using System;
using System.Collections.Generic;
using System.Text;
using System.Web.Caching;
using System.Threading;

namespace Ant.ORM.Cache
{
    /// <summary>
    /// 全局缓存类
    /// </summary>
    /// <example><code>
    /// 使用示例：
    /// 实例化： CacheManage cache=CacheManage.Instance;
    /// 添加：   cache.Add("路过秋天",new MDataTable);
    /// 判断：   if(cache.Contains("路过秋天"))
    ///          {
    /// 获取：       MDataTable table=cache.Get("路过秋天") as MDataTable;
    ///          }
    /// </code></example>
    public class CacheManage
    {
        private readonly System.Web.HttpContext H = new System.Web.HttpContext(new System.Web.HttpRequest("Null.File", "http://cyq1162.cnblogs.com", String.Empty), new System.Web.HttpResponse(null));
        private System.Web.Caching.Cache theCache = null;
        private Dictionary<string, CacheDependencyInfo> cacheState = new Dictionary<string, CacheDependencyInfo>();
        private DateTime workTime;
        /// <summary>
        /// 缓存信息
        /// </summary>
        public Dictionary<string, CacheDependencyInfo> CacheInfo
        {
            get
            {
                return cacheState;
            }
        }
        private CacheManage()
        {
            theCache = H.Cache;
            Thread thread = new Thread(new ThreadStart(ClearState));
            thread.IsBackground = true;
            thread.Start();
            workTime = DateTime.Now.AddMinutes(5);
        }
        private void ClearState()
        {
            List<string> removeKeys = new List<string>();
            while (true)
            {
                try
                {
                    Thread.Sleep(5 * 60 * 1000);//五分钟休眠时间
                    if (theCache.Count != cacheState.Count)//准备同步
                    {
                        foreach (KeyValuePair<string, CacheDependencyInfo> item in cacheState)
                        {
                            if ((item.Value.CreaeTime.AddMinutes(4) < DateTime.Now && item.Value.CallCount < 2) || //缓存调用次数太少
                            item.Value.CreaeTime.AddMinutes(item.Value.CacheMinutes) < DateTime.Now)//清过期cacheState进行同步
                            {
                                if (!removeKeys.Contains(item.Key))
                                {
                                    removeKeys.Add(item.Key);
                                }
                            }
                        }
                        foreach (string key in removeKeys)
                        {
                            Remove(key);//移除
                        }
                        clearCount = removeKeys.Count;
                        removeKeys.Clear();
                    }
                    workTime = DateTime.Now.AddMinutes(5);
                }
                catch
                {
                    System.Threading.Thread.Sleep(TimeSpan.FromHours(1));
                }
            }
        }
        private int errorCount = 0;//缓存捕异常次数
        private int clearCount = 0;//清除的缓存数
        /// <summary>
        /// 缓存工作信息
        /// </summary>
        public string WorkInfo
        {
            get
            {
                return string.Format("try catch error:{0}(times)--clear count:{1}--next clear work time at:{2}", errorCount, clearCount, workTime);
            }
        }
        /// <summary>
        /// 获和缓存总数
        /// </summary>
        public int Count
        {
            get
            {
                return theCache == null ? 0 : theCache.Count;
            }
        }
        /// <summary>
        /// 返回唯一实例
        /// </summary>
        public static CacheManage Instance
        {
            get
            {
                return Shell.instance;
            }
        }

        class Shell
        {
            internal static readonly CacheManage instance = new CacheManage();
        }
        /// <summary>
        /// 还可用的缓存百分比
        /// </summary>
        public long RemainMemoryPercentage
        {
            get
            {
                return theCache.EffectivePercentagePhysicalMemoryLimit;
            }
        }
        /// <summary>
        /// 还可用的缓存字节数
        /// </summary>
        public long RemainMemoryBytes
        {
            get
            {
                return theCache.EffectivePrivateBytesLimit;
            }
        }

        /// <summary>
        /// 获得一个Cache对象
        /// </summary>
        /// <param name="key">标识</param>
        /// <returns></returns>
        public object Get(string key)
        {
            if (Contains(key))
            {
                try
                {
                    cacheState[key].CallCount++;
                }
                catch
                {
                    errorCount++;
                }
                return theCache[key];
            }
            return null;
        }
        /// <summary>
        /// 是否存在缓存
        /// </summary>
        /// <param name="key">标识</param>
        /// <returns></returns>
        public bool Contains(string key)
        {
            if (theCache[key] != null)
            {
                return true;
            }
            else
            {
                if (cacheState.ContainsKey(key))
                {
                    try
                    {
                        cacheState.Remove(key);
                    }
                    catch
                    {
                        errorCount++;
                    }
                }
                return false;
            }
        }
        /// <summary>
        /// 添加一个Cache对象
        /// </summary>
        /// <param name="key">标识</param>
        /// <param name="value">对象值</param>
        public void Add(string key, object value)
        {
            Add(key, value, null, 0);
        }
        public void Add(string key, object value, string filePath)
        {
            Add(key, value, filePath, 0);//再插入Cache
        }
        public void Add(string key, object value, string filePath, double cacheTimeMinutes)
        {
            if (Contains(key))
            {
                Remove(key);
            }
            Insert(key, value, filePath, cacheTimeMinutes);//再插入Cache

