/*
    * $Header$
    * $Revision$
    * $Date$
    *
    * ====================================================================
    *
    * Copyright 2000-2002 bob mcwhirter & James Strachan.
    * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   * 
   *   * Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the following disclaimer.
   * 
   *   * Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in the
   *     documentation and/or other materials provided with the distribution.
   * 
   *   * Neither the name of the Jaxen Project nor the names of its
   *     contributors may be used to endorse or promote products derived 
   *     from this software without specific prior written permission.
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
   * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
   * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * ====================================================================
   * This software consists of voluntary contributions made by many 
   * individuals on behalf of the Jaxen Project and was originally 
   * created by bob mcwhirter <bob@werken.com> and 
   * James Strachan <jstrachan@apache.org>.  For more information on the 
   * Jaxen Project, please see <http://www.jaxen.org/>.
   * 
   * $Id$
   */
  
  ////////////////////////////////////////////////////////////////////
  // Inner class for a Namespace node.
  ////////////////////////////////////////////////////////////////////
  
  package org.jaxen.dom;
  
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.HashMap;
  
  import org.jaxen.pattern.Pattern;
  import org.w3c.dom.DOMException;
  import org.w3c.dom.Document;
  import org.w3c.dom.NamedNodeMap;
  import org.w3c.dom.Node;
  import org.w3c.dom.NodeList;
  import org.w3c.dom.UserDataHandler;
  
  
  /**
   * Extension DOM2/DOM3 node type for a namespace node.
   *
   * <p>This class implements the DOM2 and DOM3 {@link Node} interface
   * to allow namespace nodes to be included in the result
   * set of an XPath selectNodes operation, even though DOM does
   * not model namespaces in scope as separate nodes.</p>
   *
   * <p>
   * While all of the DOM2 methods are implemented with reasonable
   * defaults, there will be some unexpected surprises, so users are
   * advised to test for NamespaceNodes and filter them out from the
   * result sets as early as possible.
   * </p>
   *
   * <ol>
   *
   * <li>The {@link #getNodeType} method returns {@link #NAMESPACE_NODE},
   * which is not one of the usual DOM2 node types.  Generic code may
   * fall unexpectedly out of switch statements, for example.</li>
   *
   * <li>The {@link #getOwnerDocument} method returns the owner document
   * of the parent node, but that owner document will know nothing about
   * the namespace node.</li>
   *
   * <li>The {@link #isSupported} method always returns false.</li>
   *
   * <li>The DOM3 methods sometimes throw UnsupportedOperationException.
   *     They're here only to allow this class to be compiled with Java 1.5.
   *     Do not call or rely on them.</li>
   * </ol>
   *
   * <p>All attempts to modify a <code>NamespaceNode</code> will fail with a {@link
  * DOMException} ({@link
  * DOMException#NO_MODIFICATION_ALLOWED_ERR}).</p>
  *
  * @author David Megginson
  * @author Elliotte Rusty Harold
  * @see DocumentNavigator
  */
 public class NamespaceNode implements Node
 {
 
     /**
      * Constant: this is a NamespaceNode.
      *
      * @see #getNodeType
      */
     public final static short NAMESPACE_NODE = Pattern.NAMESPACE_NODE;
 
     // FIXME "Note: Numeric codes up to 200 are reserved to W3C for possible future use."
     // We should be using higher codes. Here we're using 13, the same as DOM 3's type for XPathNamespace.
     // However, that's only a note not a recommendation.
 
     /**
      * Create a new NamespaceNode.
      *
      * @param parent the DOM node to which the namespace is attached
      * @param name the namespace prefix
      * @param value the namespace URI
      */
     public NamespaceNode (Node parent, String name, String value)
     {
         this.parent = parent;
         this.name = name == null ? "" : name;
         this.value = value;
     }
 
 
     /**
      * Constructor.
      *
      * @param parent the DOM node to which the namespace is attached
      * @param attribute the DOM attribute object containing the
      *        namespace declaration
      */
     NamespaceNode (Node parent, Node attribute)
     {
         String attributeName = attribute.getNodeName();
     
         if (attributeName.equals("xmlns")) {
             this.name = "";
         }
         else if (attributeName.startsWith("xmlns:")) {
             this.name = attributeName.substring(6); // the part after "xmlns:"
         }
         else { // workaround for Crimson bug; Crimson incorrectly reports the prefix as the node name
             this.name = attributeName;
         }
         this.parent = parent;
         this.value = attribute.getNodeValue();
     }
 
