2 files changed, 66 insertions, 28 deletions

diff --git a/lib/data.dart b/lib/data.dart
index 7d5f938..e4d7524 100644
--- a/lib/data.dart
+++ b/lib/data.dart
@@ -4,9 +4,8 @@ import 'dart:async';
 import 'package:flutter/foundation.dart';
 import 'package:mqtt_client/mqtt_client.dart';
 import 'package:mqtt_client/mqtt_server_client.dart';
-import 'package:path_provider/path_provider.dart';
-import 'package:sqlite3/sqlite3.dart';
-import 'package:path/path.dart' as p;
+
+import 'db.dart';
 
 const int brokerPort = 1883;
 const String topicPrefix = 'sia';
@@ -28,6 +27,8 @@ enum MachineEvent {
 }
 
 class AppState with ChangeNotifier {
+  final DB db = DB();
+
   static const Map<MachineState, Map<MachineEvent, MachineState>> machine = <MachineState, Map<MachineEvent, MachineState>> {
     MachineState.init: <MachineEvent, MachineState> {
       MachineEvent.connect: MachineState.disconnected,
@@ -56,33 +57,15 @@ class AppState with ChangeNotifier {
   String fqdn = '';
 
   AppState() {
-    loadPersistence();
+    unawaited(loadPersistence());
   }
 
-  void loadPersistence() async {
-    supportDir = await getApplicationSupportDirectory();
-    String dbPath = p.join(supportDir.path, 'main.sqlite3');
-
-    final Database db = sqlite3.open(dbPath);
-    try {
-      ResultSet result = db.select('PRAGMA user_version;');
-      final int version = result.first.values.first as int;
-      if (version != 0) {
-        return;  // DB schema version 0 required, no migrations implemented
-      }
-
-      result = db.select(
-        'SELECT value FROM key_value WHERE key = \'server_fqdn\';'
-      );
-      if (result.length == 1) {
-        fqdn = result[0]['value'];
-        notifyListeners();
-      }
-    } catch (e) {
-      return;
-    } finally {
-      db.close();
-    }
+  Future<void> loadPersistence() async {
+    await db.connect();
+    String? dbFqdn = await db.getServerFqdn();
+    if (dbFqdn == null) return;
+    fqdn = dbFqdn;
+    notifyListeners();
   }
 
   void setFqdn(String value) {
diff --git a/lib/db.dart b/lib/db.dart
new file mode 100644
index 0000000..8afd3eb
--- /dev/null
+++ b/lib/db.dart
@@ -0,0 +1,55 @@
+import 'dart:io';
+import 'dart:async';
+
+import 'package:path_provider/path_provider.dart';
+import 'package:sqlite3/sqlite3.dart';
+import 'package:path/path.dart' as p;
+
+class DB {
+  final Completer<Database?> _dbCompleter = Completer<Database?>();
+
+  Future<void> connect() async {
+    String path = await _getDbPath();
+    Database candidate = sqlite3.open(path);
+
+    int? userVersion = _getUserVersion(candidate);
+    if (userVersion == null || userVersion != 0) {
+      _dbCompleter.complete(null);
+      return;
+    }
+
+    _dbCompleter.complete(candidate);
+  }
+
+  void dispose() async {
+    if (_dbCompleter.isCompleted == false) {
+      return;
+    }
+    Database? db = await _dbCompleter.future;
+    if (db == null) return;
+    db.close();
+  }
+
+  static Future<String> _getDbPath() async {
+    Directory supportDir = await getApplicationSupportDirectory();
+    return p.join(supportDir.path, 'main.sqlite3');
+  }
+
+  static int? _getUserVersion(Database db) {
+    ResultSet result = db.select('PRAGMA user_version;');
+    if (result.length != 1) return null;
+    return result.first.values.first as int;
+  }
+
+  Future<String?> getServerFqdn() async {
+    Database? db = await _dbCompleter.future;
+    if (db == null) return null;
+
+    ResultSet result = db.select(
+      'SELECT value FROM key_value WHERE key = \'server_fqdn\';'
+    );
+    if (result.length != 1) return null;
+
+    return result[0]['value'];
+  }
+}