package org.apache.torque.engine.database.model;

 /*

  * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE

  * file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file

  * to you under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0

  * 

  * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on

  * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the

  * specific language governing permissions and limitations under the License.

  */

 import java.util.Hashtable;

 import java.util.List;

 import org.apache.torque.engine.EngineException;

 /**

  * A name generation factory.

  * 

  * @author <a href="mailto:dlr@finemaltcoding.com>Daniel Rall</a>

  * @version $Id: NameFactory.java,v 1.1 2007-10-21 07:57:27 abyrne Exp $

  */

 public class NameFactory {

     /**

      * The fully qualified class name of the Java name generator.

      */

     public static final String JAVA_GENERATOR = JavaNameGenerator.class.getName();

     /**

      * The fully qualified class name of the constraint name generator.

      */

     public static final String CONSTRAINT_GENERATOR = ConstraintNameGenerator.class.getName();

     /**

      * The single instance of this class.

      */

     private static NameFactory instance = new NameFactory();

     /**

      * The cache of <code>NameGenerator</code> algorithms in use for name generation, keyed by fully qualified class

      * name.

      */

     private Hashtable algorithms;

     /**

      * Creates a new instance with storage for algorithm implementations.

      */

     protected NameFactory() {

         algorithms = new Hashtable(5);

     }

     /**

      * Factory method which retrieves an instance of the named generator.

      * 

      * @param name

      *            The fully qualified class name of the name generation algorithm to retrieve.

      * @return A name generator

      */

     protected NameGenerator getAlgorithm(String name) throws EngineException {

         synchronized (algorithms) {

             NameGenerator algorithm = (NameGenerator) algorithms.get(name);

             if (algorithm == null) {

                 try {

                     algorithm = (NameGenerator) Class.forName(name).newInstance();

                 } catch (InstantiationException e) {

                     throw new EngineException("Unable to instantiate class " + name

                             + ": Make sure it's in your run-time classpath", e);

                 } catch (Exception e) {

                     throw new EngineException(e);

                 }

                 algorithms.put(name, algorithm);

             }

             return algorithm;

         }

     }

     /**

      * Given a list of <code>String</code> objects, implements an algorithm which produces a name.

      * 

      * @param algorithmName

      *            The fully qualified class name of the {@link org.apache.torque.engine.database.model.NameGenerator}

      *            implementation to use to generate names.

      * @param inputs

      *            Inputs used to generate a name.

      * @return The generated name.

      * @throws EngineException

      *             an exception

      */

     public static String generateName(String algorithmName, List inputs) throws EngineException {

         NameGenerator algorithm = instance.getAlgorithm(algorithmName);

         return algorithm.generateName(inputs);

     }

 }