/*
    * @(#)$Id: Db4oStorageEngine.java 730 2009-08-05 21:17:30Z kurmannu $
    *
    * Author       :   Ueli Kurmann, igesture@uelikurmann.ch
    *	
    * Purpose      : 	Storage engine implementation for db4o.
    *
    * -----------------------------------------------------------------------
    *
   * Revision Information:
   *
   * Date             Who         Reason
   *
   * Dec 26, 2006     ukurmann    Initial Release
   * Mar 22, 2007     bsigner     Cleanup
   *
   * -----------------------------------------------------------------------
   *
   * Copyright 1999-2009 ETH Zurich. All Rights Reserved.
   *
   * This software is the proprietary information of ETH Zurich.
   * Use is subject to license terms.
   * 
   */
  
  package org.ximtec.igesture.storage;
  
  import java.io.File;
  import java.util.ArrayList;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  
  import org.ximtec.igesture.configuration.Configuration;
  import org.ximtec.igesture.core.DataObject;
  import org.ximtec.igesture.core.GestureSet;
  import org.ximtec.igesture.core.TestSet;
  
  import com.db4o.Db4o;
  import com.db4o.ObjectContainer;
  import com.db4o.ObjectSet;
  import com.db4o.query.Predicate;
  
  /**
   * Storage engine implementation for db4o.
   * 
   * @version 1.0, Dec 2006
   * @author Ueli Kurmann, igesture@uelikurmann.ch
   * @author Beat Signer, signer@inf.ethz.ch
   */
  public class Db4oStorageEngine extends DefaultStorageEngine {
  
    ObjectContainer db;
  
    private Set<Object> objectCache;
    private Set<Object> objectsToRemove;
  
    /**
     * Constructs a new db4o engine.
     * 
     * @param filename
     *          the database file.
     */
    public Db4oStorageEngine(String filename) {
      Db4o.configure().activationDepth(Integer.MAX_VALUE);
      Db4o.configure().updateDepth(Integer.MAX_VALUE);
      Db4o.configure().allowVersionUpdates(true);
      Db4o.configure().callConstructors(true);
  
      db = Db4o.openFile(filename);
      objectCache = new HashSet<Object>();
      objectsToRemove = new HashSet<Object>();
    }
  
    public void dispose() {
      db.rollback();
      objectCache.clear();
      db.close();
  
    } // dispose
  
    @SuppressWarnings("serial")
    public <T extends DataObject> T load(final Class<T> clazz, final String id) {
      T result = null;
      final ObjectSet<T> os = db.query(new Predicate<T>() {
  
        @Override
        public boolean match(T dataObject) {
          return dataObject.getClass().equals(clazz) && dataObject.getId().equals(id);
        }
      });
  
      if (!os.isEmpty()) {
        result = os.get(0);
      }
      objectCache.add(result);
      return result;
    } // load
  
   public <T extends DataObject> List<T> load(Class<T> clazz) {
     List<T> result = new ArrayList<T>(db.query(clazz));
     objectCache.addAll(result);
     return result;
   } // load
 
   public void store(DataObject dataObject) {
     db.set(dataObject);
     objectCache.add(dataObject);
   } // store
 
   public void update(DataObject dataObject) {
     db.set(dataObject);
     objectCache.add(dataObject);
   } // update
 
   public void remove(DataObject dataObject) {
     db.delete(dataObject);
     objectCache.remove(dataObject);
     objectsToRemove.add(dataObject);
   } // remove
 
   @Override
   public synchronized void commit() {
     for (Object obj : objectCache) {
       db.set(obj);
     }
     for (Object obj : objectsToRemove) {
       db.delete(obj);
     }
 
     db.commit();
   }
 
   /*
    * (non-Javadoc)
    * 
    * @see org.ximtec.igesture.storage.StorageEngine#copyTo(java.io.File)
    */
   @Override
   public synchronized void copyTo(File file) {
 
     ObjectContainer workingCopy = Db4o.openFile(file.getAbsolutePath());
     for (GestureSet gestureSet : db.query(GestureSet.class)) {
       workingCopy.set(gestureSet);
     }
     for (Configuration configuration : db.query(Configuration.class)) {
       workingCopy.set(configuration);
     }
     for (TestSet testSet : db.query(TestSet.class)) {
       workingCopy.set(testSet);
     }
     workingCopy.commit();
     workingCopy.close();
 
     db.rollback();
     db.close();
 
     db = Db4o.openFile(file.getName());
 
   }
 
 }