/*
    * ModeShape (http://www.modeshape.org)
    * See the COPYRIGHT.txt file distributed with this work for information
    * regarding copyright ownership.  Some portions may be licensed
    * to Red Hat, Inc. under one or more contributor license agreements.
    * See the AUTHORS.txt file in the distribution for a full listing of 
    * individual contributors.
    *
    * ModeShape is free software. Unless otherwise indicated, all code in ModeShape
   * is licensed to you under the terms of the GNU Lesser General Public License as
   * published by the Free Software Foundation; either version 2.1 of
   * the License, or (at your option) any later version.
   * 
   * ModeShape is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this software; if not, write to the Free
   * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
   * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
   */
  package org.modeshape.jcr;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import javax.jcr.PropertyType;
  import javax.jcr.Session;
  import javax.jcr.Value;
  import javax.jcr.nodetype.ConstraintViolationException;
  import javax.jcr.nodetype.NodeDefinitionTemplate;
  import javax.jcr.nodetype.NodeTypeDefinition;
  import javax.jcr.nodetype.NodeTypeTemplate;
  import javax.jcr.nodetype.PropertyDefinitionTemplate;
  import javax.jcr.version.OnParentVersionAction;
  import net.jcip.annotations.NotThreadSafe;
  import org.modeshape.common.collection.Problems;
  import org.modeshape.common.collection.SimpleProblems;
  import org.modeshape.common.util.CheckArg;
  import org.modeshape.common.util.IoUtil;
  import org.modeshape.graph.ExecutionContext;
  import org.modeshape.graph.Graph;
  import org.modeshape.graph.Location;
  import org.modeshape.graph.Subgraph;
  import org.modeshape.graph.SubgraphNode;
  import org.modeshape.graph.connector.inmemory.InMemoryRepositorySource;
  import org.modeshape.graph.io.Destination;
  import org.modeshape.graph.io.GraphBatchDestination;
  import org.modeshape.graph.property.Name;
  import org.modeshape.graph.property.NameFactory;
  import org.modeshape.graph.property.Path;
  import org.modeshape.graph.property.PathFactory;
  import org.modeshape.graph.property.Property;
  import org.modeshape.graph.property.ValueFactories;
  import org.modeshape.graph.property.ValueFactory;
  import org.modeshape.graph.property.basic.LocalNamespaceRegistry;
  
  /**
   * A base class for loading content into a graph with the standard format used by ModeShape.
   * <p>
   * The root node of the graph should have zero or more children. Each child of the root node represents a type to be registered
   * and the name of the node should be the name of the node type to be registered. Additionally, any facets of the node type that
   * are specified should be set in a manner consistent with the JCR specification for the {@code nt:nodeType} built-in node type.
   * The {@code jcr:primaryType} property does not need to be set on these nodes, but the nodes must be semantically valid as if the
   * {@code jcr:primaryType} property was set.
   * </p>
   * <p>
   * Each node type node may have zero or more children, each with the name {@code jcr:propertyDefinition} or {@code
   * jcr:childNodeDefinition}, as per the definition of the {@code nt:nodeType} built-in type. Each property definition and child
   * node definition must obey the semantics of {@code jcr:propertyDefinition} and {@code jcr:childNodeDefinition} respectively
   * However these nodes also do not need to have the {@code jcr:primaryType} property set.
   * </p>
   * <p>
   * For example, one valid graph is:
   * 
   * <pre>
   * &lt;root&gt;
   * +---- test:testMixinType
   *        +--- jcr:nodeTypeName               =  test:testMixinType  (PROPERTY)
   *        +--- jcr:isMixin                    =  true                (PROPERTY)    
   *        +--- jcr:childNodeDefinition                               (CHILD NODE)
   *        |     +--- jcr:name                 =  test:childNodeA     (PROPERTY)
   *        |     +--- jcr:mandatory            =  true                (PROPERTY)
   *        |     +--- jcr:autoCreated          =  true                (PROPERTY)
   *        |     +--- jcr:defaultPrimaryType   =  nt:base             (PROPERTY)
   *        |     +--- jcr:requiredPrimaryTypes =  nt:base             (PROPERTY)
   *        +--- jcr:propertyDefinition                                (CHILD NODE)
   *              +--- jcr:name                 =  test:propertyA      (PROPERTY)
   *              +--- jcr:multiple             =  true                (PROPERTY)
  *              +--- jcr:requiredType         =  String              (PROPERTY)
  * </pre>
  * 
  * This graph (when registered) would create a mixin node named "test:testMixinType" with a mandatory, autocreated child node
  * named "test:childNodeA" with a default and required primary type of "nt:base" and a multi-valued string property named
  * "test:propertyA".
  * </p>
  */
 @NotThreadSafe
 class GraphNodeTypeReader implements Iterable<NodeTypeDefinition> {
 
