Finish creating payment/add handler

handlers/payment.go

@@ -109,7 +109,9 @@ func PaymentAdd(c *gin.Context) {
 		return
 	}
 	deletableIfRollback = append(deletableIfRollback, payment)
+	var substractFromCard uint64 = 0
 	for _, uItemBought := range updates.Items {
+		var totalCost uint64 = 0
 		// Creating item and adding it to rollback if itemID is set to 0
 		if uItemBought.ItemID == 0 {
 			newItem := &db.Item{
@@ -133,12 +135,13 @@ func PaymentAdd(c *gin.Context) {
 				return
 			}
 			deletableIfRollback = append(deletableIfRollback, newItem)
+			totalCost = newItem.Price * uint64(uItemBought.Quantity)
 			newItemBought := &db.ItemBought{
 				ItemID:      newItem.ID,
 				PaymentID:   payment.ID,
 				TypeID:      uItemBought.TypeID,
 				Quantity:    uItemBought.Quantity,
-				TotalCost:   newItem.Price * uint64(uItemBought.Quantity),
+				TotalCost:   totalCost,
 				MetricType:  uItemBought.MetricType,
 				MetricValue: uItemBought.MetricValue,
 			}
@@ -155,8 +158,73 @@ func PaymentAdd(c *gin.Context) {
 			deletableIfRollback = append(deletableIfRollback, newItemBought)
 			newItemBought.Item = newItem
 		} else {
-			// TODO: check if Item has same userID and potentially update Item
+			dbItem := &db.Item{}
+			if err := dbc.Find(dbItem, uItemBought.ItemID).Error; err != nil {
+				c.JSON(500, types.ErrorResponse{Message: err.Error()})
+				weNeedRollback = true
+				return
 			}
+			if dbItem.UserID != userID {
+				c.JSON(500, types.ErrorResponse{Message: "ItemID is not your"})
+				weNeedRollback = true
+				return
+			}
+			if dbItem.Price != uItemBought.Price {
+				dbItem.Price = uItemBought.Price
+				if err := dbc.Save(dbItem).Error; err != nil {
+					c.JSON(500, types.ErrorResponse{Message: err.Error()})
+					weNeedRollback = true
+					return
+				}
+			}
+			totalCost = dbItem.Price * uint64(uItemBought.Quantity)
+			newItemBought := &db.ItemBought{
+				ItemID:      dbItem.ID,
+				PaymentID:   payment.ID,
+				TypeID:      uItemBought.TypeID,
+				Quantity:    uItemBought.Quantity,
+				TotalCost:   totalCost,
+				MetricType:  uItemBought.MetricType,
+				MetricValue: uItemBought.MetricValue,
+			}
+			if err := dbc.Create(newItemBought).Error; err != nil {
+				c.JSON(500, types.ErrorResponse{Message: err.Error()})
+				weNeedRollback = true
+				return
+			}
+			if newItemBought.ID == 0 {
+				c.JSON(500, types.ErrorResponse{Message: "Internal error: ERR.P.A.4"})
+				weNeedRollback = true
+				return
+			}
+			deletableIfRollback = append(deletableIfRollback, newItemBought)
+			newItemBought.Item = dbItem
+		}
+		// As totalCost is calculated either way AND db.Item.BeforeSave have db.Item.Price check
+		//  we can gently assume that totalCost != 0
+		substractFromCard += totalCost
+	}
+
+	// Checks for db.Card.UserID != db.Payment.UserID for payment is done in db.Payment hooks
+	card := &db.Card{}
+	if err := dbc.Find(card, payment.CardID).Error; err != nil {
+		c.JSON(500, types.ErrorResponse{Message: err.Error()})
+		weNeedRollback = true
+		return
+	}
+	// TODO: Examine if that would be better to calculate substractFromCard
+	//  BEFORE update.Items loop and therefore this check can be done before
+	//  processing payment's ItemBought entities
+	if card.Balance < substractFromCard {
+		c.JSON(500, types.ErrorResponse{Message: fmt.Sprintf("Card %s (%s) has Balance lower than overall Payment cost. Rollback.", card.Name, card.LastDigits)})
+		weNeedRollback = true
+		return
+	}
+	card.Balance -= substractFromCard
+	if err := dbc.Save(card).Error; err != nil {
+		c.JSON(500, types.ErrorResponse{Message: err.Error()})
+		weNeedRollback = true
+		return
 	}
 
 	c.JSON(200, types.Message{Info: fmt.Sprintf("Entity with %d ID is created successfully!", payment.ID)})