/*
    * 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 org.apache.syncope.core.rest.cxf;
  
  import java.io.IOException;
  import javax.ws.rs.container.ContainerRequestContext;
  import javax.ws.rs.container.ContainerResponseContext;
  import javax.ws.rs.container.ContainerResponseFilter;
  import javax.ws.rs.core.EntityTag;
  import javax.ws.rs.core.HttpHeaders;
  import javax.ws.rs.ext.Provider;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.syncope.common.lib.to.AnyTO;
  import org.apache.syncope.common.lib.to.EntityTO;
  import org.apache.syncope.common.lib.to.ProvisioningResult;
  
  /**
   * Adds the {@code ETag} header to any response containing an instance of {@link AnyTO} as entity.
   * The actual ETag value is computed on the basis of last change date (or creation date if not available).
   */
  @Provider
  public class AddETagFilter implements ContainerResponseFilter {
  
      @Override
      public void filter(final ContainerRequestContext reqCtx, final ContainerResponseContext resCtx) throws IOException {
          if (resCtx.getEntityTag() == null) {
              AnyTO annotated = null;
              if (resCtx.getEntity() instanceof AnyTO) {
                  annotated = (AnyTO) resCtx.getEntity();
              } else if (resCtx.getEntity() instanceof ProvisioningResult) {
                  EntityTO entity = ((ProvisioningResult<?>) resCtx.getEntity()).getEntity();
                  if (entity instanceof AnyTO) {
                      annotated = (AnyTO) entity;
                  }
              }
              if (annotated != null) {
                  String etagValue = annotated.getETagValue();
                  if (StringUtils.isNotBlank(etagValue)) {
                      resCtx.getHeaders().add(HttpHeaders.ETAG, new EntityTag(etagValue).toString());
                  }
              }
          }
      }
  }