package org.kuali.ole.sys.context;
   
   import java.util.Enumeration;
   
   import org.apache.log4j.Appender;
   import org.apache.log4j.ConsoleAppender;
   import org.apache.log4j.Layout;
   import org.apache.log4j.Logger;
   import org.apache.log4j.PatternLayout;
  
  /**
   * Provides a method to add a ConsoleAppender to a Logger if one has not already been configured.
   */
  public class BatchLogger {
      public static final String DEFAULT_CONVERSION_PATTERN = "%d [%t] u:%X{user}/d:%X{docId} %-5p %c :: %m%n";
      public static final Layout DEFAULT_PATTERN_LAYOUT = new PatternLayout(DEFAULT_CONVERSION_PATTERN);
      public static final String LOG_FILE_APPENDER_NAME = "LogFile";
      
      /**
       * Adds a ConsoleAppender to the Logger if one doesn't already exist. 
       * Attempts to use the layout from the 'LogFile' appender if it exists, otherwise it uses the DEFAULT_CONVERSION_PATTERN
       * 
       * @param logger the Logger to which to add a ConsoleAppender
       */
      public static void addConsoleAppender(Logger logger) {
          if (!isConsoleAppenderExists(logger)) {       
              
              Appender console = new ConsoleAppender(getLogFileAppenderLayout(logger));
  
              logger.addAppender(console);
          }
      }
      
      /**
       * Returns the layout for the 'LogFile' appender. Returns the DEFAULT_PATTERN_LAYOUT if the 'LogFile' doesn't exist.
       * 
       * @return the layout for the 'LogFile' appender
       */
      public static Layout getLogFileAppenderLayout() {
          return getLogFileAppenderLayout(null);
      }
      
      /**
       * Checks whether a ConsoleAppender has already been added to either the RootLogger or to the requested Logger
       * 
       * @param logger the Logger to check
       * @return true if a ConsoleAppender has already been added to the RootLogger or to the requested Logger, false otherwise
       */
      private static boolean isConsoleAppenderExists(Logger logger) {        
          Enumeration<Appender> rootAppenders = Logger.getRootLogger().getAllAppenders();
          while(rootAppenders.hasMoreElements()) {
              Appender appender = rootAppenders.nextElement();
              if (appender instanceof ConsoleAppender) {
                  return true;
              }
          }
          
          Enumeration<Appender> appenders = logger.getAllAppenders();        
          while(appenders.hasMoreElements()) {
              Appender appender = appenders.nextElement();
              if (appender instanceof ConsoleAppender) {
                  return true;
              }
          }
          return false;
      }
      
      /**
       * @return the appender for 'LogFile' if it exists on the RootLogger or the requested Logger, null otherwise
       */
      private static Appender getLogFileAppender(Logger logger) {
          if (Logger.getRootLogger() != null) {
              return Logger.getRootLogger().getAppender(LOG_FILE_APPENDER_NAME);
          }
          else if (logger != null ) {
              return logger.getAppender(LOG_FILE_APPENDER_NAME);
          }
          return null;
      }
      
      /**
       * Returns the layout for the 'LogFile' appender.
       * 
       * @param logger the Logger to check
       * @return the Layout for the 'LogFile' appender, the DEFAULT_PATTERN_LAYOUT if 'LogFile' doesn't exist
       */
      private static Layout getLogFileAppenderLayout(Logger logger) {
          Appender logFileAppender = getLogFileAppender(logger);
          
          if (logFileAppender != null) {
              return logFileAppender.getLayout();
          }
          else {
              System.out.println(BatchLogger.class.getName() +": Could not find '"+ LOG_FILE_APPENDER_NAME +"' appender on RootLogger. Using DEFAULT_CONVERSION_PATTERN for layout to console");
              return DEFAULT_PATTERN_LAYOUT;
          }
      }
  }