Introduce class DB

This centralises database related code in one class.

1 files changed, 55 insertions, 0 deletions

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'];
+  }
+}