using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.ExceptionServices;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Threading;
using Tango.Logging;

namespace Tango.Logging
{
    /// <summary>
    /// Represents an optimized WPF global exception trapper.
    /// </summary>
    /// <seealso cref="Tango.Logging.IGlobalExceptionTrapper" />
    public class WpfGlobalExceptionTrapper : IGlobalExceptionTrapper
    {
        private DateTime _lastGlobalExceptionTime = DateTime.Now.AddMinutes(-1);
        private Application _app;

        /// <summary>
        /// Occurs when the global exception trapper has detected an unhandled exception.
        /// </summary>
        public event EventHandler<ApplicationCrashedEventArgs> ApplicationCrashed;

        /// <summary>
        /// Initializes the specified application.
        /// </summary>
        /// <param name="app">The application.</param>
        public void Initialize(Application app)
        {
            _app = app;
            AppDomain.CurrentDomain.UnhandledException += CurrentDomain_UnhandledException;
            app.Dispatcher.UnhandledException += Dispatcher_UnhandledException;
            Application.Current.DispatcherUnhandledException += Current_DispatcherUnhandledException;
            TaskScheduler.UnobservedTaskException += TaskScheduler_UnobservedTaskException;
        }

        /// <summary>
        /// Use only when need to simulate application crash!
        /// </summary>
        public void Disable()
        {
            AppDomain.CurrentDomain.UnhandledException -= CurrentDomain_UnhandledException;
            _app.Dispatcher.UnhandledException -= Dispatcher_UnhandledException;
            Application.Current.DispatcherUnhandledException -= Current_DispatcherUnhandledException;
            TaskScheduler.UnobservedTaskException -= TaskScheduler_UnobservedTaskException;
        }

        /// <summary>
        /// Handles the UnobservedTaskException event of the TaskScheduler control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="UnobservedTaskExceptionEventArgs"/> instance containing the event data.</param>
        private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
        {
            e.SetObserved();
            OnApplicationCrash(e.Exception);
        }

        /// <summary>
        /// Handles the DispatcherUnhandledException event of the Current control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="System.Windows.Threading.DispatcherUnhandledExceptionEventArgs"/> instance containing the event data.</param>
        private void Current_DispatcherUnhandledException(object sender, System.Windows.Threading.DispatcherUnhandledExceptionEventArgs e)
        {
            e.Handled = OnApplicationCrash(e.Exception);
        }

        /// <summary>
        /// Handles the UnhandledException event of the Dispatcher control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="System.Windows.Threading.DispatcherUnhandledExceptionEventArgs"/> instance containing the event data.</param>
        private void Dispatcher_UnhandledException(object sender, System.Windows.Threading.DispatcherUnhandledExceptionEventArgs e)
        {
            e.Handled = OnApplicationCrash(e.Exception);
        }

        /// <summary>
        /// Handles the UnhandledException event of the CurrentDomain control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="UnhandledExceptionEventArgs"/> instance containing the event data.</param>
        private void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
        {
            OnApplicationCrash(new Exception(e.ExceptionObject.ToStringSafe()));
        }

        /// <summary>
        /// Called when any unhandled application exception has occurred and write to log.
        /// </summary>
        /// <param name="error">The error.</param>
        private bool OnApplicationCrash(Exception exception)
        {
            if (DateTime.Now < _lastGlobalExceptionTime.AddSeconds(1))
            {
                _lastGlobalExceptionTime = DateTime.Now;
                return true;
            }

            _lastGlobalExceptionTime = DateTime.Now;

            ApplicationCrashedEventArgs e = new ApplicationCrashedEventArgs(exception);

            ApplicationCrashed?.Invoke(this, e);

            return e.TryRecover;
        }

        public Task<MessageLogItem> GetLastApplicationCrashEventLog(int maxMinutes = 10)
        {
            return Task.Factory.StartNew<MessageLogItem>(() =>
            {
                MessageLogItem logItem = null;

                try
                {
                    var applicationEvents = new EventLog("Application");
                    var events = applicationEvents.Entries.Cast<EventLogEntry>().Where(x => x.EntryType == EventLogEntryType.Error && x.Source == ".NET Runtime" && x.TimeWritten > DateTime.Now.AddMinutes(-maxMinutes)).OrderByDescending(x => x.TimeWritten).ToList();

                    Regex reg = new Regex("Application: (.+)");

                    foreach (var ev in events)
                    {
                        Match match = reg.Match(ev.Message);
                        if (match.Groups.Count > 1)
                        {
                            String exeName = match.Groups[1].Value;
                            String assemblyName = Path.GetFileNameWithoutExtension(exeName);

                            if (assemblyName == Assembly.GetEntryAssembly().GetName().Name)
                            {
                                logItem = new MessageLogItem();
                                logItem.Message = "Application terminated unexpectedly in the previous run!\n";
                                logItem.Message += "This crash report was retrieved from the windows event logs.\n";
                                logItem.Message += "---------------------------------------------------------------------------\n\n";
                                logItem.Message += ev.Message;
                                logItem.TimeStamp = DateTime.Now;
                                logItem.Category = LogCategory.Critical;
                                break;
                            }
                        }
                    }
                }
                catch { }

                return logItem;
            });
        }
    }
}