/*
    * This file is a part of CAST project.
    * (c) Copyright 2007, AGH University of Science & Technology
    * https://caribou.iisg.agh.edu.pl/trac/cast
    *
    * Licensed under the Eclipse Public License, Version 1.0 (the "License").
    * You may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    * http://www.eclipse.org/legal/epl-v10.html
   */
  /*
   * File: PersistenceProviderLocator.java
   * Created: 2009-07-06
   * Author: tmilos
   * $Id$
   */
  
  package pl.edu.agh.cast.data.persistence;
  
  import java.util.LinkedList;
  import java.util.List;
  
  import org.apache.log4j.Logger;
  import org.eclipse.core.runtime.CoreException;
  import org.eclipse.core.runtime.IConfigurationElement;
  import org.eclipse.core.runtime.Platform;
  
  import pl.edu.agh.cast.Activator;
  import pl.edu.agh.cast.data.persistence.serialize.SerializationPersistenceProviderFactory;
  
  /**
   * Locator of {@link TransparentPersistenceProvider} instance.
   *
   * @author AGH CAST Team
   */
  @SuppressWarnings("nls")
  public final class PersistenceProviderLocator {
  
  	private static Logger log = Activator.getLogger();
  
  	// BEGIN Persistence Provider Extension Point Specification
  
  	/**
  	 * Name of persistence provider extension point id.
  	 */
  	private static final String PERSISTENCE_PROVIDER_EXTENSION_ID = "pl.edu.agh.cast.persistence.provider";
  
  	/**
  	 * Name of attribute holding persistence provider factory class.
  	 */
  	private static final String PERSISTENCE_PROVIDER_FACTORY = "factory";
  
  	/**
  	 * Name of attribute holding persistence provider ID.
  	 */
  	private static final String PERSISTENCE_PROVIDER_ID = "id";
  
  	/**
  	 * Name of attribute holding persistence provider name.
  	 */
  	private static final String PERSISTENCE_PROVIDER_NAME = "name";
  
  	/**
  	 * Name of attribute holding persistence provider description.
  	 */
  	private static final String PERSISTENCE_PROVIDER_DESCRIPTION = "description";
  
  	/**
  	 * Persistence provider specification holder.
  	 *
  	 * @author AGH CAST Team
  	 */
  	private static final class PersistenceProviderSpecification {
  
  		private String id;
  
  		private String name;
  
  		private String description;
  
  		public final String getId() {
  			return id;
  		}
  
  		public final void setId(String id) {
  			this.id = id;
  		}
  
  		public final String getName() {
  			return name;
  		}
  
  		public final void setName(String name) {
  			this.name = name;
  		}
  
  		public final String getDescription() {
  			return description;
  		}
 
 		public final void setDescription(String description) {
 			this.description = description;
 		}
 
 	}
 
 	// END Persistence Provider Extension Point Specification
 
 	/**
 	 * Persistence provider instance holder.
 	 *
 	 * @author AGH CAST Team
 	 */
 	private static final class PersistenceProviderHolder {
 		private static final TransparentPersistenceProvider INSTANCE = createProvider();
 	}
 
 	/**
 	 * Returns the instance of persistence provider.
 	 *
 	 * @return the instance of persistence provider
 	 */
 	public static TransparentPersistenceProvider getProvider() {
 		return PersistenceProviderHolder.INSTANCE;
 	}
 
 	private static TransparentPersistenceProvider createProvider() {
 		return new TransparentPersistenceProvider();
 	}
 
 	/**
 	 * Attempts to create an instance of persistence provider with given ID using the specified persistence file.
 	 *
 	 * @param providerId
 	 *            the ID of the persistence provider
 	 * @param filePath
 	 *            the path to persistence file
 	 * @return a new instance of persistence provider
 	 *
 	 * @throws PersistenceException
 	 *             if provider with given ID could not be created
 	 */
 	public static IPersistenceProvider createPersistenceProvider(String providerId, String filePath)
 	        throws PersistenceException {
 		IPersistenceProviderFactory factory = getPersistenceProviderFactory(providerId);
 		if (factory == null) {
 			throw new PersistenceException(String.format("Failed to initialize persistence provider with ID: %s",
 			        providerId));
 		}
 		return factory.createPersistenceProvider(filePath);
 	}
 
 	/**
 	 * Selects a persistence provider to be used in a new project.
 	 *
 	 * @return the ID of selected persistence provider
 	 */
 	public static String selectPersistenceProvider() {
 		return SerializationPersistenceProviderFactory.PROVIDER_ID;
 	}
 
 	/**
 	 * Returns the path to persistence file for provider with given ID.
 	 *
 	 * @param providerId
 	 *            the ID of the persistence provider
 	 * @return the path to the persistence file (relative to the project directory)
 	 */
 	public static String getPersistenceFilePath(String providerId) {
 		IPersistenceProviderFactory factory = getPersistenceProviderFactory(providerId);
 		if (factory != null) {
 			return factory.getPersistenceFilePath();
 		}
 		return String.format("%s.data", providerId);
 	}
 
 	// BEGIN Extension Helper Methods
 
 	private static List<PersistenceProviderSpecification> getPersistenceProviderSpecifications() {
 		IConfigurationElement[] elements = Platform.getExtensionRegistry().getConfigurationElementsFor(
 		        PERSISTENCE_PROVIDER_EXTENSION_ID);
 		List<PersistenceProviderSpecification> specs = new LinkedList<PersistenceProviderSpecification>();
 		for (IConfigurationElement element : elements) {
 			PersistenceProviderSpecification spec = new PersistenceProviderSpecification();
 			spec.setId(element.getAttribute(PERSISTENCE_PROVIDER_ID));
 			spec.setName(element.getAttribute(PERSISTENCE_PROVIDER_NAME));
 			spec.setDescription(element.getAttribute(PERSISTENCE_PROVIDER_DESCRIPTION));
 			specs.add(spec);
 		}
 		return specs;
 	}
 
 	private static IPersistenceProviderFactory getPersistenceProviderFactory(String providerId) {
 		if (providerId == null) {
 			throw new IllegalArgumentException("Provider ID cannot be null"); //$NON-NLS-1$
 		}
 
 		IConfigurationElement[] elements = Platform.getExtensionRegistry().getConfigurationElementsFor(
 		        PERSISTENCE_PROVIDER_EXTENSION_ID);
 
 		for (IConfigurationElement element : elements) {
 			if (providerId.equals(element.getAttribute(PERSISTENCE_PROVIDER_ID))) {
 				try {
 					return (IPersistenceProviderFactory)element.createExecutableExtension(PERSISTENCE_PROVIDER_FACTORY);
 				} catch (CoreException e) {
 					log.error(String.format(
 					        "Failed to instantiate persistence provider factory provided by extension: %1$s ", element
 					                .getDeclaringExtension().getUniqueIdentifier()), e);
 					return null;
 				}
 			}
 		}
 
 		log.error(String.format("Failed to locate persistence provider factory with given ID: %1$s", providerId));
 
 		return null;
 	}
 
 	// END Extension Helper Methods
 
 }