using Microsoft.Extensions.Caching.Memory;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text.RegularExpressions;

namespace Performance.Infrastructure
{
    public class MemoryCacheHelper
    {
        private static readonly MemoryCache Cache = new MemoryCache(new MemoryCacheOptions());

        /// <summary>
        /// 验证缓存项是否存在
        /// </summary>
        /// <param name="key">缓存Key</param>
        /// <returns></returns>
        public bool Exists(string key)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));
            return Cache.TryGetValue(key, out _);
        }


        /// <summary>
        ///  时间转时间戳Unix-时间戳精确到秒
        /// </summary> 
        public TimeSpan ToUnixTimestampBySeconds(DateTime dt)
        {
            DateTimeOffset dto = new DateTimeOffset(dt);
            return TimeSpan.FromSeconds(dto.ToUnixTimeSeconds());
        }

        /// <summary>
        /// 添加缓存
        /// </summary>
        /// <param name="key">缓存Key</param>
        /// <param name="value">缓存Value</param>
        /// <param name="expiresSliding">滑动过期时长（如果在过期时间内有操作，则以当前时间点延长过期时间）</param>
        /// <param name="expiressAbsoulte">绝对过期时长</param>
        /// <returns></returns>
        public bool Set(string key, object value, TimeSpan expiresSliding, TimeSpan expiressAbsoulte)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));
            if (value == null)
                throw new ArgumentNullException(nameof(value));

            Cache.Set(key, value,
                new MemoryCacheEntryOptions().SetSlidingExpiration(expiresSliding)
                    .SetAbsoluteExpiration(expiressAbsoulte));
            return Exists(key);
        }

        /// <summary>
        /// 添加缓存
        /// </summary>
        /// <param name="key">缓存Key</param>
        /// <param name="value">缓存Value</param>
        /// <param name="expiresIn">缓存时长</param>
        /// <param name="isSliding">是否滑动过期（如果在过期时间内有操作，则以当前时间点延长过期时间）</param>
        /// <returns></returns>
        public bool Set(string key, object value, TimeSpan expiresIn, bool isSliding = false)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));
            if (value == null)
                throw new ArgumentNullException(nameof(value));

            Cache.Set(key, value,
                isSliding
                    ? new MemoryCacheEntryOptions().SetSlidingExpiration(expiresIn)
                    : new MemoryCacheEntryOptions().SetAbsoluteExpiration(expiresIn));

            return Exists(key);
        }

        #region 删除缓存

        /// <summary>
        /// 删除缓存
        /// </summary>
        /// <param name="key">缓存Key</param>
        /// <returns></returns>
        public void Remove(string key)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));

            Cache.Remove(key);
        }

        /// <summary>
        /// 批量删除缓存
        /// </summary>
        /// <returns></returns>
        public void RemoveAll(IEnumerable<string> keys)
        {
            if (keys == null)
                throw new ArgumentNullException(nameof(keys));

            keys.ToList().ForEach(item => Cache.Remove(item));
        }
        #endregion

        #region 获取缓存

        /// <summary>
        /// 获取缓存
        /// </summary>
        /// <param name="key">缓存Key</param>
        /// <returns></returns>
        public T Get<T>(string key) where T : class
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));

            return Cache.Get(key) as T;
        }

        /// <summary>
        /// 获取缓存
        /// </summary>
        /// <param name="key">缓存Key</param>
        /// <returns></returns>
        public object Get(string key)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));

            return Cache.Get(key);
        }

        /// <summary>
        /// 获取缓存集合
        /// </summary>
        /// <param name="keys">缓存Key集合</param>
        /// <returns></returns>
        public IDictionary<string, object> GetAll(IEnumerable<string> keys)
        {
            if (keys == null)
                throw new ArgumentNullException(nameof(keys));

            var dict = new Dictionary<string, object>();
            keys.ToList().ForEach(item => dict.Add(item, Cache.Get(item)));
            return dict;
        }
        #endregion

        /// <summary>
        /// 删除所有缓存
        /// </summary>
        public void RemoveCacheAll()
        {
            var l = GetCacheKeys();
            foreach (var s in l)
            {
                Remove(s);
            }
        }

        /// <summary>
        /// 删除匹配到的缓存
        /// </summary>
        /// <param name="pattern"></param>
        /// <returns></returns>
        public void RemoveCacheRegex(string pattern)
        {
            IList<string> l = SearchCacheRegex(pattern);
            foreach (var s in l)
            {
                Remove(s);
            }
        }

        /// <summary>
        /// 搜索 匹配到的缓存
        /// </summary>
        /// <param name="pattern"></param>
        /// <returns></returns>
        public IList<string> SearchCacheRegex(string pattern)
        {
            var cacheKeys = GetCacheKeys();
            var l = cacheKeys.Where(k => Regex.IsMatch(k, pattern)).ToList();
            return l.AsReadOnly();
        }

        /// <summary>
        /// 获取所有缓存键
        /// </summary>
        /// <returns></returns>
        public List<string> GetCacheKeys()
        {
            const BindingFlags flags = BindingFlags.Instance | BindingFlags.NonPublic;
            var entries = Cache.GetType().GetField("_entries", flags).GetValue(Cache);
            var cacheItems = entries as IDictionary;
            var keys = new List<string>();
            if (cacheItems == null) return keys;
            foreach (DictionaryEntry cacheItem in cacheItems)
            {
                keys.Add(cacheItem.Key.ToString());
            }
            return keys;
        }
    }
}
