/*
 * Copyright (c) 2020 PANTHEON.tech, s.r.o. 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.binding.api.query;

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import org.eclipse.jdt.annotation.NonNullByDefault;
import org.opendaylight.yangtools.concepts.Immutable;
import org.opendaylight.yangtools.yang.binding.DataObject;
import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;

/**
 * Result of executing a {@link QueryExpression}. It is composed of one or more result values, which can be accessed via
 * {@link #spliterator()}, {@link #stream()} and {@link #getValues()} methods.
 *
 * @param <T> Result object type
 */
@NonNullByDefault
public interface QueryResult<T extends DataObject> extends Iterable<QueryResult.Item<T>>, Immutable {
    /**
     * A single item in the result set. It is identified by its path and the corresponding object..
     *
     * @param <T> Result object type
     */
    interface Item<T extends DataObject> extends Immutable {
        /**
         * Return the result object.
         *
         * @return Result object
         */
        T object();

        /**
         * Return the {@link InstanceIdentifier} of the result object. This is guaranteed to be non-wildcard.
         *
         * @return InstanceIdentifier of the result object
         */
        InstanceIdentifier<T> path();
    }

    /**
     * Returns a sequential {@link Stream} of values from the result.
     *
     * @return A stream of non-null values.
     */
    default Stream<Item<T>> stream() {
        return StreamSupport.stream(spliterator(), false);
    }

    /**
     * Returns a parallel {@link Stream} of values from the result.
     *
     * @return A stream of non-null values.
     */
    default Stream<Item<T>> parallelStream() {
        return StreamSupport.stream(spliterator(), true);
    }

    default List<? extends T> getValues() {
        return stream().map(Item::object).collect(Collectors.toUnmodifiableList());
    }

    default List<? extends Item<T>> getItems() {
        return stream().collect(Collectors.toUnmodifiableList());
    }
}