content: /*
   *  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.causeway.applib.services.registry;
  
  import java.util.Comparator;
  
  import jakarta.annotation.Priority;
  
  import org.springframework.context.annotation.Primary;
  
  import org.apache.causeway.applib.annotation.PriorityPrecedence;
  import org.apache.causeway.commons.internal.reflection._Reflect;
  
  /**
   * A comparator that orders objects according to their {@link Priority} annotation.
   *
   * @since 2.0  {@index}
   */
  public class InstanceByPriorityComparator implements Comparator<Object> {
  
      private static final InstanceByPriorityComparator INSTANCE =
              new InstanceByPriorityComparator();
  
      public static InstanceByPriorityComparator instance() {
          return INSTANCE;
      }
  
      @Override
      public int compare(final Object o1, final Object o2) {
  
          if (o1 == null) {
              if (o2 == null) {
                  return 0;
              } else {
                  return -1; // o1 later (lower) priority than o2
              }
          }
          if (o2 == null) {
              return 1; // o1 earlier (higher) priority than o2
          }
  
          var primaryAnnot1 = _Reflect.getAnnotation(o1.getClass(), Primary.class);
          var primaryAnnot2 = _Reflect.getAnnotation(o2.getClass(), Primary.class);
          if(primaryAnnot1 != null && primaryAnnot2 == null) { return +1; }
          if(primaryAnnot1 == null && primaryAnnot2 != null) { return -1; }
  
          var prioAnnot1 = _Reflect.getAnnotation(o1.getClass(), Priority.class);
          var prioAnnot2 = _Reflect.getAnnotation(o2.getClass(), Priority.class);
          var prio1 = prioAnnot1 != null ? prioAnnot1.value() : PriorityPrecedence.LAST;
          var prio2 = prioAnnot2 != null ? prioAnnot2.value() : PriorityPrecedence.LAST;
          return Integer.compare(prio2, prio1);
      }
  
  }
  