 
 
     ////////////////////////////////////////////////////////////////////
     // Implementation of org.w3c.dom.Node.
     ////////////////////////////////////////////////////////////////////
 
 
     /**
      * Get the namespace prefix.
      *
      * @return the namespace prefix, or "" for the default namespace
      */
     public String getNodeName ()
     {
         return name;
     }
 
 
     /**
      * Get the namespace URI.
      *
      * @return the namespace URI
      */
     public String getNodeValue ()
     {
         return value;
     }
 
 
     /**
      * Change the namespace URI (always fails).
      *
      * @param value the new URI
      * @throws DOMException always
      */
     public void setNodeValue (String value) throws DOMException
     {
         disallowModification();
     }
 
 
     /**
      * Get the node type.
      *
      * @return always {@link #NAMESPACE_NODE}.
      */
     public short getNodeType ()
     {
         return NAMESPACE_NODE;
     }
 
 
     /**
      * Get the parent node.
      *
      * <p>This method returns the element that was queried for Namespaces
      * in effect, <em>not</em> necessarily the actual element containing
      * the Namespace declaration.</p>
      *
      * @return the parent node (not null)
      */
     public Node getParentNode ()
     {
         return parent;
     }
 
 
     /**
      * Get the list of child nodes.
      *
      * @return an empty node list
      */
     public NodeList getChildNodes ()
     {
         return new EmptyNodeList();
     }
 
 
     /**
      * Get the first child node.
      *
      * @return null
      */
     public Node getFirstChild ()
     {
         return null;
     }
 
 
     /**
      * Get the last child node.
      *
      * @return null
      */
     public Node getLastChild ()
     {
         return null;
     }
 
 
     /**
      * Get the previous sibling node.
      *
      * @return null
      */
     public Node getPreviousSibling ()
     {
         return null;
     }
 
 
     /**
      * Get the next sibling node.
      *
      * @return null
      */
     public Node getNextSibling ()
     {
         return null;
     }
 
 
     /**
      * Get the attribute nodes.
      *
      * @return null
      */
     public NamedNodeMap getAttributes ()
     {
         return null;
     }
 
 
     /**
      * Get the owner document.
      *
      * @return the owner document <em>of the parent node</em>
      */
     public Document getOwnerDocument ()
     {
         if (parent == null) return null;
         return parent.getOwnerDocument();
     }
 
 
     /**
      * Insert a new child node (always fails).
      * 
      * @param newChild the node to add
      * @param refChild ignored
      * @return never
      * @throws DOMException always
      * @see Node#insertBefore
      */
     public Node insertBefore (Node newChild, Node refChild)
     throws DOMException
     {
         disallowModification();
         return null;
     }
 
 
     /**
      * Replace a child node (always fails).
      *
      * @param newChild the node to add
      * @param oldChild the child node to replace
      * @return never
      * @throws DOMException always
      * @see Node#replaceChild
      */
     public Node replaceChild (Node newChild, Node oldChild) throws DOMException
     {
         disallowModification();
         return null;
     }
 
 
     /**
      * Remove a child node (always fails).
      *
      * @param oldChild the child node to remove
      * @return never
      * @throws DOMException always
      * @see Node#removeChild
      */
     public Node removeChild(Node oldChild) throws DOMException
     {
         disallowModification();
         return null;
     }
 
 
     /**
      * Append a new child node (always fails).
      *
      * @param newChild the node to add
      * @return never
      * @throws DOMException always
      * @see Node#appendChild
      */
     public Node appendChild(Node newChild) throws DOMException
     {
         disallowModification();
         return null;
     }
 
 
     /**
      * Test for child nodes.
      *
      * @return false
      */
     public boolean hasChildNodes()
     {
         return false;
     }
 
