using System;
using System.IO;
using NewLife.Log;
using NewLife.Threading;

namespace NewLife.Configuration
{
    /// <summary>文件配置提供者</summary>
    /// <remarks>
    /// 每个提供者实例对应一个配置文件，支持热更新
    /// </remarks>
    public abstract class FileConfigProvider : ConfigProvider
    {
        #region 属性
        /// <summary>文件名。最高优先级，优先于模型特性指定的文件名</summary>
        public String FileName { get; set; }

        /// <summary>更新周期。默认30秒</summary>
        public Int32 Period { get; set; } = 30;
        #endregion

        #region 构造
        /// <summary>销毁</summary>
        /// <param name="disposing"></param>
        protected override void Dispose(Boolean disposing)
        {
            base.Dispose(disposing);

            _timer.TryDispose();
        }

        /// <summary>已重载。输出友好信息</summary>
        /// <returns></returns>
        public override String ToString() => $"{GetType().Name} FileName={FileName}";
        #endregion

        #region 方法
        /// <summary>初始化</summary>
        /// <param name="value"></param>
        public override void Init(String value)
        {
            base.Init(value);

            // 加上文件名
            if (FileName.IsNullOrEmpty() && !value.IsNullOrEmpty())
            {
                // 加上配置目录
                var str = value;
                if (!str.StartsWithIgnoreCase("Config/", "Config\\")) str = "Config".CombinePath(str);

                FileName = str;
            }
        }

        /// <summary>加载配置</summary>
        public override Boolean LoadAll()
        {
            // 准备文件名
            var fileName = FileName;
            if (fileName.IsNullOrEmpty()) throw new ArgumentNullException(nameof(FileName));

            fileName = fileName.GetBasePath();

            IsNew = true;

            //if (!File.Exists(fileName)) throw new FileNotFoundException("找不到文件", fileName);
            if (!File.Exists(fileName)) return false;

            // 读取文件，换个对象，避免数组元素在多次加载后重叠
            var section = new ConfigSection { };
            OnRead(fileName, section);
            Root = section;

            IsNew = false;
            _lastTime = fileName.AsFile().LastWriteTime;

            return true;
        }

        /// <summary>读取配置文件</summary>
        /// <param name="fileName">文件名</param>
        /// <param name="section">配置段</param>
        protected abstract void OnRead(String fileName, IConfigSection section);

        /// <summary>保存配置树到数据源</summary>
        public override Boolean SaveAll()
        {
            // 准备文件名
            var fileName = FileName;
            if (fileName.IsNullOrEmpty()) throw new ArgumentNullException(nameof(FileName));

            fileName = fileName.GetBasePath();
            fileName.EnsureDirectory(true);

            // 写入文件
            OnWrite(fileName, Root);
            _lastTime = fileName.AsFile().LastWriteTime;

            // 通知绑定对象，配置数据有改变
            NotifyChange();

            return true;
        }

        /// <summary>保存模型实例</summary>
        /// <typeparam name="T">模型</typeparam>
        /// <param name="model">模型实例</param>
        /// <param name="path">路径。配置树位置</param>
        public override Boolean Save<T>(T model, String path = null)
        {
            // 文件存储，直接覆盖Root
            Root.Childs.Clear();
            Root.MapFrom(model);

            return SaveAll();
        }

        /// <summary>写入配置文件</summary>
        /// <param name="fileName">文件名</param>
        /// <param name="section">配置段</param>
        protected virtual void OnWrite(String fileName, IConfigSection section)
        {
            var str = GetString(section);
            var old = "";
            if (File.Exists(fileName)) old = File.ReadAllText(fileName);

            if (str != old)
            {
                XTrace.WriteLine("保存配置 {0}", fileName);

                File.WriteAllText(fileName, str);
            }
        }

        /// <summary>获取字符串形式</summary>
        /// <param name="section">配置段</param>
        /// <returns></returns>
        public virtual String GetString(IConfigSection section = null) => null;
        #endregion

        #region 绑定
        /// <summary>绑定模型，使能热更新，配置存储数据改变时同步修改模型属性</summary>
        /// <typeparam name="T">模型</typeparam>
        /// <param name="model">模型实例</param>
        /// <param name="autoReload">是否自动更新。默认true</param>
        /// <param name="path">路径。配置树位置，配置中心等多对象混合使用时</param>
        public override void Bind<T>(T model, Boolean autoReload = true, String path = null)
        {
            base.Bind<T>(model, autoReload, path);

            if (autoReload) InitTimer();
        }

        private TimerX _timer;
        private void InitTimer()
        {
            if (_timer != null) return;
            lock (this)
            {
                if (_timer != null) return;

                var p = Period;
                if (p <= 0) p = 60;
                _timer = new TimerX(DoRefresh, null, p * 1000, p * 1000) { Async = true };
            }
        }

        private Boolean _reading;
        private DateTime _lastTime;
        private void DoRefresh(Object state)
        {
            if (_reading) return;

            var fileName = FileName.GetBasePath();
            var fi = FileName.AsFile();
            if (!fi.Exists) return;

            fi.Refresh();
            if (_lastTime.Year > 2000 & fi.LastWriteTime <= _lastTime) return;
            _lastTime = fi.LastWriteTime;

            XTrace.WriteLine("配置文件改变，重新加载 {0}", fileName);

            _reading = true;
            try
            {
                var section = new ConfigSection { };
                OnRead(fileName, section);
                Root = section;

                NotifyChange();
            }
            catch (Exception ex)
            {
                XTrace.WriteException(ex);
            }
            finally
            {
                _reading = false;
            }
        }
        #endregion
    }
}