using Avalonia.Threading;

using MeWeb.Shared;

namespace MeWeb.App.Services;

public static class ErrorLog
{
  const long MaxBytes = 256 * 1024;
  static string FilePath => Path.Combine(AppServices.Folder, "errors.log");
  static readonly Lock Gate = new();

  public static void Watch()
  {
    Dispatcher.UIThread.UnhandledException += OnDispatcher;
    TaskScheduler.UnobservedTaskException += OnUnobserved;
    AppDomain.CurrentDomain.UnhandledException += OnDomain;
  }

  public static void Write(Exception error)
  {
    if (error is null) return;
    lock (Gate)
    {
      try
      {
        Directory.CreateDirectory(Path.GetDirectoryName(FilePath));
        if (File.Exists(FilePath) && new FileInfo(FilePath).Length > MaxBytes) File.Delete(FilePath);
        File.AppendAllText(FilePath, $"{DateTimeOffset.UtcNow:O} me-web? {BuildInfo.Version}{Environment.NewLine}{error}{Environment.NewLine}{Environment.NewLine}");
      }
      catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
      {
      }
    }
  }

  static void OnDispatcher(object sender, DispatcherUnhandledExceptionEventArgs e)
  {
    Write(e.Exception);
    e.Handled = true;
  }

  static void OnUnobserved(object sender, UnobservedTaskExceptionEventArgs e)
  {
    Write(e.Exception);
    e.SetObserved();
  }

  static void OnDomain(object sender, UnhandledExceptionEventArgs e) => Write(e.ExceptionObject as Exception);
}