/*
 * Copyright (c) 2014 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.mdsal.dom.spi.store;

import com.google.common.util.concurrent.FluentFuture;
import com.google.common.util.concurrent.MoreExecutors;
import java.util.Optional;
import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.mdsal.common.api.ReadFailedException;
import org.opendaylight.mdsal.dom.api.query.DOMQuery;
import org.opendaylight.mdsal.dom.api.query.DOMQueryResult;
import org.opendaylight.mdsal.dom.spi.query.DOMQueryEvaluator;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;

public interface DOMStoreReadTransaction extends DOMStoreTransaction {
    /**
     * Reads data from provided logical data store located at provided path.
     *
     * @param path
     *            Path which uniquely identifies subtree which client want to
     *            read
     * @return a FluentFuture containing the result of the read. The Future blocks until the
     *         commit operation is complete. Once complete:
     *         <ul>
     *         <li>If the data at the supplied path exists, the Future returns an Optional object
     *         containing the data.</li>
     *         <li>If the data at the supplied path does not exist, the Future returns
     *         Optional.empty().</li>
     *         <li>If the read of the data fails, the Future will fail with a
     *         {@link ReadFailedException} or an exception derived from ReadFailedException.</li>
     *         </ul>
     */
    FluentFuture<Optional<NormalizedNode>> read(YangInstanceIdentifier path);

    /**
     * Checks if data is available in the logical data store located at provided path.
     *
     * <p>
     * Note: a successful result from this method makes no guarantee that a subsequent call to {@link #read}
     * will succeed. It is possible that the data resides in a data store on a remote node and, if that
     * node goes down or a network failure occurs, a subsequent read would fail. Another scenario is if
     * the data is deleted in between the calls to <code>exists</code> and <code>read</code>
     *
     * @param path
     *            Path which uniquely identifies subtree which client want to
     *            check existence of
     * @return a FluentFuture containing the result of the check.
     *         <ul>
     *         <li>If the data at the supplied path exists, the Future returns a Boolean
     *         whose value is true, false otherwise</li>
     *         <li>If checking for the data fails, the Future will fail with a
     *         {@link ReadFailedException} or an exception derived from ReadFailedException.</li>
     *         </ul>
     */
    FluentFuture<Boolean> exists(YangInstanceIdentifier path);

    /**
     * Executes a query on the provided logical data store.
     *
     * <p>
     * Default operation invokes {@code read(query.getRoot())} and then executes the result with
     * {@link DOMQueryEvaluator}. Implementations are encouraged to provide a more efficient implementation as
     * appropriate.
     *
     * @param query DOMQuery to execute
     * @return a FluentFuture containing the result of the query. The Future blocks until the operation is complete.
     *         Once complete:
     *         <ul>
     *           <li>The Future returns the result of the query</li>
     *           <li>If the query execution fails, the Future will fail with a {@link ReadFailedException} or
     *               an exception derived from ReadFailedException.
     *            </li>
     *         </ul>
     * @throws NullPointerException if any of the arguments is null
     * @throws IllegalArgumentException if the query is not supported
     */
    default @NonNull FluentFuture<DOMQueryResult> execute(final DOMQuery query) {
        return read(query.getRoot()).transform(
            node -> node.map(data -> DOMQueryEvaluator.evaluateOn(query, data)).orElse(DOMQueryResult.of()),
            MoreExecutors.directExecutor());
    }
}