/*
 * Copyright (c) 2008, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Linda DeMichiel - 2.1
//     Linda DeMichiel - 2.0

package jakarta.persistence.spi;

/**
 * Utility interface implemented by the persistence provider.  This
 * interface is invoked by the {@link
 * jakarta.persistence.PersistenceUtil} implementation to determine
 * the load status of an entity or entity attribute.
 *
 * @since 2.0
 */
public interface ProviderUtil { 

    /**
     * If the provider determines that the entity has been provided
     * by itself and that the state of the specified attribute has
     * been loaded, this method returns <code>LoadState.LOADED</code>.
     * <p> If the provider determines that the entity has been provided
     * by itself and that either entity attributes with <code>FetchType.EAGER</code> 
     * have not been loaded or that the state of the specified
     * attribute has not been loaded, this methods returns
     * <code>LoadState.NOT_LOADED</code>.
     * <p> If a provider cannot determine the load state, this method
     * returns <code>LoadState.UNKNOWN</code>.
     * <p> The provider's implementation of this method must not obtain
     * a reference to an attribute value, as this could trigger the
     * loading of entity state if the entity has been provided by a
     * different provider.
     * @param entity  entity instance
     * @param attributeName  name of attribute whose load status is
     *        to be determined
     * @return load status of the attribute
     */
    public LoadState isLoadedWithoutReference(Object entity, String attributeName);

    /**
     * If the provider determines that the entity has been provided
     * by itself and that the state of the specified attribute has
     * been loaded, this method returns <code>LoadState.LOADED</code>.
     * <p> If a provider determines that the entity has been provided
     * by itself and that either the entity attributes with <code>FetchType.EAGER</code>
     * have not been loaded or that the state of the specified
     * attribute has not been loaded, this method returns
     * return <code>LoadState.NOT_LOADED</code>.
     * <p> If the provider cannot determine the load state, this method
     * returns <code>LoadState.UNKNOWN</code>.
     * <p> The provider's implementation of this method is permitted to
     * obtain a reference to the attribute value.  (This access is
     * safe because providers which might trigger the loading of the
     * attribute state will have already been determined by
     * <code>isLoadedWithoutReference</code>. )
     *
     * @param entity  entity instance
     * @param attributeName  name of attribute whose load status is
     *        to be determined
     * @return load status of the attribute
     */
    public LoadState isLoadedWithReference(Object entity, String attributeName);

    /**
     * If the provider determines that the entity has been provided
     * by itself and that the state of all attributes for which
     * <code>FetchType.EAGER</code> has been specified have been loaded, this 
     * method returns <code>LoadState.LOADED</code>.
     * <p> If the provider determines that the entity has been provided
     * by itself and that not all attributes with <code>FetchType.EAGER</code> 
     * have been loaded, this method returns <code>LoadState.NOT_LOADED</code>.
     * <p> If the provider cannot determine if the entity has been
     * provided by itself, this method returns <code>LoadState.UNKNOWN</code>.
     * <p> The provider's implementation of this method must not obtain
     * a reference to any attribute value, as this could trigger the
     * loading of entity state if the entity has been provided by a
     * different provider.
     * @param entity whose loaded status is to be determined
     * @return load status of the entity
     */
    public LoadState isLoaded(Object entity);
}
