/**
    *    Copyright 2009-2019 the original author or authors.
    *
    *    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.ibatis.builder.xml;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.Locale;
  
  import org.apache.ibatis.io.Resources;
  import org.xml.sax.EntityResolver;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  
  /**
   * Offline entity resolver for the MyBatis DTDs.
   *
   * @author Clinton Begin
   * @author Eduardo Macarron
   */
  public class XMLMapperEntityResolver implements EntityResolver {
  
    private static final String IBATIS_CONFIG_SYSTEM = "ibatis-3-config.dtd";
    private static final String IBATIS_MAPPER_SYSTEM = "ibatis-3-mapper.dtd";
    private static final String MYBATIS_CONFIG_SYSTEM = "mybatis-3-config.dtd";
    private static final String MYBATIS_MAPPER_SYSTEM = "mybatis-3-mapper.dtd";
  
    private static final String MYBATIS_CONFIG_DTD = "org/apache/ibatis/builder/xml/mybatis-3-config.dtd";
    private static final String MYBATIS_MAPPER_DTD = "org/apache/ibatis/builder/xml/mybatis-3-mapper.dtd";
  
    /**
     * Converts a public DTD into a local one.
     *
     * @param publicId The public id that is what comes after "PUBLIC"
     * @param systemId The system id that is what comes after the public id.
     * @return The InputSource for the DTD
     *
     * @throws org.xml.sax.SAXException If anything goes wrong
     */
    @Override
    public InputSource resolveEntity(String publicId, String systemId) throws SAXException {
      try {
        if (systemId != null) {
          String lowerCaseSystemId = systemId.toLowerCase(Locale.ENGLISH);
          if (lowerCaseSystemId.contains(MYBATIS_CONFIG_SYSTEM) || lowerCaseSystemId.contains(IBATIS_CONFIG_SYSTEM)) {
            return getInputSource(MYBATIS_CONFIG_DTD, publicId, systemId);
          } else if (lowerCaseSystemId.contains(MYBATIS_MAPPER_SYSTEM) || lowerCaseSystemId.contains(IBATIS_MAPPER_SYSTEM)) {
            return getInputSource(MYBATIS_MAPPER_DTD, publicId, systemId);
          }
        }
        return null;
      } catch (Exception e) {
        throw new SAXException(e.toString());
      }
    }
  
    private InputSource getInputSource(String path, String publicId, String systemId) {
      InputSource source = null;
      if (path != null) {
        try {
          InputStream in = Resources.getResourceAsStream(path);
          source = new InputSource(in);
          source.setPublicId(publicId);
          source.setSystemId(systemId);
        } catch (IOException e) {
          // ignore, null is ok
        }
      }
      return source;
    }
  
  }