/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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 groovy.util;

import groovy.lang.Closure;
import groovy.lang.GString;
import groovy.lang.GroovyRuntimeException;
import groovy.lang.MetaProperty;
import groovy.lang.MissingPropertyException;
import org.codehaus.groovy.runtime.InvokerHelper;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;

/**
 * A builder for creating object graphs.<br>
 * Each node defines the class to be created and the property on its parent (if
 * any) at the same time.
 */
public class ObjectGraphBuilder extends FactoryBuilderSupport {
    public static final String NODE_CLASS = "_NODE_CLASS_";
    public static final String NODE_NAME = "_NODE_NAME_";
    public static final String OBJECT_ID = "_OBJECT_ID_";
    public static final String LAZY_REF = "_LAZY_REF_";

    public static final String CLASSNAME_RESOLVER_KEY = "name";
    public static final String CLASSNAME_RESOLVER_REFLECTION = "reflection";
    public static final String CLASSNAME_RESOLVER_REFLECTION_ROOT = "root";

    // Regular expression pattern used to identify words ending in 'y' preceded by a consonant
    private static final Pattern PLURAL_IES_PATTERN = Pattern.compile(".*[^aeiouy]y", Pattern.CASE_INSENSITIVE);

    private ChildPropertySetter childPropertySetter;
    private ClassNameResolver classNameResolver;
    private IdentifierResolver identifierResolver;
    private NewInstanceResolver newInstanceResolver;
    private final ObjectFactory objectFactory = new ObjectFactory();
    private final ObjectBeanFactory objectBeanFactory = new ObjectBeanFactory();
    private final ObjectRefFactory objectRefFactory = new ObjectRefFactory();
    private ReferenceResolver referenceResolver;
    private RelationNameResolver relationNameResolver;
    private final Map<String, Class> resolvedClasses = new HashMap<String, Class>();
    private ClassLoader classLoader;
    private boolean lazyReferencesAllowed = true;
    private final List<NodeReference> lazyReferences = new ArrayList<NodeReference>();
    private String beanFactoryName = "bean";

    public ObjectGraphBuilder() {
        classNameResolver = new DefaultClassNameResolver();
        newInstanceResolver = new DefaultNewInstanceResolver();
        relationNameResolver = new DefaultRelationNameResolver();
        childPropertySetter = new DefaultChildPropertySetter();
        identifierResolver = new DefaultIdentifierResolver();
        referenceResolver = new DefaultReferenceResolver();

        addPostNodeCompletionDelegate(new Closure(this, this) {
            private static final long serialVersionUID = 7282290918368141309L;

            public void doCall(ObjectGraphBuilder builder, Object parent, Object node) {
                if (parent == null) {
                    builder.resolveLazyReferences();
                    builder.dispose();
                }
            }
        });
    }

    /**
     * Returns the current name of the 'bean' node.
     */
    public String getBeanFactoryName() {
        return beanFactoryName;
    }

    /**
     * Returns the current ChildPropertySetter.
     */
    public ChildPropertySetter getChildPropertySetter() {
        return childPropertySetter;
    }

    /**
     * Returns the classLoader used to load a node's class.
     */
    public ClassLoader getClassLoader() {
        return classLoader;
    }

    /**
     * Returns the current ClassNameResolver.
     */
    public ClassNameResolver getClassNameResolver() {
        return classNameResolver;
    }

    /**
     * Returns the current NewInstanceResolver.
     */
    public NewInstanceResolver getNewInstanceResolver() {
        return newInstanceResolver;
    }

    /**
     * Returns the current RelationNameResolver.
     */
    public RelationNameResolver getRelationNameResolver() {
        return relationNameResolver;
    }

    /**
     * Returns true if references can be resolved lazily
     */
    public boolean isLazyReferencesAllowed() {
        return lazyReferencesAllowed;
    }

    /**
     * Sets the name for the 'bean' node.
     */
    public void setBeanFactoryName(String beanFactoryName) {
        this.beanFactoryName = beanFactoryName;
    }

