/*
 * Copyright (c) 2013, 2017 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.controller.config.spi;

import javax.annotation.concurrent.NotThreadSafe;
import org.opendaylight.controller.config.api.ModuleIdentifier;
import org.opendaylight.yangtools.concepts.Identifiable;

/**
 * Represents one service that is to be configured. These methods need to be
 * implemented in addition to the usual attribute getters/setters. Dependencies
 * should always be injected as ObjectName references to the corresponding
 * ConfigBeans.
 * <p>
 * In order to guide dependency resolution, the setter method should be
 * annotated with
 * {@link org.opendaylight.controller.config.api.annotations.RequireInterface}.
 * </p>
 * <p>
 * Thread safety note: implementations of this interface are not required to be
 * thread safe as thread safety is enforced by configuration manager.
 * </p>
 */
@NotThreadSafe
public interface Module extends Identifiable<ModuleIdentifier> {
    /**
     * This method will be called as first phase in two phase commit. Instance can
     * check attributes, but is not allowed to do any kind of work that could leave
     * any resources open. It is prohibited to call {@link #getInstance()} on
     * dependent {@link Module} because it would destroy separation between
     * validation and commit phase.
     *
     */
    void validate();

    /**
     * Returns 'live' object that was configured using this object. It is allowed to
     * call this method only after all ConfigBeans were validated. In this method
     * new resources might be opened or old instance might be modified. This method
     * must be implemented so that it returns same result for a single transaction.
     * Since Module is created per transaction this means that it must be safe to
     * cache result of first call.
     *
     *
     * @return closeable instance: After bundle update the factory might be able to
     *         copy old configuration into new one without being able to cast Module
     *         or the instance. Thus to clean up old instance, it will call close().
     */
    AutoCloseable getInstance();

    /**
     * Compare current module with oldModule and if the instance/live object
     * produced by the old module can be reused in this module as well return true.
     * Typically true should be returned if the old module had the same
     * configuration.
     *
     *
     * @param oldModule
     *            old instance of Module
     * @return true if the instance produced by oldModule can be reused with current
     *         instance as well.
     */
    boolean canReuse(Module oldModule);
}