/*
    * 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: XStreamInitializer.java
   * Created: 2007-00-00
   * Author: kpietak, awos
   * $Id: XStreamInitializer.java 3020 2009-07-17 14:41:19Z kpietak $
   */
  
  package pl.edu.agh.cast.backward.resources.xml;
  
  import java.lang.reflect.Field;
  import java.util.Arrays;
  import java.util.Comparator;
  import java.util.Map;
  
  import pl.edu.agh.cast.Activator;
  import pl.edu.agh.cast.model.attributes.Attribute;
  import pl.edu.agh.cast.model.attributes.AttributeManager;
  import pl.edu.agh.cast.model.attributes.AttributeMergePolicy;
  import pl.edu.agh.cast.model.attributes.AttributeValue;
  import pl.edu.agh.cast.model.visual.backward.Connection;
  import pl.edu.agh.cast.model.visual.backward.Diagram;
  import pl.edu.agh.cast.model.visual.backward.DiagramSettings;
  import pl.edu.agh.cast.model.visual.backward.IDiagramSettings;
  import pl.edu.agh.cast.model.visual.backward.ModelElement;
  import pl.edu.agh.cast.model.visual.backward.Node;
  import pl.edu.agh.cast.model.visual.backward.VisualModelCachingFactory;
  
  import com.thoughtworks.xstream.XStream;
  import com.thoughtworks.xstream.converters.reflection.FieldDictionary;
  import com.thoughtworks.xstream.converters.reflection.FieldKey;
  import com.thoughtworks.xstream.converters.reflection.FieldKeySorter;
  import com.thoughtworks.xstream.converters.reflection.Sun14ReflectionProvider;
  import com.thoughtworks.xstream.core.util.OrderRetainingMap;
  
  /**
   * Helper class which is responsible for providing and initialization of XStream object.
   *
   * @author AGH CAST Team
   */
  public class XStreamInitializer {
  
  	/**
  	 * A custom XStream {@link FieldKeySorter} that puts all attribute managers to the beginning. This prevents problems
  	 * with marshaling attribute values before attributes were marshaled.
  	 *
  	 * @author AGH CAST Team
  	 */
  	private static final class AttributeManagersFirstKeySorter implements FieldKeySorter {
  
  		/**
  		 * Compares field key names so that those with ATTRIBUTE_MANAGER_FIELD_NAME_SUBSTRING are first.
  		 *
  		 * @author AGH CAST Team
  		 */
  		private static final class FieldKeyComparator implements Comparator<FieldKey> {
  			public int compare(FieldKey o1, FieldKey o2) {
  				if (isAttributeManagerField(o1)) {
  					return -1;
  				} else if (isAttributeManagerField(o2)) {
  					return 1;
  				} else {
  					return 0;
  				}
  			}
  
  			private boolean isAttributeManagerField(FieldKey fieldKey) {
  				try {
  					Field field = fieldKey.getDeclaringClass().getDeclaredField(fieldKey.getFieldName());
  					return AttributeManager.class.isAssignableFrom(field.getType());
  				} catch (Exception e) {
  					// this should not happen, but anyway...
  					Activator.getLogger().warn("Exception when sorting fields", e); //$NON-NLS-1$
  					return false;
  				}
  			}
  		}
  
  		@SuppressWarnings("unchecked")
  		public Map sort(Class type, Map keyedByFieldKey) {
  
  			if (Diagram.class.isAssignableFrom(type)) {
  				/**
  				 * Move all AttributeManager type fields at the beginning of the map
  				 */
  				FieldKey[] fieldKeys = (FieldKey[])keyedByFieldKey.keySet().toArray(
  				        new FieldKey[keyedByFieldKey.size()]);
  				Arrays.sort(fieldKeys, new FieldKeyComparator());
  
  				Map result = new OrderRetainingMap();
 				for (int i = 0; i < fieldKeys.length; i++) {
 					result.put(fieldKeys[i], keyedByFieldKey.get(fieldKeys[i]));
 				}
 				return result;
 			} else {
 				// only change field order for descendants of Diagram
 				return keyedByFieldKey;
 			}
 		}
 	}
 
 	private static final Class<?>[] CLASSES_WITH_ALIASES = { XMLProjectContainer.class, Diagram.class,
 		DiagramSettings.class, ModelElement.class, VisualModelCachingFactory.class, Connection.class, Node.class,
 	   	AttributeValue.class, Attribute.class, AttributeMergePolicy.MergePolicyAlwaysFirst.class,
 	   	AttributeMergePolicy.MergePolicyAlwaysSecond.class, AttributeMergePolicy.MergePolicyLogicalAnd.class,
 	   	AttributeMergePolicy.MergePolicyLogicalOr.class };
 
 	/**
 	 * Creates and initializes a new XStream instance with default set of classes.
 	 *
 	 * @return a new instance of XStream
 	 */
 	public static XStream createXStreamInstance() {
 		return init(null);
 	}
 
 	/**
 	 * Creates and initializes a new XStream instance.
 	 *
 	 * @param classes
 	 *            which contains annotations for XStream
 	 * @return a new instance of XStream
 	 */
 	public static XStream createXStreamInstance(Class<?>[] classes) {
 		return init(classes);
 	}
 
 	private static XStream init(Class<?>[] additionalClassesWithAliases) {
 		XStream xstream = new XStream(new Sun14ReflectionProvider(new FieldDictionary(
 		        new AttributeManagersFirstKeySorter())));
 
 		// read aliases
 		xstream.processAnnotations(CLASSES_WITH_ALIASES);
 		if (additionalClassesWithAliases != null) {
 			xstream.processAnnotations(additionalClassesWithAliases);
 		}
 		// autodetect annotations in classes extending default visual model
 		// classes
 		xstream.autodetectAnnotations(true);
 
 		// add default implementations to avoid
 		// class attribute in xml tag
 		xstream.addDefaultImplementation(DiagramSettings.class, IDiagramSettings.class);
 
 		// add custom converters
 		xstream.registerConverter(new VisualModelCachingFactoryConverter());
 		xstream.registerConverter(new AttributeManagerConverter());
 		xstream.registerConverter(new AttributeValuesConverter());
 
 		return xstream;
 	}
 
 }