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.core.metamodel.facets.objectvalue.mandatory;
  
  import org.apache.causeway.core.metamodel.facetapi.Facet;
  import org.apache.causeway.core.metamodel.facetapi.FacetHolder;
  import org.apache.causeway.core.metamodel.interactions.ValidatingInteractionAdvisor;
  import org.apache.causeway.core.metamodel.object.ManagedObject;
  
  import org.jspecify.annotations.NonNull;
  
  /**
   * Whether a property or a parameter is mandatory (not optional).
   *
   * <p>
   * For a mandatory property, the object cannot be saved/updated without the
   * value being provided. For a mandatory parameter, the action cannot be invoked
   * without the value being provided.
   *
   */
  public interface MandatoryFacet
  extends Facet, ValidatingInteractionAdvisor {
  
      public enum Semantics {
          REQUIRED,
          OPTIONAL;
  
          public static Semantics required(final boolean required) {
              return required ? REQUIRED: OPTIONAL;
          }
  
          public boolean isRequired() {
              return this == REQUIRED;
          }
  
          public boolean isOptional() {
              return this == OPTIONAL;
          }
      }
  
      /**
       * Whether this value is required but has not been provided (and is
       * therefore invalid).
       *
       * <p>
       * If the value has been provided, <i>or</i> if the property or parameter is
       * not required, then will return <tt>false</tt>.
       */
      boolean isRequiredButNull(ManagedObject adapter);
  
      /**
       * Indicates that the implementation is overriding the usual semantics, in
       * other words that the {@link FacetHolder} to which this {@link Facet} is
       * attached is <i>not</i> mandatory.
       */
      Semantics getSemantics();
  
      /**
       * Used to generate validation message, when there are conflicting mandatory semantics.
       */
      default String summarize() {
          return String.format("%s->%s", getClass().getSimpleName(), getSemantics().name());
      }
  
      // -- UTILITY
  
      static boolean isMandatory(final @NonNull FacetHolder facetHolder) {
          var mandatoryFacet = facetHolder.getFacet(MandatoryFacet.class);
          if(mandatoryFacet == null) {
              // absence of the mandatory facet indicates OPTIONAL
              return false;
          }
          return mandatoryFacet.getSemantics()==null
                  || mandatoryFacet.getSemantics().isRequired();
      }
  }
  