        }
        /// <summary>
        /// 缓存设置：有则更新，无则添加
        /// </summary>
        /// <param name="key"></param>
        /// <param name="value"></param>
        public void Set(string key, object value)
        {
            if (Contains(key))
            {
                theCache[key] = value;
            }
            else
            {
                Insert(key, value, null, 0);//再插入Cache
            }
        }
        /// <summary>
        /// 更新缓存，缓存存在则更更新，不存在则跳过
        /// </summary>
        public void Update(string key, object value)
        {
            if (Contains(key))
            {
                theCache[key] = value;
            }
        }
        /// <summary>
        /// 相对底层Cache添加方法,添加一个Cache请用Add方法
        /// </summary>
        /// <param name="key">标识</param>
        /// <param name="value">对象值</param>
        /// <param name="filePath">文件依赖路径</param>
        /// <param name="cacheTimeMinutes">缓存分钟数</param>
        private void Insert(string key, object value, string filePath, double cacheTimeMinutes)
        {
            CacheDependency theCacheDependency = null;
            if (!string.IsNullOrEmpty(filePath))
            {
                theCacheDependency = new CacheDependency(filePath);
            }
            double cacheTime = cacheTimeMinutes;
            if (cacheTimeMinutes == 0)
            {
                cacheTime = 30;
            }
            theCache.Insert(key, value == null ? string.Empty : value, theCacheDependency, DateTime.Now.AddMinutes(cacheTime), TimeSpan.Zero, CacheItemPriority.Default, null);
            CacheDependencyInfo info = new CacheDependencyInfo(theCacheDependency, cacheTime);
            if (cacheState.ContainsKey(key))
            {
                cacheState[key] = info;
            }
            else
            {
                try
                {
                    cacheState.Add(key, info);
                }
                catch { }
            }
        }

        /// <summary>
        /// 删除一个Cache对象
        /// </summary>
        /// <param name="key">标识</param>
        public void Remove(string key)
        {
            if (Contains(key))//检测存在时中会自动清除cacheState
            {
                try
                {
                    theCache.Remove(key);
                    cacheState.Remove(key);
                }
                catch
                {
                    errorCount++;
                }
            }
        }
        /// <summary>
        /// 清除所有缓存
        /// </summary>
        public void Clear()
        {
            try
            {
                foreach (KeyValuePair<string, CacheDependencyInfo> item in cacheState)
                {
                    theCache.Remove(item.Key);
                }
                cacheState.Clear();
            }
            catch
            {
                errorCount++;
            }
        }

        /// <summary>
        /// 用户手动设置缓存对象已更改
        /// </summary>
        /// <param name="key"></param>
        /// <param name="change"></param>
        public void SetChange(string key, bool change)
        {
            if (cacheState.ContainsKey(key) && Contains(key))
            {
                CacheDependencyInfo info = cacheState[key];
                if (info != null)
                {
                    info.UserSetChange(change);
                }
            }
            else
            {
                Add("Ant.ORM.Cache:Temp_" + key, change, null, 0.1);//缓存失效时，产生6秒的key缓冲
            }
        }
        /// <summary>
        /// 获取缓存对象是否已被用户手动设置更改
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public bool GetHasChanged(string key)
        {
            if (cacheState.ContainsKey(key) && Contains(key))
            {
                CacheDependencyInfo info = cacheState[key];
                if (info != null)
                {
                    return info.IsChanged ? false : info.UserChange;
                }
            }
            else if (Contains("Ant.ORM.Cache:Temp_" + key))
            {
                return (bool)theCache.Get("Ant.ORM.Cache:Temp_" + key);
            }
            return false;
        }
    }
    /// <summary>
    /// 缓存依赖信息
    /// </summary>
    public class CacheDependencyInfo
    {
        public int CallCount = 0;
        /// <summary>
        /// 缓存产生的时间
        /// </summary>
        public DateTime CreaeTime;
        /// <summary>
        /// 缓存多少分钟
        /// </summary>
        public Double CacheMinutes = 0;
        DateTime CacheChangeTime = DateTime.MinValue;
        CacheDependency FileDependency = null;
        public CacheDependencyInfo(CacheDependency dependency, double cacheMinutes)
        {
            if (dependency != null)
            {
                FileDependency = dependency;
                CacheChangeTime = FileDependency.UtcLastModified;
            }
            CreaeTime = DateTime.Now;
            CacheMinutes = cacheMinutes;
        }
        /// <summary>
        /// 系统文件依赖是否发生改变
        /// </summary>
        public bool IsChanged
        {
            get
            {
                if (FileDependency != null && (FileDependency.HasChanged || CacheChangeTime != FileDependency.UtcLastModified))
                {
                    CacheChangeTime = FileDependency.UtcLastModified;
                    return true;
                }
                return false;
            }
        }

        internal bool UserChange = false;

        public void UserSetChange(bool change)
        {
            UserChange = IsChanged ? false : change;
        }
    }
}