using System;
using System.IO;
using System.Threading;
using JD.Kernel.Classes;
using JD.Kernel.StaticHelpers;
using JD.Serializers.Xml;

namespace JD.PropertyService
{
    /// <summary>
    /// Properties that load/save automatically to/from a file.
    /// </summary>
    internal class AutoSavingProperties : PropertiesWrapper, IDisposable
    {
        #region Variables

        private static readonly TimeSpan AutoSavePeriod = TimeSpan.FromMinutes(5);

        private readonly string m_filename;
        private readonly Timer m_saveTimer;

        private bool m_isDirty;
        private readonly object m_saveLock = new object();

        #endregion

        #region Constructor

        /// <summary>
        /// Constructor.
        /// </summary>
        public AutoSavingProperties(string filename, IProperties wrappedProperties)
            : base(wrappedProperties)
        {
            Throw.IfEmpty(filename, "filename");
            Throw.IfNull(wrappedProperties, "wrappedProperties");

            m_filename = filename;

            string directory = Path.GetDirectoryName(m_filename);

            if (!Directory.Exists(directory))
            {
                Directory.CreateDirectory(directory);
            }

            if (File.Exists(m_filename))
            {
                try
                {
                    using (XmlSerializerReader reader = new XmlSerializerReader(File.OpenRead(filename)))
                    {
                        Wrapped.ReadFromXml(reader);
                    }
                }
                catch
                {
                    Clear();
                }
            }

            wrappedProperties.PropertyChanged += wrappedProperties_PropertyChanged;

            m_saveTimer = new Timer(TimerCallback, null, AutoSavePeriod, AutoSavePeriod);                
            
        }

        public void Dispose()
        {
            Wrapped.PropertyChanged -= wrappedProperties_PropertyChanged;
            DisposableHelper.SafeDispose(m_saveTimer);
            
            // Save it
            Save();
        }

        #endregion
        
        #region Methods

        /// <summary>
        /// Saves the properties to disk.
        /// </summary>
        public override bool Save()
        {
            if (m_isDirty)
            {
                lock (m_saveLock)
                {
                    if (m_isDirty)
                    {
                        try
                        {
                            using (var stream = System.IO.File.OpenWrite(m_filename))
                            {
                                using (XmlSerializerWriter writer = new XmlSerializerWriter(stream))
                                {
                                    m_isDirty = false;
                                    Wrapped.WriteToXml(writer);
                                }
                            }
                        }
                        catch (Exception)
                        {
                            return false;
                        }
                    }
                }
            }
            return true;
        }

        #endregion

        #region Event Handlers

        private void TimerCallback(object arg)
        {
            Save();
        }

        void wrappedProperties_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            m_isDirty = true;
        }

        #endregion
    }
}