    /**
     * Sets the current ChildPropertySetter.<br>
     * It will assign DefaultChildPropertySetter if null.<br>
     * It accepts a ChildPropertySetter instance or a Closure.
     */
    public void setChildPropertySetter(final Object childPropertySetter) {
        if (childPropertySetter instanceof ChildPropertySetter) {
            this.childPropertySetter = (ChildPropertySetter) childPropertySetter;
        } else if (childPropertySetter instanceof Closure) {
            final ObjectGraphBuilder self = this;
            this.childPropertySetter = (parent, child, parentName, propertyName) -> {
                Closure cls = (Closure) childPropertySetter;
                cls.setDelegate(self);
                cls.call(parent, child, parentName, propertyName);
            };
        } else {
            this.childPropertySetter = new DefaultChildPropertySetter();
        }
    }

    /**
     * Sets the classLoader used to load a node's class.
     */
    public void setClassLoader(ClassLoader classLoader) {
        this.classLoader = classLoader;
    }

    /**
     * Sets the current ClassNameResolver.<br>
     * It will assign DefaultClassNameResolver if null.<br>
     * It accepts a ClassNameResolver instance, a String, a Closure or a Map.
     */
    public void setClassNameResolver(final Object classNameResolver) {
        if (classNameResolver instanceof ClassNameResolver) {
            this.classNameResolver = (ClassNameResolver) classNameResolver;
        } else if (classNameResolver instanceof String) {
            this.classNameResolver = classname -> makeClassName((String) classNameResolver, classname);
        } else if (classNameResolver instanceof Closure) {
            final ObjectGraphBuilder self = this;
            this.classNameResolver = classname -> {
                Closure cls = (Closure) classNameResolver;
                cls.setDelegate(self);
                return (String) cls.call(new Object[]{classname});
            };
        } else if (classNameResolver instanceof Map) {
            Map classNameResolverOptions = (Map) classNameResolver;

            String resolverName = (String) classNameResolverOptions.get(CLASSNAME_RESOLVER_KEY);

            if (resolverName == null) {
                throw new RuntimeException("key '" + CLASSNAME_RESOLVER_KEY + "' not defined");
            }

            if (CLASSNAME_RESOLVER_REFLECTION.equals(resolverName)) {
                String root = (String) classNameResolverOptions.get(CLASSNAME_RESOLVER_REFLECTION_ROOT);

                if (root == null) {
                    throw new RuntimeException("key '" + CLASSNAME_RESOLVER_REFLECTION_ROOT + "' not defined");
                }

                this.classNameResolver = new ReflectionClassNameResolver(root);
            } else {
                throw new RuntimeException("unknown class name resolver " + resolverName);
            }
        } else {
            this.classNameResolver = new DefaultClassNameResolver();
        }
    }

    /**
     * Sets the current IdentifierResolver.<br>
     * It will assign DefaultIdentifierResolver if null.<br>
     * It accepts a IdentifierResolver instance, a String or a Closure.
     */
    public void setIdentifierResolver(final Object identifierResolver) {
        if (identifierResolver instanceof IdentifierResolver) {
            this.identifierResolver = (IdentifierResolver) identifierResolver;
        } else if (identifierResolver instanceof String) {
            this.identifierResolver = nodeName -> (String) identifierResolver;
        } else if (identifierResolver instanceof Closure) {
            final ObjectGraphBuilder self = this;
            this.identifierResolver = nodeName -> {
                Closure cls = (Closure) identifierResolver;
                cls.setDelegate(self);
                return (String) cls.call(new Object[]{nodeName});
            };
        } else {
            this.identifierResolver = new DefaultIdentifierResolver();
        }
    }

    /**
     * Sets whether references can be resolved lazily or not.
     */
    public void setLazyReferencesAllowed(boolean lazyReferencesAllowed) {
        this.lazyReferencesAllowed = lazyReferencesAllowed;
    }

