using System;
using System.Runtime.Caching;

namespace OS.Common.Modules.CacheModule
{
    /// <summary>
    /// 
    /// </summary>
    public class Cache : ICache
    {
        /// <summary>
        /// 添加缓存，已存在不更新
        /// </summary>
        /// <typeparam name="T">添加缓存对象类型</typeparam>
        /// <param name="key">添加对象的key</param>
        /// <param name="obj">值</param>
        /// <param name="slidingExpiration">相对过期的TimeSpan</param>
        /// <param name="absoluteExpiration"> 绝对过期时间 </param>
        /// <param name="db"> 缓存分区db </param>
        /// <returns>是否添加成功</returns>
        public bool Add<T>(string key, T obj, TimeSpan slidingExpiration, DateTime? absoluteExpiration = null)
        {
            return Add(key, obj, slidingExpiration, absoluteExpiration,  false);
        }

        /// <summary>
        /// 添加缓存,如果存在则更新
        /// </summary>
        /// <typeparam name="T">添加缓存对象类型</typeparam>
        /// <param name="key">添加对象的key</param>
        /// <param name="obj">值</param>
        /// <param name="slidingExpiration">相对过期的TimeSpan  如果使用固定时间  =TimeSpan.Zero</param>
        /// <param name="absoluteExpiration"> 绝对过期时间 </param>
        /// <param name="db"> 缓存分区db </param>
        /// <returns>是否添加成功</returns>
        public bool AddOrUpdate<T>(string key, T obj, TimeSpan slidingExpiration, DateTime? absoluteExpiration = null)
        {
            return Add(key, obj, slidingExpiration, absoluteExpiration, true);
        }

        /// <summary>
        /// 
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="key"></param>
        /// <param name="obj"></param>
        /// <param name="slidingExpiration"></param>
        /// <param name="absoluteExpiration"></param>
        /// <param name="isUpdate"></param>
        /// <returns></returns>
        private static bool Add<T>(string key, T obj, TimeSpan slidingExpiration, DateTime? absoluteExpiration, bool isUpdate)
        {
            if (slidingExpiration == TimeSpan.Zero && absoluteExpiration == null)
                throw new ArgumentNullException("slidingExpiration", "缓存过期时间不正确,需要设置固定过期时间或者相对过期时间");

            var cachePllicy = new CacheItemPolicy();

            if (slidingExpiration == TimeSpan.Zero)
            {
                cachePllicy.AbsoluteExpiration = new DateTimeOffset(absoluteExpiration.Value);
            }
            else
            {
                cachePllicy.SlidingExpiration = slidingExpiration;
            }

            if (isUpdate)
            {
                MemoryCache.Default.Set(key, obj, cachePllicy);
                return true;
            }
            return MemoryCache.Default.Add(key, obj, cachePllicy);
        }

        /// <summary>
        /// 获取缓存对象
        /// </summary>
        /// <typeparam name="T">获取缓存对象类型</typeparam>
        /// <param name="key">key</param>
        /// <returns>获取指定key对应的值 </returns>
        public T Get<T>(string key)
        {
            return (T)MemoryCache.Default.Get(key);
        }


        /// <summary>
        /// 移除缓存对象
        /// </summary>
        /// <param name="key"></param>
        /// <returns>是否成功</returns>
        public bool Remove(string key)
        {
            return MemoryCache.Default.Remove(key)!=null;
        }


        /// <summary>
        ///   判断是否存在缓存对象
        /// </summary>
        /// <param name="key">  key值  </param>
        /// <returns></returns>
        public bool Contains(string key)
        {
            return MemoryCache.Default.Contains(key);
        }
    }
}