/*
 * The contents of this file are subject to the terms of the Common Development and
 * Distribution License (the License). You may not use this file except in compliance with the
 * License.
 *
 * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
 * specific language governing permission and limitations under the License.
 *
 * When distributing Covered Software, include this CDDL Header Notice in each file and include
 * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
 * Header, with the fields enclosed by brackets [] replaced by your own identifying
 * information: "Portions Copyright [year] [name of copyright owner]".
 *
 * Copyright 2008 Sun Microsystems, Inc.
 */
package org.opends.server.admin;



import java.util.Collection;
import java.util.Collections;

import org.opends.server.admin.client.ClientConstraintHandler;
import org.opends.server.admin.server.ServerConstraintHandler;



/**
 * An interface for enforcing constraints and dependencies between
 * managed objects and their properties. Constraints express
 * relationships between managed objects and their properties, for
 * example:
 * <ul>
 * <li>referential integrity: where one managed object references
 * another a constraint can enforce referential integrity. The
 * constraint can prevent creation of references to non-existent
 * managed objects, and also prevent deletion of referenced managed
 * objects
 * <li>property dependencies: for example, when a boolean property is
 * <code>true</code>, one or more additional properties must be
 * specified. This is useful for features like SSL, which when
 * enabled, requires that various SSL related configuration options
 * are specified
 * <li>property constraints: for example, when an upper limit
 * property must not have a value which is less than the lower limit
 * property.
 * </ul>
 * On the client-side constraints are enforced immediately before a
 * write operation is performed. That is to say, immediately before a
 * new managed object is created, changes to a managed object are
 * applied, or an existing managed object is deleted.
 */
public abstract class Constraint {

  /**
   * Creates a new constraint.
   */
  protected Constraint() {
    // No implementation required.
  }



  /**
   * Gets the client-side constraint handlers which will be used to
   * enforce this constraint in client applications. The default
   * implementation is to return an empty set of client constraint
   * handlers.
   *
   * @return Returns the client-side constraint handlers which will be
   *         used to enforce this constraint in client applications.
   *         The returned collection must not be <code>null</code>
   *         but maybe empty (indicating that the constraint can only
   *         be enforced on the server-side).
   */
  public Collection<ClientConstraintHandler> getClientConstraintHandlers() {
    return Collections.emptySet();
  }



  /**
   * Gets the server-side constraint handlers which will be used to
   * enforce this constraint within the server. The default
   * implementation is to return an empty set of server constraint
   * handlers.
   *
   * @return Returns the server-side constraint handlers which will be
   *         used to enforce this constraint within the server. The
   *         returned collection must not be <code>null</code> and
   *         must not be empty, since constraints must always be
   *         enforced on the server.
   */
  public Collection<ServerConstraintHandler> getServerConstraintHandlers() {
    return Collections.emptySet();
  }



  /**
   * Initializes this constraint. The default implementation is to do
   * nothing.
   *
   * @throws Exception
   *           If this constraint could not be initialized.
   */
  protected void initialize() throws Exception {
    // Default implementation is to do nothing.
  }

}