/**
    * Copyright 2005-2014 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.krad.data.provider.util;
  
  import com.google.common.collect.Sets;
  import org.apache.commons.collections.CollectionUtils;
  import org.apache.commons.lang.ArrayUtils;
  import org.apache.commons.lang.StringUtils;
  import org.apache.commons.lang3.reflect.FieldUtils;
  import org.kuali.rice.krad.data.DataObjectService;
  import org.kuali.rice.krad.data.DataObjectWrapper;
  import org.kuali.rice.krad.data.link.Link;
  import org.kuali.rice.krad.data.metadata.DataObjectAttributeRelationship;
  import org.kuali.rice.krad.data.metadata.DataObjectCollection;
  import org.kuali.rice.krad.data.metadata.DataObjectMetadata;
  import org.kuali.rice.krad.data.metadata.DataObjectRelationship;
  import org.kuali.rice.krad.data.metadata.MetadataChild;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.beans.PropertyAccessor;
  import org.springframework.beans.PropertyAccessorUtils;
  import org.springframework.core.annotation.AnnotationUtils;
  
  import java.lang.reflect.Field;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * The ReferenceLinker provides functionality that allows for ensuring that relationships and foreign key state are
   * populated and kept in sync as changes are made to a data object.
   *
   * <p>This may include fetching relationships as keys are changed that would necessitate updating the object graph, and
   * may also ensure that foreign key values are kept in sync in situations where a data object may have more than one
   * field or object that stores the same foreign key.</p>
   *
   * <p>This class has a single method {@link #linkChanges(Object, java.util.Set)} which takes a data object and a list
   * of property paths for fields which have been modified. It then uses this information determine how to link up
   * relationships and foreign key fields, recursing through the object graph as needed.</p>
   *
   * <p>Linking occurs from the bottom up, such that this class will attempt to perform a post-order traversal to visit
   * the modified objects furthest from the root first, and then backtracking and linking back to the root. The linking
   * algorithm handles circular references as well to ensure that the linking process terminates successfully.</p>
   *
   * <p>The ReferenceLinker requires access to the {@link DataObjectService} so it must be injected using the
   * provided {@link #setDataObjectService(org.kuali.rice.krad.data.DataObjectService)} method.</p>
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class ReferenceLinker {
  
      private static final Logger LOG = LoggerFactory.getLogger(ReferenceLinker.class);
  
      private DataObjectService dataObjectService;
  
      /**
       * Returns the DataObjectService used by this class
       *
       * @return the DataObjectService used by this class
       */
      public DataObjectService getDataObjectService() {
          return dataObjectService;
      }
  
      /**
       * Specify the DataObjectService to be used during linking.
       *
       * <p>The linker will use the DataObjectService to fetch relationships and query metadata.</p>
       *
       * @param dataObjectService the DataObjectService to inject
       */
      public void setDataObjectService(DataObjectService dataObjectService) {
          this.dataObjectService = dataObjectService;
      }
  
      /**
       * Performs linking of references and keys for the given root object based on the given set of changed property
       * paths that should be considered during the linking process.
       *
       * <p>The root object should be non-null and also a valid data object (such that
       * {@link DataObjectService#supports(Class)} returns true for it). If neither of these conditions is true, this
       * method will return immediately.</p>
      *
      * <p>See class-level documentation for specifics on how the linking algorithm functions.</p>
      *
      * @param rootObject the root object from which to perform the linking
      * @param changedPropertyPaths the set of property paths relative to the root object that should be considered
      * modified by the linking algorithm
      */
     public void linkChanges(Object rootObject, Set<String> changedPropertyPaths) {
         if (rootObject == null || CollectionUtils.isEmpty(changedPropertyPaths)) {
             return;
         }
         Class<?> type = rootObject.getClass();
         if (!dataObjectService.supports(type)) {
             LOG.info("Object supplied for linking is not a supported data object type: " + type);
             return;
         }
         if (LOG.isInfoEnabled()) {
             LOG.info("Performing linking on instance of " + type + " with the following changed property paths: " +
                     Arrays.toString(changedPropertyPaths.toArray()));
         }
         Map<String, Set<String>> decomposedPaths = decomposePropertyPaths(changedPropertyPaths);
         linkChangesInternal(rootObject, decomposedPaths, new HashSet<Object>());
     }
 
