public async Task <AggregateApplicationResult> ApplyEventAsync(BaseEvent evt)
{
// Lets have a constraint for item Name uniqueness
ItemAggregate aggregate;
BaseItemEvent itemEvent;
switch (evt)
{
case ItemCreatedEvent created:
var itemsWithSameName = await aggregatesRepository.GetByNameAsync(created.Name);
if (itemsWithSameName.Any(x => x.LastEvent != null && !(x.LastEvent is ItemDeletedEvent)))
{
return(new ItemAlreadyExistsApplicationResult("Item with the same name already exists"));
}
aggregate = new ItemAggregate(created.ItemId);
itemEvent = created;
break;
case ItemDeletedEvent deleted:
aggregate = await aggregatesRepository.GetByIdAsync(deleted.ItemId);
if (aggregate == null || aggregate.LastEvent == null)
{
return(new ItemNotFoundApplicationResult());
}
if (aggregate.LastEvent is ItemDeletedEvent)
{
// It is already deleted
return(new SuccessAggregateApplicationResult());
}
itemEvent = deleted;
break;
case ItemUpdatedEvent updated:
aggregate = await aggregatesRepository.GetByIdAsync(updated.ItemId);
if (aggregate == null || aggregate.LastEvent == null || aggregate.LastEvent is ItemDeletedEvent)
{
return(new ItemNotFoundApplicationResult());
}
if (aggregate.LastEvent is ItemUpdatedEvent lastUpdated && lastUpdated.Name.Equals(updated.Name))
{
// This aggregate has already got this name
return(new SuccessAggregateApplicationResult());
}
// Looking for another aggregate with this name
var itemsWithSameNameForUpdate = await aggregatesRepository.GetByNameAsync(updated.Name);
if (itemsWithSameNameForUpdate.Any(x => x.LastEvent != null && !(x.LastEvent is ItemDeletedEvent)))
{
return(new ItemAlreadyExistsApplicationResult("Item with the same name already exists"));
}
itemEvent = updated;
break;
default:
return(new FailedAggregateApplicationResult($"Specified event type {evt.GetType().Name} is not supported"));
}
var applicationResult = aggregate.ApplyEvent(itemEvent);
switch (applicationResult)
{
case SuccessAggregateApplicationResult success:
// This method might be a root specific, because of several aggregate repositories might be impacted by one event
this.stagedAggregates.Add(aggregate);
break;
}
return(applicationResult);
}