/*
 * Copyright (c) 2016 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.cluster.databroker.actors.dds;

import com.google.common.util.concurrent.ListenableFuture;
import org.opendaylight.controller.sal.core.spi.data.DOMStoreThreePhaseCommitCohort;

/**
 * An {@link AbstractTransactionCommitCohort} for use with empty transactions. This relies on the fact that no backends
 * have been touched, hence all state book-keeping needs to happen only locally and shares fate with the coordinator.
 *
 * Therefore all methods can finish immediately without any effects.
 *
 * @author Robert Varga
 */
final class EmptyTransactionCommitCohort extends AbstractTransactionCommitCohort {
    static final DOMStoreThreePhaseCommitCohort INSTANCE = new EmptyTransactionCommitCohort();

    private EmptyTransactionCommitCohort() {
        // Hidden
    }

    @Override
    public ListenableFuture<Boolean> canCommit() {
        return TRUE_FUTURE;
    }

    @Override
    public ListenableFuture<Void> preCommit() {
        return VOID_FUTURE;
    }

    @Override
    public ListenableFuture<Void> abort() {
        return VOID_FUTURE;
    }

    @Override
    public ListenableFuture<Void> commit() {
        return VOID_FUTURE;
    }
}