// BootstrapResolver.java - Resolve entities and URIs internally

/*
 * Copyright 2001-2004 The Apache Software Foundation or its licensors,
 * as applicable.
 * 
 * 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 com.sun.org.apache.xml.internal.resolver.helpers;

import java.util.Hashtable;
import java.net.URL;
import java.net.MalformedURLException;
import java.io.InputStream;

import javax.xml.transform.URIResolver;
import javax.xml.transform.Source;
import javax.xml.transform.sax.SAXSource;
import javax.xml.transform.TransformerException;

import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;

/**
 * A simple bootstrapping resolver.
 *
 * <p>This class is used as the entity resolver when reading XML Catalogs.
 * It searches for the OASIS XML Catalog DTD, Relax NG Grammar and W3C XML Schema
 * as resources (e.g., in the resolver jar file).</p>
 *
 * <p>If you have your own DTDs or schemas, you can extend this class and
 * set the BootstrapResolver in your CatalogManager.</p>
 *
 * @see com.sun.org.apache.xml.internal.resolver.CatalogManager
 *
 * @author Norman Walsh
 * <a href="mailto:Norman.Walsh@Sun.COM">Norman.Walsh@Sun.COM</a>
 *
 * @version 1.0
 */
public class BootstrapResolver implements EntityResolver, URIResolver {
  /** URI of the W3C XML Schema for OASIS XML Catalog files. */
  public static final String xmlCatalogXSD = "http://www.oasis-open.org/committees/entity/release/1.0/catalog.xsd";

  /** URI of the RELAX NG Grammar for OASIS XML Catalog files. */
  public static final String xmlCatalogRNG = "http://www.oasis-open.org/committees/entity/release/1.0/catalog.rng";

  /** Public identifier for OASIS XML Catalog files. */
  public static final String xmlCatalogPubId = "-//OASIS//DTD XML Catalogs V1.0//EN";

  /** System identifier for OASIS XML Catalog files. */
  public static final String xmlCatalogSysId = "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd";

  /** Private hash used for public identifiers. */
  private Hashtable publicMap = new Hashtable();

  /** Private hash used for system identifiers. */
  private Hashtable systemMap = new Hashtable();

  /** Private hash used for URIs. */
  private Hashtable uriMap = new Hashtable();

  /** Constructor. */
  public BootstrapResolver() {
    URL url = this.getClass().getResource("/com/sun/org/apache/xml/internal/resolver/etc/catalog.dtd");
    if (url != null) {
      publicMap.put(xmlCatalogPubId, url.toString());
      systemMap.put(xmlCatalogSysId, url.toString());
    }

    url = this.getClass().getResource("/com/sun/org/apache/xml/internal/resolver/etc/catalog.rng");
    if (url != null) {
      uriMap.put(xmlCatalogRNG, url.toString());
    }

    url = this.getClass().getResource("/com/sun/org/apache/xml/internal/resolver/etc/catalog.xsd");
    if (url != null) {
      uriMap.put(xmlCatalogXSD, url.toString());
    }
  }

  /** SAX resolveEntity API. */
  public InputSource resolveEntity (String publicId, String systemId) {
    String resolved = null;

    if (systemId != null && systemMap.containsKey(systemId)) {
      resolved = (String) systemMap.get(systemId);
    } else if (publicId != null && publicMap.containsKey(publicId)) {
      resolved = (String) publicMap.get(publicId);
    }

    if (resolved != null) {
      try {
	InputSource iSource = new InputSource(resolved);
	iSource.setPublicId(publicId);

	// Ideally this method would not attempt to open the
	// InputStream, but there is a bug (in Xerces, at least)
	// that causes the parser to mistakenly open the wrong
	// system identifier if the returned InputSource does
	// not have a byteStream.
	//
	// It could be argued that we still shouldn't do this here,
	// but since the purpose of calling the entityResolver is
	// almost certainly to open the input stream, it seems to
	// do little harm.
	//
	URL url = new URL(resolved);
	InputStream iStream = url.openStream();
	iSource.setByteStream(iStream);

	return iSource;
      } catch (Exception e) {
	// FIXME: silently fail?
	return null;
      }
    }

    return null;
  }

  /** Transformer resolve API. */
  public Source resolve(String href, String base)
    throws TransformerException {

    String uri = href;
    String fragment = null;
    int hashPos = href.indexOf("#");
    if (hashPos >= 0) {
      uri = href.substring(0, hashPos);
      fragment = href.substring(hashPos+1);
    }

    String result = null;
    if (href != null && uriMap.containsKey(href)) {
      result = (String) uriMap.get(href);
    }

    if (result == null) {
      try {
	URL url = null;

	if (base==null) {
	  url = new URL(uri);
	  result = url.toString();
	} else {
	  URL baseURL = new URL(base);
	  url = (href.length()==0 ? baseURL : new URL(baseURL, uri));
	  result = url.toString();
	}
      } catch (java.net.MalformedURLException mue) {
	// try to make an absolute URI from the current base
	String absBase = makeAbsolute(base);
	if (!absBase.equals(base)) {
	  // don't bother if the absBase isn't different!
	  return resolve(href, absBase);
	} else {
	  throw new TransformerException("Malformed URL "
					 + href + "(base " + base + ")",
					 mue);
	}
      }
    }

    SAXSource source = new SAXSource();
    source.setInputSource(new InputSource(result));
    return source;
  }

  /** Attempt to construct an absolute URI */
  private String makeAbsolute(String uri) {
    if (uri == null) {
      uri = "";
    }

    try {
      URL url = new URL(uri);
      return url.toString();
    } catch (MalformedURLException mue) {
      try {
	URL fileURL = FileURL.makeURL(uri);
	return fileURL.toString();
      } catch (MalformedURLException mue2) {
	// bail
	return uri;
      }
    }
  }
}