3 files changed, 20 insertions, 12 deletions
diff --git a/app/controllers/api/carts_controller.rb b/app/controllers/api/carts_controller.rb
index c33f76e..0e14c17 100644
--- a/app/controllers/api/carts_controller.rb
+++ b/app/controllers/api/carts_controller.rb
@@ -10,24 +10,21 @@ module Api
     end
 
     def create
-      product_cart = @cart.product_carts.new(product_id: permitted_params[:product_id],
-                                             quantity: permitted_params[:quantity])
+      product_cart = @cart.add_product(permitted_params[:product_id], permitted_params[:quantity])
 
-      if product_cart.save
+      if product_cart.errors.empty?
         render json: serialized_object.serializable_hash, status: :ok
       else
-        render json: { errors: product_cart.as_json }, status: :unprocessable_entity
+        render json: { errors: product_cart.errors.as_json }, status: :unprocessable_entity
       end
     end
 
     def destroy
-      product = @cart.product_carts.products.find_by(public_id: params[:id])
-
-      render status: :not_found and return if product.nil?
-
-      @cart.product_carts.find_by(cart_id: @cart.id, product_id: product.id).destroy
-
-      render status: :no_content
+      if @cart.delete_product(product.id)
+        render status: :no_content
+      else
+        render status: :not_found
+      end
     end
 
     private
diff --git a/app/models/cart.rb b/app/models/cart.rb
index 996d107..b08fc13 100644
--- a/app/models/cart.rb
+++ b/app/models/cart.rb
@@ -9,7 +9,9 @@ class Cart < ApplicationRecord
   def delete_product(product_id)
     relation = product_carts.find_by(product_id:, cart_id:)
 
-    relation&.destroy
+    return false if relation.nil?
+
+    relation.destroy and return true
   end
 
   def add_product(product_id, quantity)
diff --git a/app/models/product_cart.rb b/app/models/product_cart.rb
index 10d4a4c..eb9cf9f 100644
--- a/app/models/product_cart.rb
+++ b/app/models/product_cart.rb
@@ -5,4 +5,13 @@
 class ProductCart < ApplicationRecord
   belongs_to :cart
   belongs_to :product
+
+  validates :quantity, presence: true, comparison: { greater_than: 0 }
+  validate :sole_product_in_cart
+
+  def sole_product_in_cart
+    return if cart.products.find_by(id: product_id).nil?
+
+    errors.add(:product_id, "cart already has product with id #{product_id}")
+  end
 end