basic file management for transactions

loc_chain_app/lib/util/transaction.dart

@@ -1,5 +0,0 @@
-import 'package:flutter/services.dart';
-import 'package:fast_rsa/model/bridge.pb.dart';
-import 'package:fast_rsa/rsa.dart';
-
-class Transaction {}

loc_chain_app/lib/util/transaction_manager.dart

@@ -0,0 +1,25 @@
+import 'package:fast_rsa/model/bridge.pb.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:sqflite/sqflite.dart';
+import 'package:fast_rsa/rsa.dart';
+
+import 'dart:io';
+
+class Transaction {
+  Transaction({required this.otherUserID}) {
+    SharedPreferences.getInstance().then((s) => _id = s.getString('id') ?? '0');
+  }
+  late final String _id;
+  final String otherUserID;
+  static Hash? makeTransactionHash() {}
+}
+
+class TransactionsDBManager {
+  static Future<Database> get _localFile async {
+    return openDatabase('transactions.db');
+  }
+
+  static Future<List<Transaction>?> readTransactions() async {}
+
+  static Future<void> writeKeyPair(KeyPair pair) async {}
+}