using Microsoft.Win32;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Data.Entity.Validation;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Tango.Core.Commands;
using Tango.DAL.Local.DB;
using Tango.BL.Entities;
using Tango.DAL.Remote.DB;
using Tango.Logging;
using Tango.MachineStudio.Common.Notifications;
using Tango.MachineStudio.Common.StudioApplication;
using Tango.MachineStudio.Synchronization.Navigation;
using Tango.Settings;
using Tango.SharedUI;
using Tango.Synchronization;
using Tango.Synchronization.Local;
using Tango.Synchronization.Remote;
using Microsoft.Practices.ServiceLocation;

namespace Tango.MachineStudio.Synchronization.ViewModels
{
    /// <summary>
    /// Represents the 'Semi Remote Synchronization' view model.
    /// </summary>
    /// <seealso cref="Tango.SharedUI.ViewModel" />
    /// <seealso cref="Tango.MachineStudio.Common.StudioApplication.IShutdownRequestBlocker" />
    public class RemoteSynchronizationViewVM : ViewModel, IShutdownRequestBlocker
    {
        private SyncNavigationManager _navigation;
        private String _slaveDBFile;
        private INotificationProvider _notification;
        private bool _isWorking;
        private RemoteDBComparer _comparer;
        private RemoteDB _remoteDB;
        private LocalDB _localDB;
        private MainViewVM _mainView;

        #region Constructors

        /// <summary>
        /// Initializes a new instance of the <see cref="LocalSynchronizationViewVM"/> class.
        /// </summary>
        /// <param name="navigation">The navigation.</param>
        /// <param name="notification">The notification.</param>
        public RemoteSynchronizationViewVM(SyncNavigationManager navigation, INotificationProvider notification)
        {
            _navigation = navigation;
            _notification = notification;

            BackCommand = new RelayCommand(() => _navigation.NavigateTo(NavigationView.MenuView));

            Differences = new ObservableCollection<Diff>();

            BrowseSlaveDBCommand = new RelayCommand(BrowseSlaveDB, (x) => !_isWorking);
            CompareCommand = new RelayCommand(Compare, (x) => SlaveDBFile != null && !_isWorking && SelectedMachine != null);
            CommitCommand = new RelayCommand(Commit, (x) => SelectedDifference != null && !_isWorking && SelectedMachine != null);
            CommitAllCommand = new RelayCommand(CommitAll, (x) => Differences.Count > 0 && !_isWorking && SelectedMachine != null);
            CleanCommand = new RelayCommand(CleanSlave, (x) => !_isWorking && SlaveDBFile != null);

            if (File.Exists(SettingsManager.Default.MachineStudio.SynchronizationModule.RemoteSQLiteFile))
            {
                SlaveDBFile = SettingsManager.Default.MachineStudio.SynchronizationModule.RemoteSQLiteFile;
                SlaveDBName = Path.GetFileName(SlaveDBFile);
            }
        }

        #endregion

        #region Commands

        /// <summary>
        /// Gets or sets the back command.
        /// </summary>
        public RelayCommand BackCommand { get; set; }

        /// <summary>
        /// Gets or sets the browse master database command.
        /// </summary>
        public RelayCommand BrowseMasterDBCommand { get; set; }

        /// <summary>
        /// Gets or sets the browse slave database command.
        /// </summary>
        public RelayCommand BrowseSlaveDBCommand { get; set; }

        /// <summary>
        /// Gets or sets the compare command.
        /// </summary>
        public RelayCommand CompareCommand { get; set; }

        /// <summary>
        /// Gets or sets the commit command.
        /// </summary>
        public RelayCommand CommitCommand { get; set; }

        /// <summary>
        /// Gets or sets the commit all command.
        /// </summary>
        public RelayCommand CommitAllCommand { get; set; }

        /// <summary>
        /// Gets or sets the clean command.
        /// </summary>
        public RelayCommand CleanCommand { get; set; }

