Add variants selecting

cart-utils/src/main/java/ru/touchin/roboswag/cart_utils/models/CartModel.kt

@@ -20,7 +20,9 @@ abstract class CartModel<TProductModel : ProductModel> {
 
     fun getPriceWithPromocode(): Int = promocodeList
             .sortedByDescending { it.discount is PromocodeDiscount.ByPercent }
-            .fold(initial = totalPrice) { price, promo -> promo.discount.applyTo(price) }
+            .fold(initial = totalPrice) { price, promo ->
+                promo.discount.applyTo(price)
+            }
 
     abstract fun <TCart> copyWith(
             products: List<TProductModel> = this.products,

cart-utils/src/main/java/ru/touchin/roboswag/cart_utils/models/ProductModel.kt

@@ -8,11 +8,16 @@ abstract class ProductModel {
     abstract val isDeleted: Boolean
 
     open val bonuses: Int? = null
+
     open val variants: List<ProductModel> = emptyList()
+    open val selectedVariantId: Int? = null
+
+    val selectedVariant get() = variants.find { it.id == selectedVariantId }
 
     abstract fun <TProduct> copyWith(
             countInCart: Int = this.countInCart,
             isDeleted: Boolean = this.isDeleted,
+            selectedVariantId: Int? = this.selectedVariantId
     ): TProduct
 
     @Suppress("UNCHECKED_CAST")

cart-utils/src/main/java/ru/touchin/roboswag/cart_utils/repositories/LocalCartRepository.kt

@@ -64,6 +64,19 @@ class LocalCartRepository<TCart : CartModel<TProduct>, TProduct : ProductModel>(
         _currentCart.update { it.copyWith(usedBonuses = bonuses) }
     }
 
+    fun chooseVariant(productId: Int, variantId: Int?) {
+        updateCartProducts {
+            updateProduct(productId) {
+                if (variantId != null) {
+                    check(variants.any { it.id == variantId }) {
+                        "Product with id=$productId doesn't have variant with id=$variantId"
+                    }
+                }
+                copyWith(selectedVariantId = variantId)
+            }
+        }
+    }
+
     private fun updateCartProducts(updateAction: MutableList<TProduct>.() -> Unit) {
         _currentCart.update { cart ->
             cart.copyWith(products = cart.products.toMutableList().apply(updateAction))