/***
    * Simple Web Spider - <http://simplewebspider.sourceforge.net/>
    * Copyright (C) 2009  <berendona@users.sourceforge.net>
    *
    * This program 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 3 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package simplespider.simplespider.dao.db4o;
  
  import java.io.IOException;
  import java.sql.SQLException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import simplespider.simplespider.dao.DbHelper;
  import simplespider.simplespider.dao.DbHelperFactory;
  
  import com.db4o.ObjectContainer;
  import com.db4o.ObjectServer;
  import com.db4o.constraints.UniqueFieldValueConstraint;
  import com.db4o.cs.Db4oClientServer;
  import com.db4o.cs.config.ServerConfiguration;
  import com.db4o.defragment.Defragment;
  import com.db4o.diagnostic.ClassHasNoFields;
  import com.db4o.diagnostic.Diagnostic;
  import com.db4o.diagnostic.DiagnosticBase;
  import com.db4o.diagnostic.DiagnosticListener;
  import com.db4o.ext.ExtObjectContainer;
  import com.db4o.ext.SystemInfo;
  import com.db4o.reflect.ReflectClass;
  
  public class Db4oDbHelperFactory implements DbHelperFactory {
  
  	private static final Log	LOG	= LogFactory.getLog(Db4oDbHelperFactory.class);
  
  	private ObjectServer		server;
  
  	public Db4oDbHelperFactory(final String filename) {
  
  		final ServerConfiguration dbConfig = Db4oClientServer.newServerConfiguration();
  		dbConfig.common().objectClass(Hash.class).objectField(Hash.HASH).indexed(true);
  		dbConfig.common().add(new UniqueFieldValueConstraint(Hash.class, Hash.HASH));
  
  		dbConfig.common().allowVersionUpdates(true);
  		dbConfig.common().detectSchemaChanges(true);
  		dbConfig.common().exceptionsOnNotStorable(true);
  		dbConfig.common().optimizeNativeQueries(true);
  		dbConfig.common().messageLevel(1);
  		dbConfig.common().activationDepth(1);
  
  		if (LOG.isDebugEnabled()) {
  			dbConfig.common().diagnostic().addListener(new DiagnosticListener() {
  				public void onDiagnostic(final Diagnostic arg0) {
  
  					if (arg0 instanceof ClassHasNoFields) {
  						return; // Ignore
  					}
  					if (arg0 instanceof DiagnosticBase) {
  						final DiagnosticBase d = (DiagnosticBase) arg0;
  						LOG.debug("Diagnostic: " + d.getClass() + " : " + d.problem() + " : " + d.solution() + " : " + d.reason(), new Exception(
  								"debug"));
  					} else {
  						LOG.debug("Diagnostic: " + arg0 + " : " + arg0.getClass(), new Exception("debug"));
  					}
  				}
  			});
  		}
  
  		/* TURN OFF SHUTDOWN HOOK.
  		 * The shutdown hook does auto-commit. 
  		 * And it close database after getting signal (or pressing CTRL-C) */
  		dbConfig.common().automaticShutDown(false);
  
  		// LAZY appears to cause ClassCastException's relating to db4o objects inside db4o code. :(
  		// Also it causes duplicates if we activate immediately.
  		// And the performance gain for e.g. RegisterMeRunner isn't that great.
  		//		dbConfig.queries().evaluationMode(QueryEvaluationMode.LAZY);
  		//		dbConfig.common().queries().evaluationMode(QueryEvaluationMode.SNAPSHOT);
  
  		// Reduce memory usage. After running eight hours with an 350 MB DB (than 400 MB) freeslot requires 14 MB instead of 0.4 MB on application startup
  		dbConfig.file().freespace().useBTreeSystem();
  
  		/* Block size 8 should have minimal impact since pointers are this
  		 * long, and allows databases of up to 16GB. 
  		 * FIXME make configurable by user. */
  		dbConfig.file().blockSize(8);
  
 		if (LOG.isInfoEnabled()) {
 			LOG.info("Start defragmentation database file... This could took some while...");
 		}
 		try {
 			Defragment.defrag(filename);
 		} catch (final IOException e) {
 			LOG.warn("Failed to defragment database file \"" + filename + "\"", e);
 		}
 
 		if (LOG.isInfoEnabled()) {
 			LOG.info("Opening database file... This could took some while...");
 		}
 		try {
 			this.server = Db4oClientServer.openServer(dbConfig, filename, 0);
 		} catch (final RuntimeException e) {
 			throw new RuntimeException("Failed to open database file \"" + filename + "\"", e);
 		}
 
 		if (LOG.isInfoEnabled()) {
 			final ObjectContainer container = getConnection();
 			try {
 				final ExtObjectContainer ext = container.ext();
 
 				final ReflectClass[] knownClasses = ext.knownClasses();
 				final StringBuffer sb = new StringBuffer();
 				sb.append("Known classes: ");
 				for (final ReflectClass knownClass : knownClasses) {
 					sb.append(knownClass.getName());
 					sb.append(";");
 				}
 				LOG.info(sb.toString());
 
 				final SystemInfo systemInfo = ext.systemInfo();
 				LOG.info("Total size: " + systemInfo.totalSize());
 				LOG.info("Freespace size: " + systemInfo.freespaceSize());
 				LOG.info("Freespace entry count: " + systemInfo.freespaceEntryCount());
 
 			} finally {
 				container.close();
 			}
 		}
 	}
 
 	@Override
 	public DbHelper buildDbHelper() throws SQLException {
 		final Db4oDbHelper dbHelper = new Db4oDbHelper();
 
 		dbHelper.createConnection(this);
 		return dbHelper;
 	}
 
 	ObjectContainer getConnection() {
 		return this.server.openClient();
 	}
 
 	void shutdown() {
 		this.server.close();
 		this.server = null;
 	}
 
 }