     private static final Map<String, Integer> PROPERTY_TYPE_VALUES_FROM_NAME;
 
     static {
         Map<String, Integer> temp = new HashMap<String, Integer>();
 
         temp.put(PropertyType.TYPENAME_BINARY.toUpperCase(), PropertyType.BINARY);
         temp.put(PropertyType.TYPENAME_BOOLEAN.toUpperCase(), PropertyType.BOOLEAN);
         temp.put(PropertyType.TYPENAME_DATE.toUpperCase(), PropertyType.DATE);
         temp.put(PropertyType.TYPENAME_DECIMAL.toUpperCase(), PropertyType.DECIMAL);
         temp.put(PropertyType.TYPENAME_DOUBLE.toUpperCase(), PropertyType.DOUBLE);
         temp.put(PropertyType.TYPENAME_LONG.toUpperCase(), PropertyType.LONG);
         temp.put(PropertyType.TYPENAME_NAME.toUpperCase(), PropertyType.NAME);
         temp.put(PropertyType.TYPENAME_PATH.toUpperCase(), PropertyType.PATH);
         temp.put(PropertyType.TYPENAME_STRING.toUpperCase(), PropertyType.STRING);
         temp.put(PropertyType.TYPENAME_REFERENCE.toUpperCase(), PropertyType.REFERENCE);
         temp.put(PropertyType.TYPENAME_WEAKREFERENCE.toUpperCase(), PropertyType.WEAKREFERENCE);
         temp.put(PropertyType.TYPENAME_UNDEFINED.toUpperCase(), PropertyType.UNDEFINED);
         temp.put(PropertyType.TYPENAME_URI.toUpperCase(), PropertyType.URI);
 
         PROPERTY_TYPE_VALUES_FROM_NAME = Collections.unmodifiableMap(temp);
     }
 
     protected final Problems problems = new SimpleProblems();
     protected final List<NodeTypeDefinition> types = new ArrayList<NodeTypeDefinition>();
     protected final List<NodeTypeDefinition> immutableTypes = Collections.unmodifiableList(types);
     protected final ExecutionContext context;
     protected final ValueFactories valueFactories;
     protected final PathFactory pathFactory;
     protected final NameFactory nameFactory;
     protected final ValueFactory<Boolean> booleanFactory;
     protected final ValueFactory<String> stringFactory;
     protected final Path root;
 
     /**
      * Create a new node type factory that reads CND files.
      * 
      * @param session the session that will be used to register the node types; may not be null and must be a ModeShape Session.
      */
     protected GraphNodeTypeReader( Session session ) {
         this(CheckArg.getInstanceOf(session, JcrSession.class, "session").getExecutionContext());
     }
 
     /**
      * Create a new node type factory that reads CND files.
      * 
      * @param executionContext the session that will be used to load the node types; may not be null and must be a ModeShape
      *        Session.
      */
     protected GraphNodeTypeReader( ExecutionContext executionContext ) {
         LocalNamespaceRegistry localRegistry = new LocalNamespaceRegistry(executionContext.getNamespaceRegistry());
         context = executionContext.with(localRegistry);
         valueFactories = context.getValueFactories();
         pathFactory = valueFactories.getPathFactory();
         nameFactory = valueFactories.getNameFactory();
         booleanFactory = valueFactories.getBooleanFactory();
         stringFactory = valueFactories.getStringFactory();
         root = pathFactory.createRootPath();
     }
 
     /**
      * Import the node types from the supplied stream and add all of the node type definitions to this factory's list.
      * 
      * @param stream the stream containing the node types
      * @param resourceName a logical name for the resource name to be used when reporting problems; may be null if there is no
      *        useful name
      * @throws IOException if there is a problem reading from the supplied stream
      */
     public void read( InputStream stream,
                       String resourceName ) throws IOException {
         read(IoUtil.read(stream), resourceName);
     }
 
