#nullable enable
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;

namespace Masuit.Tools
{
    public static partial class IEnumerableExtensions
    {
        /// <summary>
        /// 按字段去重
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TKey"></typeparam>
        /// <param name="source"></param>
        /// <param name="keySelector"></param>
        /// <returns></returns>
        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
        {
            var hash = new HashSet<TKey>();
            return source.Where(p => hash.Add(keySelector(p)));
        }

        /// <summary>
        /// 添加多个元素
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="this"></param>
        /// <param name="values"></param>
        public static void AddRange<T>(this ICollection<T> @this, params T[] values)
        {
            foreach (var obj in values)
            {
                @this.Add(obj);
            }
        }

        /// <summary>
        /// 添加符合条件的多个元素
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="this"></param>
        /// <param name="predicate"></param>
        /// <param name="values"></param>
        public static void AddRangeIf<T>(this ICollection<T> @this, Func<T, bool> predicate, params T[] values)
        {
            foreach (var obj in values)
            {
                if (predicate(obj))
                {
                    @this.Add(obj);
                }
            }
        }

        /// <summary>
        /// 添加不重复的元素
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="this"></param>
        /// <param name="values"></param>
        public static void AddRangeIfNotContains<T>(this ICollection<T> @this, params T[] values)
        {
            foreach (T obj in values)
            {
                if (!@this.Contains(obj))
                {
                    @this.Add(obj);
                }
            }
        }

        /// <summary>
        /// 移除符合条件的元素
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="this"></param>
        /// <param name="where"></param>
        public static void RemoveWhere<T>(this ICollection<T> @this, Func<T, bool> @where)
        {
            foreach (var obj in @this.Where(where).ToList())
            {
                @this.Remove(obj);
            }
        }

        /// <summary>
        /// 在元素之后添加元素
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="list"></param>
        /// <param name="condition">条件</param>
        /// <param name="value">值</param>
        public static void InsertAfter<T>(this IList<T> list, Func<T, bool> condition, T value)
        {
            foreach (var item in list.Select((item, index) => new { item, index }).Where(p => condition(p.item)).OrderByDescending(p => p.index))
            {
                if (item.index + 1 == list.Count)
                {
                    list.Add(value);
                }
                else
                {
                    list.Insert(item.index + 1, value);
                }
            }
        }

        /// <summary>
        /// 在元素之后添加元素
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="list"></param>
        /// <param name="index">索引位置</param>
        /// <param name="value">值</param>
        public static void InsertAfter<T>(this IList<T> list, int index, T value)
        {
            foreach (var item in list.Select((v, i) => new { Value = v, Index = i }).Where(p => p.Index == index).OrderByDescending(p => p.Index))
            {
                if (item.Index + 1 == list.Count)
                {
                    list.Add(value);
                }
                else
                {
                    list.Insert(item.Index + 1, value);
                }
            }
        }

        /// <summary>
        /// 转HashSet
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public static HashSet<TResult> ToHashSet<T, TResult>(this IEnumerable<T> source, Func<T, TResult> selector)
        {
            var set = new HashSet<TResult>();
            set.UnionWith(source.Select(selector));
            return set;
        }

        /// <summary>
        /// 遍历IEnumerable
        /// </summary>
        /// <param name="objs"></param>
        /// <param name="action">回调方法</param>
        /// <typeparam name="T"></typeparam>
        public static void ForEach<T>(this IEnumerable<T> objs, Action<T> action)
        {
            foreach (var o in objs)
            {
                action(o);
            }
        }

        /// <summary>
        /// 异步foreach
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <param name="maxParallelCount">最大并行数</param>
        /// <param name="action"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public static async Task ForeachAsync<T>(this IEnumerable<T> source, Func<T, Task> action, int maxParallelCount, CancellationToken cancellationToken = default)
        {
            var list = new List<Task>();
            foreach (var item in source)
            {
                if (cancellationToken.IsCancellationRequested)
                {
                    return;
                }

                list.Add(action(item));
                if (list.Count >= maxParallelCount)
                {
                    await Task.WhenAll(list);
                    list.Clear();
                }
            }

            await Task.WhenAll(list);
        }

        /// <summary>
        /// 异步foreach
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <param name="action"></param>
        /// <returns></returns>
        public static Task ForeachAsync<T>(this IEnumerable<T> source, Func<T, Task> action, CancellationToken cancellationToken = default)
        {
            return ForeachAsync(source, action, source.Count(), cancellationToken);
        }

        /// <summary>
        /// 异步Select
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public static Task<TResult[]> SelectAsync<T, TResult>(this IEnumerable<T> source, Func<T, Task<TResult>> selector)
        {
            return Task.WhenAll(source.Select(selector));
        }

        /// <summary>
        /// 异步Select
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public static Task<TResult[]> SelectAsync<T, TResult>(this IEnumerable<T> source, Func<T, int, Task<TResult>> selector)
        {
            return Task.WhenAll(source.Select(selector));
        }