    /**
     * Sets the current NewInstanceResolver.<br>
     * It will assign DefaultNewInstanceResolver if null.<br>
     * It accepts a NewInstanceResolver instance or a Closure.
     */
    public void setNewInstanceResolver(final Object newInstanceResolver) {
        if (newInstanceResolver instanceof NewInstanceResolver) {
            this.newInstanceResolver = (NewInstanceResolver) newInstanceResolver;
        } else if (newInstanceResolver instanceof Closure) {
            final ObjectGraphBuilder self = this;
            this.newInstanceResolver = (klass, attributes) -> {
                Closure cls = (Closure) newInstanceResolver;
                cls.setDelegate(self);
                return cls.call(klass, attributes);
            };
        } else {
            this.newInstanceResolver = new DefaultNewInstanceResolver();
        }
    }

    /**
     * Sets the current ReferenceResolver.<br>
     * It will assign DefaultReferenceResolver if null.<br>
     * It accepts a ReferenceResolver instance, a String or a Closure.
     */
    public void setReferenceResolver(final Object referenceResolver) {
        if (referenceResolver instanceof ReferenceResolver) {
            this.referenceResolver = (ReferenceResolver) referenceResolver;
        } else if (referenceResolver instanceof String) {
            this.referenceResolver = nodeName -> (String) referenceResolver;
        } else if (referenceResolver instanceof Closure) {
            final ObjectGraphBuilder self = this;
            this.referenceResolver = nodeName -> {
                Closure cls = (Closure) referenceResolver;
                cls.setDelegate(self);
                return (String) cls.call(new Object[]{nodeName});
            };
        } else {
            this.referenceResolver = new DefaultReferenceResolver();
        }
    }

    /**
     * Sets the current RelationNameResolver.<br>
     * It will assign DefaultRelationNameResolver if null.
     */
    public void setRelationNameResolver(RelationNameResolver relationNameResolver) {
        this.relationNameResolver = relationNameResolver != null ? relationNameResolver
                : new DefaultRelationNameResolver();
    }

    @Override
    protected void postInstantiate(Object name, Map attributes, Object node) {
        super.postInstantiate(name, attributes, node);
        Map context = getContext();
        String objectId = (String) context.get(OBJECT_ID);
        if (objectId != null && node != null) {
            setVariable(objectId, node);
        }
    }

    @Override
    protected void preInstantiate(Object name, Map attributes, Object value) {
        super.preInstantiate(name, attributes, value);
        Map context = getContext();
        context.put(OBJECT_ID,
                attributes.remove(identifierResolver.getIdentifierFor((String) name)));
    }

    @Override
    protected Factory resolveFactory(Object name, Map attributes, Object value) {
        // let custom factories be resolved first
        Factory factory = super.resolveFactory(name, attributes, value);
        if (factory != null) {
            return factory;
        }
        if (attributes.get(referenceResolver.getReferenceFor((String) name)) != null) {
            return objectRefFactory;
        }
        if (beanFactoryName != null && beanFactoryName.equals((String) name)) {
            return objectBeanFactory;
        }
        return objectFactory;
    }

    /**
     * Strategy for setting a child node on its parent.<br>
     * Useful for handling Lists/Arrays vs normal properties.
     */
    public interface ChildPropertySetter {
        /**
         * @param parent       the parent's node value
         * @param child        the child's node value
         * @param parentName   the name of the parent node
         * @param propertyName the resolved relation name of the child
         */
        void setChild(Object parent, Object child, String parentName, String propertyName);
    }

    /**
     * Strategy for resolving a classname.
     */
    public interface ClassNameResolver {
        /**
         * @param classname the node name as written on the building code
         */
        String resolveClassname(String classname);
    }

