using System;
using System.Runtime.Caching;

namespace BLL
{
    public class CacheHelper
    {
        private static readonly ObjectCache Cache = MemoryCache.Default;

        /// <summary>
        /// 添加缓存项
        /// </summary>
        /// <param name="key">缓存键</param>
        /// <param name="value">缓存值</param>
        /// <param name="absoluteExpiration">绝对过期时间</param>
        public static void Add(string key, object value, DateTimeOffset absoluteExpiration)
        {
            if (string.IsNullOrEmpty(key))
            {
                throw new ArgumentNullException(nameof(key));
            }

            Cache.Set(key, value, absoluteExpiration);
        }

        /// <summary>
        /// 获取缓存项（泛型）
        /// </summary>
        /// <typeparam name="T">返回类型</typeparam>
        /// <param name="key">缓存键</param>
        /// <returns>缓存值</returns>
        public static T Get<T>(string key)
        {
            if (string.IsNullOrEmpty(key))
            {
                throw new ArgumentNullException(nameof(key));
            }

            object value = Cache[key];
            if (value is T tValue)
            {
                return tValue;
            }
            return default(T);
        }

        /// <summary>
        /// 获取缓存项
        /// </summary>
        /// <param name="key">缓存键</param>
        /// <returns>缓存值</returns>
        public static object Get(string key)
        {
            if (string.IsNullOrEmpty(key))
            {
                throw new ArgumentNullException(nameof(key));
            }

            return Cache[key];
        }

        /// <summary>
        /// 移除缓存项
        /// </summary>
        /// <param name="key">缓存键</param>
        public static void Remove(string key)
        {
            if (string.IsNullOrEmpty(key))
            {
                throw new ArgumentNullException(nameof(key));
            }

            Cache.Remove(key);
        }

        /// <summary>
        /// 清空所有缓存
        /// </summary>
        public static void Clear()
        {
            foreach (var item in Cache)
            {
                Cache.Remove(item.Key);
            }
        }

        /// <summary>
        /// 检查缓存项是否存在
        /// </summary>
        /// <param name="key">缓存键</param>
        /// <returns>是否存在</returns>
        public static bool Exists(string key)
        {
            if (string.IsNullOrEmpty(key))
            {
                throw new ArgumentNullException(nameof(key));
            }

            return Cache.Contains(key);
        }
    }
}