Frontend WIP - just websocket support left

frontend/lib/providers/auth.dart

@@ -1,12 +1,60 @@
+import 'package:jwt_decoder/jwt_decoder.dart';
+import 'package:logging/logging.dart';
 import 'package:riverpod_annotation/riverpod_annotation.dart';
 import 'package:shared_models/jwt.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
 part 'auth.g.dart';
 
+final logger = Logger('provider/auth');
+
 @riverpod
 class JwtNotifier extends _$JwtNotifier {
   @override
-  JWTBody? build() {
-    return null;
+  Future<JWTBody?> build() async {
+    if (!await SharedPreferencesAsync().containsKey('jwt')) {
+      logger.fine('No JWT saved to client');
+      return null;
+    }
+    final jwtString = await SharedPreferencesAsync().getString('jwt');
+    if (jwtString == null) {
+      logger.fine('Saved JWT came back null, removing key');
+      SharedPreferencesAsync().remove('jwt');
+      return null;
+    }
+
+    final payload = JwtDecoder.tryDecode(jwtString);
+    if (payload == null) {
+      logger.fine('Failed to decode JWT, removing key.');
+      SharedPreferencesAsync().remove('jwt');
+      return null;
+    }
+
+    try {
+      final body = JWTBody.fromJson(payload);
+      return body;
+    } catch (e) {
+      logger.shout('Failed to parse JWT payload to JWTBody, something is wrong:', e, StackTrace.current);
+      return null;
+    }
+  }
+
+  Future<void> setJwt(String jwt) async {
+    final payload = JwtDecoder.tryDecode(jwt);
+    if (payload == null) {
+      logger.info('Tried to set JWT token that did not decode to payload');
+      state = AsyncValue.error('JWT set to invalid token', StackTrace.current);
+      return;
+    }
+
+    logger.fine('Saving jwt token to shared prefs');
+    await SharedPreferencesAsync().setString('jwt', jwt);
+
+    try {
+      final jwtBody = JWTBody.fromJson(payload);
+      state = AsyncValue.data(jwtBody);
+    } catch (e) {
+      state = AsyncError(e, StackTrace.current);
+    }
   }
 }