/// <summary>
/// Verifies that the command precondition has been met.
/// </summary>
private async Task <bool> PreconditionHasBeenMet(IScheduledCommand scheduledCommand)
{
return(await etagChecker.IsPreconditionSatisfied(scheduledCommand));
}
private async Task ApplyScheduledCommand(
IStore <TAggregate> store,
IScheduledCommand <TAggregate> scheduled)
{
TAggregate aggregate = null;
Exception exception;
try
{
if (!await etagChecker.IsPreconditionSatisfied(scheduled))
{
await FailScheduledCommand(store,
scheduled,
new PreconditionNotMetException(scheduled.DeliveryPrecondition));
return;
}
aggregate = await store.Get(scheduled.TargetId);
var isConstructorCommand = scheduled.Command is ConstructorCommand <TAggregate>;
if (aggregate == null)
{
if (isConstructorCommand)
{
var ctor = typeof(TAggregate).GetConstructor(new[] { scheduled.Command.GetType() });
if (ctor == null)
{
throw new InvalidOperationException($"No constructor was found on type {typeof(TAggregate)} for constructor command {scheduled.Command}.");
}
aggregate = (TAggregate)ctor.Invoke(new[] { scheduled.Command });
}
else
{
throw new PreconditionNotMetException(
$"No {typeof(TAggregate).Name} was found with id {scheduled.TargetId} so the command could not be applied.");
}
}
else if (isConstructorCommand)
{
throw new ConcurrencyException($"Command target having id {scheduled.TargetId} already exists");
}
else
{
await aggregate.ApplyAsync(scheduled.Command);
}
await store.Put(aggregate);
scheduled.Result = new CommandSucceeded(scheduled);
return;
}
catch (Exception ex)
{
exception = ex;
}
await FailScheduledCommand(store, scheduled, exception, aggregate);
}