     /**
      * Import the node types from the supplied file and add all of the node type definitions to this factory's list.
      * 
      * @param file the file containing the node types
      * @throws IOException if there is a problem reading from the supplied stream
      */
     public void read( File file ) throws IOException {
         read(IoUtil.read(file), file.getCanonicalPath());
     }
 
     /**
      * Import the node types from the file at the supplied URL and add all of the node type definitions to this factory's list.
      * 
      * @param url the URL to the file containing the node types
      * @throws IOException if there is a problem reading from the supplied stream
      */
     public void read( URL url ) throws IOException {
         InputStream stream = url.openStream();
         try {
             read(IoUtil.read(stream), url.toString());
         } finally {
             stream.close();
         }
     }
 
     /**
      * Import the node types from the supplied file and add all of the node type definitions to this factory's list.
      * 
      * @param resourceFile the name of the resource file on the classpath containing the node types
      * @throws IOException if there is a problem reading from the supplied resource
      */
     public void read( String resourceFile ) throws IOException {
         InputStream stream = getClass().getResourceAsStream(resourceFile);
         if (stream != null) {
             try {
                 read(IoUtil.read(stream), resourceFile);
             } finally {
                 stream.close();
             }
         }
     }
 
     /**
      * Import the node types from the supplied string and add all of the node type definitions to this factory's list.
      * 
      * @param content the string containing the node types
      * @param resourceName a logical name for the resource name to be used when reporting problems; may be null if there is no
      *        useful name
      */
     @SuppressWarnings( "cast" )
     public void read( String content,
                       String resourceName ) {
         InMemoryRepositorySource source = new InMemoryRepositorySource();
         source.setName("Node Type Import Source");
         Graph graph = Graph.create(source, context);
 
         // Create the batch and load the graph ...
         Graph.Batch batch = graph.batch();
         Destination destination = new GraphBatchDestination(batch);
         try {
             importFrom(destination, root, content, resourceName);
             List<NodeTypeDefinition> types = readTypesFrom(graph, root, null);
             this.types.addAll(types);
         } catch (Throwable t) {
             problems.addError(t, JcrI18n.errorImportingNodeTypeContent, (Object)resourceName, t.getMessage());
         }
     }
 
     /**
      * Import the node types from the supplied location in the specified graph.
      * 
      * @param graph the graph containing the standard ModeShape CND content
      * @param parentOfTypes the path to the parent of the node type definition nodes
      * @param resourceName a logical name for the resource name to be used when reporting problems; may be null if there is no
      *        useful name
      */
     public void read( Graph graph,
                       Path parentOfTypes,
                       String resourceName ) {
         this.types.addAll(readTypesFrom(graph, parentOfTypes, null));
     }
 
     /**
      * Import the node types from the supplied location in the specified graph.
      * 
      * @param graph the graph containing the standard ModeShape CND content
      * @param parentOfTypes the path to the parent of the node type definition nodes
      * @param nodeTypesToRead the names of the node types that should be read; null means that all node types should be read
      * @param resourceName a logical name for the resource name to be used when reporting problems; may be null if there is no
      *        useful name
      */
     public void read( Graph graph,
                       Path parentOfTypes,
                       Collection<Name> nodeTypesToRead,
                       String resourceName ) {
         this.types.addAll(readTypesFrom(graph, parentOfTypes, nodeTypesToRead));
     }
 
     /**
      * Import the node types from the supplied location in the specified graph.
      * 
      * @param subgraph the subgraph containing the standard ModeShape CND content
      * @param locationOfParent the location to the parent of the node type definition nodes
      * @param resourceName a logical name for the resource name to be used when reporting problems; may be null if there is no
      *        useful name
      */
     public void read( Subgraph subgraph,
                       Location locationOfParent,
                       String resourceName ) {
         this.types.addAll(readTypesFrom(subgraph, locationOfParent, null));
     }
 
     /**
      * Get the problems where warnings and error messages were recorded by this factory.
      * 
      * @return the problems; never null
      */
     public Problems getProblems() {
         return problems;
     }
 
     /**
      * Returns the node type definitions created by this factory.
      * 
      * @return the {@link NodeTypeDefinition}s
      */
     public NodeTypeDefinition[] getNodeTypeDefinitions() {
         return types.toArray(new NodeTypeDefinition[types.size()]);
     }
 
