feat: alphabet list, change Layout etc

lib/database/stock_queries.dart

@@ -21,6 +21,7 @@ class ProductNotFoundException implements Exception {
 /// Atomic stock updates shared by the product and tab services, so they can
 /// run inside either one's transaction.
 extension StockQueries on AppDatabase {
+  /// Products with infinite stock are only checked for existence.
   Future<void> decreaseStock(String productId, int amount) async {
     _validateStockAmount(amount);
 
@@ -28,6 +29,7 @@ extension StockQueries on AppDatabase {
         await (update(products)..where(
               (row) =>
                   row.id.equals(productId) &
+                  row.infiniteStock.not() &
                   row.stockQuantity.isBiggerOrEqualValue(amount),
             ))
             .write(
@@ -38,28 +40,34 @@ extension StockQueries on AppDatabase {
 
     if (updatedRows == 1) return;
 
-    final product = await (select(
-      products,
-    )..where((row) => row.id.equals(productId))).getSingleOrNull();
-
-    if (product == null) throw ProductNotFoundException(productId);
-
-    throw const InsufficientStockException();
+    final product = await _findProduct(productId);
+    if (!product.infiniteStock) throw const InsufficientStockException();
   }
 
   Future<void> increaseStock(String productId, int amount) async {
     _validateStockAmount(amount);
 
     final updatedRows =
-        await (update(
-          products,
-        )..where((row) => row.id.equals(productId))).write(
-          ProductsCompanion.custom(
-            stockQuantity: products.stockQuantity + Variable(amount),
-          ),
-        );
+        await (update(products)..where(
+              (row) => row.id.equals(productId) & row.infiniteStock.not(),
+            ))
+            .write(
+              ProductsCompanion.custom(
+                stockQuantity: products.stockQuantity + Variable(amount),
+              ),
+            );
 
-    if (updatedRows != 1) throw ProductNotFoundException(productId);
+    if (updatedRows != 1) await _findProduct(productId);
+  }
+
+  Future<ProductRow> _findProduct(String productId) async {
+    final product = await (select(
+      products,
+    )..where((row) => row.id.equals(productId))).getSingleOrNull();
+
+    if (product == null) throw ProductNotFoundException(productId);
+
+    return product;
   }
 
   void _validateStockAmount(int amount) {