App: Add option to restore database when a DB error occurs at startup

Elwig/App.xaml.cs

@@ -93,11 +93,15 @@ namespace Elwig {
 
             try {
                 await AppDbUpdater.CheckDb();
+            } catch (FileNotFoundException exc) {
+                InteractionService.ShowException("Datenbank nicht gefunden", "Die Datenbank konnte nicht gefunden werden", exc);
             } catch (Exception exc) {
                 if (Config.UpdateUrl != null && Utils.HasInternetConnectivity()) {
                     await CheckForUpdates();
                 }
-                InteractionService.ShowException("Fehlerhafte Datenbank", "Fehlerhafte Datenbank", exc);
+                InteractionService.ShowException("Fehlerhafte Datenbank", "Schwerwiegender Fehler in der Datenbank, unbedingt den Programmierern melden!", exc);
+                if (InteractionService.AskQuestion("Backup wiederherstellen", "Soll die Datenbank aus einem Backup wiederhergestellt werden?\n\nAchtung: Das kann zu Datenverlust führen!", false))
+                    await BackupService.RestoreDatabase();
                 Shutdown();
                 return;
             }
@@ -112,7 +116,9 @@ namespace Elwig {
                 try {
                     Client = new(ctx);
                 } catch (Exception exc) {
-                    InteractionService.ShowException("Fehler", "Fehler beim Laden der Mandantendaten", exc);
+                    InteractionService.ShowException("Fehler", "Fehler beim Laden der Mandantendaten, unbedingt den Programmierern melden!", exc);
+                    if (InteractionService.AskQuestion("Backup wiederherstellen", "Soll die Datenbank aus einem Backup wiederhergestellt werden?\n\nAchtung: Das kann zu Datenverlust führen!", false))
+                        await BackupService.RestoreDatabase();
                     Shutdown();
                     return;
                 }

Elwig/Helpers/AppDbUpdater.cs

@@ -14,10 +14,17 @@ namespace Elwig.Helpers {
         private static int VersionOffset = 0;
 
         public static async Task<Version> CheckDb() {
+            if (!File.Exists(App.Config.DatabaseFile))
+                throw new FileNotFoundException($"Die Datei \"{App.Config.DatabaseFile}\" exisitiert nicht");
+
             long? applId, schemaVers;
             using (var cnx = await AppDbContext.ConnectAsync()) {
+
+                await cnx.QuickCheck();
+
                 applId = (long?)await cnx.ExecuteScalar("PRAGMA application_id") ?? 0;
-                if (applId != 0x454C5747) throw new Exception($"Invalid application_id in database (0x{applId:X08})");
+                if (applId != 0x454C5747)
+                    throw new FileFormatException($"Invalid application_id in database (0x{applId:X08})");
 
                 schemaVers = (long?)await cnx.ExecuteScalar("PRAGMA schema_version") ?? 0;
                 VersionOffset = (int)(schemaVers % 100);
@@ -76,16 +83,16 @@ namespace Elwig.Helpers {
             try {
                 using var cnx = await AppDbContext.ConnectAsync();
                 await cnx.ExecuteBatch("PRAGMA locking_mode = EXCLUSIVE");
+
+                await cnx.IntegrityCheck();
+                await cnx.ForeignKeyCheck();
+
                 foreach (var script in toExecute) {
                     await cnx.ExecuteEmbeddedScript(asm, script);
                 }
 
-                var violations = await cnx.ForeignKeyCheck();
-                if (violations.Length > 0) {
-                    throw new Exception($"Foreign key violations ({violations.Length}):\n" + string.Join("\n", violations
-                        .Take(50)
-                        .Select(v => $"{v.Table} - {v.RowId} - {v.Parent} - {v.FkId}")));
-                }
+                await cnx.IntegrityCheck();
+                await cnx.ForeignKeyCheck();
 
                 await cnx.ExecuteBatch("VACUUM");
                 await cnx.ExecuteBatch($"PRAGMA schema_version = {toVersion * 100 + VersionOffset}");

Elwig/Helpers/Extensions.cs

@@ -135,11 +135,39 @@ namespace Elwig.Helpers {
             return await cmd.ExecuteScalarAsync();
         }
 
