/*
 * (c) Siemens Business Services GmbH
 */
package at.gv.egovernment.moa.ss.erechtclient.init;

import java.io.FileInputStream;
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;

/**
 * @author Gregor Karlinger (mailto:gregor.karlinger@siemens.com)
 */
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";
  protected static final String XERCES_AUGMENT_PSI_ =
	"http://apache.org/xml/features/validation/schema/augment-psvi";
	  
  private static final int BIG_PRIME = 2039;

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

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

  /**
   * 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.INIT_PROPS_LOC_);
    if (initPropsLoc == null)
    {
      logger_.fatal("System property \"" + Constants.INIT_PROPS_LOC_ + "\" not set.");
      logger_.fatal("Web application initialization failed.");
      return;
    }
    
    // Load init properties
    try
    {
      logger_.debug("Init properties location \"" + initPropsLoc + "\" will be used.");
      
      // Try to interpret init properties location as relative to the web application root
      InputStream initPropsIS = context.getResourceAsStream(initPropsLoc);
      
      if (initPropsIS == null)
      {
        // If this does not work, try to interpret init properties location as an absolute file system path
        initPropsIS = new FileInputStream(initPropsLoc);
      }
      
      Properties initProps = new Properties();
      initProps.load(initPropsIS);
      context.setAttribute(Constants.WSCP_INIT_PROPS_, initProps);

      // Prepare application bean knowing about init properties
      InitPropertiesBean initPropsBean = new InitPropertiesBean(initProps);
      context.setAttribute(Constants.WSCP_INITPROPS_BEAN_, initPropsBean);
    }
    catch (IOException e)
    {
      logger_.fatal("Cannot load initialization properties from location \"" + initPropsLoc + "\".", e);
      logger_.fatal("Web application initialization failed.");
      return;
    }
    
    // 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 MOA 1.3
    // TODO Maybe remove this?
    Properties initProps = (Properties) context.getAttribute(Constants.WSCP_INIT_PROPS_);
    String moaSchemaLoc = initProps.getProperty(Constants.IP_MOA_SCHEMA_);
    if (!preparseSchema(context, preparser, moaSchemaLoc)) 
    {
      logger_.fatal("Web application initialization failed.");
      return;
    }
    
    // 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(XERCES_AUGMENT_PSI_, false); 
      xmlParser.setErrorHandler(new XMLParserErrorHandler(false, true, true));
    }
    catch (SAXException e)
    {
      String message = "Initialization of XML parser failed.";
      logger_.fatal(message, e);
      logger_.fatal("Web application initialization failed.");
      return;
    }
    context.setAttribute(Constants.WSCP_XMLPARSER_, xmlParser);
    
    String message = "Web application initialization succeeded.";
    logger_.info(message);
  }

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

  /**
   * 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 boolean preparseSchema(ServletContext context, XMLGrammarPreparser preparser, String schemaLoc) 
  {
    InputStream schemaIS = context.getResourceAsStream(schemaLoc);
    if (schemaIS == null)
    {
      String message = "Cannot load schema from location \"" + schemaLoc + "\".";
      logger_.fatal(message);
      return false;
    }
    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_.fatal(message, e);
      return false;
    }
    return true;
  }
}