feat: compelete bal pending screen

lib/data/repositories/bal_repository.dart

@@ -50,6 +50,22 @@ class BalRepository {
     }
   }
 
+  bool isABalOngoing() {
+    return _bals?.where((bal) => bal.state == BalState.ongoing).isNotEmpty ??
+        false;
+  }
+
+  Future<Result<Bal>> startBal(int id) async {
+    if (isABalOngoing()) {
+      return Result.error(
+        Exception("Cannot have multiple BAL ongoing at the same time !"),
+      );
+    }
+    final result = await _apiClient.startBal(id);
+    _getBalsNoCache();
+    return result;
+  }
+
   Future<Result<Bal>> editBal(
     int id,
     String name,
@@ -57,13 +73,13 @@ class BalRepository {
     DateTime end,
   ) async {
     final result = await _apiClient.editBal(id, name, start, end);
-    _getBalsNoCache();
+    await _getBalsNoCache();
     return result;
   }
 
   Future<Result<void>> addBal(String name, DateTime start, DateTime end) async {
     final result = await _apiClient.addBal(name, start, end);
-    _getBalsNoCache();
+    await _getBalsNoCache();
     return result;
   }
 }

lib/data/services/api_client.dart

@@ -42,6 +42,33 @@ class ApiClient {
  * =================
 */
 
+  Future<Result<Bal>> startBal(int id) async {
+    final client = Client();
+    try {
+      final headers = await _getHeaders();
+      final response = await client.post(
+        Uri.parse("https://$apiBasePath/bal/${id.toString()}/start"),
+        headers: headers,
+      );
+      if (response.statusCode == 200) {
+        final json = jsonDecode(response.body);
+        return Result.ok(Bal.fromJSON(json));
+      } else if (response.statusCode == 403) {
+        throw "You don't own the specified BAL";
+      } else if (response.statusCode == 404) {
+        throw "No BAL with specified ID found";
+      } else if (response.statusCode == 409) {
+        throw "Cannot have multiple BAl ongoing at the same time!";
+      } else {
+        throw "Unknown error";
+      }
+    } catch (e) {
+      return Result.error(Exception(e));
+    } finally {
+      client.close();
+    }
+  }
+
   Future<Result<Bal>> editBal(
     int id,
     String name,

lib/ui/bal_page/view_model/bal_view_model.dart

@@ -15,6 +15,22 @@ class BalViewModel extends ChangeNotifier {
   Bal? _bal;
   int? id;
   Bal? get bal => _bal;
+  bool isABalOngoing = false;
+
+  Future<Result<void>> startBal(int id) async {
+    if (isABalOngoing) {
+      return Result.error(Exception("Cannot have multiple BALs ongoing !"));
+    }
+    final result = await _balRepository.startBal(id);
+    switch (result) {
+      case Ok():
+        _bal = result.value;
+        notifyListeners();
+        break;
+      default:
+    }
+    return result;
+  }
 
   Future<Result<void>> editBal(
     int id,
@@ -46,6 +62,7 @@ class BalViewModel extends ChangeNotifier {
   bool isLoaded = false;
 
   Future<Result<void>> _load() async {
+    isABalOngoing = _balRepository.isABalOngoing();
     final result1 = await _loadBal();
     switch (result1) {
       case Ok():

lib/ui/bal_page/widget/pending/bal_pending_screen.dart

@@ -12,6 +12,7 @@ class BalPendingScreen extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final theme = Theme.of(context);
     return Scaffold(
       bottomNavigationBar: AppNavigationBar(startIndex: 0),
       appBar: AppBar(
@@ -31,7 +32,15 @@ class BalPendingScreen extends StatelessWidget {
       ),
       body: Center(
         child: ElevatedButton(
-          onPressed: () {},
+          onPressed: viewModel.isABalOngoing
+              ? () {
+                  ScaffoldMessenger.of(context).showSnackBar(
+                    SnackBar(content: Text("Une BAL est déjà en cours.")),
+                  );
+                }
+              : () {
+                  viewModel.startBal(viewModel.bal!.id);
+                },
           child: Text("Démarrer cette BAL"),
         ),
       ),