feat: add payment card grouping and analysis

lib/utils/subscription_grouping_helper.dart

@@ -0,0 +1,155 @@
+import 'package:flutter/material.dart';
+
+import '../l10n/app_localizations.dart';
+import '../models/payment_card_model.dart';
+import '../models/subscription_model.dart';
+import '../providers/category_provider.dart';
+import '../providers/payment_card_provider.dart';
+import 'subscription_category_helper.dart';
+
+enum SubscriptionGroupingMode { category, paymentCard }
+
+class SubscriptionGroupData {
+  final String id;
+  final String title;
+  final List<SubscriptionModel> subscriptions;
+  final SubscriptionGroupingMode mode;
+  final PaymentCardModel? paymentCard;
+  final bool isUnassignedCard;
+  final String? categoryKey;
+  final String? subtitle;
+
+  const SubscriptionGroupData({
+    required this.id,
+    required this.title,
+    required this.subscriptions,
+    required this.mode,
+    this.paymentCard,
+    this.isUnassignedCard = false,
+    this.categoryKey,
+    this.subtitle,
+  });
+}
+
+class SubscriptionGroupingHelper {
+  static const _unassignedCardKey = '__unassigned__';
+
+  static List<SubscriptionGroupData> buildGroups({
+    required BuildContext context,
+    required List<SubscriptionModel> subscriptions,
+    required SubscriptionGroupingMode mode,
+    required CategoryProvider categoryProvider,
+    required PaymentCardProvider paymentCardProvider,
+  }) {
+    if (mode == SubscriptionGroupingMode.paymentCard) {
+      return _groupByPaymentCard(
+        context: context,
+        subscriptions: subscriptions,
+        paymentCardProvider: paymentCardProvider,
+      );
+    }
+
+    return _groupByCategory(
+      context: context,
+      subscriptions: subscriptions,
+      categoryProvider: categoryProvider,
+    );
+  }
+
+  static List<SubscriptionGroupData> _groupByCategory({
+    required BuildContext context,
+    required List<SubscriptionModel> subscriptions,
+    required CategoryProvider categoryProvider,
+  }) {
+    final localizedMap = SubscriptionCategoryHelper.categorizeSubscriptions(
+        subscriptions, categoryProvider, context);
+
+    final orderMap = <String, int>{};
+    for (var i = 0; i < categoryProvider.categories.length; i++) {
+      orderMap[categoryProvider.categories[i].name] = i;
+    }
+
+    final groups = localizedMap.entries.map((entry) {
+      final title =
+          categoryProvider.getLocalizedCategoryName(context, entry.key);
+      return SubscriptionGroupData(
+        id: entry.key,
+        title: title,
+        subscriptions: entry.value,
+        mode: SubscriptionGroupingMode.category,
+        categoryKey: entry.key,
+      );
+    }).toList();
+
+    groups.sort((a, b) {
+      final ai = orderMap[a.categoryKey] ?? 999;
+      final bi = orderMap[b.categoryKey] ?? 999;
+      if (ai != bi) {
+        return ai.compareTo(bi);
+      }
+      return a.title.compareTo(b.title);
+    });
+
+    return groups;
+  }
+
+  static List<SubscriptionGroupData> _groupByPaymentCard({
+    required BuildContext context,
+    required List<SubscriptionModel> subscriptions,
+    required PaymentCardProvider paymentCardProvider,
+  }) {
+    final map = <String, List<SubscriptionModel>>{};
+
+    for (final sub in subscriptions) {
+      final key = sub.paymentCardId ?? _unassignedCardKey;
+      map.putIfAbsent(key, () => []).add(sub);
+    }
+
+    final loc = AppLocalizations.of(context);
+    final groups = <SubscriptionGroupData>[];
+
+    map.forEach((key, subs) {
+      if (key == _unassignedCardKey) {
+        groups.add(
+          SubscriptionGroupData(
+            id: key,
+            title: loc.paymentCardUnassigned,
+            subtitle: loc.paymentCardUnassigned,
+            subscriptions: subs,
+            mode: SubscriptionGroupingMode.paymentCard,
+            isUnassignedCard: true,
+          ),
+        );
+      } else {
+        final card = paymentCardProvider.getCardById(key);
+        final title = card?.issuerName ?? loc.paymentCardUnassigned;
+        final subtitle =
+            card != null ? '****${card.last4}' : loc.paymentCardUnassigned;
+        groups.add(
+          SubscriptionGroupData(
+            id: key,
+            title: title,
+            subtitle: subtitle,
+            subscriptions: subs,
+            mode: SubscriptionGroupingMode.paymentCard,
+            paymentCard: card,
+          ),
+        );
+      }
+    });
+
+    groups.sort((a, b) {
+      if (a.isUnassignedCard != b.isUnassignedCard) {
+        return a.isUnassignedCard ? 1 : -1;
+      }
+      final aDefault = a.paymentCard?.isDefault ?? false;
+      final bDefault = b.paymentCard?.isDefault ?? false;
+      if (aDefault != bDefault) {
+        return aDefault ? -1 : 1;
+      }
+      return a.title.toLowerCase().compareTo(b.title.toLowerCase());
+    });
+
+    return groups;
+  }
+}