/*
    * Copyright 2007 Edward Kuns
    *
    * 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.
   *
   * $Id: XMLBuilder.java 0000 2007-01-11 00:00:00Z ekuns $
   */
  package org.castor.xmlctf.xmldiff.xml;
  
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Stack;
  
  import org.castor.xmlctf.xmldiff.xml.nodes.Attribute;
  import org.castor.xmlctf.xmldiff.xml.nodes.Element;
  import org.castor.xmlctf.xmldiff.xml.nodes.Namespace;
  import org.castor.xmlctf.xmldiff.xml.nodes.ParentNode;
  import org.castor.xmlctf.xmldiff.xml.nodes.ProcessingInstruction;
  import org.castor.xmlctf.xmldiff.xml.nodes.Root;
  import org.castor.xmlctf.xmldiff.xml.nodes.Text;
  import org.xml.sax.Attributes;
  import org.xml.sax.ContentHandler;
  import org.xml.sax.Locator;
  import org.xml.sax.SAXException;
  
  /**
   * A ContentHandler implementation that builds a tree of XMLNodes.
   *
   * @author <a href="mailto:edward.kuns@aspect.com">Edward Kuns</a>
   * @version $Revision: 0000 $ $Date: 2007-01-11 00:00:00 -0600 (Thu, 11 Jan 2007) $
   * @since Castor 1.1
   */
  public class XMLContentHandler implements ContentHandler {
  
    /** The current node stack. */
    private final Stack _nodeStack = new Stack();
    /** Root BaseNode, the BaseNode being created.. */
    private final Root _root = new Root();
  
    /** SAX document Locator, set by a SAX Parser. */
    private Locator _locator = null;
    /** The current node to which we are adding content. */
    private ParentNode _currentNode = null;
    /** Keeps track of all URL mapping prefixes currently defined. */
    private Map _prefixes = new HashMap();
  
    /**
     * Creates a new XMLBuilder.
     */
    public XMLContentHandler() {
      _nodeStack.push(_root);
      _currentNode = _root;
    }
  
    /**
     * Creates a new text node from incoming characters.
     *
     * @param chars The character array containing the XML content
     * @param start First index of character for our new Text node
     * @param length count of characters for our Text node.
     * @throws org.xml.sax.SAXException never
     */
    public void characters(final char[] chars, final int start, final int length)
        throws org.xml.sax.SAXException {
      _currentNode.addChild(new Text(new String(chars, start, length)));
    }
  
    /**
     * Signals the end of the document.
     * 
     * @throws org.xml.sax.SAXException never
     */
    public void endDocument() throws org.xml.sax.SAXException {
      // Nothing to do
    }
  
    /**
     * Signals the end of an Element.
     * 
     * @param uri The namespace URI
     * @param name the local name of the element.
     * @param qName the qualified naem of the element
     * @throws org.xml.sax.SAXException if we have a mismatched end element tag
     */
    public void endElement(final String uri, final String name, final String qName)
        throws org.xml.sax.SAXException {
      final String localName = name;
  
      final int idx = qName.indexOf(':');
      final String prefix = (idx >= 0) ? qName.substring(0, idx) : "";
 
     // Check the prefix to make sure it is appropriate
     String uriOfPrefix = _currentNode.getNamespaceURI(prefix);
     String uriOfElement = _currentNode.getNamespaceURI();
     if ((uriOfPrefix == null ^ uriOfElement == null)
         || (uriOfPrefix != null && !uriOfPrefix.equals(uriOfElement))) {
       throw new org.xml.sax.SAXException("In Element " + qName + ", URI of prefix " + uriOfPrefix
           + " does not match URI of Element " + uriOfElement);
     }
 
     String cName = _currentNode.getLocalName();
     if (!cName.equals(localName)) {
       String err =
           "Element end tag mismatch:  expecting </" + cName + "> but recieved </" + localName + ">";
       throw new SAXException(err);
     }
 
     _nodeStack.pop();
     _currentNode = (ParentNode) _nodeStack.peek();
   }
 
   /**
    * Signals the end of prefix mapping.
    * 
    * @param prefix The namespace prefix mapping that is ending
    * @throws org.xml.sax.SAXException never
    */
   public void endPrefixMapping(final String prefix) throws SAXException {
     _prefixes.remove(prefix);
   }
 