     /**
      * {@inheritDoc}
      * 
      * @see java.lang.Iterable#iterator()
      */
     @Override
     public Iterator<NodeTypeDefinition> iterator() {
         return immutableTypes.iterator();
     }
 
     protected List<NodeTypeDefinition> readTypesFrom( Graph graph,
                                                       Path parentOfTypes,
                                                       Collection<Name> nodeTypesToRead ) {
         Subgraph subgraph = graph.getSubgraphOfDepth(5).at(parentOfTypes);
         return readTypesFrom(subgraph, subgraph.getLocation(), nodeTypesToRead);
     }
 
     protected List<NodeTypeDefinition> readTypesFrom( Subgraph nodeTypeSubgraph,
                                                       Location locationOfParentOfNodeTypes,
                                                       Collection<Name> nodeTypesToRead ) {
         List<Location> nodeTypeLocations = nodeTypeSubgraph.getNode(locationOfParentOfNodeTypes).getChildren();
         List<NodeTypeDefinition> results = new ArrayList<NodeTypeDefinition>(nodeTypeLocations.size());
         boolean shouldFilterNodes = locationOfParentOfNodeTypes.hasPath() && nodeTypesToRead != null;
 
         for (Location location : nodeTypeLocations) {
             SubgraphNode nodeTypeNode = nodeTypeSubgraph.getNode(location);
             assert location.getPath() != null;
 
             Path relativeNodeTypePath = shouldFilterNodes ? location.getPath().relativeTo(locationOfParentOfNodeTypes.getPath()) : null;
             if (shouldFilterNodes && !nodeTypesToRead.contains(relativeNodeTypePath.getSegment(0).getName())) {
                 continue;
             }
 
             try {
                 NodeTypeDefinition nodeType = nodeTypeFrom(nodeTypeNode, nodeTypeSubgraph);
                 results.add(nodeType);
             } catch (ConstraintViolationException e) {
                 String resource = stringFactory.create(locationOfParentOfNodeTypes.getPath());
                 problems.addError(e, JcrI18n.errorImportingNodeTypeContent, resource, e.getMessage());
             }
         }
         return results;
     }
 
     @SuppressWarnings( "unchecked" )
     protected NodeTypeTemplate nodeTypeFrom( SubgraphNode nodeTypeNode,
                                              Subgraph subgraph ) throws ConstraintViolationException {
         List<Location> children = nodeTypeNode.getChildren();
 
         String name = readString(nodeTypeNode, JcrLexicon.NODE_TYPE_NAME, null);
         String primaryItemName = readString(nodeTypeNode, JcrLexicon.PRIMARY_ITEM_NAME, null);
 
         boolean mixin = readBoolean(nodeTypeNode, JcrLexicon.IS_MIXIN, false);
         boolean isAbstract = readBoolean(nodeTypeNode, JcrLexicon.IS_ABSTRACT, false);
         boolean queryable = readBoolean(nodeTypeNode, JcrLexicon.IS_QUERYABLE, true);
         boolean orderableChildNodes = readBoolean(nodeTypeNode, JcrLexicon.HAS_ORDERABLE_CHILD_NODES, false);
         List<String> supertypes = readStrings(nodeTypeNode, JcrLexicon.SUPERTYPES);
 
         NodeTypeTemplate template = new JcrNodeTypeTemplate(context);
         template.setAbstract(isAbstract);
         template.setDeclaredSuperTypeNames(supertypes.toArray(new String[supertypes.size()]));
         template.setMixin(mixin);
         template.setName(name);
         template.setOrderableChildNodes(orderableChildNodes);
         template.setPrimaryItemName(primaryItemName);
         template.setQueryable(queryable);
 
         for (Location childLocation : children) {
             if (JcrLexicon.PROPERTY_DEFINITION.equals(childLocation.getPath().getLastSegment().getName())) {
                 template.getPropertyDefinitionTemplates().add(propertyDefinitionFrom(subgraph, childLocation));
             } else if (JcrLexicon.CHILD_NODE_DEFINITION.equals(childLocation.getPath().getLastSegment().getName())) {
                 template.getNodeDefinitionTemplates().add(childNodeDefinitionFrom(subgraph, childLocation));
             } else {
                 throw new IllegalStateException("Unexpected child of node type at: " + childLocation);
             }
         }
 
         return template;
     }
 
     protected PropertyDefinitionTemplate propertyDefinitionFrom( Subgraph nodeTypeGraph,
                                                                  Location propertyLocation ) throws ConstraintViolationException {
         SubgraphNode propertyDefinitionNode = nodeTypeGraph.getNode(propertyLocation);
 
