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.persistence.jpa.eclipselink.metamodel;
  
  import java.util.Optional;
  
  import jakarta.persistence.EntityManager;
  import jakarta.persistence.metamodel.EntityType;
  import jakarta.persistence.metamodel.SingularAttribute;
  
  import org.eclipse.persistence.mappings.foundation.AbstractColumnMapping;
  import org.jspecify.annotations.NonNull;
  
  import org.apache.causeway.commons.collections.Can;
  import org.apache.causeway.commons.functional.Try;
  import org.apache.causeway.commons.internal.base._NullSafe;
  import org.apache.causeway.commons.internal.exceptions._Exceptions;
  import org.apache.causeway.core.config.beans.CausewayBeanMetaData.PersistenceStack;
  import org.apache.causeway.core.metamodel.facets.object.entity.EntityOrmMetadata;
  import org.apache.causeway.core.metamodel.facets.object.entity.EntityOrmMetadata.ColumnOrmMetadata;
  
  import lombok.SneakyThrows;
  import lombok.experimental.UtilityClass;
  
  /**
   * Utility that provides vendor independent ORM metadata {@link EntityOrmMetadata}.
   * @since 3.4.0 
   */
  @UtilityClass
  public class EclipseLinkMetadataUtils {
      
      public EntityOrmMetadata ormMetadataFor(
              final @NonNull EntityManager entityManager,
              final @NonNull Class<?> entityClass) {
  
          final EntityType<?> typeMetadata = lookupJpaMetadata(entityManager, entityClass)
                  .orElseThrow(()->
                      _Exceptions.noSuchElement("cannot find JPA metadata for entity %s", entityClass));
          var classDescriptor = _EclipseLinkInternals.getClassDescriptor(typeMetadata);
  
          return new EntityOrmMetadata(
                  PersistenceStack.JPA,
                  Optional.of(classDescriptor.getTableName()),
                  //TODO not sure if this is the correct method to lookup the schema String
                  Optional.of(classDescriptor.getDefaultTable().getTableQualifier()), 
                  typeMetadata.getIdType().getJavaType(),
                  columns(typeMetadata),
                  classDescriptor);
      }
  
      // -- HELPER
      
      private Can<ColumnOrmMetadata> columns(final EntityType<?> typeMetadata) {
          return _NullSafe.stream(typeMetadata.getSingularAttributes())
                  .map(EclipseLinkMetadataUtils::column)
                  .collect(Can.toCan());
      }
      
      @SneakyThrows
      private ColumnOrmMetadata column(final SingularAttribute<?, ?> sa) {
          var databaseMapping = _EclipseLinkInternals.getDatabaseMapping(sa);
          String colName = (databaseMapping instanceof AbstractColumnMapping abstractColumnMapping)
                  ? abstractColumnMapping.getField().getName()
                  : "?";
          return new ColumnOrmMetadata(colName, sa.getName(), sa.getBindableJavaType().getName(), databaseMapping);
      }
  
      /**
       * find the JPA meta-model associated with this (corresponding) entity
       */
      private <T> Optional<EntityType<T>> lookupJpaMetadata(
              final EntityManager entityManager,
              final Class<T> entityClass) {
          
          var entityType = Try.call(()->entityManager.getMetamodel().entity(entityClass))
                  .getValue();
          return entityType;
      }
      
  }
  