() +
                        " resulted in an error", e);
            }
        } else {
            try {
                result = evaluate(primaryContext);
            } catch (JaxenException e) {
                handleException("Evaluation of the XPath expression " + this.toString() +
                        " resulted in an error", e);
            }
        }
        return result;
    }

    public void addNamespace(OMNamespace ns) throws JaxenException {
        addNamespace(ns.getPrefix(), ns.getNamespaceURI());
        domNamespaceMap.addNamespace(ns.getPrefix(), ns.getNamespaceURI());
        ParserComponent.addToNameSpaceMap(ns.getPrefix(), ns.getNamespaceURI());
    }

    /**
     * Create a {@link Context} wrapper for the provided object.
     * This methods implements the following class specific behavior:
     * <dl>
     *   <dt>{@link MessageContext}</dt>
     *   <dd>The XPath expression is evaluated against the SOAP envelope
     *       and the functions and variables defined by
     *       {@link SynapseXPathFunctionContext} and
     *       {@link SynapseXPathVariableContext} are
     *       available.</dd>
     *   <dt>{@link SOAPEnvelope}</dt>
     *   <dd>The variables defined by {@link SynapseXPathVariableContext}
     *       are available.</dd>
     * </dl>
     * For all other object types, the behavior is identical to
     * {@link BaseXPath#getContext(Object)}.
     * <p>
     * Note that the behavior described here also applies to all evaluation
     * methods such as {@link #evaluate(Object)} or {@link #selectSingleNode(Object)},
     * given that these methods all use {@link #getContext(Object)}.
     *
     * @see SynapseXPathFunctionContext#getFunction(String, String, String)
     * @see SynapseXPathVariableContext#getVariableValue(String, String, String)
     */
    @Override
    protected Context getContext(Object obj) {
        if (obj instanceof MessageContext) {
            MessageContext synCtx = (MessageContext)obj;
            ContextSupport baseContextSupport = getContextSupport();
            ContextSupport contextSupport =
                    new ContextSupport(baseContextSupport.getNamespaceContext(),
                            new SynapseXPathFunctionContext(baseContextSupport.getFunctionContext(), synCtx),
                            new SynapseXPathVariableContext(baseContextSupport.getVariableContext(), synCtx),
                            baseContextSupport.getNavigator());
            Context context = new Context(contextSupport);
            context.setNodeSet(new SingletonList(synCtx.getEnvelope()));
            return context;
        } else if (obj instanceof SOAPEnvelope) {
            SOAPEnvelope env = (SOAPEnvelope)obj;
            ContextSupport baseContextSupport = getContextSupport();
            ContextSupport contextSupport =
                    new ContextSupport(baseContextSupport.getNamespaceContext(),
                            baseContextSupport.getFunctionContext(),
                            new SynapseXPathVariableContext(baseContextSupport.getVariableContext(), env),
                            baseContextSupport.getNavigator());
            Context context = new Context(contextSupport);
            context.setNodeSet(new SingletonList(env));
            return context;
        } else if (obj instanceof ContextWrapper) {
            ContextWrapper wrapper = (ContextWrapper) obj;
            ContextSupport baseContextSupport = getContextSupport();
            ContextSupport contextSupport =
                    new ContextSupport(baseContextSupport.getNamespaceContext(),
                            baseContextSupport.getFunctionContext(),
                            new SynapseXPathVariableContext(baseContextSupport.getVariableContext(), wrapper.getMessageCtxt(),
                                    wrapper.getEnvelope()),
                            baseContextSupport.getNavigator());
            Context context = new Context(contextSupport);
            context.setNodeSet(new SingletonList(wrapper.getEnvelope()));
            return context;
        } else {
            return super.getContext(obj);
        }
    }

    public boolean isForceDisableStreamXpath() {
    	return forceDisableStreamXpath;
    }

	public void setForceDisableStreamXpath(boolean forceDisableStreamXpath) {
    	this.forceDisableStreamXpath = forceDisableStreamXpath;
    }

    /**
     * This is a wrapper class used to inject both envelope and message contexts for xpath
     * We use this to resolve function scope xpath variables
     */
    private static class ContextWrapper{
        private MessageContext ctxt;
        private SOAPEnvelope env;

        public ContextWrapper(SOAPEnvelope env, MessageContext ctxt){
            this.env = env;
            this.ctxt = ctxt;
        }

        public SOAPEnvelope getEnvelope() {
            return env;
        }

        public MessageContext getMessageCtxt() {
            return ctxt;
        }
    }

    public synchronized String evaluateDOMXPath(MessageContext synCtx) throws XPathExpressionException {

        OMElement element = synCtx.getEnvelope().getBody().getFirstElement();
        OMElement doomElement;
        if (element == null) {
            doomElement = new DOMSOAPFactory().createOMElement(new QName(""));
        } else {
            doomElement = convertToDOOM(element);
        }
        domXpath.setNamespaceContext(domNamespaceMap);
        domXpath.setXPathFunctionResolver(new GetPropertyFunctionResolver(synCtx));
        domXpath.setXPathVariableResolver(new DOMSynapseXPathVariableResolver(this.getVariableContext(), synCtx));
        /* Compile the original expression again with Saxon to be evaluated with XPath 2.0 */
        XPathExpression expr = domXpath.compile(getExpression());
        Object result = expr.evaluate(doomElement);

        if (result != null) {
            return result.toString();
        }
        return null;

    }

    private OMElement convertToDOOM(OMElement element) {

        XMLStreamReader llomReader = element.getXMLStreamReader();
        OMFactory doomFactory = DOOMAbstractFactory.getOMFactory();
        StAXOMBuilder doomBuilder = new StAXOMBuilder(doomFactory, llomReader);
        return doomBuilder.getDocumentElement();
    }

    /**
     * Checks whether Streaming Xpath supported Content-Type
     *
     * @param contentType Content-Type string
     * @return true if Content-Type is Streaming Xpath supported.
     */
    private boolean isStreamingXpathSupportedContentType(String contentType) {
        return contentType != null &&
                (contentType.indexOf(SOAP11Constants.SOAP_11_CONTENT_TYPE) != -1 ||
                        contentType.indexOf(SOAP12Constants.SOAP_12_CONTENT_TYPE) != -1 ||
                        contentType.indexOf(SynapseConstants.XML_CONTENT_TYPE) != -1);
    }

//    private InputStream getMessageInputStreamBR(MessageContext context) throws IOException {
//        InputStream temp;
//        SOAPEnvelope envelope = context.getEnvelope();
//        OMElement contentEle = envelope.getBody().getFirstElement();
//
//        if (contentEle != null) {
//
//            OMNode node = contentEle.getFirstOMChild();
//
//            if (node != null && (node instanceof OMText)) {
//
//                OMText binaryDataNode = (OMText) node;
//                DataHandler dh = (DataHandler) binaryDataNode.getDataHandler();
//                DataSource dataSource = dh.getDataSource();
//
//                if (dataSource instanceof StreamingOnRequestDataSource) {
//                    // preserve the content while reading the incoming data stream
//                    ((StreamingOnRequestDataSource) dataSource).setLastUse(false);
//                    // forcing to consume the incoming data stream
//                    temp = dataSource.getInputStream();
//                    return temp;
//                }
//            }
//        }
//        return null;
//    }
}