         String name = readString(propertyDefinitionNode, JcrLexicon.NAME, null);
         String onParentVersionName = readString(propertyDefinitionNode,
                                                 JcrLexicon.ON_PARENT_VERSION,
                                                 OnParentVersionAction.nameFromValue(OnParentVersionAction.COPY));
         int onParentVersion = OnParentVersionAction.valueFromName(onParentVersionName);
 
         int requiredType = PROPERTY_TYPE_VALUES_FROM_NAME.get(readString(propertyDefinitionNode, JcrLexicon.REQUIRED_TYPE, null));
 
         boolean mandatory = readBoolean(propertyDefinitionNode, JcrLexicon.MANDATORY, false);
         boolean multiple = readBoolean(propertyDefinitionNode, JcrLexicon.MULTIPLE, false);
         boolean autoCreated = readBoolean(propertyDefinitionNode, JcrLexicon.AUTO_CREATED, false);
         boolean isProtected = readBoolean(propertyDefinitionNode, JcrLexicon.PROTECTED, false);
         boolean isSearchable = readBoolean(propertyDefinitionNode, JcrLexicon.IS_FULL_TEXT_SEARCHABLE, true);
         boolean isOrderable = readBoolean(propertyDefinitionNode, JcrLexicon.IS_QUERY_ORDERABLE, true);
         List<Value> defaultValues = readValues(propertyDefinitionNode, JcrLexicon.DEFAULT_VALUES, requiredType);
         List<String> constraints = readStrings(propertyDefinitionNode, JcrLexicon.VALUE_CONSTRAINTS);
         List<String> queryOps = readStrings(propertyDefinitionNode, JcrLexicon.QUERY_OPERATORS);
 
         PropertyDefinitionTemplate template = new JcrPropertyDefinitionTemplate(context);
         if (name != null) {
             template.setName(name);
         }
         template.setAutoCreated(autoCreated);
         template.setMandatory(mandatory);
         template.setMultiple(multiple);
         template.setProtected(isProtected);
         template.setFullTextSearchable(isSearchable);
         template.setAvailableQueryOperators(queryOps.toArray(new String[queryOps.size()]));
         template.setQueryOrderable(isOrderable);
         template.setProtected(isProtected);
         template.setOnParentVersion(onParentVersion);
         template.setDefaultValues(defaultValues.toArray(new Value[defaultValues.size()]));
         template.setRequiredType(requiredType);
         template.setValueConstraints(constraints.toArray(new String[constraints.size()]));
         return template;
     }
 
     protected NodeDefinitionTemplate childNodeDefinitionFrom( Subgraph nodeTypeGraph,
                                                               Location childNodeLocation ) throws ConstraintViolationException {
         SubgraphNode childNodeDefinitionNode = nodeTypeGraph.getNode(childNodeLocation);
 
         String childNodeName = readString(childNodeDefinitionNode, JcrLexicon.NAME, null);
         String defaultPrimaryTypeName = readString(childNodeDefinitionNode, JcrLexicon.DEFAULT_PRIMARY_TYPE, null);
         String onParentVersionName = readString(childNodeDefinitionNode,
                                                 JcrLexicon.ON_PARENT_VERSION,
                                                 OnParentVersionAction.nameFromValue(OnParentVersionAction.COPY));
         int onParentVersion = OnParentVersionAction.valueFromName(onParentVersionName);
 
         boolean mandatory = readBoolean(childNodeDefinitionNode, JcrLexicon.MANDATORY, false);
         boolean allowsSns = readBoolean(childNodeDefinitionNode, JcrLexicon.SAME_NAME_SIBLINGS, false);
         boolean autoCreated = readBoolean(childNodeDefinitionNode, JcrLexicon.AUTO_CREATED, false);
         boolean isProtected = readBoolean(childNodeDefinitionNode, JcrLexicon.PROTECTED, false);
         List<String> requiredTypes = readStrings(childNodeDefinitionNode, JcrLexicon.REQUIRED_PRIMARY_TYPES);
 