 
     /**
      * Create a copy of this node.
      *
      * @param deep make a deep copy (no effect, since namespace nodes
      *        don't have children).
      * @return a new copy of this namespace node
      */
     public Node cloneNode (boolean deep)
     {
         return new NamespaceNode(parent, name, value);
     }
 
 
     /**
      * Normalize the text descendants of this node.
      *
      * <p>This method has no effect, since namespace nodes have no
      * descendants.</p>
      */
     public void normalize ()
     {
     // no op
     }
 
 
     /**
      * Test if a DOM2 feature is supported. (None are.)
      *
      * @param feature the feature name
      * @param version the feature version
      * @return false
      */
     public boolean isSupported(String feature, String version)
     {
         return false;
     }
 
 
     /**
      * Get the namespace URI of this node.
      *
      * <p>Namespace declarations are not themselves
      * Namespace-qualified.</p>
      *
      * @return null
      */
     public String getNamespaceURI()
     {
        return null;
     }
 
 
     /**
      * Get the namespace prefix of this node.
      *
      * <p>Namespace declarations are not themselves
      * namespace-qualified.</p>
      *
      * @return null
      * @see #getLocalName
      */
     public String getPrefix()
     {
         return null;
     }
 
 
     /**
      * Change the namespace prefix of this node (always fails).
      *
      * @param prefix the new prefix
      * @throws DOMException always thrown
      */
     public void setPrefix(String prefix)
     throws DOMException
     {
         disallowModification();
     }
 
 
     /**
      * Get the XPath name of the namespace node;; i.e. the
      * namespace prefix.
      *
      * @return the namespace prefix
      */
     public String getLocalName ()
     {
         return name;
     }
 
 
     /**
      * Test if this node has attributes.
      *
      * @return false
      */
     public boolean hasAttributes ()
     {
         return false;
     }
 
 
     /**
      * Throw a NO_MODIFICATION_ALLOWED_ERR DOMException.
      *
      * @throws DOMException always thrown
      */
     private void disallowModification () throws DOMException
     {
         throw new DOMException(DOMException.NO_MODIFICATION_ALLOWED_ERR,
                    "Namespace node may not be modified");
     }
 
 
 
     ////////////////////////////////////////////////////////////////////
     // Override default methods from java.lang.Object.
     ////////////////////////////////////////////////////////////////////
 
 
     /**
      * Generate a hash code for a namespace node.
      *
      * @return a hash code for this node
      */
     public int hashCode ()
     {
         return hashCode(parent) + hashCode(name) + hashCode(value);
     }
 
 
     /**
      * Test for equivalence with another object.
      *
      * <p>Two Namespace nodes are considered equivalent if their parents,
      * names, and values are equal.</p>
      *
      * @param o the object to test for equality
      * @return true if the object is equivalent to this node, false
      *         otherwise
      */
     public boolean equals (Object o)
     {
         if (o == this) return true;
         else if (o == null) return false;
         else if (o instanceof NamespaceNode) {
             NamespaceNode ns = (NamespaceNode)o;
             return (equals(parent, ns.getParentNode()) &&
                 equals(name, ns.getNodeName()) &&
                 equals(value, ns.getNodeValue()));
         } else {
             return false;
         }
     }
 
 
     /**
      * Helper method for generating a hash code.
      *
      * @param o the object for generating a hash code (possibly null)
      * @return the object's hash code, or 0 if the object is null
      * @see java.lang.Object#hashCode
      */
     private int hashCode (Object o)
     {
         return (o == null ? 0 : o.hashCode());
     }
 
 
     /**
      * Helper method for comparing two objects.
      *
      * @param a the first object to compare (possibly null)
      * @param b the second object to compare (possibly null)
      * @return true if the objects are equivalent or are both null
      * @see java.lang.Object#equals
      */
     private boolean equals (Object a, Object b)
     {
         return ((a == null && b == null) ||
           (a != null && a.equals(b)));
     }
 
 
     ////////////////////////////////////////////////////////////////////
     // Internal state.
     ////////////////////////////////////////////////////////////////////
 
     private Node parent;
     private String name;
     private String value;
 
 
 
     ////////////////////////////////////////////////////////////////////
     // Inner class: empty node list.
     ////////////////////////////////////////////////////////////////////
 
