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 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/**

 * 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 com.sun.org.apache.xml.internal.security.utils;

import java.lang.reflect.Constructor;

import java.lang.reflect.Method;

import java.lang.reflect.Modifier;

import javax.xml.transform.ErrorListener;

import javax.xml.transform.SourceLocator;

import javax.xml.transform.TransformerException;

import com.sun.org.apache.xml.internal.security.transforms.implementations.FuncHere;

import com.sun.org.apache.xml.internal.utils.PrefixResolver;

import com.sun.org.apache.xml.internal.utils.PrefixResolverDefault;

import com.sun.org.apache.xpath.internal.Expression;

import com.sun.org.apache.xpath.internal.XPath;

import com.sun.org.apache.xpath.internal.XPathContext;

import com.sun.org.apache.xpath.internal.compiler.FunctionTable;

import com.sun.org.apache.xpath.internal.objects.XObject;

import org.w3c.dom.Document;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

/**

 * An implementation of XPathAPI using Xalan. This supports the "here()" function defined in the digital

 * signature spec.

 */

public class XalanXPathAPI implements XPathAPI {

    private static final com.sun.org.slf4j.internal.Logger LOG =

        com.sun.org.slf4j.internal.LoggerFactory.getLogger(XalanXPathAPI.class);

    private String xpathStr;

    private XPath xpath;

    private static FunctionTable funcTable;

    private static boolean installed;

    private XPathContext context;

    static {

        fixupFunctionTable();

    }

    /**

     *  Use an XPath string to select a nodelist.

     *  XPath namespace prefixes are resolved from the namespaceNode.

     *

     *  @param contextNode The node to start searching from.

     *  @param xpathnode

     *  @param str

     *  @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.

     *  @return A NodeIterator, should never be null.

     *

     * @throws TransformerException

     */

    public NodeList selectNodeList(

        Node contextNode, Node xpathnode, String str, Node namespaceNode

    ) throws TransformerException {

        // Execute the XPath, and have it return the result

        XObject list = eval(contextNode, xpathnode, str, namespaceNode);

        // Return a NodeList.

        return list.nodelist();

    }

    /**

     * Evaluate an XPath string and return true if the output is to be included or not.

     *  @param contextNode The node to start searching from.

     *  @param xpathnode The XPath node

     *  @param str The XPath expression

     *  @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.

     */

    public boolean evaluate(Node contextNode, Node xpathnode, String str, Node namespaceNode)

        throws TransformerException {

        XObject object = eval(contextNode, xpathnode, str, namespaceNode);

        return object.bool();

    }

    /**

     * Clear any context information from this object

     */

    public void clear() {

        xpathStr = null;

        xpath = null;

        context = null;

    }

    public static synchronized boolean isInstalled() {

        return installed;

    }

    private XObject eval(Node contextNode, Node xpathnode, String str, Node namespaceNode)

        throws TransformerException {

        if (context == null) {

            context = new XPathContext(xpathnode);

            context.setSecureProcessing(true);

        }

        // Create an object to resolve namespace prefixes.

        // XPath namespaces are resolved from the input context node's document element

        // if it is a root node, or else the current context node (for lack of a better

        // resolution space, given the simplicity of this sample code).

        Node resolverNode =

            (namespaceNode.getNodeType() == Node.DOCUMENT_NODE)

                ? ((Document) namespaceNode).getDocumentElement() : namespaceNode;

        PrefixResolverDefault prefixResolver = new PrefixResolverDefault(resolverNode);

        if (!str.equals(xpathStr)) {

            if (str.indexOf("here()") > 0) {

                context.reset();

            }

            xpath = createXPath(str, prefixResolver);

            xpathStr = str;

        }

        // Execute the XPath, and have it return the result

        int ctxtNode = context.getDTMHandleFromNode(contextNode);

        return xpath.execute(context, ctxtNode, prefixResolver);

    }

    private XPath createXPath(String str, PrefixResolver prefixResolver) throws TransformerException {

        XPath xpath = null;

        Class<?>[] classes = new Class<?>[]{String.class, SourceLocator.class, PrefixResolver.class, int.class,

                                      ErrorListener.class, FunctionTable.class};

        Object[] objects =

            new Object[]{str, null, prefixResolver, XPath.SELECT, null, funcTable};

        try {

            Constructor<?> constructor = XPath.class.getConstructor(classes);

            xpath = (XPath) constructor.newInstance(objects);

        } catch (Exception ex) {

            LOG.debug(ex.getMessage(), ex);

        }

        if (xpath == null) {

            xpath = new XPath(str, null, prefixResolver, XPath.SELECT, null);

        }

        return xpath;

    }

    private static synchronized void fixupFunctionTable() {

        installed = false;

        LOG.debug("Registering Here function");

        /**

         * Try to register our here() implementation as internal function.

         */

        try {

            Class<?>[] args = {String.class, Expression.class};

            Method installFunction = FunctionTable.class.getMethod("installFunction", args);

            if ((installFunction.getModifiers() & Modifier.STATIC) != 0) {

                Object[] params = {"here", new FuncHere()};

                installFunction.invoke(null, params);

                installed = true;

            }

        } catch (Exception ex) {

            LOG.debug("Error installing function using the static installFunction method", ex);

        }

        if (!installed) {

            try {

                funcTable = new FunctionTable();

                Class<?>[] args = {String.class, Class.class};

                Method installFunction = FunctionTable.class.getMethod("installFunction", args);

                Object[] params = {"here", FuncHere.class};

                installFunction.invoke(funcTable, params);

                installed = true;

            } catch (Exception ex) {

                LOG.debug("Error installing function using the static installFunction method", ex);

            }

        }

        if (installed) {

            LOG.debug("Registered class {} for XPath function 'here()' function in internal table", FuncHere.class.getName());

        } else {

            LOG.debug("Unable to register class {} for XPath function 'here()' function in internal table", FuncHere.class.getName());

        }

    }

}