firka: show weighted avg when adding ghost grades

firka/lib/ui/components/common_bottom_sheets.dart

@@ -1051,18 +1051,6 @@ class _GradeCalculatorSheetContentState
   int weightPercent = 100;
   final List<(int grade, int weight)> entries = [];
 
-  double get _weightedAverage {
-    if (entries.isEmpty) return 0;
-    double sum = 0;
-    double weightTotal = 0;
-    for (final e in entries) {
-      final w = e.$2 / 100.0;
-      weightTotal += w;
-      sum += e.$1 * w;
-    }
-    return weightTotal > 0 ? sum / weightTotal : 0;
-  }
-
   @override
   Widget build(BuildContext context) {
     return Column(

firka/lib/ui/phone/pages/home/home_grades_subject.dart

@@ -1,3 +1,4 @@
+import 'package:firka/ui/phone/widgets/grade_summary_bar.dart';
 import 'package:kreta_api/kreta_api.dart';
 import 'package:firka/core/extensions.dart';
 import 'package:firka/ui/components/common_bottom_sheets.dart';
@@ -312,6 +313,12 @@ class _HomeGradesSubjectScreen extends FirkaState<HomeGradesSubjectScreen> {
                     GradeChartWithInteraction(
                       grades: _gradesWithGhosts(aGrade.subject),
                     ),
+                    SizedBox(height: 2),
+                    GradeSummaryBar(
+                      grades: _gradesWithGhosts(aGrade.subject),
+                      l10n: widget.data.l10n,
+                      showAverage: ghostGradeWidgets.isNotEmpty,
+                    ),
                     SizedBox(height: 12),
                     Padding(
                       padding: EdgeInsets.only(left: 4),

firka/lib/ui/phone/widgets/grade_summary_bar.dart

@@ -1,3 +1,4 @@
+import 'package:firka/core/average_helper.dart';
 import 'package:kreta_api/kreta_api.dart';
 import 'package:firka/ui/components/grade.dart';
 import 'package:firka/ui/components/grade_helpers.dart';
@@ -11,8 +12,14 @@ import 'package:firka/ui/theme/style.dart';
 class GradeSummaryBar extends StatefulWidget {
   final List<Grade> grades;
   final AppLocalizations l10n;
+  final bool showAverage;
 
-  const GradeSummaryBar({super.key, required this.grades, required this.l10n});
+  const GradeSummaryBar({
+    super.key,
+    required this.grades,
+    required this.l10n,
+    this.showAverage = false,
+  });
 
   @override
   State<GradeSummaryBar> createState() => _GradeSummaryBarState();
@@ -32,6 +39,9 @@ class _GradeSummaryBarState extends State<GradeSummaryBar> {
       appStyle.colors.grade5,
     ];
     final totalCounted = countsByGrade.reduce((a, b) => a + b);
+    final averageText = widget.showAverage
+        ? calculateAverage(widget.grades).toStringAsFixed(2)
+        : '';
 
     return Card(
       shadowColor: Colors.transparent,
@@ -49,7 +59,9 @@ class _GradeSummaryBarState extends State<GradeSummaryBar> {
               Row(
                 children: [
                   Text(
-                    widget.l10n.gradesCount(total),
+                    widget.showAverage
+                        ? '${widget.l10n.gradesCount(total)} ($averageText)'
+                        : widget.l10n.gradesCount(total),
                     style: appStyle.fonts.B_16SB.apply(
                       color: appStyle.colors.textPrimary,
                     ),