-        public static async Task<(string Table, long RowId, string Parent, long FkId)[]> ForeignKeyCheck(this SqliteConnection cnx) {
+        public static async Task QuickCheck(this SqliteConnection cnx) {
+            using var cmd = cnx.CreateCommand();
+            cmd.CommandText = "PRAGMA quick_check";
+            using var reader = await cmd.ExecuteReaderAsync();
+            var list = new List<string>();
+            while (await reader.ReadAsync()) {
+                list.Add(reader.GetString(0));
+            }
+
+            if (list.Count != 1 || list[0] != "ok") {
+                throw new FileFormatException($"Integrity problems ({list.Count}):\n" + string.Join("\n", list.Take(50)));
+            }
+        }
+
+        public static async Task IntegrityCheck(this SqliteConnection cnx) {
+            using var cmd = cnx.CreateCommand();
+            cmd.CommandText = "PRAGMA integrity_check";
+            using var reader = await cmd.ExecuteReaderAsync();
+            var list = new List<string>();
+            while (await reader.ReadAsync()) {
+                list.Add(reader.GetString(0));
+            }
+
+            if (list.Count != 1 || list[0] != "ok") {
+                throw new FileFormatException($"Integrity problems ({list.Count}):\n" + string.Join("\n", list.Take(50)));
+            }
+        }
+
+        public static async Task ForeignKeyCheck(this SqliteConnection cnx) {
             using var cmd = cnx.CreateCommand();
             cmd.CommandText = "PRAGMA foreign_key_check";
             using var reader = await cmd.ExecuteReaderAsync();
-            var list = new List<(string, long, string, long)>();
+            var list = new List<(string Table, long RowId, string Parent, long FkId)>();
             while (await reader.ReadAsync()) {
                 var table = reader.GetString(0);
                 var rowid = reader.GetInt64(1);
@@ -147,7 +175,11 @@ namespace Elwig.Helpers {
                 var fkid = reader.GetInt64(3);
                 list.Add((table, rowid, parent, fkid));
             }
-            return [.. list];
+
+            if (list.Count > 0) {
+                throw new InvalidDataException($"Foreign key violations ({list.Count}):\n" + string.Join("\n", list.Take(50)
+                    .Select(v => $"{v.Table} - {v.RowId} - {v.Parent} - {v.FkId}")));
+            }
         }
 
         public static IEnumerable<T> Join<T>(this IEnumerable<T> src, Func<T> separatorFactory) {

Elwig/Services/BackupService.cs

@@ -1,11 +1,13 @@
 using Elwig.Helpers;
 using Elwig.Helpers.Export;
+using Microsoft.Win32;
 using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
+using System.Windows.Input;
 
 namespace Elwig.Services {
     public static class BackupService {
@@ -106,5 +108,26 @@ namespace Elwig.Services {
                 } catch { }
             }
         }
+
+        public static async Task RestoreDatabase() {
+            try {
+                var d = new OpenFileDialog() {
+                    Title = "Datenbank wiederherstellen - Elwig",
+                    DefaultDirectory = App.Config.BackupPath,
+                    InitialDirectory = App.Config.BackupPath,
+                    DefaultExt = "sql.zip",
+                    Filter = "SQLite-Datenbank (*.sqlite3, *.sqlite3.zip, *.sql, *.sql.zip)|*.sqlite3;*.sqlite3.zip;*.sql;*.sql.zip",
+                };
+                if (d.ShowDialog() == true) {
+                    if (!InteractionService.AskContinue("Datenbank wiederherstellen", "Soll die Datenbank wirklich unwiederruflich durch die wiederhergestellte Version ersetzt werden?"))
+                        return;
+                    Mouse.OverrideCursor = Cursors.Wait;
+                    await App.ReplaceDatabase(d.FileName);
+                }
+            } catch (Exception exc) {
+                InteractionService.ShowException(exc);
+            }
+            Mouse.OverrideCursor = null;
+        }
     }
 }

Elwig/Windows/MainWindow.xaml.cs

@@ -182,24 +182,7 @@ namespace Elwig.Windows {
         }
 
         private async void Menu_Database_Restore_Click(object sender, RoutedEventArgs evt) {
-            try {
-                var d = new OpenFileDialog() {
-                    Title = "Datenbank wiederherstellen - Elwig",
-                    DefaultDirectory = App.Config.BackupPath,
-                    InitialDirectory = App.Config.BackupPath,
-                    DefaultExt = "sql.zip",
-                    Filter = "SQLite-Datenbank (*.sqlite3, *.sqlite3.zip, *.sql, *.sql.zip)|*.sqlite3;*.sqlite3.zip;*.sql;*.sql.zip",
-                };
-                if (d.ShowDialog() == true) {
-                    if (!InteractionService.AskContinue("Datenbank wiederherstellen", "Soll die Datenbank wirklich unwiederruflich durch die wiederhergestellte Version ersetzt werden?"))
-                        return;
-                    Mouse.OverrideCursor = Cursors.Wait;
-                    await App.ReplaceDatabase(d.FileName);
-                }
-            } catch (Exception exc) {
-                InteractionService.ShowException(exc);
-            }
-            Mouse.OverrideCursor = null;
+            await BackupService.RestoreDatabase();
         }
 
         private async void SyncButton_Click(object sender, RoutedEventArgs evt) {