/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 2001-2004 The Apache Software Foundation.  
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. 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.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xerces" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
 * ITS 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 Apache Software Foundation and was
 * originally based on software copyright (c) 2001, International
 * Business Machines, Inc., http://www.apache.org.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package org.apache.xerces.util;


import org.apache.xerces.xni.XNIException;
import org.apache.xerces.xni.XMLResourceIdentifier;
import org.apache.xerces.xni.grammars.XMLGrammarDescription;
import org.apache.xerces.xni.parser.XMLEntityResolver;
import org.apache.xerces.xni.parser.XMLInputSource;

import org.w3c.dom.ls.LSResourceResolver;
import org.w3c.dom.ls.LSInput;

import java.io.InputStream;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;


/**
 * This class wraps DOM entity resolver to XNI entity resolver.
 *
 * @see LSResourceResolver
 *
 * @author Gopal Sharma, SUN MicroSystems Inc.
 * @author Elena Litani, IBM 
 * @author Ramesh Mandava, Sun Microsystems
 * @version $Id: DOMEntityResolverWrapper.java,v 1.10 2004/01/22 15:51:48 mrglavas Exp $
 */
public class DOMEntityResolverWrapper
    implements XMLEntityResolver {

    //
    // Data
    //

    /** XML 1.0 type constant according to DOM L3 LS CR spec "http://www.w3.org/TR/2003/CR-DOM-Level-3-LS-20031107" */
    private static final String XML_TYPE = "http://www.w3.org/TR/REC-xml";
    
    /** XML Schema constant according to DOM L3 LS CR spec "http://www.w3.org/TR/2003/CR-DOM-Level-3-LS-20031107" */
    private static final String XSD_TYPE = "http://www.w3.org/2001/XMLSchema";

    /** The DOM entity resolver. */
    protected LSResourceResolver fEntityResolver;

    //
    // Constructors
    //

    /** Default constructor. */
    public DOMEntityResolverWrapper() {}

    /** Wraps the specified DOM entity resolver. */
    public DOMEntityResolverWrapper(LSResourceResolver entityResolver) {
        setEntityResolver(entityResolver);
    } // LSResourceResolver

    //
    // Public methods
    //

    /** Sets the DOM entity resolver. */
    public void setEntityResolver(LSResourceResolver entityResolver) {
        fEntityResolver = entityResolver;
    } // setEntityResolver(LSResourceResolver)

    /** Returns the DOM entity resolver. */
    public LSResourceResolver getEntityResolver() {
        return fEntityResolver;
    } // getEntityResolver():LSResourceResolver

    //
    // XMLEntityResolver methods
    //
    
    /**
     * Resolves an external parsed entity. If the entity cannot be
     * resolved, this method should return null.
     *
     * @param resourceIdentifier	description of the resource to be revsoved
     * @throws XNIException Thrown on general error.
     * @throws IOException  Thrown if resolved entity stream cannot be
     *                      opened or some other i/o error occurs.
     */
    public XMLInputSource resolveEntity(XMLResourceIdentifier resourceIdentifier)
        throws XNIException, IOException {
        // resolve entity using DOM entity resolver
        if (fEntityResolver != null) {
            try {
                // For entity resolution the type of the resource would be  XML TYPE
                // DOM L3 LS spec mention only the XML 1.0 recommendation right now
                LSInput inputSource =
                    resourceIdentifier == null
                        ? fEntityResolver.resolveResource(
                            null,
                            null,
                            null,
                            null,
                            null)
                        : fEntityResolver.resolveResource(
                            getType(resourceIdentifier),
                            resourceIdentifier.getNamespace(),
                            resourceIdentifier.getPublicId(),
                            resourceIdentifier.getLiteralSystemId(),
                            resourceIdentifier.getBaseSystemId());
                if (inputSource != null) {
                    String publicId = inputSource.getPublicId();
                    String systemId = inputSource.getSystemId();
                    String baseSystemId = inputSource.getBaseURI();
                    InputStream byteStream = inputSource.getByteStream();
                    Reader charStream = inputSource.getCharacterStream();
                    String encoding = inputSource.getEncoding();
                    String data = inputSource.getStringData();
                    XMLInputSource xmlInputSource =
                        new XMLInputSource(publicId, systemId, baseSystemId);

                    if (charStream != null) {
                        xmlInputSource.setCharacterStream(charStream);
                    }
                    if (byteStream != null) {
                        xmlInputSource.setByteStream((InputStream) byteStream);
                    }
                    if (data != null && data.length() != 0) {
                        xmlInputSource.setCharacterStream(
                            new StringReader(data));
                    }
                    xmlInputSource.setEncoding(encoding);
                    return xmlInputSource;
                }
            }

            // error resolving entity
            catch (Exception e) {
                // REVISIT:
                // can at this point we receive wrapped exception?

                throw new XNIException(e);
            }
        }

        // unable to resolve entity
        return null;

    } // resolveEntity(String,String,String):XMLInputSource
    
    /** Determines the type of resource being resolved **/
    private String getType(XMLResourceIdentifier resourceIdentifier) {
        if (resourceIdentifier instanceof XMLGrammarDescription) {
            XMLGrammarDescription desc = (XMLGrammarDescription) resourceIdentifier;
            if (XMLGrammarDescription.XML_SCHEMA.equals(desc.getGrammarType())) {
                return XSD_TYPE;
            }
        }
        return XML_TYPE;
    } // getType(XMLResourceIdentifier):String
    
} // DOMEntityResolverWrapper