 
     /**
      * A node list with no members.
      *
      * <p>This class is necessary for the {@link Node#getChildNodes}
      * method, which must return an empty node list rather than
      * null when there are no children.</p>
      */
     private static class EmptyNodeList implements NodeList
     {
 
         /**
          * @see NodeList#getLength
          */
         public int getLength ()
         {
             return 0;
         }
     
     
         /**
          * @see NodeList#item
          */
         public Node item(int index)
         {
             return null;
         }
     
     }
 
     ////////////////////////////////////////////////////////////////////
     // DOM Level 3 methods
     ////////////////////////////////////////////////////////////////////
 
     /**
      * Return the base URI of the document containing this node. 
      * This only works in DOM 3.
      *
      * @return null
      */
     public String getBaseURI() {
         Class<Node> clazz = Node.class;
         try {
             Class[] args = new Class[0];
             Method getBaseURI = clazz.getMethod("getBaseURI", args);
             String base = (String) getBaseURI.invoke(this.getParentNode(), args);
             return base;
         }
         catch (Exception ex) {
             return null;
         }
     }
 
 
     /**
      * Compare relative position of this node to another nbode. (Always fails).
      * This method is included solely for compatibility with the superclass.
      * 
      * @param other the node to compare to
      *
      * @return never
      * @throws DOMException NOT_SUPPORTED_ERR
      */
     public short compareDocumentPosition(Node other) throws DOMException {
         DOMException ex = new DOMException(
           DOMException.NOT_SUPPORTED_ERR,
           "DOM level 3 interfaces are not fully implemented in Jaxen's NamespaceNode class"
         );
         throw ex;
     }
 
 
     /**
      * Return the namespace URI.
      *
      * @return the namespace URI
      * @see #getNodeValue
      */
     public String getTextContent() {
         return value;
     }
 
 
     /**
      * Change the value of this node (always fails).
      * This method is included solely for compatibility with the superclass.
      *
      * @param textContent the new content
      * @throws DOMException always
      */
     public void setTextContent(String textContent) throws DOMException {
         disallowModification();
     }
 
 
     /**
      * Returns true if and only if this object represents the same XPath namespace node
      * as the argument; that is, they have the same parent, the same prefix, and the
      * same URI.
      * 
      * @param other the node to compare to
      * @return true if this object represents the same XPath namespace node
      *     as other; false otherwise
      */
     public boolean isSameNode(Node other)  {
         boolean a = this.isEqualNode(other);
         // a bit flaky (should really be 
         // this.getParentNode().isEqual(other.getParentNode())
         // but we want this to compile in Java 1.4 without problems
         // Note that this will mess up code coverage since you can't cover both
         // branches in the same VM
         boolean b;
         Node thisParent = this.getParentNode();
         Node thatParent = other.getParentNode();
         try {
             Class<Node> clazz = Node.class;
             Class[] args = {clazz};
             Method isEqual = clazz.getMethod("isEqual", args);
             Object[] args2 = new Object[1];
             args2[0] = thatParent;
             Boolean result = (Boolean) isEqual.invoke(thisParent, args2);
             b = result.booleanValue();
         }
         catch (NoSuchMethodException ex) {
             b = thisParent.equals(thatParent);
         }
         catch (InvocationTargetException ex) {
             b = thisParent.equals(thatParent);
         }
         catch (IllegalAccessException ex) {
             b = thisParent.equals(thatParent);
         }
         
         return a && b;
         
     }
 
 
     /**
      * Return the prefix bound to this namespace URI within the scope
      * of this node. 
      * 
      * @param namespaceURI the URI to find a prefix binding for
      *
      * @return a prefix matching this namespace URI
      * @throws UnsupportedOperationException in DOM 2
      */
     public String lookupPrefix(String namespaceURI) {
         // This could be fully implemented even in Java 1.4. See
         // http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407/namespaces-algorithms.html#lookupNamespaceURIAlgo
         // It hardly seems worth the effort though.
         
