/*

   Copyright 1999-2003  The Apache Software Foundation 

   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.

*/

package org.apache.batik.transcoder;

import java.io.IOException;

import org.apache.batik.dom.util.DocumentFactory;
import org.apache.batik.dom.util.SAXDocumentFactory;
import org.apache.batik.transcoder.keys.BooleanKey;
import org.apache.batik.transcoder.keys.DOMImplementationKey;
import org.apache.batik.transcoder.keys.StringKey;
import org.apache.batik.util.XMLResourceDescriptor;
import org.w3c.dom.DOMException;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;

/**
 * This class may be the base class of all transcoders which take an
 * XML document as input and which need to build a DOM tree. In order
 * to take advantage of this class, you have to specify the following
 * transcoding hints:
 *
 * <ul>
 * <li><tt>KEY_DOM_IMPLEMENTATION</tt>: the DOM Implementation to use
 *
 * <li><tt>KEY_DOCUMENT_ELEMENT_NAMESPACE_URI</tt>: the namespace URI of the
 * document to create
 *
 * <li><tt>KEY_DOCUMENT_ELEMENT</tt>: the qualified name of the document type
 * to create
 * </ul>
 *
 * @author <a href="mailto:Thierry.Kormann@sophia.inria.fr">Thierry Kormann</a>
 * @version $Id$
 */
public abstract class XMLAbstractTranscoder extends AbstractTranscoder {

    /**
     * Constructs a new <tt>XMLAbstractTranscoder</tt>.
     */
    protected XMLAbstractTranscoder() {
	hints.put(KEY_XML_PARSER_VALIDATING, Boolean.FALSE);
    }

    /**
     * Transcodes the specified XML input in the specified output. All
     * <tt>TranscoderException</tt> exceptions not catched previously
     * are tagged as fatal errors (ie. call the <tt>fatalError</tt>
     * method of the <tt>ErrorHandler</tt>).
     *
     * @param input the XML input to transcode
     * @param output the ouput where to transcode
     * @exception TranscoderException if an error occured while transcoding
     */
    public void transcode(TranscoderInput input, TranscoderOutput output)
            throws TranscoderException {

        Document document = null;
        String uri = input.getURI();
        if (input.getDocument() != null) {
            document = input.getDocument();
        } else {
            String parserClassname =
                (String)hints.get(KEY_XML_PARSER_CLASSNAME);
            String namespaceURI =
                (String)hints.get(KEY_DOCUMENT_ELEMENT_NAMESPACE_URI);
            String documentElement =
                (String)hints.get(KEY_DOCUMENT_ELEMENT);
            DOMImplementation domImpl =
                (DOMImplementation)hints.get(KEY_DOM_IMPLEMENTATION);
	    
            if (parserClassname == null) {
                parserClassname = XMLResourceDescriptor.getXMLParserClassName();
            }
            if (domImpl == null) {
                handler.fatalError(new TranscoderException(
                    "Unspecified transcoding hints: KEY_DOM_IMPLEMENTATION"));
                return;
            }
            if (namespaceURI == null) {
                handler.fatalError(new TranscoderException(
                "Unspecified transcoding hints: KEY_DOCUMENT_ELEMENT_NAMESPACE_URI"));
                return;
            }
            if (documentElement == null) {
                handler.fatalError(new TranscoderException(
                    "Unspecified transcoding hints: KEY_DOCUMENT_ELEMENT"));
                return;
            }
            // parse the XML document
            DocumentFactory f = createDocumentFactory(domImpl, parserClassname);
	    boolean b =
		((Boolean)hints.get(KEY_XML_PARSER_VALIDATING)).booleanValue();
	    f.setValidating(b);
            try {
                if (input.getInputStream() != null) {
                    document = f.createDocument(namespaceURI,
                                                documentElement,
                                                input.getURI(),
                                                input.getInputStream());
                } else if (input.getReader() != null) {
                    document = f.createDocument(namespaceURI,
                                                documentElement,
                                                input.getURI(),
                                                input.getReader());
                } else if (input.getXMLReader() != null) {
                    document = f.createDocument(namespaceURI,
                                                documentElement,
                                                input.getURI(),
                                                input.getXMLReader());
                } else if (uri != null) {
                    document = f.createDocument(namespaceURI,
                                                documentElement,
                                                uri);
                } 
            } catch (DOMException ex) {
                handler.fatalError(new TranscoderException(ex));
            } catch (IOException ex) {
                ex.printStackTrace();
                handler.fatalError(new TranscoderException(ex));
            }
        }
        // call the dedicated transcode method
        if (document != null) {
            try {
                transcode(document, uri, output);
            } catch(TranscoderException ex) {
                // at this time, all TranscoderExceptions are fatal errors
                handler.fatalError(ex);
                return;
            }
        }
    }

