/*
 * 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.ode.bpel.elang.xpath10.runtime;

import org.apache.ode.bpel.elang.xpath10.o.OXPath10Expression;
import org.apache.ode.bpel.o.OXslSheet;
import org.apache.ode.utils.StreamUtils;
import org.apache.ode.utils.fs.FileUtils; 
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import javax.xml.transform.URIResolver;
import javax.xml.transform.Source;
import javax.xml.transform.TransformerException;
import javax.xml.transform.stream.StreamSource;
import java.net.URI;
import java.net.URISyntaxException;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream; 
import java.io.StringReader;

/**
 * Used to give the Xsl processor a way to access included XSL sheets
 * by using the maps of sheets pre-processed at compilation time and
 * stored in the OXPath10Expression.
 */
public class XslRuntimeUriResolver implements URIResolver {

  private static final Log __log = LogFactory.getLog(XslRuntimeUriResolver.class);

  private OXPath10Expression _expr;
  private final URI _baseResourceURI;

  public XslRuntimeUriResolver(OXPath10Expression expr, URI baseResourceURI) {
    _expr = expr;
    _baseResourceURI= baseResourceURI;
  }

  public Source resolve(String href, String base) throws TransformerException {
      String result;
      URI uri;
      try {
          uri = new URI(FileUtils.encodePath(href));
      } catch (URISyntaxException e) {
          return null;
      }

      OXslSheet sheet = _expr.xslSheets.get(uri);
      if( sheet != null) {
          result = sheet.sheetBody;
      } else {
          result = getResourceAsString(uri);
      }

      if( result != null ) {
          return new StreamSource(new StringReader(result));
      } else {
          return null;
      }
  }

  /**
   * Given a URI this function will attempt to retrieve the resource declared at that URI location
   * as a string.  (Hopefully everything's character encodings are all ok...)  This URI can be
   * defined as being relative to the executing process instance's physical file location.
   *
   * @param docUri - the URI to resolve
   * @return String - the resource contents, or null if none found.
   */
  private String getResourceAsString(URI docUri) {
      URI resolvedURI= _baseResourceURI.resolve(docUri);
      InputStream is = null;
      try {
          File f = new File(resolvedURI);
          if (!f.exists()) return null;
          is = new FileInputStream(f);
          return new String(StreamUtils.read(is));
      } catch (IOException e) {
          __log.info("Couldn't load XSL resource " + docUri);
      } finally {
          try {
              if (is != null) is.close();
          } catch (Exception ex) {
              // No worries.
          }
      }
      return null;
  }

}