        #endregion

        #region Event Handlers

        private void Comparer_Progress(object sender, string e)
        {
            if (_mainView == null)
            {
                _mainView = ServiceLocator.Current.GetInstance<MainViewVM>();
                _mainView.Log = String.Empty;
            }

            _mainView.Log += ("[" + DateTime.Now.ToTimeString() + "]  " + e + Environment.NewLine);
        }

        #endregion

        #region Properties

        private ObservableCollection<Diff> _differences;
        /// <summary>
        /// Gets or sets the differences.
        /// </summary>
        public ObservableCollection<Diff> Differences
        {
            get { return _differences; }
            set { _differences = value; RaisePropertyChanged(nameof(Differences)); }
        }

        private Diff _selectedDifference;
        /// <summary>
        /// Gets or sets the selected difference.
        /// </summary>
        public Diff SelectedDifference
        {
            get { return _selectedDifference; }
            set { _selectedDifference = value; RaisePropertyChanged(nameof(SelectedDifference)); InvalidateRelayCommands(); }
        }

        private String _slaveDBName;
        /// <summary>
        /// Gets or sets the name of the slave database.
        /// </summary>
        public String SlaveDBName
        {
            get { return _slaveDBName; }
            set { _slaveDBName = value; RaisePropertyChanged(nameof(SlaveDBName)); }
        }

        private Machine _selectedMachine;
        /// <summary>
        /// Gets or sets the selected machine.
        /// </summary>
        public Machine SelectedMachine
        {
            get { return _selectedMachine; }
            set { _selectedMachine = value; RaisePropertyChangedAuto(); InvalidateRelayCommands(); }
        }

        /// <summary>
        /// Gets or sets the slave database file.
        /// </summary>
        public String SlaveDBFile
        {
            get { return _slaveDBFile; }
            set { _slaveDBFile = value; RaisePropertyChangedAuto(); }
        }
        #endregion

        #region Private Methods

        /// <summary>
        /// Cleans the slave database file.
        /// </summary>
        private async void CleanSlave()
        {
            if (_notification.ShowQuestion("Are you sure you want to erase all data on slave database?"))
            {
                using (_notification.PushTaskItem("Clearing database..."))
                {
                    try
                    {
                        _isWorking = true;
                        await Task.Factory.StartNew(() =>
                        {
                            SQLiteDataBase localDB = new SQLiteDataBase(SlaveDBFile);
                            localDB.LoadTables();
                            localDB.ClearDataBase();
                            try
                            {
                                localDB.Dispose();
                            }
                            catch{ }
                        });

                        Differences.Clear();
                    }
                    catch (Exception ex)
                    {
                        ShowError(LogManager.Log(ex).Message);
                    }
                    finally
                    {
                        _isWorking = false;
                        InvalidateRelayCommands();
                        SelectedDifference = null;
                    }
                }
            }
        }

        /// <summary>
        /// Compares the remote database with the selected database file.
        /// </summary>
        private void Compare()
        {
            Task.Factory.StartNew(() =>
            {
                using (_notification.PushTaskItem("Comparing Databases..."))
                {
                    try
                    {
                        if (_comparer != null)
                        {
                            _comparer.Dispose();
                        }

                        _remoteDB = RemoteDB.CreateDefault();
                        _localDB = new LocalDB(SlaveDBFile);
                        _comparer = new RemoteDBComparer(_remoteDB, _localDB, SelectedMachine.SerialNumber);
                        _comparer.Progress += Comparer_Progress;
                        _isWorking = true;
                        InvalidateRelayCommands();
                        Thread.Sleep(1500);
                        var diffs = _comparer.Compare();
                        Differences = new ObservableCollection<Diff>(diffs);

                        if (diffs.Where(x => x.Action != DiffAction.ReplaceTableDataInSlave).Count() > 0)
                        {
                            ShowInfo("Found " + Differences.Where(x => x.Action != DiffAction.ReplaceTableDataInSlave).Count() + " differences.");
                        }
                        else
                        {
                            ShowInfo("The master and slave databases are synchronized.");
                        }
                    }
                    catch (Exception ex)
                    {
                        ShowError(ex.Message);
                    }
                    finally
                    {
                        _isWorking = false;
                        SelectedDifference = null;
                        InvalidateRelayCommands();