    /**
     * Creates the <tt>DocumentFactory</tt> used to create the DOM
     * tree. Override this method if you have to use another
     * implementation of the <tt>DocumentFactory</tt> (ie. for SVG,
     * you have to use the <tt>SAXSVGDocumentFactory</tt>).
     *
     * @param domImpl the DOM Implementation to use
     * @param parserClassname the XML parser classname
     */
    protected DocumentFactory createDocumentFactory(DOMImplementation domImpl,
                                                    String parserClassname) {
	return new SAXDocumentFactory(domImpl, parserClassname);
    }

    /**
     * Transcodes the specified Document in the specified output.
     *
     * @param document the document to transcode
     * @param uri the uri of the document or null if any
     * @param output the ouput where to transcode
     * @exception TranscoderException if an error occured while transcoding
     */
    protected abstract void transcode(Document document,
                                      String uri,
                                      TranscoderOutput output)
            throws TranscoderException;

    // --------------------------------------------------------------------
    // Keys definition
    // --------------------------------------------------------------------

    /**
     * XML parser classname key.
     * <TABLE BORDER="0" CELLSPACING="0" CELLPADDING="1">
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Key: </TH>
     * <TD VALIGN="TOP">KEY_XML_PARSER_CLASSNAME</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Value: </TH>
     * <TD VALIGN="TOP">String</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Default: </TH>
     * <TD VALIGN="TOP">null</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Required: </TH>
     * <TD VALIGN="TOP">Yes</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Description: </TH>
     * <TD VALIGN="TOP">Specify the XML parser classname to use.</TD></TR>
     * </TABLE>
     */
    public static final TranscodingHints.Key KEY_XML_PARSER_CLASSNAME
        = new StringKey();

    /**
     * The validation mode of the XML parser.
     * <TABLE BORDER="0" CELLSPACING="0" CELLPADDING="1">
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Key: </TH>
     * <TD VALIGN="TOP">KEY_XML_PARSER_VALIDATING</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Value: </TH>
     * <TD VALIGN="TOP">Boolean</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Default: </TH>
     * <TD VALIGN="TOP">false</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Required: </TH>
     * <TD VALIGN="TOP">No</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Description: </TH>
     * <TD VALIGN="TOP">Specify the validation mode of the XML parser.</TD></TR>
     * </TABLE>
     */
    public static final TranscodingHints.Key KEY_XML_PARSER_VALIDATING
        = new BooleanKey();

    /**
     * Document element key.
     * <TABLE BORDER="0" CELLSPACING="0" CELLPADDING="1">
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Key: </TH>
     * <TD VALIGN="TOP">KEY_DOCUMENT_ELEMENT</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Value: </TH>
     * <TD VALIGN="TOP">String</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Default: </TH>
     * <TD VALIGN="TOP">null</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Required: </TH>
     * <TD VALIGN="TOP">Yes</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Description: </TH>
     * <TD VALIGN="TOP">Specify the qualified name of the document
     * type to be created.</TD></TR>
     * </TABLE>
     */
    public static final TranscodingHints.Key KEY_DOCUMENT_ELEMENT
        = new StringKey();

    /**
     * Document element namespace URI key.
     * <TABLE BORDER="0" CELLSPACING="0" CELLPADDING="1">
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Key: </TH>
     * <TD VALIGN="TOP">KEY_DOCUMENT_ELEMENT_NAMESPACE_URI</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Value: </TH>
     * <TD VALIGN="TOP">String</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Default: </TH>
     * <TD VALIGN="TOP">null</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Required: </TH>
     * <TD VALIGN="TOP">Yes</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Description: </TH>
     *
     * <TD VALIGN="TOP">Specify the namespace URI of the document
     * element.</TD></TR>
     * </TABLE>
     */
    public static final TranscodingHints.Key KEY_DOCUMENT_ELEMENT_NAMESPACE_URI
        = new StringKey();

    /**
     * DOM Implementation key.
     * <TABLE BORDER="0" CELLSPACING="0" CELLPADDING="1">
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Key: </TH>
     * <TD VALIGN="TOP">KEY_DOM_IMPLEMENTATION</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Value: </TH>
     * <TD VALIGN="TOP">String</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Default: </TH>
     * <TD VALIGN="TOP">null</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Required: </TH>
     * <TD VALIGN="TOP">Yes</TD></TR>
     * <TR>
     * <TH VALIGN="TOP" ALIGN="RIGHT"><P ALIGN="RIGHT">Description: </TH>
     *
     * <TD VALIGN="TOP">Specify the DOM Implementation to use.</TD></TR>
     * </TABLE>
     */
    public static final TranscodingHints.Key KEY_DOM_IMPLEMENTATION
        = new DOMImplementationKey();
}