     /**
      * Internal implementation of link changes which is implemented to support recursion through the object graph.
      *
      * @param object the object from which to link
      * @param changedPropertyPaths a decomposed property path map where the key of the map is a direct property path
      * relative to the given object and the values are the remainder of the path relative to the parent path, see
      * {@link #decomposePropertyPaths(java.util.Set)}
      * @param linked a set containing objects which have already been linked, used to prevent infinite recursion due to
      * circular references
      */
     protected void linkChangesInternal(Object object, Map<String, Set<String>> changedPropertyPaths,
             Set<Object> linked) {
         if (object == null || linked.contains(object) || !dataObjectService.supports(object.getClass()) ||
                 changedPropertyPaths.isEmpty()) {
             return;
         }
         linked.add(object);
         DataObjectWrapper<?> wrapped = dataObjectService.wrap(object);
 
         // execute the linking
         linkRelationshipChanges(wrapped, changedPropertyPaths, linked);
         linkCollectionChanges(wrapped, changedPropertyPaths, linked);
         cascadeLinkingAnnotations(wrapped, changedPropertyPaths, linked);
     }
 
     /**
      * Link changes for relationships on the given wrapped data object.
      *
      * @param wrapped the wrapped data object
      * @param decomposedPaths the decomposed map of changed property paths
      * @param linked a set containing objects which have already been linked
      */
     protected void linkRelationshipChanges(DataObjectWrapper<?> wrapped, Map<String, Set<String>> decomposedPaths,
             Set<Object> linked) {
         List<DataObjectRelationship> relationships = wrapped.getMetadata().getRelationships();
         for (DataObjectRelationship relationship : relationships) {
             String relationshipName = relationship.getName();
 
             // let's get the current value and recurse down if it's a relationship that is cascaded on save
             if (relationship.isSavedWithParent() && decomposedPaths.containsKey(relationshipName)) {
                 Object value = wrapped.getPropertyValue(relationshipName);
                 Map<String, Set<String>> nextPropertyPaths =
                         decomposePropertyPaths(decomposedPaths.get(relationshipName));
                 linkChangesInternal(value, nextPropertyPaths, linked);
             }
 
             // once we have linked from the bottom up,
             // let's check if any FK attribute modifications have occurred for this relationship
             List<DataObjectAttributeRelationship> attributeRelationships = relationship.getAttributeRelationships();
             boolean modifiedAttributeRelationship = false;
             for (DataObjectAttributeRelationship attributeRelationship : attributeRelationships) {
                 if (decomposedPaths.containsKey(attributeRelationship.getParentAttributeName())) {
                     modifiedAttributeRelationship = true;
                     break;
                 }
             }
             if (modifiedAttributeRelationship) {
                 // use FK attributes and nullify dangling relationship
                 wrapped.fetchRelationship(relationshipName, true, true);
             } else if (decomposedPaths.containsKey(relationshipName)) {
                 // check if any portion of the primary key has been modified
                 Class<?> targetType = relationship.getRelatedType();
                 DataObjectMetadata targetMetadata =
                         dataObjectService.getMetadataRepository().getMetadata(targetType);
                 Set<String> modifiedPropertyPaths = decomposedPaths.get(relationshipName);
                 if (isPrimaryKeyModified(targetMetadata, modifiedPropertyPaths)) {
                     // if the primary key is modified, fetch and replace the related object
                     // this will also copy FK values back to the parent object if it has FK values
                     wrapped.fetchRelationship(relationshipName, false, false);
                 } else {
                     // otherwise, we still want to backward copy keys on the relationship, since this relationship has
                     // been explicity included in the set of changes, we pass false for onlyLinkReadyOnly because we
                     // don't care if the FK field is read only or not, we want to copy back the value regardless
                     wrapped.linkForeignKeys(relationshipName, false);
                 }
             }
         }
     }
 