        /// <summary>
        /// 异步For
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <param name="maxParallelCount">最大并行数</param>
        /// <param name="cancellationToken">取消口令</param>
        /// <returns></returns>
        public static async Task ForAsync<T>(this IEnumerable<T> source, Func<T, int, Task> selector, int maxParallelCount, CancellationToken cancellationToken = default)
        {
            var list = new List<Task>();
            int index = 0;
            foreach (var item in source)
            {
                if (cancellationToken.IsCancellationRequested)
                {
                    return;
                }

                list.Add(selector(item, index++));
                if (list.Count >= maxParallelCount)
                {
                    await Task.WhenAll(list);
                    list.Clear();
                }
            }

            await Task.WhenAll(list);
        }

        /// <summary>
        /// 异步For
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <param name="cancellationToken">取消口令</param>
        /// <returns></returns>
        public static Task ForAsync<T>(this IEnumerable<T> source, Func<T, int, Task> selector, CancellationToken cancellationToken = default)
        {
            return ForAsync(source, selector, source.Count(), cancellationToken);
        }

        /// <summary>
        /// 取最大值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public static TResult MaxOrDefault<TSource, TResult>(this IQueryable<TSource> source, Expression<Func<TSource, TResult>> selector) => source.Select(selector).DefaultIfEmpty().Max();

        /// <summary>
        /// 取最大值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static TResult MaxOrDefault<TSource, TResult>(this IQueryable<TSource> source, Expression<Func<TSource, TResult>> selector, TResult defaultValue) => source.Select(selector).DefaultIfEmpty(defaultValue).Max();

        /// <summary>
        /// 取最大值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <param name="source"></param>
        /// <returns></returns>
        public static TSource MaxOrDefault<TSource>(this IQueryable<TSource> source) => source.DefaultIfEmpty().Max();

        /// <summary>
        /// 取最大值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <param name="source"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static TSource MaxOrDefault<TSource>(this IQueryable<TSource> source, TSource defaultValue) => source.DefaultIfEmpty(defaultValue).Max();

        /// <summary>
        /// 取最大值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static TResult MaxOrDefault<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector, TResult defaultValue) => source.Select(selector).DefaultIfEmpty(defaultValue).Max();

        /// <summary>
        /// 取最大值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public static TResult MaxOrDefault<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector) => source.Select(selector).DefaultIfEmpty().Max();

        /// <summary>
        /// 取最大值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <param name="source"></param>
        /// <returns></returns>
        public static TSource MaxOrDefault<TSource>(this IEnumerable<TSource> source) => source.DefaultIfEmpty().Max();

        /// <summary>
        /// 取最大值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <param name="source"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static TSource MaxOrDefault<TSource>(this IEnumerable<TSource> source, TSource defaultValue) => source.DefaultIfEmpty(defaultValue).Max();

        /// <summary>
        /// 取最小值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public static TResult MinOrDefault<TSource, TResult>(this IQueryable<TSource> source, Expression<Func<TSource, TResult>> selector) => source.Select(selector).DefaultIfEmpty().Min();

        /// <summary>
        /// 取最小值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static TResult MinOrDefault<TSource, TResult>(this IQueryable<TSource> source, Expression<Func<TSource, TResult>> selector, TResult defaultValue) => source.Select(selector).DefaultIfEmpty(defaultValue).Min();

        /// <summary>
        /// 取最小值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <param name="source"></param>
        /// <returns></returns>
        public static TSource MinOrDefault<TSource>(this IQueryable<TSource> source) => source.DefaultIfEmpty().Min();

        /// <summary>
        /// 取最小值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <param name="source"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static TSource MinOrDefault<TSource>(this IQueryable<TSource> source, TSource defaultValue) => source.DefaultIfEmpty(defaultValue).Min();

        /// <summary>
        /// 取最小值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public static TResult MinOrDefault<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector) => source.Select(selector).DefaultIfEmpty().Min();

        /// <summary>
        /// 取最小值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static TResult MinOrDefault<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector, TResult defaultValue) => source.Select(selector).DefaultIfEmpty(defaultValue).Min();

        /// <summary>
        /// 取最小值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <param name="source"></param>
        /// <returns></returns>
        public static TSource MinOrDefault<TSource>(this IEnumerable<TSource> source) => source.DefaultIfEmpty().Min();

        /// <summary>
        /// 取最小值
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <param name="source"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static TSource MinOrDefault<TSource>(this IEnumerable<TSource> source, TSource defaultValue) => source.DefaultIfEmpty(defaultValue).Min();

        /// <summary>
        /// 标准差
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <param name="selector"></param>
        /// <returns></returns>
        public static TResult StandardDeviation<T, TResult>(this IEnumerable<T> source, Func<T, TResult> selector) where TResult : IConvertible
        {
            return StandardDeviation(source.Select(t => selector(t).ConvertTo<double>())).ConvertTo<TResult>();
        }

        /// <summary>
        /// 标准差
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <returns></returns>
        public static T StandardDeviation<T>(this IEnumerable<T> source) where T : IConvertible
        {
            return StandardDeviation(source.Select(t => t.ConvertTo<double>())).ConvertTo<T>();
        }

        /// <summary>
        /// 标准差
        /// </summary>
        /// <param name="source"></param>
        /// <returns></returns>
        public static double StandardDeviation(this IEnumerable<double> source)
        {
            double result = 0;
            int count = source.Count();
            if (count > 1)
            {
                double avg = source.Average();
                double sum = source.Sum(d => (d - avg) * (d - avg));
                result = Math.Sqrt(sum / count);
            }

            return result;
        }
    }
}