Handle and notify users of invalid account settings file

Source/AudibleUtilities/AudibleApiStorage.cs

@@ -5,19 +5,58 @@ using Newtonsoft.Json;
 
 namespace AudibleUtilities
 {
+	public class AccountSettingsLoadErrorEventArgs : ErrorEventArgs
+	{
+		/// <summary>
+		/// Create a new, empty <see cref="AccountsSettings"/> file if true, otherwise throw
+		/// </summary>
+		public bool Handled { get; set; }
+		/// <summary>
+		/// The file path of the AccountsSettings.json file
+		/// </summary>
+		public string SettingsFilePath { get; }
+
+		public AccountSettingsLoadErrorEventArgs(string path, Exception exception)
+			: base(exception)
+		{
+			SettingsFilePath = path;
+		}
+	}
+
 	public static class AudibleApiStorage
 	{
 		public static string AccountsSettingsFile => Path.Combine(Configuration.Instance.LibationFiles, "AccountsSettings.json");
 
+		public static event EventHandler<AccountSettingsLoadErrorEventArgs> LoadError;
+
 		public static void EnsureAccountsSettingsFileExists()
 		{
 			// saves. BEWARE: this will overwrite an existing file
 			if (!File.Exists(AccountsSettingsFile))
-				_ = new AccountsSettingsPersister(new AccountsSettings(), AccountsSettingsFile);
+			{
+				//Save the JSON file manually so that AccountsSettingsPersister.Saving and AccountsSettingsPersister.Saved
+				//are not fired. There's no need to fire those events on an empty AccountsSettings file.
+				var accountSerializerSettings = AudibleApi.Authorization.Identity.GetJsonSerializerSettings();
+				File.WriteAllText(AccountsSettingsFile, JsonConvert.SerializeObject(new AccountsSettings(), Formatting.Indented, accountSerializerSettings));
+			}
 		}
 
 		/// <summary>If you use this, be a good citizen and DISPOSE of it</summary>
-		public static AccountsSettingsPersister GetAccountsSettingsPersister() => new AccountsSettingsPersister(AccountsSettingsFile);
+		public static AccountsSettingsPersister GetAccountsSettingsPersister()
+		{
+			try
+			{
+				return new AccountsSettingsPersister(AccountsSettingsFile);
+			}
+			catch (Exception ex)
+			{
+				var args = new AccountSettingsLoadErrorEventArgs(AccountsSettingsFile, ex);
+				LoadError?.Invoke(null, args);
+				if (args.Handled)
+					return GetAccountsSettingsPersister();
+				throw;
+			}
+		}
 
 		public static string GetIdentityTokensJsonPath(this Account account)
 			=> GetIdentityTokensJsonPath(account.AccountId, account.Locale?.Name);

Source/FileManager/FileUtility.cs

@@ -157,7 +157,7 @@ namespace FileManager
 		/// <param name="extension">File extension override to use for <paramref name="destination"/></param>
 		/// <param name="overwrite">If <c>false</c> and <paramref name="destination"/> exists, append " (n)" to filename and try again.</param>
 		/// <returns>The actual destination filename</returns>
-		public static string SaferMoveToValidPath(
+		public static LongPath SaferMoveToValidPath(
 			LongPath source,
 			LongPath destination,
 			ReplacementCharacters replacements,

Source/LibationAvalonia/Views/MainWindow.axaml.cs

@@ -1,6 +1,9 @@
+using AudibleUtilities;
 using Avalonia.Input;
 using Avalonia.ReactiveUI;
+using Avalonia.Threading;
 using DataLayer;
+using FileManager;
 using LibationAvalonia.ViewModels;
 using LibationFileManager;
 using LibationUiBase.GridView;
@@ -18,6 +21,7 @@ namespace LibationAvalonia.Views
 		{
 			DataContext = new MainVM(this);
 
+			AudibleApiStorage.LoadError += AudibleApiStorage_LoadError;
 			InitializeComponent();
 			Configure_Upgrade();
 