         try {
             Class<Node> clazz = Node.class;
             Class[] argTypes = {String.class};
             Method lookupPrefix = clazz.getMethod("lookupPrefix", argTypes);
             String[] args = {namespaceURI};
             String result = (String) lookupPrefix.invoke(parent, args);
             return result;
         }
         catch (NoSuchMethodException ex) {
             throw new UnsupportedOperationException("Cannot lookup prefixes in DOM 2");
         }
         catch (InvocationTargetException ex) {
             throw new UnsupportedOperationException("Cannot lookup prefixes in DOM 2");
         }
         catch (IllegalAccessException ex) {
             throw new UnsupportedOperationException("Cannot lookup prefixes in DOM 2");
         }
         
     }
 
 
     /**
      * Return true if the specified URI is the default namespace in
      * scope (always fails). This method is included solely for 
      * compatibility with the superclass.
      * 
      * @param namespaceURI the URI to check
      *
      * @return never
      * @throws UnsupportedOperationException always
      */
     public boolean isDefaultNamespace(String namespaceURI) {
         return namespaceURI.equals(this.lookupNamespaceURI(null));
     }
 
 
     /**
      * Return the namespace URI mapped to the specified
      * prefix within the scope of this namespace node.
      * 
      * @param prefix the prefix to search for
      *
      * @return the namespace URI mapped to this prefix
      * @throws UnsupportedOperationException in DOM 2
      */
     public String lookupNamespaceURI(String prefix) {
         // This could be fully implemented even in Java 1.4. See
         // http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407/namespaces-algorithms.html#lookupNamespaceURIAlgo
         // It hardly seems worth the effort though.
         
         try {
             Class<Node> clazz = Node.class;
             Class[] argTypes = {String.class};
             Method lookupNamespaceURI = clazz.getMethod("lookupNamespaceURI", argTypes);
             String[] args = {prefix};
             String result = (String) lookupNamespaceURI.invoke(parent, args);
             return result;
         }
         catch (NoSuchMethodException ex) {
             throw new UnsupportedOperationException("Cannot lookup namespace URIs in DOM 2");
         }
         catch (InvocationTargetException ex) {
             throw new UnsupportedOperationException("Cannot lookup namespace URIs in DOM 2");
         }
         catch (IllegalAccessException ex) {
             throw new UnsupportedOperationException("Cannot lookup namespace URIs in DOM 2");
         }
     }
 
 
     /**
      * Returns true if this object binds the same prefix to the same URI.
      * That is, this object has the same prefix and URI as the argument.
      * 
      * @param arg the node to compare to
      * @return true if this object has the same prefix and URI as the argument; false otherwise
      */
     public boolean isEqualNode(Node arg) {
         if (arg.getNodeType() == this.getNodeType()) {
             NamespaceNode other = (NamespaceNode) arg;
             if (other.name == null && this.name != null) return false;
             else if (other.name != null && this.name == null) return false;
             else if (other.value == null && this.value != null) return false;
             else if (other.value != null && this.value == null) return false;
             else if (other.name == null && this.name == null) {
                 return other.value.equals(this.value);
             }
 
             return other.name.equals(this.name) && other.value.equals(this.value);
         }
         return false;
     }
 
 
     /**
      * Returns the value of the requested feature. Always returns null.
      * 
      * @return null
      */
     public Object getFeature(String feature, String version) {
         return null;
     }
 
     
     // XXX userdata needs testing
     private HashMap<String, Object> userData = new HashMap<String, Object>();
 
     /**
      * Associates an object with a key. 
      * 
      * @param key the key by which the data will be retrieved
      * @param data the object to store with the key
      * @param handler ignored since namespace nodes cannot be imported, cloned, or renamed
      * 
      * @return the value previously associated with this key; or null
      *     if there isn't any such previous value
      */
     public Object setUserData(String key, Object data, UserDataHandler handler) {
         Object oldValue = getUserData(key);
         userData.put(key, data);
         return oldValue;
     }
 
 
     /**
      * Returns the user data associated with the given key. 
      * 
      * @param key the lookup key
      * 
      * @return the object associated with the key; or null if no such object is available
      */
     public Object getUserData(String key) {
         return userData.get(key);
     }
     
 }
 
 // end of NamespaceNode.java