/*
 * Created on 18.11.2003
 *
 * (c) Stabsstelle IKT-Strategie des Bundes
 */
package at.gv.egovernment.moa.spss.slinterface.listeners;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.apache.log4j.Logger;
import org.apache.xerces.parsers.DOMParser;
import org.apache.xerces.parsers.XMLGrammarPreparser;
import org.apache.xerces.util.SymbolTable;
import org.apache.xerces.util.XMLGrammarPoolImpl;
import org.apache.xerces.xni.grammars.XMLGrammarDescription;
import org.apache.xerces.xni.grammars.XMLGrammarPool;
import org.apache.xerces.xni.parser.XMLInputSource;
import org.xml.sax.SAXException;

import at.gv.egovernment.moa.spss.slinterface.Constants;
import at.gv.egovernment.moa.spss.slinterface.URLRewriter;

/**
 * @author Gregor Karlinger (mailto:gregor.karlinger@cio.gv.at)
 */
public class ContextListener implements ServletContextListener
{
  private static final String SAX_NAMESPACES_FEATURE = "http://xml.org/sax/features/namespaces";
  private static final String SAX_VALIDATION_FEATURE = "http://xml.org/sax/features/validation";

  private static final String XERCES_SCHEMA_VALIDATION_FEATURE = 
    "http://apache.org/xml/features/validation/schema";
  private static final String XERCES_NORMALIZED_VALUE_FEATURE =  
    "http://apache.org/xml/features/validation/schema/normalized-value";
  private static final String XERCES_INCLUDE_IGNORABLE_WHITESPACE_FEATURE =
    "http://apache.org/xml/features/dom/include-ignorable-whitespace";
  private static final String XERCES_CREATE_ENTITY_REF_NODES_FEATURE =
    "http://apache.org/xml/features/dom/create-entity-ref-nodes";
  protected static final String XERCES_DEFER_NODE_EXPANSION_ =
    "http://apache.org/xml/features/dom/defer-node-expansion";

  private static final int BIG_PRIME = 2039;

  private static Logger logger_ = Logger.getLogger(Constants.LH_LISTENERS_);

  /* ---------------------------------------------------------------------------------------------------- */

  /**
   * Initializes the web application.
   * 
   * @see javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)
   */
  public void contextInitialized(ServletContextEvent event)
  {
    logger_.debug("Context is being initialized.");
    
    ServletContext context = event.getServletContext();
    
    String initPropsLoc = System.getProperty(Constants.SP_INIT_PROPS_LOC_);
    if (initPropsLoc == null)
    {
      logger_.error("System property \"" + Constants.SP_INIT_PROPS_LOC_ + "\" not set.");
      return;
    }
    
    // Load init properties
    try
    {
      InputStream initPropsIS = context.getResourceAsStream(initPropsLoc);
      Properties initProps = new Properties();
      initProps.load(initPropsIS);
      context.setAttribute(Constants.WSCP_INIT_PROPS_, initProps);
    }
    catch (IOException e)
    {
      logger_.error("Cannot load initialization properties from location \"" + initPropsLoc + "\".", e);
    }

    // Put helper object for rewriting URLs in the result page into the context
    URLRewriter urlRewriter = new URLRewriter((Properties)context.getAttribute(Constants.WSCP_INIT_PROPS_));
    context.setAttribute(Constants.WSCP_URL_REWRITER_, urlRewriter);

    // Initialize XML parser
    SymbolTable symbolTable = new SymbolTable(BIG_PRIME);
    XMLGrammarPool grammarPool = new XMLGrammarPoolImpl();

    XMLGrammarPreparser preparser = new XMLGrammarPreparser(symbolTable);
    preparser.registerPreparser(XMLGrammarDescription.XML_SCHEMA, null);
    preparser.setProperty(org.apache.xerces.impl.Constants.XERCES_PROPERTY_PREFIX
      + org.apache.xerces.impl.Constants.XMLGRAMMAR_POOL_PROPERTY, grammarPool);
    preparser.setFeature(SAX_NAMESPACES_FEATURE, true);
    preparser.setFeature(SAX_VALIDATION_FEATURE, true);

    // Schema for Security-Layer 1.2 alpha (including LocRefContent)
    Properties initProps = (Properties) context.getAttribute(Constants.WSCP_INIT_PROPS_);
    String slSchemaLoc = initProps.getProperty(Constants.IP_SL_SCHEMA_);
    preparseSchema(context, preparser, slSchemaLoc);

    // Schema for MOA 1.2
    String moaSchemaLoc = initProps.getProperty(Constants.IP_MOA_SCHEMA_);
    preparseSchema(context, preparser, moaSchemaLoc);
    
    // Schema for SLXHTML 1.0
    String slxhtmlSchemaLoc = initProps.getProperty(Constants.IP_SLXHTML_SCHEMA_);
    preparseSchema(context, preparser, slxhtmlSchemaLoc);
    
    // TODO parser is not threadsafe
    DOMParser xmlParser = new DOMParser(symbolTable, grammarPool);
    try
    {
      xmlParser.setFeature(SAX_NAMESPACES_FEATURE, true);
      xmlParser.setFeature(SAX_VALIDATION_FEATURE, true);
      xmlParser.setFeature(XERCES_SCHEMA_VALIDATION_FEATURE, true);
      xmlParser.setFeature(XERCES_NORMALIZED_VALUE_FEATURE, false);
      xmlParser.setFeature(XERCES_INCLUDE_IGNORABLE_WHITESPACE_FEATURE, true);
      xmlParser.setFeature(XERCES_CREATE_ENTITY_REF_NODES_FEATURE, false);
      xmlParser.setFeature(XERCES_DEFER_NODE_EXPANSION_, true);
      xmlParser.setFeature("http://apache.org/xml/features/validation/schema/augment-psvi", false); // TODO Stringkonstante
      xmlParser.setErrorHandler(new XMLParserErrorHandler(false, true, true));

    }
    catch (SAXException e)
    {
      String message = "Initialization of XML parser failed.";
      logger_.error(message, e);
    }
    context.setAttribute(Constants.WSCP_XMLPARSER_, xmlParser);
  }

  /* ---------------------------------------------------------------------------------------------------- */

  /**
   * Does some clean up at finalization of the web application.
   * 
   * @see javax.servlet.ServletContextListener#contextDestroyed(javax.servlet.ServletContextEvent)
   */
  public void contextDestroyed(ServletContextEvent event)
  {
    // Remove init properties from web service context
    Properties initProps = (Properties) event.getServletContext().getAttribute(Constants.WSCP_INIT_PROPS_);
    if (initProps != null) event.getServletContext().removeAttribute(Constants.WSCP_INIT_PROPS_);
  }

  /* ---------------------------------------------------------------------------------------------------- */

  private void preparseSchema(ServletContext context, XMLGrammarPreparser preparser, String schemaLoc) 
  {
    InputStream schemaIS = context.getResourceAsStream(schemaLoc);
    if (schemaIS == null)
    {
      String message = "Cannot load schema from location \"" + schemaLoc + "\".";
      logger_.error(message);
    }
    try
    {
      String schemaSystemId = context.getResource(schemaLoc).toExternalForm();
      preparser.preparseGrammar(XMLGrammarDescription.XML_SCHEMA,
        new XMLInputSource(null, schemaSystemId, null, schemaIS, null));
    }
    catch (Exception e)
    {
      String message = "Parsing schema loaded from location \"" + schemaLoc + "\" failed.";
      logger_.error(message, e);
    }
  }


}