How Promotion Engine is called during Order flow

• Out of the box, OrderPrepareCmd calls PrepareOrderCmd which calls OrderCalculateCmd.
• OrderCalculateCmd is the interface and the implementation class is PromotionEngineOrderCalculateCmdImpl.
• PromotionEngineOrderCalculateCmdImpl is the command that invokes the promotion engine to apply the applicable promotions.
• PromotionCodeAddRemoveControllerCmd - Command use to add promocode to an order.

Mode details  

OrderPrepareCmdImpl
 For each order specified to prepare:

•     check whether the order is locked by others or not.
•     check the order status is in either of P,I,E,W,N.
•     If the order is generated from quote, check the quote's expire date. if quote is expired, reset the price flag.
•     Call ValidateShippingAdjustmentCmd command to validate shipping adjustment.
•     Call PrepareOrderCmd command to prepare the order.