/* This file is part of the project "Hilbert II" - http://www.qedeq.org" target="alexandria_uri">http://www.qedeq.org
    *
    * Copyright 2000-2014,  Michael Meyling <mime@qedeq.org>.
    *
    * "Hilbert II" 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 of the License, or (at your option) any later version.
    *
   * This program 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.
   */
  
  package org.qedeq.kernel.xml.parser;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.Reader;
  
  import javax.xml.parsers.ParserConfigurationException;
  import javax.xml.parsers.SAXParser;
  import javax.xml.parsers.SAXParserFactory;
  
  import org.qedeq.base.io.IoUtility;
  import org.qedeq.base.trace.Trace;
  import org.qedeq.kernel.se.base.list.Element;
  import org.qedeq.kernel.se.common.ModuleService;
  import org.qedeq.kernel.se.common.SourceFileExceptionList;
  import org.qedeq.kernel.xml.handler.common.SaxDefaultHandler;
  import org.qedeq.kernel.xml.handler.list.BasicHandler;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  import org.xml.sax.XMLReader;
  
  /**
   * Parse {@link Element}s.
   *
   * @author  Michael Meyling
   *
   */
  public final class BasicParser {
  
      /** This class. */
      private static final Class CLASS = BasicParser.class;
  
      /** Here we handle the events. */
      private SaxDefaultHandler handler;
  
      /** XML reader. */
      private XMLReader reader;
  
      /** Here we describe this "plugin". */
      private static ModuleService plugin = new ModuleService() {
          public String getServiceDescription() {
              return "parses element lists and atoms";
          }
          public String getServiceId() {
              return BasicParser.class.getName();
          }
          public String getServiceAction() {
              return "element parser";
          }
      };
  
  
      /**
       * Constructor.
       *
       * @param   handler Default handler for this application.
       * @throws  ParserConfigurationException    Severe parser configuration problem.
       * @throws  SAXException    Parse problems.
       */
      private BasicParser(final SaxDefaultHandler handler)
              throws ParserConfigurationException, SAXException {
          super();
          this.handler = handler;
          final String factoryImpl = System.getProperty("javax.xml.parsers.SAXParserFactory");
          if (factoryImpl == null) {
              System.setProperty("javax.xml.parsers.SAXParserFactory",
                  "org.apache.xerces.jaxp.SAXParserFactoryImpl");
          }
          SAXParserFactory factory = SAXParserFactory.newInstance();
          factory.setNamespaceAware(false);
          factory.setValidating(false);
  
          final SAXParser parser = factory.newSAXParser();
          reader = parser.getXMLReader();
      }
  
      /**
       * Parse input source.
       *
       * @param   url             Source URL. Only for information.
       * @param   in              Parse data from this source.
       * @throws  SAXException    Syntactical or semantical problem occurred.
       * @throws  IOException     Technical problem occurred.
       */
     private void parse(final String url, final Reader in)
             throws IOException, SAXException {
         final String method = "parse(URL, boolean, InputStream)";
         BufferedReader dis = null;
         SourceFileExceptionList exceptionList = new SourceFileExceptionList();;
         try {
             dis = new BufferedReader(in);
             final InputSource input = new InputSource(dis);
             reader.setErrorHandler(new SaxErrorHandler(plugin,
                 url, exceptionList));
             handler.setExceptionList(exceptionList);
             reader.setContentHandler(handler);
             handler.setUrl(url);
             reader.parse(input);
         } finally {
             if (dis != null) {
                 try {
                     dis.close();
                 } catch (Exception e) {
                     Trace.trace(CLASS, this, method, e);
                 }
             }
         }
     }
 
     /**
      * Create elements out of XML string.
      *
      * @param   xml     XML document part. XML header not necessary.
      * @return  Created elements.
      * @throws  ParserConfigurationException    Problem configuring parser.
      * @throws  SAXException                    Parsing problem.
      */
     public static final Element[] createElements(final String xml)
             throws ParserConfigurationException, SAXException {
         try {
             String data = "<?xml version=\"1.0\" encoding=\"ISO-8859-1\"?>\n"
                 + "<basic>\n"
                 + xml + "\n"
                 + "</basic>\n";
             SaxDefaultHandler handler = new SaxDefaultHandler(plugin);
             BasicHandler simple = new BasicHandler(handler);
             handler.setBasisDocumentHandler(simple);
             BasicParser parser = new BasicParser(handler);
             parser.parse("memory", IoUtility.stringToReader(data));
             return (Element[]) simple.getElements().toArray(new Element[]{});
         } catch (SAXException e) {
             Trace.trace(BasicParser.class, "createElement", e);
             Trace.trace(BasicParser.class, "createElement", e.getCause());
             throw e;
         } catch (IOException e) {
             Trace.trace(BasicParser.class, "createElement", e);
             // should not happen, hej we are parsing a String!
             throw new RuntimeException(e);
         }
     }
 
     /**
      * Create element out of XML string.
      *
      * @param   xml     XML document part. XML header not necessary.
      * @return  Created element.
      * @throws  ParserConfigurationException    Problem configuring parser.
      * @throws  SAXException                    Parsing problem.
      */
     public static final Element createElement(final String xml)
             throws ParserConfigurationException, SAXException {
         final Element[] elements = createElements(xml);
         if (elements == null || elements.length == 0) {
             return null;
         }
         return elements[0];
     }
 
 }