/*
 * 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.base.Preconditions;
import com.google.common.base.Verify;
import java.util.function.Consumer;
import javax.annotation.concurrent.NotThreadSafe;
import org.opendaylight.controller.cluster.access.commands.AbortLocalTransactionRequest;
import org.opendaylight.controller.cluster.access.commands.CommitLocalTransactionRequest;
import org.opendaylight.controller.cluster.access.commands.ModifyTransactionRequest;
import org.opendaylight.controller.cluster.access.commands.PersistenceProtocol;
import org.opendaylight.controller.cluster.access.commands.TransactionPurgeRequest;
import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
import org.opendaylight.controller.cluster.access.concepts.Response;
import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
import org.opendaylight.controller.cluster.datastore.util.AbstractDataTreeModificationCursor;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification;
import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeSnapshot;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A read-only specialization of {@link LocalProxyTransaction}.
 *
 * @author Robert Varga
 */
@NotThreadSafe
final class LocalReadOnlyProxyTransaction extends LocalProxyTransaction {
    private static final Logger LOG = LoggerFactory.getLogger(LocalReadOnlyProxyTransaction.class);

    private final DataTreeSnapshot snapshot;

    LocalReadOnlyProxyTransaction(final ProxyHistory parent, final TransactionIdentifier identifier,
        final DataTreeSnapshot snapshot) {
        super(parent, identifier);
        this.snapshot = Preconditions.checkNotNull(snapshot);
    }

    @Override
    boolean isSnapshotOnly() {
        return true;
    }

    @Override
    DataTreeSnapshot readOnlyView() {
        return snapshot;
    }

    @Override
    void doDelete(final YangInstanceIdentifier path) {
        throw new UnsupportedOperationException("Read-only snapshot");
    }

    @Override
    void doMerge(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data) {
        throw new UnsupportedOperationException("Read-only snapshot");
    }

    @Override
    void doWrite(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data) {
        throw new UnsupportedOperationException("Read-only snapshot");
    }

    @Override
    CommitLocalTransactionRequest commitRequest(final boolean coordinated) {
        throw new UnsupportedOperationException("Read-only snapshot");
    }

    @Override
    void doSeal() {
        // No-op
    }

    @Override
    void flushState(final AbstractProxyTransaction successor) {
        // No-op
    }

    @Override
    void applyModifyTransactionRequest(final ModifyTransactionRequest request,
            final Consumer<Response<?, ?>> callback) {
        Verify.verify(request.getModifications().isEmpty());

        final PersistenceProtocol protocol = request.getPersistenceProtocol().get();
        Verify.verify(protocol == PersistenceProtocol.ABORT);
        abort();
    }

    @Override
    void forwardToRemote(final RemoteProxyTransaction successor, final TransactionRequest<?> request,
            final Consumer<Response<?, ?>> callback) {
        if (request instanceof CommitLocalTransactionRequest) {
            final CommitLocalTransactionRequest req = (CommitLocalTransactionRequest) request;
            final DataTreeModification mod = req.getModification();

            LOG.debug("Applying modification {} to successor {}", mod, successor);
            mod.applyToCursor(new AbstractDataTreeModificationCursor() {
                @Override
                public void write(final PathArgument child, final NormalizedNode<?, ?> data) {
                    successor.write(current().node(child), data);
                }

                @Override
                public void merge(final PathArgument child, final NormalizedNode<?, ?> data) {
                    successor.merge(current().node(child), data);
                }

                @Override
                public void delete(final PathArgument child) {
                    successor.delete(current().node(child));
                }
            });

            successor.ensureSealed();

            final ModifyTransactionRequest successorReq = successor.commitRequest(req.isCoordinated());
            successor.sendRequest(successorReq, callback);
        } else if (request instanceof AbortLocalTransactionRequest) {
            LOG.debug("Forwarding abort {} to successor {}", request, successor);
            successor.abort();
        } else if (request instanceof TransactionPurgeRequest) {
            LOG.debug("Forwarding purge {} to successor {}", request, successor);
            successor.purge();
        } else {
            throw new IllegalArgumentException("Unhandled request" + request);
        }
    }
}