public CommandStatus Handle(Increment cmd)
{
var e = new Incremented {
Name = cmd.Name
};
_es.Record(e);
return(new Success());
}
public Value.Result Handle(Value query)
{
return(new Value.Result {
Value = _es.Replay()
.Where(Filter)
.Select(Apply).Sum()
});
bool Filter(Event e) =>
e switch
{
Incremented i => i.Name == query.Name,
Decremented d => d.Name == query.Name
};
int Apply(Event e) =>
e switch
{
Incremented _ => 1,
Decremented _ => - 1
};
}
}