    /**
     * Default impl that calls parent.propertyName = child<br>
     * If parent.propertyName is a Collection it will try to add child to the
     * collection.
     */
    public static class DefaultChildPropertySetter implements ChildPropertySetter {
        @Override
        public void setChild(Object parent, Object child, String parentName, String propertyName) {
            try {
                Object property = InvokerHelper.getProperty(parent, propertyName);
                if (property != null && Collection.class.isAssignableFrom(property.getClass())) {
                    ((Collection) property).add(child);
                } else {
                    InvokerHelper.setProperty(parent, propertyName, child);
                }
            } catch (MissingPropertyException mpe) {
                // ignore
            }
        }
    }

    /**
     * Default impl that capitalizes the classname.
     */
    public static class DefaultClassNameResolver implements ClassNameResolver {
        @Override
        public String resolveClassname(String classname) {
            if (classname.length() == 1) {
                return classname.toUpperCase();
            }
            return classname.substring(0, 1)
                    .toUpperCase() + classname.substring(1);
        }
    }

    /**
     * Build objects using reflection to resolve class names.
     */
    public class ReflectionClassNameResolver implements ClassNameResolver {
        private final String root;

        /**
         * @param root package where the graph root class is located
         */
        public ReflectionClassNameResolver(String root) {
            this.root = root;
        }

        @Override
        public String resolveClassname(String classname) {
            Object currentNode = getContext().get(CURRENT_NODE);

            if (currentNode == null) {
                return makeClassName(root, classname);
            } else {
                try {
                    Class klass = currentNode.getClass().getDeclaredField(classname).getType();

                    if (Collection.class.isAssignableFrom(klass)) {
                        Type type = currentNode.getClass().getDeclaredField(classname).getGenericType();
                        if (type instanceof ParameterizedType) {
                            ParameterizedType ptype = (ParameterizedType) type;
                            Type[] actualTypeArguments = ptype.getActualTypeArguments();
                            if (actualTypeArguments.length != 1) {
                                throw new RuntimeException("can't determine class name for collection field " + classname + " with multiple generics");
                            }

                            Type typeArgument = actualTypeArguments[0];
                            if (typeArgument instanceof Class) {
                                klass = (Class) actualTypeArguments[0];
                            } else {
                                throw new RuntimeException("can't instantiate collection field " + classname + " elements as they aren't a class");
                            }
                        } else {
                            throw new RuntimeException("collection field " + classname + " must be genericised");
                        }
                    }

                    return klass.getName();
                } catch (NoSuchFieldException e) {
                    throw new RuntimeException("can't find field " + classname + " for node class " + currentNode.getClass().getName(), e);
                }
            }
        }
    }

    /**
     * Default impl, always returns 'id'
     */
    public static class DefaultIdentifierResolver implements IdentifierResolver {
        @Override
        public String getIdentifierFor(String nodeName) {
            return "id";
        }
    }

    /**
     * Default impl that calls Class.newInstance()
     */
    public static class DefaultNewInstanceResolver implements NewInstanceResolver {
        @Override
        public Object newInstance(Class klass, Map attributes) throws InstantiationException,
                IllegalAccessException {
            try {
                return klass.getDeclaredConstructor().newInstance();
            } catch (InvocationTargetException | NoSuchMethodException e) {
                throw new GroovyRuntimeException("Unable to create instance resolver", e);
            }
        }
    }

    /**
     * Default impl, always returns 'refId'
     */
    public static class DefaultReferenceResolver implements ReferenceResolver {
        @Override
        public String getReferenceFor(String nodeName) {
            return "refId";
        }
    }

    /**
     * Default impl that returns parentName and childName accordingly.
     */
    public static class DefaultRelationNameResolver implements RelationNameResolver {
        /**
         * Handles the common English regular plurals with the following rules.
         * <ul>
         * <li>If childName ends in {consonant}y, replace 'y' with "ies". For example, allergy to allergies.</li>
         * <li>Otherwise, append 's'. For example, monkey to monkeys; employee to employees.</li>
         * </ul>
         * If the property does not exist then it will return childName unchanged.
         *
         * @see <a href="http://en.wikipedia.org/wiki/English_plural">English_plural</a>
         */
        @Override
        public String resolveChildRelationName(String parentName, Object parent, String childName,
                                               Object child) {
            boolean matchesIESRule = PLURAL_IES_PATTERN.matcher(childName).matches();
            String childNamePlural = matchesIESRule ? childName.substring(0, childName.length() - 1) + "ies" : childName + "s";

