/*
 * 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.html.dom;


import java.util.Vector;

import org.apache.xerces.dom.ElementImpl;
import org.apache.xerces.dom.ProcessingInstructionImpl;
import org.w3c.dom.Node;
import org.w3c.dom.html.HTMLDocument;
import org.xml.sax.AttributeList;
import org.xml.sax.DocumentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;


/**
 * This is a SAX document handler that is used to build an HTML document.
 * It can build a document from any SAX parser, but is specifically tuned
 * for working with the OpenXML HTML parser.
 * 
 * 
 * @version $Revision$ $Date$
 * @author <a href="mailto:arkin@openxml.org">Assaf Arkin</a>
 */
public class HTMLBuilder
    implements DocumentHandler
{


    /**
     * The document that is being built.
     */
    protected HTMLDocumentImpl    _document;
    
    
    /**
     * The current node in the document into which elements, text and
     * other nodes will be inserted. This starts as the document itself
     * and reflects each element that is currently being parsed.
     */
    protected ElementImpl        _current;


    /**
     * Applies only to whitespace appearing between element tags in element content,
     * as per the SAX definition, and true by default.
     */
    private boolean         _ignoreWhitespace = true;


    /**
     * Indicates whether finished building a document. If so, can start building
     * another document. Must be initially true to get the first document processed.
     */
    private boolean         _done = true;


    /**    
     * The document is only created the same time as the document element, however, certain
     * nodes may precede the document element (comment and PI), and they are accumulated
     * in this vector.
     */
    protected Vector         _preRootNodes;

    
    public void startDocument()
        throws SAXException
    {
        if ( ! _done )
	    throw new SAXException( "HTM001 State error: startDocument fired twice on one builder." );
	_document = null;
	_done = false;
    }


    public void endDocument()
        throws SAXException
    {
        if ( _document == null )
            throw new SAXException( "HTM002 State error: document never started or missing document element." );
	if ( _current != null )
	    throw new SAXException( "HTM003 State error: document ended before end of document element." );
        _current = null;
	_done = true;
    }


    public synchronized void startElement( String tagName, AttributeList attrList )
        throws SAXException
    {
        ElementImpl elem;
        int         i;
        
	if ( tagName == null )
	    throw new SAXException( "HTM004 Argument 'tagName' is null." );

	// If this is the root element, this is the time to create a new document,
	// because only know we know the document element name and namespace URI.
	if ( _document == null )
	{
	    // No need to create the element explicitly.
	    _document = new HTMLDocumentImpl();
	    elem = (ElementImpl) _document.getDocumentElement();
	    _current = elem;
	    if ( _current == null )
		throw new SAXException( "HTM005 State error: Document.getDocumentElement returns null." );

	    // Insert nodes (comment and PI) that appear before the root element.
	    if ( _preRootNodes != null )
	    {
		for ( i = _preRootNodes.size() ; i-- > 0 ; )
		    _document.insertBefore( (Node) _preRootNodes.elementAt( i ), elem );
		_preRootNodes = null;
	    }
	     
	}
	else
	{
	    // This is a state error, indicates that document has been parsed in full,
	    // or that there are two root elements.
	    if ( _current == null )
		throw new SAXException( "HTM006 State error: startElement called after end of document element." );
	    elem = (ElementImpl) _document.createElement( tagName );
	    _current.appendChild( elem );
	    _current = elem;
	}

	// Add the attributes (specified and not-specified) to this element.
        if ( attrList != null )
        {
            for ( i = 0 ; i < attrList.getLength() ; ++ i )
                elem.setAttribute( attrList.getName( i ), attrList.getValue( i ) );
        }
    }

    
    public void endElement( String tagName )
        throws SAXException
    {
        if ( _current == null )
            throw new SAXException( "HTM007 State error: endElement called with no current node." );
	if ( ! _current.getNodeName().equalsIgnoreCase( tagName ))
	    throw new SAXException( "HTM008 State error: mismatch in closing tag name " + tagName + "\n" + tagName);

	// Move up to the parent element. When you reach the top (closing the root element).
	// the parent is document and current is null.
	if ( _current.getParentNode() == _current.getOwnerDocument() )
	    _current = null;
	else
	    _current = (ElementImpl) _current.getParentNode();
    }


    public void characters( String text )
        throws SAXException
    {
	if ( _current == null )
            throw new SAXException( "HTM009 State error: character data found outside of root element." );
        _current.appendChild( _document.createTextNode(text) );
    }

    
    public void characters( char[] text, int start, int length )
        throws SAXException
    {
	if ( _current == null )
            throw new SAXException( "HTM010 State error: character data found outside of root element." );
        _current.appendChild( _document.createTextNode(new String(text, start, length)) );
    }
    
    
    public void ignorableWhitespace( char[] text, int start, int length )
        throws SAXException
    {        
        if ( ! _ignoreWhitespace )
            _current.appendChild( _document.createTextNode(new String(text, start, length)) );
     }
    
    
    public void processingInstruction( String target, String instruction )
        throws SAXException
    {        
	// Processing instruction may appear before the document element (in fact, before the
	// document has been created, or after the document element has been closed.
        if ( _current == null && _document == null )
	{
	    if ( _preRootNodes == null )
		_preRootNodes = new Vector();
	    _preRootNodes.addElement( new ProcessingInstructionImpl( null, target, instruction ) );
	}
	else
        if ( _current == null && _document != null )
            _document.appendChild( _document.createProcessingInstruction(target, instruction) );
	else
        _current.appendChild( _document.createProcessingInstruction(target, instruction) );
    }
    
    
    public HTMLDocument getHTMLDocument()
    {
        return _document;
    }

    
    public void setDocumentLocator( Locator locator )
    {
        // ignored
    }


}
