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/*
 * Copyright (c) 2008-2024, Hazelcast, Inc. All Rights Reserved.
 *
 * Licensed 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
 *
 * http://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.
 */

package com.hazelcast.internal.util;

import com.hazelcast.internal.serialization.Data;
import com.hazelcast.internal.serialization.SerializationService;

import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import static com.hazelcast.internal.util.Preconditions.checkNotNull;

/**
 * Various collection utility methods.
 */
public final class CollectionUtil {

    private CollectionUtil() {
    }

    /**
     * Returns {@code true} if the given collection is {@code null} or empty, otherwise returns {@code false}.
     *
     * @param collection the given collection
     * @return {@code true} if collection is empty
     */
    public static boolean isEmpty(Collection collection) {
        return collection == null || collection.isEmpty();
    }

    /**
     * Returns {@code true} if the given collection is not {@code null} and not empty, otherwise returns {@code false}.
     *
     * @param collection the given collection
     * @return {@code true} if collection is not empty
     */
    public static boolean isNotEmpty(Collection collection) {
        return !isEmpty(collection);
    }

    /**
     * Returns the n-th item or {@code null} if collection is smaller.
     *
     * @param collection the given collection
     * @param position   position of the wanted item
     * @return the item on position or {@code null} if the given collection is too small
     * @throws NullPointerException if collection is {@code null}
     */
    public static  T getItemAtPositionOrNull(Collection collection, int position) {
        if (position >= collection.size() || position < 0) {
            return null;
        }
        if (collection instanceof List) {
            return ((List) collection).get(position);
        }
        Iterator iterator = collection.iterator();
        T item = null;
        for (int i = 0; i < position + 1; i++) {
            item = iterator.next();
        }
        return item;
    }

    /**
     * Converts a collection of any type to a collection of {@link Data}.
     *
     * @param collection           the given collection
     * @param serializationService will be used for converting object to {@link Data}
     * @return collection of data
     * @throws NullPointerException if collection is {@code null} or contains a {@code null} item
     */
    public static  Collection objectToDataCollection(Collection collection,
                                                              SerializationService serializationService) {
        List dataCollection = new ArrayList<>(collection.size());
        objectToDataCollection(collection, dataCollection, serializationService, null);
        return dataCollection;
    }

    /**
     * Converts a collection of any type to a collection of {@link Data}.
     *
     * @param objectCollection     object items
     * @param dataCollection       data items
     * @param serializationService will be used for converting object to {@link Data}
     * @param errorMessage         the errorMessage when an item is null
     * @throws NullPointerException if collection is {@code null} or contains a {@code null} item
     */
    public static  void objectToDataCollection(Collection objectCollection, Collection dataCollection,
                                                  SerializationService serializationService, String errorMessage) {
        for (C item : objectCollection) {
            checkNotNull(item, errorMessage);
            dataCollection.add(serializationService.toData(item));
        }
    }

    /**
     * Converts a {@link Collection} of {@link Integer} to a primitive {@code int[]} array.
     *
     * @param collection the given collection
     * @return a primitive int[] array
     * @throws NullPointerException if collection is {@code null}
     */
    public static int[] toIntArray(Collection collection) {
        int[] collectionArray = new int[collection.size()];
        int index = 0;
        for (Integer item : collection) {
            collectionArray[index++] = item;
        }
        return collectionArray;
    }

    /**
     * Adapts an int array to an Integer {@link List}.
     * 
     * The returned list is not serializable. If serializability is required,
     * use {@code Arrays.stream(array).boxed().toList()}.
     *
     * @throws NullPointerException if array is null.
     */
    public static List asIntegerList(int[] array) {
        checkNotNull(array, "null array");
        return new AbstractList<>() {
            @Override
            public Integer get(int index) {
                return array[index];
            }

            @Override
            public int size() {
                return array.length;
            }
        };
    }

    /** Returns an empty Collection if argument is null. **/
    public static  Collection nullToEmpty(Collection collection) {
        return collection == null ? Collections.emptyList() : collection;
    }
}