            MetaProperty metaProperty = InvokerHelper.getMetaClass(parent)
                    .hasProperty(parent, childNamePlural);

            return metaProperty != null ? childNamePlural : childName;
        }

        /**
         * Follow the most conventional pattern, returns the parentName
         * unchanged.
         */
        @Override
        public String resolveParentRelationName(String parentName, Object parent,
                                                String childName, Object child) {
            return parentName;
        }
    }

    /**
     * Strategy for picking the correct synthetic identifier.
     */
    public interface IdentifierResolver {
        /**
         * Returns the name of the property that will identify the node.<br>
         *
         * @param nodeName the name of the node
         */
        String getIdentifierFor(String nodeName);
    }

    /**
     * Strategy for creating new instances of a class.<br>
     * Useful for plug-in calls to non-default constructors.
     */
    public interface NewInstanceResolver {
        /**
         * Create a new instance of Class klass.
         *
         * @param klass      the resolved class name
         * @param attributes the attribute Map available for the node
         */
        Object newInstance(Class klass, Map attributes) throws InstantiationException,
                IllegalAccessException;
    }

    /**
     * Strategy for picking the correct synthetic reference identifier.
     */
    public interface ReferenceResolver {
        /**
         * Returns the name of the property that references another node.<br>
         *
         * @param nodeName the name of the node
         */
        String getReferenceFor(String nodeName);
    }

    /**
     * Strategy for resolving a relationship property name.
     */
    public interface RelationNameResolver {
        /**
         * Returns the mapping name of child -&gt; parent
         *
         * @param parentName the name of the parent node
         * @param parent     the parent node
         * @param childName  the name of the child node
         * @param child      the child node
         */
        String resolveChildRelationName(String parentName, Object parent, String childName,
                                        Object child);

        /**
         * Returns the mapping name of parent -&gt; child
         *
         * @param parentName the name of the parent node
         * @param parent     the parent node
         * @param childName  the name of the child node
         * @param child      the child node
         */
        String resolveParentRelationName(String parentName, Object parent, String childName,
                                         Object child);
    }

    private void resolveLazyReferences() {
        if (!lazyReferencesAllowed) return;
        for (NodeReference ref : lazyReferences) {
            if (ref.parent == null) continue;

            Object child = null;
            try {
                child = getProperty(ref.refId);
            } catch (MissingPropertyException mpe) {
                // ignore
            }
            if (child == null) {
                throw new IllegalArgumentException("There is no valid node for reference "
                        + ref.parentName + "." + ref.childName + "=" + ref.refId);
            }

            // set child first
            childPropertySetter.setChild(ref.parent, child, ref.parentName,
                    relationNameResolver.resolveChildRelationName(ref.parentName,
                            ref.parent, ref.childName, child));

            // set parent afterwards
            String propertyName = relationNameResolver.resolveParentRelationName(ref.parentName,
                    ref.parent, ref.childName, child);
            MetaProperty metaProperty = InvokerHelper.getMetaClass(child)
                    .hasProperty(child, propertyName);
            if (metaProperty != null) {
                metaProperty.setProperty(child, ref.parent);
            }
        }
    }

    private static String makeClassName(String root, String name) {
        return root + "." + name.substring(0, 1).toUpperCase() + name.substring(1);
    }

    private static class ObjectFactory extends AbstractFactory {
        @Override
        public Object newInstance(FactoryBuilderSupport builder, Object name, Object value,
                                  Map properties) throws InstantiationException, IllegalAccessException {
            ObjectGraphBuilder ogbuilder = (ObjectGraphBuilder) builder;
            String classname = ogbuilder.classNameResolver.resolveClassname((String) name);
            Class klass = resolveClass(builder, classname, name, value, properties);
            Map context = builder.getContext();
            context.put(ObjectGraphBuilder.NODE_NAME, name);
            context.put(ObjectGraphBuilder.NODE_CLASS, klass);
            return resolveInstance(builder, name, value, klass, properties);
        }