                        SettingsManager.Default.MachineStudio.SynchronizationModule.RemoteSQLiteFile = SlaveDBFile;
                        SettingsManager.SaveDefaultSettings();
                    }
                }
            });
        }

        /// <summary>
        /// Commits the selected difference.
        /// </summary>
        private void Commit()
        {
            Task.Factory.StartNew(() =>
            {
                using (_notification.PushTaskItem("Committing difference..."))
                {
                    try
                    {
                        _isWorking = true;
                        InvalidateRelayCommands();
                        Thread.Sleep(1500);
                        SelectedDifference.Commit();
                        _remoteDB.SaveChanges();
                        _localDB.SaveChanges();

                        InvokeUINow(() => Differences.Remove(SelectedDifference));
                    }
                    catch (Exception ex)
                    {
                        ShowError(ex.Message);
                    }
                    finally
                    {
                        _isWorking = false;
                        SelectedDifference = null;
                        InvalidateRelayCommands();
                    }
                }
            });
        }

        /// <summary>
        /// Commits all the differences.
        /// </summary>
        private void CommitAll()
        {
            Task.Factory.StartNew(() =>
            {
                using (_notification.PushTaskItem("Committing all differences..."))
                {
                    try
                    {
                        _isWorking = true;
                        InvalidateRelayCommands();
                        Thread.Sleep(1500);

                        for (int i = 0; i < Differences.Count; i++)
                        {
                            var diff = Differences[i];
                            using (_notification.PushTaskItem("Committing difference " + (Differences.IndexOf(diff) + 1) + "..."))
                            {
                                diff.Commit();
                                InvokeUINow(() => Differences.Remove(diff));
                                i--;
                            }
                        }

                        _remoteDB.SaveChanges();
                        _localDB.SaveChanges();
                    }
                    catch (DbEntityValidationException ex)
                    {
                        String message = "The following validation errors occurred while trying to update the database." + Environment.NewLine + Environment.NewLine;

                        foreach (var error in ex.EntityValidationErrors.SelectMany(x => x.ValidationErrors).ToList())
                        {
                            message += error.ErrorMessage + Environment.NewLine;
                        }

                        ShowError(message);
                    }
                    catch (Exception ex)
                    {
                        ShowError(ex.Message);
                    }
                    finally
                    {
                        _isWorking = false;
                        SelectedDifference = null;
                        InvalidateRelayCommands();
                    }
                }
            });
        }

        /// <summary>
        /// Browse for slave database file.
        /// </summary>
        private void BrowseSlaveDB()
        {
            String file = BrowseForFilePath();
            if (file != null)
            {
                SlaveDBFile = file;
                SlaveDBName = Path.GetFileName(file);
                InvalidateRelayCommands();
            }
        }

        /// <summary>
        /// Browse for database file.
        /// </summary>
        private String BrowseForFilePath()
        {
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.Title = "Select SQLite Database File";
            dlg.Filter = "SQLite Database|*.db";
            if (dlg.ShowDialog().Value)
            {
                return dlg.FileName;
            }
            return null;
        }

        /// <summary>
        /// Displays an error message.
        /// </summary>
        /// <param name="message">The message.</param>
        private void ShowError(String message)
        {
            InvokeUINow(() => _notification.ShowError(message));
        }

        /// <summary>
        /// Displays an information message.
        /// </summary>
        /// <param name="message">The message.</param>
        private void ShowInfo(String message)
        {
            InvokeUINow(() => _notification.ShowInfo(message));
        }

        /// <summary>
        /// Called when the application is shutting down.
        /// </summary>
        /// <returns></returns>
        public Task<bool> OnShutdownRequest()
        {
            if (_comparer != null)
            {
                _comparer.Dispose();
            }
            return Task.FromResult(true);
        }

        #endregion
    }
}