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/* XSLURIResolver.java --

   Copyright (C) 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.xml.transform;

import java.io.File;

import java.io.InputStream;

import java.io.IOException;

import java.io.Reader;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLConnection;

import java.util.HashMap;

import java.util.Map;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.transform.ErrorListener;

import javax.xml.transform.Source;

import javax.xml.transform.TransformerException;

import javax.xml.transform.URIResolver;

import javax.xml.transform.dom.DOMSource;

import javax.xml.transform.stream.StreamSource;

import org.w3c.dom.Node;

import org.xml.sax.InputSource;

import org.xml.sax.SAXException;

import gnu.xml.dom.ls.ReaderInputStream;

/**

 * URI resolver for XSLT.

 * This resolver parses external entities into DOMSources. It

 * maintains a cache of URIs to DOMSources to avoid expensive re-parsing.

 *

 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>

 */

class XSLURIResolver

  implements URIResolver

{

  Map lastModifiedCache = new HashMap();

  Map nodeCache = new HashMap();

  DocumentBuilder builder;

  URIResolver userResolver;

  ErrorListener userListener;

  void setUserResolver(URIResolver userResolver)

  {

    this.userResolver = userResolver;

  }

  void setUserListener(ErrorListener userListener)

  {

    this.userListener = userListener;

  }

  /**

   * Clear the cache.

   */

  void flush()

  {

    lastModifiedCache.clear();

    nodeCache.clear();

  }

  public Source resolve(String href, String base)

    throws TransformerException

  {

    Source source = null;

    if (userResolver != null)

      {

        source = userResolver.resolve(base, href);

      }

    return resolveDOM(source, href, base);

  }

  DOMSource resolveDOM(Source source, String base, String href)

    throws TransformerException

  {

    if (source != null && source instanceof DOMSource)

      {

        return (DOMSource) source;

      }

    String systemId = (source == null) ? null : source.getSystemId();

    long lastModified = 0L, lastLastModified = 0L;

    try

      {

        URL url = resolveURL(systemId, base, href);

        Node node = null;

        InputStream in = null;

        if (source instanceof StreamSource)

          {

            StreamSource ss = (StreamSource) source;

            in = ss.getInputStream();

            if (in == null)

              {

                Reader reader = ss.getReader();

                if (reader != null)

                  {

                    in = new ReaderInputStream(reader);

                  }

              }

          }

        if (in == null)

          {

            if (url != null)

              {

                systemId = url.toString();

                node = (Node) nodeCache.get(systemId);

                // Is the resource up to date?

                URLConnection conn = url.openConnection();

                Long llm = (Long) lastModifiedCache.get(systemId);

                if (llm != null)

                  {

                    lastLastModified = llm.longValue();

                    conn.setIfModifiedSince(lastLastModified);

                  }

                conn.connect();

                lastModified = conn.getLastModified();

                if (node != null &&

                    lastModified > 0L &&

                    lastModified <= lastLastModified)

                  {

                    // Resource unchanged

                    return new DOMSource(node, systemId);

                  }

                else

                  {

                    // Resource new or modified

                    in = conn.getInputStream();

                    nodeCache.put(systemId, node);

                    lastModifiedCache.put(systemId, new Long(lastModified));

                  }

              }

            else

              {

                throw new TransformerException("can't resolve URL: " +

                                               systemId);

              }

          }

        InputSource input = new InputSource(in);

        input.setSystemId(systemId);

        DocumentBuilder builder = getDocumentBuilder();

        node = builder.parse(input);

        return new DOMSource(node, systemId);

      }

    catch (IOException e)

      {

        throw new TransformerException(e);

      }

    catch (SAXException e)

      {

        throw new TransformerException(e);

      }

  }

  URL resolveURL(String systemId, String base, String href)

    throws IOException

  {

    URL url = null;

    try

      {

        if (systemId != null)

          {

            try

              {

                url = new URL(systemId);

              }

            catch (MalformedURLException e)

              {

                // Try building from base + href

              }

          }

        if (url == null)

          {

            if (base != null)

              {

                URL baseURL = new URL(base);

                url = new URL(baseURL, href);

              }

            else if (href != null)

              {

                url = new URL(href);

              }

            else

              {

                // See below

                throw new MalformedURLException(systemId);

              }

          }

        return url;

      }

    catch (MalformedURLException e)

      {

        // Fall back to local filesystem

        File file = null;

        if (href == null)

          {

            href = systemId;

          }

        if (base != null)

          {

            int lsi = base.lastIndexOf(File.separatorChar);

            if (lsi != -1 && lsi < base.length() - 1)

              {

                base = base.substring(0, lsi);

              }

            File baseFile = new File(base);

            file = new File(baseFile, href);

          }

        else if (href != null)

          {

            file = new File(href);

          }

        return (file == null) ? null : file.toURL();

      }

  }

  DocumentBuilder getDocumentBuilder()

    throws TransformerException

  {

    try

      {

        if (builder == null)

          {

            DocumentBuilderFactory factory =

              DocumentBuilderFactory.newInstance();

            factory.setNamespaceAware(true);

            factory.setExpandEntityReferences(true);

            builder = factory.newDocumentBuilder();

          }

        if (userResolver != null)

          {

            builder.setEntityResolver(new URIResolverEntityResolver(userResolver));

          }

        if (userListener != null)

          {

            builder.setErrorHandler(new ErrorListenerErrorHandler(userListener));

          }

        return builder;

      }

    catch (Exception e)

      {

        throw new TransformerException(e);

      }

  }

}