        protected Class resolveClass(FactoryBuilderSupport builder, String classname, Object name, Object value,
                                  Map properties) {
            ObjectGraphBuilder ogbuilder = (ObjectGraphBuilder) builder;
            Class klass = ogbuilder.resolvedClasses.get(classname);
            if (klass == null) {
                klass = loadClass(ogbuilder.classLoader, classname);
                if (klass == null) {
                    klass = loadClass(ogbuilder.getClass().getClassLoader(), classname);
                }
                if (klass == null) {
                    try {
                        klass = Class.forName(classname);
                    } catch (ClassNotFoundException e) {
                        // ignore
                    }
                }
                if (klass == null) {
                    klass = loadClass(Thread.currentThread().getContextClassLoader(), classname);
                }
                if (klass == null) {
                    throw new RuntimeException(new ClassNotFoundException(classname));
                }
                ogbuilder.resolvedClasses.put(classname, klass);
            }

            return klass;
        }

        protected Object resolveInstance(FactoryBuilderSupport builder, Object name, Object value, Class klass,
                                  Map properties) throws InstantiationException, IllegalAccessException {
            ObjectGraphBuilder ogbuilder = (ObjectGraphBuilder) builder;
            if (value != null && klass.isAssignableFrom(value.getClass())) {
                return value;
            }

            return ogbuilder.newInstanceResolver.newInstance(klass, properties);
        }

        @Override
        public void setChild(FactoryBuilderSupport builder, Object parent, Object child) {
            if (child == null) return;

            ObjectGraphBuilder ogbuilder = (ObjectGraphBuilder) builder;
            if (parent != null) {
                Map context = ogbuilder.getContext();
                Map parentContext = ogbuilder.getParentContext();

                String parentName = null;
                String childName = (String) context.get(NODE_NAME);
                if (parentContext != null) {
                    parentName = (String) parentContext.get(NODE_NAME);
                }

                String propertyName = ogbuilder.relationNameResolver.resolveParentRelationName(
                        parentName, parent, childName, child);
                MetaProperty metaProperty = InvokerHelper.getMetaClass(child)
                        .hasProperty(child, propertyName);
                if (metaProperty != null) {
                    metaProperty.setProperty(child, parent);
                }
            }
        }

        @Override
        public void setParent(FactoryBuilderSupport builder, Object parent, Object child) {
            if (child == null) return;

            ObjectGraphBuilder ogbuilder = (ObjectGraphBuilder) builder;
            if (parent != null) {
                Map context = ogbuilder.getContext();
                Map parentContext = ogbuilder.getParentContext();

                String parentName = null;
                String childName = (String) context.get(NODE_NAME);
                if (parentContext != null) {
                    parentName = (String) parentContext.get(NODE_NAME);
                }

                ogbuilder.childPropertySetter.setChild(parent, child, parentName,
                        ogbuilder.relationNameResolver.resolveChildRelationName(parentName,
                                parent, childName, child));
            }
        }

        protected Class loadClass(ClassLoader classLoader, String classname) {
            if (classLoader == null || classname == null) {
                return null;
            }
            try {
                return classLoader.loadClass(classname);
            } catch (ClassNotFoundException e) {
                return null;
            }
        }
    }

    private static class ObjectBeanFactory extends ObjectFactory {
        @Override
        public Object newInstance(FactoryBuilderSupport builder, Object name, Object value,
                                  Map properties) throws InstantiationException, IllegalAccessException {
            if(value == null) return super.newInstance(builder, name, value, properties);

