Frontend first draft

frontend/pshared/lib/provider/pfe/provider.dart

@@ -0,0 +1,51 @@
+import 'package:flutter/material.dart';
+
+import 'package:pshared/service/pfe/service.dart';
+import 'package:pshared/provider/exception.dart';
+import 'package:pshared/provider/resource.dart';
+import 'package:pshared/service/account.dart';
+
+
+class PfeProvider extends ChangeNotifier {
+  // The resource now wraps our Account? state along with its loading/error state.
+  Resource<String?> _resource = Resource(data: null);
+  Resource<String?> get resource => _resource;
+
+  String? get session => _resource.data;
+  bool get isLoggedIn => session != null;
+  bool get isLoading => _resource.isLoading;
+  Object? get error => _resource.error;
+
+  // Private helper to update the resource and notify listeners.
+  void _setResource(Resource<String?> newResource) {
+    _resource = newResource;
+    notifyListeners();
+  }
+
+
+  Future<String?> login({
+    required String email,
+    required String password,
+  }) async {
+    _setResource(_resource.copyWith(isLoading: true, error: null));
+    try {
+      final acc = await PfeService.login(email, password);
+      _setResource(Resource(data: acc, isLoading: false));
+      return acc;
+    } catch (e) {
+      _setResource(_resource.copyWith(isLoading: false, error: toException(e)));
+      rethrow;
+    }
+  }
+
+  Future<void> logout() async {
+    _setResource(_resource.copyWith(isLoading: true, error: null));
+    try {
+      await AccountService.logout();
+      _setResource(Resource(data: null, isLoading: false));
+    } catch (e) {
+      _setResource(_resource.copyWith(isLoading: false, error: toException(e)));
+      rethrow;
+    }
+  }
+}