/**
  * Helper function to set a field on an object only if the new value is not null. If you wish to
  * reset the value of a field, pass the empty string for the new value.
  *
  * @param object the object to set the value of the field
  * @param fieldName the name of the field to set
  * @param newValue the new value to set to the field. It will be ignored if it's {@code null}
  * @param deprecatedContext the XWikiContext
  * @return {@code true} if the field was set to newValue, {@code false} otherwise
  */
 protected boolean setIfNotNull(
     BaseObject object, String fieldName, Object newValue, XWikiContext deprecatedContext) {
   if (newValue != null) {
     object.set(fieldName, newValue, deprecatedContext);
     return true;
   }
   return false;
 }
  /**
   * {@inheritDoc} <br>
   * This implementation saves the added annotation in the document where the target of the
   * annotation is.
   *
   * @see org.xwiki.annotation.io.IOService#addAnnotation(String, org.xwiki.annotation.Annotation)
   */
  @Override
  public void addAnnotation(String target, Annotation annotation) throws IOServiceException {
    try {
      // extract the document name from the passed target
      // by default the fullname is the passed target
      String documentFullName = target;
      EntityReference targetReference = referenceResolver.resolve(target, EntityType.DOCUMENT);
      // try to get a document reference from the passed target reference
      EntityReference docRef = targetReference.extractReference(EntityType.DOCUMENT);
      if (docRef != null) {
        documentFullName = serializer.serialize(docRef);
      }
      // now get the document with that name
      XWikiContext deprecatedContext = getXWikiContext();
      XWikiDocument document =
          deprecatedContext.getWiki().getDocument(documentFullName, deprecatedContext);
      // create a new object in this document to hold the annotation
      int id =
          document.createXObject(configuration.getAnnotationClassReference(), deprecatedContext);
      BaseObject object = document.getXObject(configuration.getAnnotationClassReference(), id);
      updateObject(object, annotation, deprecatedContext);
      // and set additional data: author to annotation author, date to now and the annotation target
      object.set(Annotation.DATE_FIELD, new Date(), deprecatedContext);
      // TODO: maybe we shouldn't trust what we receive from the caller but set the author from the
      // context.
      // Or the other way around, set the author of the document from the annotations author.
      object.set(Annotation.AUTHOR_FIELD, annotation.getAuthor(), deprecatedContext);
      // store the target of this annotation, serialized with a local serializer, to be exportable
      // and importable
      // in a different wiki
      // TODO: figure out if this is the best idea in terms of target serialization
      // 1/ the good part is that it is a fixed value that can be searched with a query in all
      // objects in the wiki
      // 2/ the bad part is that copying a document to another space will not also update its
      // annotation targets
      // 3/ if annotations are stored in the same document they annotate, the targets are only
      // required for object
      // fields
      // ftm don't store the type of the reference since we only need to recognize the field, not to
      // also read it.
      if (targetReference.getType() == EntityType.OBJECT_PROPERTY
          || targetReference.getType() == EntityType.DOCUMENT) {
        object.set(
            Annotation.TARGET_FIELD, localSerializer.serialize(targetReference), deprecatedContext);
      } else {
        object.set(Annotation.TARGET_FIELD, target, deprecatedContext);
      }
      // set the author of the document to the current user
      document.setAuthor(deprecatedContext.getUser());
      deprecatedContext
          .getWiki()
          .saveDocument(
              document,
              "Added annotation on \"" + annotation.getSelection() + "\"",
              deprecatedContext);

      // notify listeners that an annotation was added
      ObservationManager observationManager = componentManager.lookup(ObservationManager.class);
      observationManager.notify(
          new AnnotationAddedEvent(documentFullName, object.getNumber() + ""),
          document,
          deprecatedContext);

    } catch (XWikiException e) {
      throw new IOServiceException(
          "An exception message has occurred while saving the annotation", e);
    } catch (ComponentLookupException exc) {
      this.logger.warn(
          "Could not get the observation manager to send notifications about the annotation add");
    }
  }