            Object bean = null;
            Class klass = null;
            Map context = builder.getContext();
            if(value instanceof String || value instanceof GString) {
                /*
                String classname = value.toString();
                klass = resolveClass(builder, classname, name, value, properties);
                bean = resolveInstance(builder, name, value, klass, properties);
                */
                throw new IllegalArgumentException("ObjectGraphBuilder."+((ObjectGraphBuilder)builder).getBeanFactoryName()+"() does not accept String nor GString as value.");
            } else if(value instanceof Class) {
                klass = (Class) value;
                bean = resolveInstance(builder, name, value, klass, properties);
            } else {
                klass = value.getClass();
                bean = value;
            }

            String nodename = klass.getSimpleName();
            if(nodename.length() > 1) {
                nodename = nodename.substring(0, 1).toLowerCase() + nodename.substring(1);
            } else {
                nodename = nodename.toLowerCase();
            }
            context.put(ObjectGraphBuilder.NODE_NAME, nodename);
            context.put(ObjectGraphBuilder.NODE_CLASS, klass);
            return bean;
        }
    }

    private static class ObjectRefFactory extends ObjectFactory {
        @Override
        public boolean isLeaf() {
            return true;
        }

        @Override
        public Object newInstance(FactoryBuilderSupport builder, Object name, Object value,
                                  Map properties) throws InstantiationException, IllegalAccessException {
            ObjectGraphBuilder ogbuilder = (ObjectGraphBuilder) builder;
            String refProperty = ogbuilder.referenceResolver.getReferenceFor((String) name);
            Object refId = properties.remove(refProperty);

            Object object = null;
            Boolean lazy = Boolean.FALSE;
            if (refId instanceof String) {
                try {
                    object = ogbuilder.getProperty((String) refId);
                } catch (MissingPropertyException mpe) {
                    // ignore, will try lazy reference
                }
                if (object == null) {
                    if (ogbuilder.isLazyReferencesAllowed()) {
                        lazy = Boolean.TRUE;
                    } else {
                        throw new IllegalArgumentException("There is no previous node with "
                                + ogbuilder.identifierResolver.getIdentifierFor((String) name) + "="
                                + refId);
                    }
                }
            } else {
                // assume we got a true reference to the object
                object = refId;
            }

            if (!properties.isEmpty()) {
                throw new IllegalArgumentException(
                        "You can not modify the properties of a referenced object.");
            }

            Map context = ogbuilder.getContext();
            context.put(ObjectGraphBuilder.NODE_NAME, name);
            context.put(ObjectGraphBuilder.LAZY_REF, lazy);

            if (lazy) {
                Map parentContext = ogbuilder.getParentContext();

                Object parent = null;
                String parentName = null;
                String childName = (String) name;
                if (parentContext != null) {
                    parent = context.get(CURRENT_NODE);
                    parentName = (String) parentContext.get(NODE_NAME);
                }
                ogbuilder.lazyReferences.add(new NodeReference(parent,
                        parentName,
                        childName,
                        (String) refId));
            } else {
                context.put(ObjectGraphBuilder.NODE_CLASS, object.getClass());
            }

            return object;
        }

        @Override
        public void setChild(FactoryBuilderSupport builder, Object parent, Object child) {
            Boolean lazy = (Boolean) builder.getContext().get(ObjectGraphBuilder.LAZY_REF);
            if (!lazy) super.setChild(builder, parent, child);
        }

        @Override
        public void setParent(FactoryBuilderSupport builder, Object parent, Object child) {
            Boolean lazy = (Boolean) builder.getContext().get(ObjectGraphBuilder.LAZY_REF);
            if (!lazy) super.setParent(builder, parent, child);
        }
    }

    private static final class NodeReference {
        private final Object parent;
        private final String parentName;
        private final String childName;
        private final String refId;

        private NodeReference(Object parent, String parentName, String childName, String refId) {
            this.parent = parent;
            this.parentName = parentName;
            this.childName = childName;
            this.refId = refId;
        }

        @Override
        public String toString() {
            return "[parentName=" + parentName +
                    ", childName=" + childName +
                    ", refId=" + refId +
                    "]";
        }
    }
}
