// Some of the commands should only be applied once per product or once per purchase etc.
// Putting this logic into business rule matchers would violate SRP, since each business rule matcher should take
// care only of a particular case for particular command, not for particular command as a whole.
// We need another layer taking care of removing duplicate commands. Multiple approaches can be taken here,
// for this Kata purpose I'm using a simple approach with comparer.
// This method serves as an extension point and can easily be altered later to include more complex rules and checks.
private IPurchaseProcessingCommand[] FilterCommands(PurchaseBusinessRulesProcessingContext context)
{
IPurchaseProcessingCommand[] filteredCommands = context.Commands.ToArray();
IReadOnlyCollection <IPurchaseProcessingCommandComparer> comparers = _commandComparerRepository.GetRuleComparers();
foreach (IPurchaseProcessingCommandComparer comparer in comparers)
{
filteredCommands = comparer.Filter(filteredCommands);
}
return(filteredCommands);
}
public PurchaseCommandSet ProcessPurchase(Purchase purchase)
{
PurchaseBusinessRulesProcessingContext context = new PurchaseBusinessRulesProcessingContext(purchase);
IReadOnlyCollection <IBusinessRuleMatcher> ruleMatchers = _businessRuleMatcherRepository.GetRuleMatchers();
CreateCommands(ruleMatchers, context);
var filteredCommands = FilterCommands(context);
PurchaseCommandSet ret = new PurchaseCommandSet(filteredCommands, purchase);
return(ret);
}
public IPurchaseProcessingCommand[] MatchPurchaseCommands(PurchaseBusinessRulesProcessingContext context)
{
IEnumerable <Product> products = context.Purchase.Products.Where(p => p.ProductName.DefaultEquals(ProductNameToSearchFor));
if (!products.Any())
{
return(new IPurchaseProcessingCommand[0]);
}
// Only one per purchase.
return(new IPurchaseProcessingCommand[] { new AddFreeProductToPurchaseCommand(context.Purchase, GetFreeProduct()), });
}
public IPurchaseProcessingCommand[] MatchPurchaseCommands(PurchaseBusinessRulesProcessingContext context)
{
Product[] productsWithComission = context.Purchase.Products
.Where(p => _evaluator.IsBook(p) || _evaluator.IsPhysical(p))
.ToArray();
if (!productsWithComission.Any())
{
return(new IPurchaseProcessingCommand[0]);
}
Payment payment = CalculateAgentsComissionPayment(productsWithComission);
InitiatePaymentCommand paymentCommand = new InitiatePaymentCommand(context.Purchase, payment);
return(new IPurchaseProcessingCommand[] { paymentCommand });
}
public IPurchaseProcessingCommand[] MatchPurchaseCommands(PurchaseBusinessRulesProcessingContext context)
{
IPurchaseProcessingCommand[] ret = context.Purchase.Products.Where(p => _evaluator.IsBook(p))
.Select(p => new CreateDuplicatePackingSlipCommand(context.Purchase, p)).ToArray();
return(ret);
}
private static void CreateCommands(IReadOnlyCollection <IBusinessRuleMatcher> ruleMatchers, PurchaseBusinessRulesProcessingContext context)
{
foreach (IBusinessRuleMatcher matcher in ruleMatchers)
{
IPurchaseProcessingCommand[] commands = matcher.MatchPurchaseCommands(context);
context.AddCommands(commands);
}
}
public IPurchaseProcessingCommand[] MatchPurchaseCommands(PurchaseBusinessRulesProcessingContext context)
{
IPurchaseProcessingCommand[] ret = context.Purchase.Products.Where(p => _evaluator.IsMembershipActivation(p))
.Select(p => new ActivateMembershipCommand(context.Purchase, p)).ToArray();
return(ret);
}
public IPurchaseProcessingCommand[] MatchPurchaseCommands(PurchaseBusinessRulesProcessingContext context)
{
IPurchaseProcessingCommand[] ret = context.Purchase.Products.Where(p => _evaluator.IsMembershipUpgrade(p))
.Select(p => new MembershipChangeEmailNotificationCommand(context.Purchase, p)).ToArray();
return(ret);
}
