/**
    * Copyright 2005-2016 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.rice.core.api.resourceloader;
  
  import java.util.List;
  
  import javax.xml.namespace.QName;
  
  import org.kuali.rice.core.api.reflect.ObjectDefinition;
  
  /**
   * A resource loader implementation which checks a child resource loader first and if the resource is not found there,
   * checks a parent resource loader.
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  class ParentChildResourceLoader implements ResourceLoader {
  
      private final ResourceLoader parent;
      private final ResourceLoader child;
      private QName name;
  
      ParentChildResourceLoader(ResourceLoader parent, ResourceLoader child) {
      	if (parent == null) {
      		throw new IllegalArgumentException("parent resource loader was null");
      	}
      	if (child == null) {
      		throw new IllegalArgumentException("child resource loader was null");
      	}
      	this.parent = parent;
      	this.child = child;
      	this.name = new QName(child.getName().toString() + " to parent " + parent.getName().toString());
      }
  
  	@Override
  	public <T> T getObject(ObjectDefinition definition) {
  		T object = child.<T>getObject(definition);
      	if (object == null) {
      		object = parent.<T>getObject(definition);
      	}
      	return object;
  	}
  
  	@Override
  	public <T> T getService(QName qname) {
  		T service = child.<T>getService(qname);
  		if (service == null) {
  			service = parent.<T>getService(qname);
  		}
  		return service;
      }
  
  	/**
  	 * "Starts" this resource loader.  When started, this method will simply
  	 * invoke start on the child resource loader.  It's assumed that the
  	 * parent will be started from it's context.
  	 * 
  	 * @see org.kuali.rice.core.api.lifecycle.Lifecycle#start()
  	 */
  	@Override
      public void start() throws Exception {
  		if (!child.isStarted()) {
  			child.start();
  		}
  	}
  
  	/**
  	 * Just stops the internal child resource loader.
  	 * 
  	 * @see org.kuali.rice.core.api.lifecycle.Lifecycle#stop()
  	 */
  	@Override
      public void stop() throws Exception {
      	if (child.isStarted()) {
      		child.stop();
      	}
      }
  
  	@Override
      public void addResourceLoader(ResourceLoader resourceLoader) {
      	this.child.addResourceLoader(resourceLoader);
      }
  
  	@Override
      public void addResourceLoaderFirst(ResourceLoader resourceLoader) {
      	this.child.addResourceLoaderFirst(resourceLoader);
     }
 
 	@Override
     public ResourceLoader getResourceLoader(QName name) {
     	ResourceLoader resourceLoader = this.child.getResourceLoader(name);
     	if (resourceLoader == null && parent != null) {
     		return parent.getResourceLoader(name);
     	} else {
     		return resourceLoader;
     	}
     }
   
 	@Override
     public List<QName> getResourceLoaderNames() {
 		return this.child.getResourceLoaderNames();
     }
 
 	@Override
     public List<ResourceLoader> getResourceLoaders() {
 		return this.child.getResourceLoaders();
     }
 
 	@Override
     public void removeResourceLoader(QName name) {
 		this.child.removeResourceLoader(name);
     }
 
 	@Override
 	public boolean isStarted() {
 		return false;
 	}
 
 	@Override
 	public void setName(QName name) {
 		this.name = name;
 	}
 
 	@Override
 	public QName getName() {
 		return this.name;
 	}
 
 	@Override
 	public String getContents(String indent, boolean servicePerLine) {
 		StringBuilder contents = new StringBuilder();
 		contents.append(parent.getContents(indent, servicePerLine)).append("\n");
 		contents.append(child.getContents(indent, servicePerLine));
 		return contents.toString();
 	}
 
 	
 
 }