feat: frequent category list real data (#513)

Author: lucaantonelli

lib/pages/transactions/create_transaction/widgets/category_selector.dart

@@ -30,6 +30,9 @@ class _CategorySelectorState extends ConsumerState<CategorySelector> {
     final categoriesList = ref.watch(
       categoriesByTypeProvider(transactionType.categoryType),
     );
+    final frequentCategories = ref.watch(
+      frequentCategoriesProvider(transactionType.categoryType),
+    );
     final selectedCategory = ref.watch(selectedCategoryProvider);
 
     return Container(
@@ -71,7 +74,7 @@ class _CategorySelectorState extends ConsumerState<CategorySelector> {
                     color: Theme.of(context).colorScheme.surface,
                     height: 74,
                     width: double.infinity,
-                    child: categoriesList.when(
+                    child: frequentCategories.when(
                       data: (categories) => ListView.builder(
                         itemCount: categories.length, // to prevent range error
                         scrollDirection: Axis.horizontal,

lib/providers/categories_provider.dart

@@ -208,6 +208,20 @@ Future<List<CategoryTransaction>> subcategories(Ref ref, int categoryId) async {
   return categories;
 }
 
+@riverpod
+Future<List<CategoryTransaction>> frequentCategories(
+  Ref ref,
+  CategoryTransactionType? type,
+) async {
+  List<CategoryTransaction> categories = [];
+  if (type != null) {
+    categories = await ref
+        .read(categoryRepositoryProvider)
+        .selectFrequentCategories(type);
+  }
+  return categories;
+}
+
 @Riverpod(keepAlive: true)
 Future<Map<CategoryTransaction, double>> categoryMap(Ref ref) async {
   final categoryType = ref.watch(categoryTypeProvider);

lib/services/database/repositories/category_repository.dart

@@ -1,6 +1,7 @@
 import 'package:riverpod_annotation/riverpod_annotation.dart';
 
 import '../../../model/category_transaction.dart';
+import '../../../model/transaction.dart';
 import '../sossoldi_database.dart';
 
 part 'category_repository.g.dart';
@@ -112,6 +113,33 @@ class CategoryRepository {
     }
   }
 
+  Future<List<CategoryTransaction>> selectFrequentCategories(
+    CategoryTransactionType type,
+  ) async {
+    final db = await _sossoldiDB.database;
+    // Select the last 100 transactions, group by category and return the
+    // top 5 most used categories ordered by usage count desc.
+    final result = await db.rawQuery(
+      '''
+        SELECT c.*
+        FROM "$categoryTransactionTable" c
+        JOIN (
+          SELECT * FROM "$transactionTable"
+          WHERE "${TransactionFields.type}" = ?
+          ORDER BY "${TransactionFields.date}" DESC
+          LIMIT 100
+        ) t ON t."${TransactionFields.idCategory}" = c."${CategoryTransactionFields.id}"
+        WHERE c."${CategoryTransactionFields.type}" = ?
+        GROUP BY c."${CategoryTransactionFields.id}"
+        ORDER BY COUNT(t."${TransactionFields.id}") DESC
+        LIMIT 5
+      ''',
+      [type.transactionType.code, type.code],
+    );
+
+    return result.map((json) => CategoryTransaction.fromJson(json)).toList();
+  }
+
   Future<int> updateItem(CategoryTransaction item) async {
     final db = await _sossoldiDB.database;