/* 
    * Copyright (c) 2007, Fraunhofer-Gesellschaft
    * All rights reserved.
    * 
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions are
    * met:
    * 
    * (1) Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the disclaimer at the end.
   *     Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in
   *     the documentation and/or other materials provided with the
   *     distribution.
   * 
   * (2) Neither the name of Fraunhofer nor the names of its
   *     contributors may be used to endorse or promote products derived
   *     from this software without specific prior written permission.
   * 
   * DISCLAIMER
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *  
   */
  package org.ogf.graap.wsag.server.persistence.impl;
  
  import java.text.MessageFormat;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Vector;
  
  import org.apache.log4j.Logger;
  import org.ogf.graap.wsag.server.api.EngineComponent;
  import org.ogf.graap.wsag.server.persistence.IAgreementFactoryHome;
  import org.ogf.graap.wsag.server.persistence.PersistedResourceException;
  import org.ogf.graap.wsag.server.persistence.PersistentAgreementFactory;
  
  /**
   * <p>
   * Abstract implementation of an agreement factory home. This implementation provides global
   * configuration-related functions as well as it is responsible to find and load the agreement factory
   * prototype (based on the configuration).
   * </p>
   * 
   * <p>
   * All implementations of the {@link IAgreementFactoryHome} interface should extend this abstract
   * implementation.
   * </p>
   * 
   * @author Oliver Waeldrich
   * 
   */
  public abstract class AbstractWSAG4JPersistence extends EngineComponent
      implements IAgreementFactoryHome
  {
  
      // //////////////////////////////////////////////////////////////////////////////////
      // ////// variable definition section ////////
      // //////////////////////////////////////////////////////////////////////////////////
  
      private static final Logger LOG = Logger.getLogger( AbstractWSAG4JPersistence.class );
  
      /**
       * indicates that the persistence layer has changed and a reload is required.
       */
      private boolean changed = false;
  
      /**
       * stores the persistent factories of this layer
       */
      private final Vector<PersistentAgreementFactory> persistentFactories =
          new Vector<PersistentAgreementFactory>();
  
      /**
       * stores the known factories by their ids for fast factory lookup
       */
      private final Map<String, PersistentAgreementFactory> factoriesById =
          new HashMap<String, PersistentAgreementFactory>();
  
      // //////////////////////////////////////////////////////////////////////////////////
      // ////// abstract method declaration ////////
      // //////////////////////////////////////////////////////////////////////////////////
  
      /**
       * Loads the agreement factories for this persistence layer. The load method is invoked during the
       * initialization process of the persistence layer (see {@link #initialize()}) or during a
       * {@link #find(String)}, {@link #list()} or {@link #remove(String)} operation
       * 
       * 
      * @return the loaded factories
      * 
      * @throws PersistedResourceException
      *             indicates an error while loading the persistent factories
      */
     protected abstract PersistentAgreementFactory[] doLoad() throws PersistedResourceException;
 
     /**
      * Removes a persistent factory from the persistence layer.
      * 
      * @param factory
      *            the factory to remove
      * 
      * @return <code>true</code> if the factory was removed, otherwise <code>false</code>
      * 
      * @throws PersistedResourceException
      *             indicates an error while removing the factory
      */
     protected abstract boolean doRemove( PersistentAgreementFactory factory )
         throws PersistedResourceException;
 
     // //////////////////////////////////////////////////////////////////////////////////
     // ////// getter/setter methods ////////
     // //////////////////////////////////////////////////////////////////////////////////
 
     /**
      * Indicates that the persistence layer has changed and needs to be re-initialized (see
      * {@link #initialize()}).
      * 
      * @return <code>true</code> if the persistence layer needs to be reloaded, otherwise <code>false</code>.
      */
     public boolean hasChanged()
     {
         return changed;
     }
 
     /**
      * Sets the flag to indicate that the persistence layer has changed and needs to be re-initialized (see
      * {@link #initialize()}).
      * 
      * @param changed
      *            <code>true</code> if the persistence layer needs to be reloaded, otherwise
      *            <code>false</code>
      */
     public void setChanged( boolean changed )
     {
         this.changed = changed;
     }
 
     // //////////////////////////////////////////////////////////////////////////////////
     // ////// method implementations ////////
     // //////////////////////////////////////////////////////////////////////////////////
 
     /**
      * {@inheritDoc}
      */
     @Override
     protected void doInitialize() throws Exception
     {
         synchronized ( this )
         {
 
             try
             {
                 persistentFactories.clear();
                 factoriesById.clear();
 
                 PersistentAgreementFactory[] factories = doLoad();
 
                 for ( int i = 0; i < factories.length; i++ )
                 {
                     persistentFactories.add( factories[i] );
                     factoriesById.put( factories[i].getResourceId(), factories[i] );
                 }
 
                 setChanged( false );
             }
             catch ( Exception e )
             {
                 String message =
                     MessageFormat.format(
                         "Could not load WSAG4J factory instance. Ignoring this instance. Error: {0}",
                         e.getMessage() );
                 LOG.error( message, e );
             }
 
         }
     }
 
     /**
      * Lists the agreement for the factory with the given id.
      * 
      * @param agreementFactoryId
      *            the id of the factory for which the agreements are listed
      * 
      * @return the factory with the given id
      * 
      * @throws Exception
      *             indicates an error while looking up the factory at the persistence layer
      */
     @Override
     public PersistentAgreementFactory find( String agreementFactoryId ) throws Exception
     {
         if ( hasChanged() )
         {
             doInitialize();
         }
 
         PersistentAgreementFactory persistentAgreementFactory = null;
 
         // check if the factory is known/available
         if ( factoriesById.containsKey( agreementFactoryId ) )
         {
             persistentAgreementFactory = factoriesById.get( agreementFactoryId );
         }
         else
         {
             throw new Exception( MessageFormat.format( "No agreement factory with id ''{0}'' found.",
                 agreementFactoryId ) );
         }
 
         return persistentAgreementFactory;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public PersistentAgreementFactory[] list() throws Exception
     {
 
         if ( hasChanged() )
         {
             doInitialize();
         }
 
         return persistentFactories.toArray( new PersistentAgreementFactory[persistentFactories.size()] );
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void remove( String factoryId ) throws Exception
     {
 
         if ( hasChanged() )
         {
             doInitialize();
         }
 
         if ( factoriesById.containsKey( factoryId ) )
         {
             PersistentAgreementFactory factory = factoriesById.get( factoryId );
 
             if ( doRemove( factory ) )
             {
                 persistentFactories.remove( factory );
                 factoriesById.remove( factoryId );
             }
         }
     }
 }