@@ -34,6 +38,62 @@ namespace LibationAvalonia.Views
 			}
 		}
 
+		private void AudibleApiStorage_LoadError(object sender, AccountSettingsLoadErrorEventArgs e)
+		{
+			try
+			{
+				//Backup AccountSettings.json and create a new, empty file.
+				var backupFile =
+					FileUtility.SaferMoveToValidPath(
+						e.SettingsFilePath,
+						e.SettingsFilePath,
+						ReplacementCharacters.Barebones,
+						"bak");
+				AudibleApiStorage.EnsureAccountsSettingsFileExists();
+				e.Handled = true;
+
+				showAccountSettingsRecoveredMessage(backupFile);
+			}
+			catch
+			{
+				showAccountSettingsUnrecoveredMessage();
+			}
+
+			async void showAccountSettingsRecoveredMessage(LongPath backupFile)
+			=> await MessageBox.Show(this, $"""
+				Libation could not load your account settings, so it had created a new, empty account settings file.
+
+				You will need to re-add you Audible account(s) before scanning or downloading.
+
+				The old account settings file has been archived at '{backupFile.PathWithoutPrefix}'
+
+				{e.GetException().ToString()}
+				""",
+				"Error Loading Account Settings",
+				MessageBoxButtons.OK,
+				MessageBoxIcon.Warning);
+
+			void showAccountSettingsUnrecoveredMessage()
+			{
+				var messageBoxWindow = MessageBox.Show(this, $"""
+				Libation could not load your account settings. The file may be corrupted, but Libation is unable to delete it.
+
+				Please move or delete the account settings file '{e.SettingsFilePath}'
+
+				{e.GetException().ToString()}
+				""",
+				"Error Loading Account Settings",
+				MessageBoxButtons.OK);
+
+				//Force the message box to show synchronously because we're not handling the exception
+				//and libation will crash after the event handler returns
+				var frame = new DispatcherFrame();
+				_ = messageBoxWindow.ContinueWith(static (_, s) => ((DispatcherFrame)s).Continue = false, frame);
+				Dispatcher.UIThread.PushFrame(frame);
+				messageBoxWindow.GetAwaiter().GetResult();
+			}
+		}
+
 		private async void MainWindow_Opened(object sender, EventArgs e)
 		{
 			if (Configuration.Instance.FirstLaunch)

Source/LibationWinForms/Form1._NonUI.cs

@@ -1,10 +1,8 @@
-using System;
+using System.Windows.Forms;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 using ApplicationServices;
+using AudibleUtilities;
 using Dinah.Core.WindowsDesktop.Drawing;
+using FileManager;
 using LibationFileManager;
 using LibationUiBase;
 
@@ -14,6 +12,8 @@ namespace LibationWinForms
     {
         private void Configure_NonUI()
 		{
+			AudibleApiStorage.LoadError += AudibleApiStorage_LoadError;
+
 			// init default/placeholder cover art
 			var format = System.Drawing.Imaging.ImageFormat.Jpeg;
             PictureStorage.SetDefaultImage(PictureSize._80x80, Properties.Resources.default_cover_80x80.ToBytes(format));
@@ -36,5 +36,54 @@ namespace LibationWinForms
                     beginBookBackupsToolStripMenuItem_Click();
             };
 		}
+
+		private void AudibleApiStorage_LoadError(object sender, AccountSettingsLoadErrorEventArgs e)
+		{
+			try
+			{
+				//Backup AccountSettings.json and create a new, empty file.
+				var backupFile = 
+					FileUtility.SaferMoveToValidPath(
+						e.SettingsFilePath,
+						e.SettingsFilePath,
+						ReplacementCharacters.Barebones,
+						"bak");
+
+				AudibleApiStorage.EnsureAccountsSettingsFileExists();
+				e.Handled = true;
+
+				showAccountSettingsRecoveredMessage(backupFile);
+			}
+			catch
+			{
+				showAccountSettingsUnrecoveredMessage();
+			}
+
+			void showAccountSettingsRecoveredMessage(LongPath backupFile)
+			=> MessageBox.Show(this, $"""
+				Libation could not load your account settings, so it had created a new, empty account settings file.
+
+				You will need to re-add you Audible account(s) before scanning or downloading.
+
+				The old account settings file has been archived at '{backupFile.PathWithoutPrefix}'
+
+				{e.GetException().ToString()}
+				""",
+				"Error Loading Account Settings",
+				MessageBoxButtons.OK,
+				MessageBoxIcon.Warning);
+
+			void showAccountSettingsUnrecoveredMessage()
+			=> MessageBox.Show(this, $"""
+				Libation could not load your account settings. The file may be corrupted, but Libation is unable to delete it.
+
+				Please move or delete the account settings file '{e.SettingsFilePath}'
+
+				{e.GetException().ToString()}
+				""",
+				"Error Loading Account Settings",
+				MessageBoxButtons.OK,
+				MessageBoxIcon.Error);
+		}
 	}
 }