         NodeDefinitionTemplate template = new JcrNodeDefinitionTemplate(context);
         if (childNodeName != null) {
             template.setName(childNodeName);
         }
         template.setAutoCreated(autoCreated);
         template.setMandatory(mandatory);
         template.setSameNameSiblings(allowsSns);
         template.setProtected(isProtected);
         template.setOnParentVersion(onParentVersion);
         template.setDefaultPrimaryTypeName(defaultPrimaryTypeName);
         template.setRequiredPrimaryTypeNames(requiredTypes.toArray(new String[requiredTypes.size()]));
         return template;
     }
 
     protected Name nameFrom( SubgraphNode node ) {
         return node.getLocation().getPath().getLastSegment().getName();
     }
 
     protected Name name( String name ) {
         return nameFactory.create(name);
     }
 
     protected String string( Object value ) {
         return stringFactory.create(value);
     }
 
     protected boolean readBoolean( SubgraphNode node,
                                    String propertyName,
                                    boolean defaultValue ) {
         return readBoolean(node, nameFactory.create(propertyName), defaultValue);
     }
 
     protected boolean readBoolean( SubgraphNode node,
                                    Name propertyName,
                                    boolean defaultValue ) {
         Property property = node.getProperty(propertyName);
         return property != null ? booleanFactory.create(property.getFirstValue()) : defaultValue;
     }
 
     protected String readString( SubgraphNode node,
                                  String propertyName,
                                  String defaultValue ) {
         return readString(node, nameFactory.create(propertyName), defaultValue);
     }
 
     protected String readString( SubgraphNode node,
                                  Name propertyName,
                                  String defaultValue ) {
         Property property = node.getProperty(propertyName);
         return property != null ? stringFactory.create(property.getFirstValue()) : defaultValue;
     }
 
     protected List<String> readStrings( SubgraphNode node,
                                         String propertyName ) {
         return readStrings(node, nameFactory.create(propertyName));
     }
 
     protected List<String> readStrings( SubgraphNode node,
                                         Name propertyName ) {
         List<String> results = new ArrayList<String>();
         Property property = node.getProperty(propertyName);
         if (property != null) {
             for (Object value : property) {
                 String str = stringFactory.create(value);
                 if (str != null && str.length() != 0) results.add(str);
             }
         }
         return results;
     }
 
     protected List<Value> readValues( SubgraphNode node,
                                       Name propertyName,
                                       int requiredType ) {
         List<String> results = readStrings(node, propertyName);
         List<Value> values = new ArrayList<Value>(results.size());
         for (String result : results) {
             values.add(new JcrValue(valueFactories, null, requiredType, result));
         }
         return values;
     }
 
     protected Name readName( SubgraphNode node,
                              String propertyName,
                              Name defaultValue ) {
         return readName(node, nameFactory.create(propertyName), defaultValue);
     }
 
     protected Name readName( SubgraphNode node,
                              Name propertyName,
                              Name defaultValue ) {
         Property property = node.getProperty(propertyName);
         if (property != null && !property.isEmpty()) {
             String firstValue = stringFactory.create(property.getFirstValue());
             if (firstValue != null && firstValue.trim().length() != 0) {
                 return valueFactories.getNameFactory().create(firstValue);
             }
         }
         return defaultValue;
     }
 
     protected List<Name> readNames( SubgraphNode node,
                                     String propertyName,
                                     Name defaultIfNone ) {
         return readNames(node, nameFactory.create(propertyName), defaultIfNone);
     }
 
     protected List<Name> readNames( SubgraphNode node,
                                     Name propertyName,
                                     Name defaultIfNone ) {
         List<Name> results = new ArrayList<Name>();
         Property property = node.getProperty(propertyName);
         if (property != null) {
             for (Object value : property) {
                 Name name = nameFactory.create(value);
                 if (name != null) results.add(name);
             }
         }
         if (results.isEmpty() && defaultIfNone != null) results.add(defaultIfNone);
         return results;
     }
 
     /**
      * Method that loads into the graph destination the content containing the node type definitions.
      * 
      * @param graphDestination the destination to which the node type content should be written; never null
      * @param path the path within the destination at which the node type content should be rooted; never null
      * @param content the content containing some string representation of the node types to be imported; never null
      * @param resourceName a descriptive name for this import (used only for error messages); may be null
      * @throws Exception if there is a problem importing from the content; this will be automatically recorded in the problems
      */
     protected void importFrom( Destination graphDestination,
                                Path path,
                                String content,
                                String resourceName ) throws Exception {
         throw new UnsupportedOperationException();
     }
 
 }