/**
    * Copyright 2010-2012 The Kuali Foundation
    *
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.common.util.service;
  
  import java.io.File;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.kuali.common.util.CollectionUtils;
  import org.kuali.common.util.LocationUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
  import org.springframework.context.support.AbstractApplicationContext;
  import org.springframework.context.support.ClassPathXmlApplicationContext;
  import org.springframework.util.Assert;
  
  public class DefaultSpringService implements SpringService {
  
  	private static final Logger logger = LoggerFactory.getLogger(DefaultSpringService.class);
  
  	@Override
  	public void load(String location) {
  		load(location, (String) null, (Object) null);
  	}
  
  	@Override
  	public void load(String location, String beanName, Object bean) {
  		load(location, CollectionUtils.toEmptyList(beanName), CollectionUtils.toEmptyList(bean));
  	}
  
  	@Override
  	public void load(String location, List<String> beanNames, List<Object> beans) {
  		load(CollectionUtils.toEmptyList(location), beanNames, beans);
  	}
  
  	@Override
  	public void load(List<String> locations) {
  		load(locations, (String) null, (Object) null);
  	}
  
  	@Override
  	public void load(List<String> locations, String beanName, Object bean) {
  		load(locations, CollectionUtils.toEmptyList(beanName), CollectionUtils.toEmptyList(bean));
  	}
  
  	@Override
  	public void load(List<String> locations, List<String> beanNames, List<Object> beans) {
  		// Make sure we have at least one location to load
  		Assert.isTrue(locations.size() > 0);
  
  		// Null-safe handling for non-required parameters
  		beanNames = CollectionUtils.toEmptyList(beanNames);
  		beans = CollectionUtils.toEmptyList(beans);
  		Assert.isTrue(beanNames.size() == beans.size());
  
  		// Make sure all of the locations exist
  		validate(locations);
  
  		// Convert any file names to fully qualified file system URL's
  		List<String> convertedLocations = getConvertedLocations(locations);
  
  		// The Spring classes prefer array's
  		String[] locationsArray = CollectionUtils.toStringArray(convertedLocations);
  
  		AbstractApplicationContext parent = null;
  		AbstractApplicationContext context = null;
  		try {
  			// Get a parent context with any bean's they've provided us pre-registered in the context
  			// Parent is null if there are no beans to register
  			parent = getApplicationContext(beanNames, beans);
  			// Load the locations they provided us, optionally wrapped in a parent context containing pre-registered beans
  			context = new ClassPathXmlApplicationContext(locationsArray, parent);
  		} finally {
  			// cleanup
  			closeQuietly(context);
  			closeQuietly(parent);
  		}
  	}
  
  	/**
  	 * Null safe close for a context
  	 */
  	protected void closeQuietly(AbstractApplicationContext context) {
  		if (context != null) {
  			context.close();
 		}
 	}
 
 	/**
 	 * Return an <code>AbstractApplicationContext</code> with <code>beans</code> registered in the context under <code>beanNames</code>
 	 */
 	protected AbstractApplicationContext getApplicationContext(List<String> beanNames, List<Object> beans) {
 		if (CollectionUtils.isEmpty(beanNames) && CollectionUtils.isEmpty(beans)) {
 			return null;
 		}
 		Assert.isTrue(beanNames.size() == beans.size());
 		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext();
 		context.refresh();
 		ConfigurableListableBeanFactory factory = context.getBeanFactory();
 		for (int i = 0; i < beanNames.size(); i++) {
 			String beanName = beanNames.get(i);
 			Object bean = beans.get(i);
 			logger.info("Registering [{}]", beanName);
 			factory.registerSingleton(beanName, bean);
 		}
 		return context;
 	}
 
 	/**
 	 * Make sure all of the locations actually exist
 	 */
 	protected void validate(List<String> locations) {
 		StringBuilder sb = new StringBuilder();
 		for (String location : locations) {
 			if (!LocationUtils.exists(location)) {
 				sb.append("Location [" + location + "] does not exist\n");
 			}
 		}
 		if (sb.length() > 0) {
 			throw new IllegalArgumentException(sb.toString());
 		}
 	}
 
 	/**
 	 * Format file names into fully qualified file system URL's
 	 */
 	protected List<String> getConvertedLocations(List<String> locations) {
 		List<String> converted = new ArrayList<String>();
 		for (String location : locations) {
 			if (LocationUtils.isExistingFile(location)) {
 				File file = new File(location);
 				// ClassPathXmlApplicationContext needs a fully qualified URL, not a filename
 				String url = LocationUtils.getCanonicalURLString(file);
 				converted.add(url);
 			} else {
 				converted.add(location);
 			}
 		}
 		return converted;
 	}
 
 }