   /**
    * Returns the Root node.
    * 
    * @return the root node.
    */
   public Root getRoot() {
     return _root;
   }
 
   /**
    * Ignores ignorable whitespace.
    *
    * @param chars The character array containing the XML content
    * @param start First index of the ignorable whitespace
    * @param length count of characters for the ignorable whitespace
    * @throws org.xml.sax.SAXException never
    */
   public void ignorableWhitespace(final char[] chars, final int start, final int length)
       throws org.xml.sax.SAXException {
     // Deliberately ignore -- we don't care
   }
 
   /**
    * Creates a new Processing Instruction node.
    *
    * @param target the target of the processing instruction
    * @param data the content of the processing instruction
    * @throws org.xml.sax.SAXException never
    */
   public void processingInstruction(final String target, final String data)
       throws org.xml.sax.SAXException {
     ProcessingInstruction pi = new ProcessingInstruction(target, data);
     _currentNode.addChild(pi);
   }
 
   /**
    * Configures the Locator we will use.
    *
    * @param locator the Locator used by this DocumentHandler.
    */
   public void setDocumentLocator(final Locator locator) {
     _locator = locator;
   }
 
   /**
    * Gives notification about a skipped Entity during XML parsing.
    * 
    * @param name the name of the skipped entity.
    */
   public void skippedEntity(final String name) {
     // Nothing to do
   }
 
   /**
    * Signals the beginning of the document.
    * 
    * @throws org.xml.sax.SAXException never
    */
   public void startDocument() throws SAXException {
     // Nothing to do
   }
 
   /**
    * Signals the beginning of an Element node.
    *
    * @param uri The namespace URI
    * @param name the local name of the element.
    * @param qName the qualified naem of the element
    * @param atts a list of attributes for this Element
    * @throws org.xml.sax.SAXException If we are not given an element name.
    */
   public void startElement(final String uri, final String name, final String qName,
       final Attributes atts) throws org.xml.sax.SAXException {
     if (qName == null) {
       throw new SAXException("No Element name given");
     }
 
     final String prefix;
     final String localName;
 
     int idx = qName.indexOf(':');
     if (idx >= 0) {
       prefix = qName.substring(0, idx);
       localName = qName.substring(idx + 1);
     } else {
       prefix = "";
       localName = qName;
     }
 
     Element element = new Element(null, localName);
 
     if (_locator != null) {
       element.setLocation(new Location(_locator));
     }
 
     _currentNode.addChild(element);
 
     // Add all current namespaces to this element
     for (Iterator i = _prefixes.entrySet().iterator(); i.hasNext();) {
       Map.Entry me = (Map.Entry) i.next();
       element.addNamespace(new Namespace((String) me.getKey(), (String) me.getValue()));
     }
 
     // Then add all attributes
     if (atts != null && atts.getLength() > 0) {
       for (int i = 0; i < atts.getLength(); i++) {
         String attName = atts.getQName(i);
         String ns = null;
         idx = attName.indexOf(':');
         if (idx > 0) {
           ns = element.getNamespaceURI(attName.substring(0, idx));
           attName = attName.substring(idx + 1);
         }
         element.addAttribute(new Attribute(ns, attName, atts.getValue(i)));
       }
     }
 
     // Set the namespace on this Element, if one is explicit or defaulted
     if (prefix != null && prefix.length() > 0) {
       String namespace = element.getNamespaceURI(prefix);
       element.setNamespace(namespace);
     } else {
       String namespace = element.getNamespaceURI("");
       if (namespace != null) {
         element.setNamespace(namespace);
       }
     }
 
     _nodeStack.push(element);
     _currentNode = element;
   }
 
   /**
    * Begins the scope of a prefix-URI Namespace mapping.
    * 
    * @param prefix The namespace prefix mapping that is ending
    * @param uri The namespace URI
    * @throws org.xml.sax.SAXException never
    */
   public void startPrefixMapping(final String prefix, final String uri) {
     _prefixes.put(prefix, uri);
   }
 
 }