/*
    * Copyright 2006-2013 the original author or authors.
    *
    * Licensed 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.
   */
  package org.springframework.batch.core.configuration.support;
  
  import java.util.Collections;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  import org.springframework.batch.core.Job;
  import org.springframework.batch.core.configuration.DuplicateJobException;
  import org.springframework.batch.core.configuration.JobFactory;
  import org.springframework.batch.core.configuration.JobRegistry;
  import org.springframework.batch.core.launch.NoSuchJobException;
  import org.springframework.util.Assert;
  
  /**
   * Simple, thread-safe, map-based implementation of {@link JobRegistry}.
   *
   * @author Dave Syer
   * @author Robert Fischer
   */
  public class MapJobRegistry implements JobRegistry {
  
  	/**
  	 * The map holding the registered job factories.
  	 */
  	// The "final" ensures that it is visible and initialized when the constructor resolves.
  	private final ConcurrentMap<String, JobFactory> map = new ConcurrentHashMap<String, JobFactory>();
  
  	@Override
  	public void register(JobFactory jobFactory) throws DuplicateJobException {
  		Assert.notNull(jobFactory);
  		String name = jobFactory.getJobName();
  		Assert.notNull(name, "Job configuration must have a name.");
  		JobFactory previousValue = map.putIfAbsent(name, jobFactory);
  		if (previousValue != null) {
  			throw new DuplicateJobException("A job configuration with this name [" + name
  					+ "] was already registered");
  		}
  	}
  
  	@Override
  	public void unregister(String name) {
  		Assert.notNull(name, "Job configuration must have a name.");
  		map.remove(name);
  	}
  
  	@Override
  	public Job getJob(String name) throws NoSuchJobException {
  		JobFactory factory = map.get(name);
  		if (factory == null) {
  			throw new NoSuchJobException("No job configuration with the name [" + name + "] was registered");
  		} else {
  			return factory.createJob();
  		}
  	}
  
  	/**
  	 * Provides an unmodifiable view of the job names.
  	 */
  	@Override
  	public Set<String> getJobNames() {
  		return Collections.unmodifiableSet(map.keySet());
  	}
  
  }