     /**
      * Link changes for collections on the given wrapped data object.
      *
      * @param wrapped the wrapped data object
      * @param decomposedPaths the decomposed map of changed property paths
      * @param linked a set containing objects which have already been linked
      */
     protected void linkCollectionChanges(DataObjectWrapper<?> wrapped, Map<String, Set<String>> decomposedPaths,
             Set<Object> linked) {
         List<DataObjectCollection> collections = wrapped.getMetadata().getCollections();
         for (DataObjectCollection collectionMetadata : collections) {
             // We only process collections if they are being saved with the parent
             if (collectionMetadata.isSavedWithParent()) {
                 Set<Integer> modifiedIndicies = extractModifiedIndicies(collectionMetadata, decomposedPaths);
                 if (!modifiedIndicies.isEmpty()) {
                     Object collectionValue = wrapped.getPropertyValue(collectionMetadata.getName());
                     if (collectionValue instanceof Iterable<?>) {
                         int index = 0;
                         // loop over all elements in the collection
                         for (Object element : (Iterable<?>)collectionValue) {
                             // check if index is modified, or we use MAX_VALUE to indicate a modification to the
                             // collection itself
                             if (modifiedIndicies.contains(Integer.valueOf(Integer.MAX_VALUE)) ||
                                     modifiedIndicies.contains(Integer.valueOf(index))) {
                                 // recurse down and link the collection element
                                 String pathKey = collectionMetadata.getName() + "[" + index + "]";
                                 if (decomposedPaths.containsKey(pathKey)) {
                                     Map<String, Set<String>> nextPropertyPaths =
                                             decomposePropertyPaths(decomposedPaths.get(pathKey));
                                     linkChangesInternal(element, nextPropertyPaths, linked);
                                 }
                                 if (dataObjectService.supports(element.getClass())) {
                                     DataObjectWrapper<?> elementWrapper = dataObjectService.wrap(element);
                                     linkBiDirectionalCollection(wrapped, elementWrapper, collectionMetadata);
                                 }
                             }
                             index++;
                         }
                     }
                 }
             }
         }
     }
 
     /**
      * Performs bi-directional collection linking, ensuring that for bi-directional collection relationships that both
      * sides of the relationship are properly populated.
      */
     protected void linkBiDirectionalCollection(DataObjectWrapper<?> parentWrapper,
             DataObjectWrapper<?> elementWrapper, DataObjectCollection collectionMetadata) {
         MetadataChild inverseRelationship = collectionMetadata.getInverseRelationship();
         if (inverseRelationship != null) {
             // if there is an inverse relationship, make sure the element is the collection is pointing back to it's parent
             elementWrapper.setPropertyValue(inverseRelationship.getName(), parentWrapper.getWrappedInstance());
             // if there is a foreign key value to link, then link it, not that we pass false here, since we just set
             // our reference to the relationship, we know that we want to copy the key back
             elementWrapper.linkForeignKeys(inverseRelationship.getName(), false);
         }
     }
 
     /**
      * Returns a set of indexes which have been modified in the given collection. If the returned set contains
      * {@link java.lang.Integer#MAX_VALUE} then it means that it should be treated as if all items in the collection
      * have been modified.
      */
     private Set<Integer> extractModifiedIndicies(DataObjectCollection collectionMetadata,
             Map<String, Set<String>> decomposedPaths) {
         String relationshipName = collectionMetadata.getName();
         Set<Integer> modifiedIndicies = Sets.newHashSet();
         // if it contains *exactly* the collection relationship name, then indicate that all items modified
         if (decomposedPaths.containsKey(relationshipName)) {
             modifiedIndicies.add(Integer.valueOf(Integer.MAX_VALUE));
         }
         for (String propertyName : decomposedPaths.keySet()) {
             if (relationshipName.equals(PropertyAccessorUtils.getPropertyName(relationshipName))) {
                 Integer index = extractIndex(propertyName);
                 if (index != null) {
                     modifiedIndicies.add(index);
                 }
             }
         }
         return modifiedIndicies;
     }
 
     private Integer extractIndex(String propertyName) {
         int firstIndex = propertyName.indexOf(PropertyAccessor.PROPERTY_KEY_PREFIX_CHAR);
         int lastIndex = propertyName.lastIndexOf(PropertyAccessor.PROPERTY_KEY_SUFFIX_CHAR);
         if (firstIndex != -1 && lastIndex != -1) {
             String indexValue = propertyName.substring(firstIndex + 1, lastIndex);
             try {
                 int index = Integer.parseInt(indexValue);
                 return Integer.valueOf(index);
             } catch (NumberFormatException e) {
                 // if we encounter this then it wasn't really an index, ignore
             }
         }
         return null;
     }
 
