[Woo POS] Add new items to the top of the cart (#13802)

Author: staskus

WooCommerce/Classes/POS/Presentation/CartView.swift

@@ -95,9 +95,9 @@ struct CartView: View {
                     .coordinateSpace(name: Constants.scrollViewCoordinateSpaceIdentifier)
                     .onChange(of: cartViewModel.itemToScrollToWhenCartUpdated?.id) { _ in
                         if viewModel.orderStage == .building,
-                           let last = cartViewModel.itemToScrollToWhenCartUpdated?.id {
+                           let itemToScrollTo = cartViewModel.itemToScrollToWhenCartUpdated?.id {
                             withAnimation {
-                                proxy.scrollTo(last)
+                                proxy.scrollTo(itemToScrollTo)
                             }
                         }
                     }

WooCommerce/Classes/POS/ViewModels/CartViewModel.swift

@@ -45,7 +45,8 @@ final class CartViewModel: CartViewModelProtocol {
 
     func addItemToCart(_ item: POSItem) {
         let cartItem = CartItem(id: UUID(), item: item, quantity: 1)
-        itemsInCart.append(cartItem)
+        itemsInCart.insert(cartItem, at: 0)
+        itemToScrollToWhenCartUpdated = cartItem
 
         analytics.track(.pointOfSaleAddItemToCart)
     }
@@ -58,9 +59,7 @@ final class CartViewModel: CartViewModelProtocol {
         itemsInCart.removeAll()
     }
 
-    var itemToScrollToWhenCartUpdated: CartItem? {
-        return itemsInCart.last
-    }
+    var itemToScrollToWhenCartUpdated: CartItem?
 
     var itemsInCartLabel: String? {
         switch itemsInCart.count {

WooCommerce/WooCommerceTests/POS/ViewModels/CartViewModelTests.swift

@@ -43,7 +43,7 @@ final class CartViewModelTests: XCTestCase {
         sut.submitCart()
     }
 
-    func test_cart_when_addItemToCart_is_invoked_then_adds_item_to_cart() {
+    func test_addItemToCart_then_cart_is_not_empty() {
         // Given
         XCTAssertTrue(sut.itemsInCart.isEmpty, "Initial state")
         let item = Self.makeItem()
@@ -55,6 +55,19 @@ final class CartViewModelTests: XCTestCase {
         XCTAssertTrue(sut.itemsInCart.isNotEmpty)
     }
 
+    func test_addItemToCart_when_multiple_items_added_then_latest_item_is_first() {
+        // Given
+        XCTAssertTrue(sut.itemsInCart.isEmpty, "Initial state")
+        let items = [Self.makeItem(), Self.makeItem(), Self.makeItem()]
+
+        // When
+        items.forEach(sut.addItemToCart)
+
+        // Then
+        XCTAssertEqual(sut.itemsInCart.map(\.item.itemID), items.reversed().map(\.itemID))
+        XCTAssertNotEqual(sut.itemsInCart.map(\.item.itemID), items.map(\.itemID))
+    }
+
     func test_removeItemFromCart() {
         /* TODO:
          https://github.com/woocommerce/woocommerce-ios/issues/13209
@@ -71,15 +84,15 @@ final class CartViewModelTests: XCTestCase {
         sut.addItemToCart(item)
         sut.addItemToCart(anotherItem)
         XCTAssertEqual(sut.itemsInCart.count, 2)
-        XCTAssertEqual(sut.itemsInCart.map { $0.item.name }, [item, anotherItem].map { $0.name })
+        XCTAssertEqual(sut.itemsInCart.map { $0.item.name }, [anotherItem, item].map { $0.name })
 
         // When
         let firstCartItem = try XCTUnwrap(sut.itemsInCart.first)
         sut.removeItemFromCart(firstCartItem)
 
         // Then
         XCTAssertEqual(sut.itemsInCart.count, 1)
-        XCTAssertEqual(sut.itemsInCart.map { $0.item.name }, [anotherItem.name])
+        XCTAssertEqual(sut.itemsInCart.map { $0.item.name }, [item.name])
     }
 
     func test_cart_when_removeAllItemsFromCart_is_invoked_then_removes_all_items_from_cart() {