fix: Handle zero values appropriately for product position (#35)

* Fix product.position condition to handle zero values

* Since NSUInteger is a primitive type, there's no concept of "null"

* Add unit test for product.position = 0

---------

Co-authored-by: Nahuel Alan Grimaudo <[email protected]>

Author: nag-rokt

mParticle-Google-Analytics-Firebase-GA4/MPKitFirebaseGA4Analytics.m

@@ -536,7 +536,7 @@ - (NSMutableArray *)getParametersForProducts:(id)products {
         if (product.price) {
             [productParameters setObject:product.price forKey:kFIRParameterPrice];
         }
-        if (product.position) {
+        if (product.position >= 0) {
             id indexParameter = @(product.position);
             [productParameters setObject:indexParameter forKey:kFIRParameterIndex];
         }

mParticle-Google-Analytics-Firebase-GA4Tests/MPKitFirebaseGA4AnalyticsTests.m

@@ -312,6 +312,27 @@ - (void)testProductParameters {
     XCTAssertEqual([item count], 9);
 }
 
+- (void)testProductPositionEqualZero {
+    MPKitFirebaseGA4Analytics *exampleKit = [[MPKitFirebaseGA4Analytics alloc] init];
+    [exampleKit didFinishLaunchingWithConfiguration:@{}];
+    
+    MPProduct *product = [[MPProduct alloc] initWithName:@"expensivePotato" sku:@"SKU123" quantity:@1 price:@40.0];
+    NSMutableDictionary<NSString *, id> *testProductCustomAttributes = [[@{@"productCustomAttribute": @"potato", @"store": @"Target"} mutableCopy] mutableCopy];
+    product.brand = @"LV";
+    product.category = @"vegetable";
+    product.position = 0;
+    product.userDefinedAttributes = testProductCustomAttributes;
+    
+    MPCommerceEvent *event = [[MPCommerceEvent alloc] initWithImpressionName:@"suggested products list" product:product];
+    NSSet<MPProduct *> *impressionProducts = event.impressions[@"suggested products list"];
+    
+    NSArray *itemsArray = [exampleKit getParametersForProducts:impressionProducts];
+    id item = itemsArray[0];
+    
+    // The item inside itemsArray should include 9 parameters in total including the 2 product custom attributes
+    XCTAssertEqual([item count], 9);
+}
+
 - (void)testCommerceEventCheckoutOptions {
     MPKitFirebaseGA4Analytics *exampleKit = [[MPKitFirebaseGA4Analytics alloc] init];
     [exampleKit didFinishLaunchingWithConfiguration:@{}];