From 4263997c3e419ef1cf7447d447c5582a322acf74 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Fri, 20 Jul 2018 18:14:18 +0200
Subject: Began basic login screen feature (mvp architecture)

---
 lib/auth.dart | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 lib/auth.dart

(limited to 'lib/auth.dart')

diff --git a/lib/auth.dart b/lib/auth.dart
new file mode 100644
index 0000000..6ee8a0b
--- /dev/null
+++ b/lib/auth.dart
@@ -0,0 +1,43 @@
+import 'package:beam_messenger/data/database_helper.dart';
+
+enum AuthState { LOGGED_IN, LOGGED_OUT }
+
+abstract class AuthStateListener {
+  void onAuthStateChanged(AuthState state);
+}
+
+// A naive implementation of Observer/Subscriber Pattern. Will do for now.
+class AuthStateProvider {
+  static final AuthStateProvider _instance = new AuthStateProvider.internal();
+
+  List<AuthStateListener> _subscribers;
+
+  factory AuthStateProvider() => _instance;
+  AuthStateProvider.internal() {
+    _subscribers = new List<AuthStateListener>();
+    initState();
+  }
+
+  void initState() async {
+    var db = new DatabaseHelper();
+    var isLoggedIn = await db.isLoggedIn();
+    if (isLoggedIn)
+      notify(AuthState.LOGGED_IN);
+    else
+      notify(AuthState.LOGGED_OUT);
+  }
+
+  void subscribe(AuthStateListener listener) {
+    _subscribers.add(listener);
+  }
+
+  void dispose(AuthStateListener listener) {
+    for (var l in _subscribers) {
+      if (l == listener) _subscribers.remove(l);
+    }
+  }
+
+  void notify(AuthState state) {
+    _subscribers.forEach((AuthStateListener s) => s.onAuthStateChanged(state));
+  }
+}
-- 
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