/*
 * 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
 *
 *   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 org.apache.tinkerpop.gremlin.util;

import org.apache.commons.lang3.ArrayUtils;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Utility class for working with collections and arrays.
 */
public final class CollectionUtil {
    private CollectionUtil() { }

    /**
     * Converts varargs to a {@code List}.
     */
    public static <E> List<E> asList(final E... elements) {
        return new ArrayList<>(Arrays.asList(elements));
    }

    /**
     * Converts varargs to a {@code Set}.
     */
    public static <E> LinkedHashSet<E> asSet(final E... elements) {
        return asSet(Arrays.asList(elements));
    }

    /**
     * Converts {@code Collection} to a {@code Set}.
     */
    public static <E> LinkedHashSet<E> asSet(final Collection<E> elements) {
        return new LinkedHashSet<>(elements);
    }

    /**
     * Converts varargs to a {@code Map} where the elements are key/value pairs.
     */
    public static <K,V> LinkedHashMap<K,V> asMap(final Object... elements) {
        final LinkedHashMap<K,V> map = new LinkedHashMap<>();
        for (int i = 0; i < elements.length; i+=2) {
            final K k = (K) elements[i];
            final V v = (V) (i+1 < elements.length ? elements[i+1] : null);
            map.put(k, v);
        }
        return map;
    }

    /**
     * Clones a given {@code ConcurrentHashMap} by creating a new map and copying all entries from the original map.
     * If the value of an entry is a {@code Set} or an {@code ArrayList}, a deep copy of the value is created.
     * Otherwise, the value is copied as is.
     */
    public static <K,V> ConcurrentHashMap<K,V> clone(final ConcurrentHashMap<K,V> map) {
        final ConcurrentHashMap<K, V> result = new ConcurrentHashMap<>(map.size());

        for (Map.Entry<K, V> entry : map.entrySet()) {
            V clonedValue;
            if (entry.getValue() instanceof Set) {
                clonedValue = (V) ConcurrentHashMap.newKeySet();
                ((Set) clonedValue).addAll((Set) entry.getValue());
            } else if (entry.getValue() instanceof ArrayList) {
                clonedValue = (V)((ArrayList) entry.getValue()).clone();
            } else {
                clonedValue = entry.getValue();
            }

            result.put(entry.getKey(), clonedValue);
        }

        return result;
    }

    /**
     * Adds the element argument to the start of the supplied array argument, but if the array is null then return the
     * element as a new array with just that item in it.
     */
    public static <T> T[] addFirst(final T[] array, final T element, final Class<T> clazz) {
        if (null == array) {
            final T[] singleElementArray = (T[]) Array.newInstance(clazz, 1);
            singleElementArray[0] = element;
            return singleElementArray;
        } else {
            return ArrayUtils.addFirst(array, element);
        }
    }
}
