package org.naftulin.configmgr.parsers;

 import java.io.IOException;

 import java.io.InputStream;

 import java.net.URL;

 import org.apache.log4j.Logger;

 import org.naftulin.configmgr.ConfigurationManagementEntryImpl;

 import org.naftulin.configmgr.ConfigurationManagerException;

 import org.naftulin.configmgr.ConfigurationManagementEntry;

 import org.naftulin.configmgr.ConfigurationType;

 /**

  * Log4J entry parser converts log4j configuration record into configuration management enttry.

  * It parses a log 4j file that the record describes, (re) initializes log4j 

  * engine, and stores the configuration

  * as a content of an {@link org.naftulin.configmgr.ConfigurationManagementEntry entry}.

  * 

  * @author Henry Naftulin

  * @since 1.0

  */

 public abstract class AbstractLog4JParser extends AbstractConfigEntryParser {

         private static final Logger log = Logger.getLogger(AbstractLog4JParser.class);

         /**

          * Calls appropriate log4j configurator: for DOM object it is dom configurator

          * to (re)initilize log4j engine. 

          */

         abstract void doCallLog4JConfigurator(URL fileUrl);

         /**

          * Retrurns a configuration managment entry by parsing the log4j file passed in.

          * @param key the key configuration entry will be assigned

          * @param fileUrl the file URL to be parsed.

          * @return a log4j managment entry by parsing the record passed in.

          * @throws ConfigurationManagerException if an error occurs while parsing an entry.

          */

         public ConfigurationManagementEntry getConfigurationManagementEntry(final String key, final URL fileUrl) throws ConfigurationManagerException {                

                 checkParameters(key, fileUrl);

                 final String fileName = fileUrl.getFile();                

                 String content = null;

                 try {

                         final InputStream stream = fileUrl.openStream();

                         log.debug("reading log4j configuration from file " + fileName);

                         content = readStreamContentAsString(stream);

                         log.debug("log4j configuration is " + content);

                         doCallLog4JConfigurator(fileUrl);

                         log.info("reloaded log4j configuratoin from " + fileName);

                 } catch (IOException e) {

                         log.warn("Error while reading log4j file", e);

                         throw new ConfigurationManagerException("Error while reading log4j file",e);

                 }                

                 final ConfigurationManagementEntry entry = new ConfigurationManagementEntryImpl(key, fileName , content, this, getConfigurationType());

                 log.info("configured entry " + entry);                

                 return entry;

         }

         private void checkParameters(final String key, final URL fileUrl)

                         throws ConfigurationManagerException {

                 if (fileUrl == null) {

                         throw new ConfigurationManagerException("file URL is null");

                 }

                 if (fileUrl.getFile() == null) {

                         throw new ConfigurationManagerException("file name passed in the URL " + fileUrl + " is null");

                 }

                 if (key == null) { 

                         throw new ConfigurationManagerException("key is null");

                 }

         }

         protected abstract ConfigurationType getConfigurationType();

 }