/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
 *   SPDX-License-Identifier: Apache-2.0
 */

package org.apache.jena.ontapi.model;

import org.apache.jena.ontapi.utils.Iterators;
import org.apache.jena.rdf.model.RDFList;
import org.apache.jena.rdf.model.RDFNode;
import org.apache.jena.rdf.model.Resource;

import java.util.Objects;
import java.util.Optional;
import java.util.stream.Stream;

/**
 * A parameterized analogue of the {@link RDFList Jena RDF []-List} that provides read-only access to its items.
 *
 * @param <E> the type of element-nodes in this []-list
 * @see RDFList
 */
public interface RDFNodeList<E extends RDFNode> extends Resource {

    /**
     * Lists all elements of the type {@code E} from this list.
     * Note: a real RDF-list may contain nodes with an incompatible type,
     * in this case they will not be included in the result {@code Stream}.
     * To get all {@link RDFNode RDF Node}s use the standard list representation:
     * the expression {@code Iter.asStream(this.as(RDFList.class).iterator())} will return a {@code Stream} of nodes.
     *
     * @return {@code Stream} of {@code E}-elements
     * @see #as(Class)
     * @see Iterators#asStream(java.util.Iterator)
     */
    Stream<E> members();

    /**
     * Answers {@code true} if the []-list contains the specified {@code element}.
     * More formally, returns {@code true} if and only if
     * this RDF-list contains at least one element {@code e} of the type {@code E} such that {@code element.equals(e)}.
     *
     * @param element {@code E}, not {@code null}
     * @return boolean
     */
    default boolean contains(E element) {
        Objects.requireNonNull(element);
        try (Stream<E> members = members()) {
            return members.anyMatch(element::equals);
        }
    }

    /**
     * Answers the first element of the type {@code E}.
     *
     * @return {@code Optional} around the {@code E}-item
     */
    default Optional<E> first() {
        try (Stream<E> members = members()) {
            return members.findFirst();
        }
    }

    /**
     * Answers the last element of the type {@code E}.
     *
     * @return {@code Optional} around the {@code E}-item
     */
    default Optional<E> last() {
        return members().reduce((f, s) -> s);
    }

    /**
     * Answers the number of {@link RDFNode rdf-node}s in the list.
     * Note: in general, this operation is not equivalent to the expression {@code this.members().count()},
     * since the list may contain items of an incompatible type.
     *
     * @return the real size of the []-list as an integer
     */
    default long size() {
        return as(RDFList.class).size();
    }

    /**
     * Answers {@code true} if it is a nil []-list.
     * Please note: a non-nil list may also not contain elements of the type {@code E}
     * and, therefore, be {@link #isEmpty()} empty.
     *
     * @return boolean
     * @see #isEmpty()
     */
    default boolean isNil() {
        return as(RDFList.class).isEmpty();
    }

    /**
     * Answers {@code true} if this list contains no elements of the type {@code E}.
     * A {@link #isNil() nil}-list is always empty, but the reverse is not true.
     *
     * @return boolean
     * @see #isNil()
     */
    default boolean isEmpty() {
        return first().isEmpty();
    }

}
