/*
 * Copyright (c) 2011-2025, baomidou (jobob@qq.com).
 *
 * 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.baomidou.mybatisplus.core.toolkit;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

/**
 * Collection工具类
 *
 * @author Caratacus
 * @since 2016-09-19
 */
public class CollectionUtils {

    private static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);

    private static boolean isJdk8;

    static {
        // Java 8
        // Java 9+: 9,11,17
        try {
            isJdk8 = System.getProperty("java.version").startsWith("1.8.");
        } catch (Exception ignore) {
            isJdk8 = true;
        }
    }

    /**
     * 校验集合是否为空
     *
     * @param coll 入参
     * @return boolean
     */
    public static boolean isEmpty(Collection<?> coll) {
        return (coll == null || coll.isEmpty());
    }

    /**
     * 校验集合是否不为空
     *
     * @param coll 入参
     * @return boolean
     */
    public static boolean isNotEmpty(Collection<?> coll) {
        return !isEmpty(coll);
    }

    /**
     * 判断Map是否为空
     *
     * @param map 入参
     * @return boolean
     */
    public static boolean isEmpty(Map<?, ?> map) {
        return (map == null || map.isEmpty());
    }

    /**
     * 判断Map是否不为空
     *
     * @param map 入参
     * @return boolean
     */
    public static boolean isNotEmpty(Map<?, ?> map) {
        return !isEmpty(map);
    }

    /**
     * 创建默认HashMap
     *
     * @param <K> K
     * @param <V> V
     * @return HashMap
     * @see com.google.common.collect.Maps#newHashMap()
     * @since 3.4.0
     */
    public static <K, V> HashMap<K, V> newHashMap() {
        return new HashMap<>();
    }

    /**
     * 根据预期大小创建HashMap.
     *
     * @param expectedSize 预期大小
     * @param <K>          K
     * @param <V>          V
     * @return HashMap
     * @see com.google.common.collect.Maps#newHashMapWithExpectedSize
     * @since 3.4.0
     */
    public static <K, V> HashMap<K, V> newHashMapWithExpectedSize(int expectedSize) {
        return new HashMap<>(capacity(expectedSize));
    }

    /**
     * 用来过渡下Jdk1.8下ConcurrentHashMap的性能bug
     * <a href="https://bugs.openjdk.java.net/browse/JDK-8161372">JDK-8161372</a>
     * <p>
     *  A temporary workaround for Java 8 ConcurrentHashMap#computeIfAbsent specific performance issue: JDK-8161372.</br>
     *  @see <a href="https://bugs.openjdk.java.net/browse/JDK-8161372">https://bugs.openjdk.java.net/browse/JDK-8161372</a>
     *
     * @param concurrentHashMap ConcurrentHashMap 没限制类型了，非ConcurrentHashMap就别调用这方法了
     * @param key               key
     * @param mappingFunction   function
     * @param <K>               k
     * @param <V>               v
     * @return V
     * @since 3.4.0
     */
    public static <K, V> V computeIfAbsent(Map<K, V> concurrentHashMap, K key, Function<? super K, ? extends V> mappingFunction) {
        Objects.requireNonNull(mappingFunction);
        if (isJdk8) {
            V v = concurrentHashMap.get(key);
            if (null == v) {
                // issue#11986 lock bug
                // v = map.computeIfAbsent(key, func);

                // this bug fix methods maybe cause `func.apply` multiple calls.
                v = mappingFunction.apply(key);
                if (null == v) {
                    return null;
                }
                final V res = concurrentHashMap.putIfAbsent(key, v);
                if (null != res) {
                    // if pre value present, means other thread put value already, and putIfAbsent not effect
                    // return exist value
                    return res;
                }
                // if pre value is null, means putIfAbsent effected, return current value
            }
            return v;
        } else {
            return concurrentHashMap.computeIfAbsent(key, mappingFunction);
        }

    }

    /**
     * Returns a capacity that is sufficient to keep the map from being resized as
     * long as it grows no larger than expectedSize and the load factor is >= its
     * default (0.75).
     *
     * @see com.google.common.collect.Maps#capacity(int)
     * @since 3.4.0
     */
    private static int capacity(int expectedSize) {
        if (expectedSize < 3) {
            if (expectedSize < 0) {
                throw new IllegalArgumentException("expectedSize cannot be negative but was: " + expectedSize);
            }
            return expectedSize + 1;
        }
        if (expectedSize < MAX_POWER_OF_TWO) {
            // This is the calculation used in JDK8 to resize when a putAll
            // happens; it seems to be the most conservative calculation we
            // can make.  0.75 is the default load factor.
            return (int) ((float) expectedSize / 0.75F + 1.0F);
        }
        return Integer.MAX_VALUE; // any large value
    }

    // 提供处理Map多key取值工具方法

    /**
     * 批量取出Map中的值
     *
     * @param map  map
     * @param keys 键的集合
     * @param <K>  key的泛型
     * @param <V>  value的泛型
     * @return value的泛型的集合
     */
    public static <K, V> List<V> getCollection(Map<K, V> map, Iterable<K> keys) {
        List<V> result = new ArrayList<>();
        if (map != null && !map.isEmpty() && keys != null) {
            keys.forEach(key -> Optional.ofNullable(map.get(key)).ifPresent(result::add));
        }
        return result;
    }

    /**
     * 批量取出Map中的值
     *
     * @param map        map
     * @param keys       键的集合
     * @param comparator 排序器
     * @param <K>        key的泛型
     * @param <V>        value的泛型
     * @return value的泛型的集合
     */
    public static <K, V> List<V> getCollection(Map<K, V> map, Iterable<K> keys, Comparator<V> comparator) {
        Objects.requireNonNull(comparator);
        List<V> result = getCollection(map, keys);
        result.sort(comparator);
        return result;
    }

    /**
     * 构建List
     *
     * @since 3.5.4
     */
    @SafeVarargs
    public static <T> List<T> toList(T... t) {
        if (t != null) {
            return Arrays.asList(t);
        }
        return Collections.emptyList();
    }

    /**
     * 切割集合为多个集合
     * @param entityList 数据集合
     * @param batchSize 每批集合的大小
     * @return 切割后的多个集合
     * @param <T> 数据类型
     */
    public static <T> List<List<T>> split(Collection<T> entityList, int batchSize) {
        if (isEmpty(entityList)) {
            return Collections.emptyList();
        }
        Assert.isFalse(batchSize < 1, "batchSize must not be less than one");
        final Iterator<T> iterator = entityList.iterator();
        final List<List<T>> results = new ArrayList<>(entityList.size() / batchSize);
        while (iterator.hasNext()) {
            final List<T> list = IntStream.range(0, batchSize).filter(x -> iterator.hasNext())
                .mapToObj(i -> iterator.next()).collect(Collectors.toList());
            if (!list.isEmpty()) {
                results.add(list);
            }
        }
        return results;
    }
}