     protected boolean isPrimaryKeyModified(DataObjectMetadata metadata, Set<String> modifiedPropertyPaths) {
         Set<String> primaryKeyAttributeNames = new HashSet<String>(metadata.getPrimaryKeyAttributeNames());
         for (String modifiedPropertyPath : modifiedPropertyPaths) {
             if (primaryKeyAttributeNames.contains(modifiedPropertyPath)) {
                 return true;
             }
         }
         return false;
     }
 
     protected void cascadeLinkingAnnotations(DataObjectWrapper<?> wrapped, Map<String, Set<String>> decomposedPaths,
             Set<Object> linked) {
         Field[] fields = FieldUtils.getAllFields(wrapped.getWrappedClass());
         Map<String, Field> modifiedFieldMap = new HashMap<String, Field>();
         for (Field field : fields) {
             if (decomposedPaths.containsKey(field.getName())) {
                 modifiedFieldMap.put(field.getName(), field);
             }
         }
         for (String modifiedFieldName : modifiedFieldMap.keySet()) {
             Field modifiedField = modifiedFieldMap.get(modifiedFieldName);
             Link link = modifiedField.getAnnotation(Link.class);
             if (link == null) {
                 // check if they have an @Link on the class itself
                 link = AnnotationUtils.findAnnotation(modifiedField.getType(), Link.class);
             }
             if (link != null && link.cascade()) {
                 List<String> linkingPaths = assembleLinkingPaths(link);
                 for (String linkingPath : linkingPaths) {
                     Map<String, Set<String>> decomposedLinkingPath =
                             decomposePropertyPaths(decomposedPaths.get(modifiedFieldName), linkingPath);
                     String valuePath = modifiedFieldName;
                     if (StringUtils.isNotBlank(linkingPath)) {
                         valuePath = valuePath + "." + link.path();
                     }
                     Object linkRootObject = wrapped.getPropertyValueNullSafe(valuePath);
                     linkChangesInternal(linkRootObject, decomposedLinkingPath, linked);
                 }
             }
         }
     }
 
     protected List<String> assembleLinkingPaths(Link link) {
         List<String> linkingPaths = new ArrayList<String>();
         if (ArrayUtils.isEmpty(link.path())) {
             linkingPaths.add("");
         } else {
             for (String path : link.path()) {
                 linkingPaths.add(path);
             }
         }
         return linkingPaths;
     }
 
     protected Map<String, Set<String>> decomposePropertyPaths(Set<String> changedPropertyPaths) {
         return decomposePropertyPaths(changedPropertyPaths, "");
     }
 
     protected Map<String, Set<String>> decomposePropertyPaths(Set<String> changedPropertyPaths, String prefix) {
         // strip the prefix off any changed properties
         Set<String> processedProperties = new HashSet<String>();
         if (StringUtils.isNotBlank(prefix) && changedPropertyPaths != null) {
             for (String changedPropertyPath : changedPropertyPaths) {
                 if (changedPropertyPath.startsWith(prefix)) {
                     processedProperties.add(changedPropertyPath.substring(prefix.length() + 1));
                 }
             }
         } else {
             processedProperties = changedPropertyPaths;
         }
         Map<String, Set<String>> decomposedPropertyPaths = new HashMap<String, Set<String>>();
         for (String changedPropertyPath : processedProperties) {
             int index = PropertyAccessorUtils.getFirstNestedPropertySeparatorIndex(changedPropertyPath);
             if (index == -1) {
                 decomposedPropertyPaths.put(changedPropertyPath, new HashSet<String>());
             } else {
                 String pathEntry = changedPropertyPath.substring(0, index);
                 Set<String> remainingPaths = decomposedPropertyPaths.get(pathEntry);
                 if (remainingPaths == null) {
                     remainingPaths = new HashSet<String>();
                     decomposedPropertyPaths.put(pathEntry, remainingPaths);
                 }
                 String remainingPath = changedPropertyPath.substring(index + 1);
                 remainingPaths.add(remainingPath);
             }
         }
         return decomposedPropertyPaths;
     }
 
 }