public ReservationsProgram <int?> TryAccept(Reservation reservation)
{
return(ReservationsProgram
.IsReservationInFuture(reservation)
.SelectMany(isInFuture =>
{
if (!isInFuture)
{
return ReservationsProgram <int?> .Pure(null);
}
return ReservationsProgram
.ReadReservations(reservation.Date)
.SelectMany(reservations =>
{
var reservedSeats = reservations.Sum(r => r.Quantity);
if (Capacity < reservedSeats + reservation.Quantity)
{
return ReservationsProgram <int?> .Pure(null);
}
reservation.IsAccepted = true;
return ReservationsProgram
.Create(reservation)
.Select(x => new int?(x));
});
}));
}
public static T Interpret <T>(
this ReservationsProgram <T> program,
string connectionString)
{
return(program.Match(
pure: x => x,
free: i => i.Match(
isReservationInFuture: t =>
t.Item2(IsReservationInFuture(t.Item1))
.Interpret(connectionString),
readReservations: t =>
t.Item2(ReadReservations(t.Item1, connectionString))
.Interpret(connectionString),
create: t =>
t.Item2(Create(t.Item1, connectionString))
.Interpret(connectionString))));
}