using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using Common.AppLog;
using System.Xml.Serialization;
using System.Xml;

namespace Common.Services
{
    public class XMLDataContext<T> where T: class
    {
        private string m_FileName;

        public XMLDataContext(string _fileName)
        {
            m_FileName = _fileName;
        }

        private string LoadFile()
        {
            return FSmanager.LoadFile(m_FileName);
        }

        private bool SaveFile(string _Fstring)
        {
            return FSmanager.CreateFile(m_FileName,_Fstring);
        }

        private bool SaveFile(byte[] _buffer)
        {
            return FSmanager.SavetoBinFile(m_FileName, _buffer);
        }

        private byte[] SerializeToXML(T _obj, Encoding _encoding = null)
        {
            XmlSerializer _ser = new XmlSerializer(typeof(T));
            byte[] _buffer = new byte[] {};
            using (MemoryStream _stream = new MemoryStream())
            {
                _encoding = _encoding == null ? Encoding.UTF8 : _encoding;
                using (StreamWriter _sw = new StreamWriter(_stream, _encoding))
                    _ser.Serialize(_sw, _obj);
                _buffer = _stream.ToArray();
            }
            return _buffer;
        }

        private T DeserializeFromXML(string _xml)
        {
            object _obj=null;
            XmlSerializer _ser = new XmlSerializer(typeof(T));
            try
            {
                using (TextReader _tr = new StringReader(_xml))
                    _obj = _ser.Deserialize(_tr);
            }
            catch (Exception _ex)
            {
                SysLog.SaveToLog("DataContext.DeserializeFromXML (file name - <" + m_FileName + ">):\n   " + _ex.Message);
            }
            return (T)_obj;
        }

        public T GetObject()
        {
            string _xmlFromFile=LoadFile();
            T _retObj;
            
            if (_xmlFromFile != string.Empty)
                _retObj=DeserializeFromXML(_xmlFromFile);
            else _retObj=null;

            return _retObj;
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="_obj">Object for save into the XML file</param>
        /// <param name="_encoding">System.Text.Encoding object, default encoding is UTF8 if parameter is null</param>
        /// <returns>True if object successfully saved to file</returns>
        public bool SaveObject(T _obj, Encoding _encoding=null)
        {
            bool _ret = false;
            int i = 0;
            byte[] _xmlBuffer = SerializeToXML(_obj, _encoding);
            if ( _xmlBuffer.Length> 0 )
                while (!_ret && i < 10) // 10 attempts to save into the file
                {
                    i++;
                    _ret = SaveFile(_xmlBuffer);
                }
            return _ret;
        }
    }
}