Persist changes in web backend

moor/lib/moor_web.dart

@@ -5,6 +5,7 @@
 library moor_web;
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:html';
 import 'dart:indexed_db';
 import 'dart:js';
@@ -17,3 +18,4 @@ import 'moor.dart';
 export 'moor.dart';
 
 part 'src/web/sql_js.dart';
+part 'src/web/binary_string_conversion.dart';

moor/lib/src/web/binary_string_conversion.dart

@@ -0,0 +1,45 @@
+part of 'package:moor/moor_web.dart';
+/*
+const _bin2str = _BinaryStringConversion();
+
+class _BinaryStringConversion extends Encoding {
+  const _BinaryStringConversion();
+
+  @override
+  Converter<List<int>, String> get decoder => const _Bin2String();
+
+  @override
+  Converter<String, List<int>> get encoder => const _String2Bin();
+
+  @override
+  String get name => 'bin';
+}
+
+class _String2Bin extends Converter<String, Uint8List> {
+  const _String2Bin();
+
+  @override
+  Uint8List convert(String input) {
+    final codeUnits = input.codeUnits;
+    final list = Uint8List(codeUnits.length);
+
+    for (var i = 0; i < codeUnits.length; i++) {
+      list[i] = i;
+    }
+    return list;
+  }
+}
+
+class _Bin2String extends Converter<List<int>, String> {
+  const _Bin2String();
+
+  @override
+  String convert(List<int> input) {
+    final buffer = StringBuffer();
+    for (var byte in input) {
+      buffer.writeCharCode(byte);
+    }
+    return buffer.toString();
+  }
+}
+*/

moor/lib/src/web/sql_js.dart

@@ -79,8 +79,10 @@ class WebDatabase extends QueryExecutor {
     db.close();
 
     final sql = await _initializedWasm.future;
+    final restored = _restoreDb();
     // var db = new SQL.Database()
-    _database = JsObject(sql['Database'] as JsFunction);
+    _database = JsObject(sql['Database'] as JsFunction,
+        restored != null ? [restored] : const []);
     assert(() {
       // set the window.db variable to make debugging easier
       context['db'] = _database;
@@ -99,6 +101,24 @@ class WebDatabase extends QueryExecutor {
     }
   }
 
+  String get _persistenceKey => 'moor_db_str_$name';
+
+  // todo base64 works, but is very slow. Figure out why bin2str is broken
+
+  Uint8List _restoreDb() {
+    final raw = window.localStorage[_persistenceKey];
+    if (raw != null) {
+      return base64.decode(raw);
+    }
+    return null;
+  }
+
+  void _storeDb() {
+    final data = _database.callMethod('export') as Uint8List;
+    final binStr = base64.encode(data);
+    window.localStorage[_persistenceKey] = binStr;
+  }
+
   @override
   Future<void> runBatched(List<BatchedStatement> statements) {
     throw StateError(
@@ -141,21 +161,29 @@ class WebDatabase extends QueryExecutor {
   @override
   Future<int> runDelete(String statement, List args) {
     _runSimple(statement, args);
-    return Future.value(_getModifiedRows());
+    return _handlePotentialUpdate();
-  }
-
-  @override
-  Future<int> runInsert(String statement, List args) {
-    // todo get last insert id
-//    _runSimple("INSERT INTO todo_entries (content) VALUES ('test')", const []);
-    _runSimple(statement, args);
-    return Future.value(42);
   }
 
   @override
   Future<int> runUpdate(String statement, List args) {
     _runSimple(statement, args);
-    return Future.value(_getModifiedRows());
+    return _handlePotentialUpdate();
+  }
+
+  Future<int> _handlePotentialUpdate() {
+    final modified = _getModifiedRows();
+    if (modified > 0) {
+      _storeDb();
+    }
+    return Future.value(modified);
+  }
+
+  @override
+  Future<int> runInsert(String statement, List args) {
+    // todo get last insert id
+    _runSimple(statement, args);
+    _handlePotentialUpdate();
+    return Future.value(42);
   }
 
   @override