/* After this call is executed successfully, the occupied parking stand
* becomes Available,and the used runway is InOperation for the
* length of operation duration parameter and can't handle any other
* operations during this time. After operation finishes, the runway becomes
* Available again. The call is non-blocking, i.e. it returns before the
* runway is cleared. */
public PerformResult PerformTakeOff(TakeOffRequestToken token)
{
token.Stop();
token.Elapsed -= OnExpiredTakeOffToken;
if (DateTime.Now <= token.expiration && !token.hasExpired)
{
Runway runway = GetRunwayById(token.runwayId);
// Check if the runway exists and if it has been properly reserved
if (runway == null || runway.state != Runway.RunwayState.Reserved)
{
ReleaseTakeOffResources(token);
return(PerformResult.InvalidParameters);
}
runway.aircraftId = token.aircraftId;
runway.Elapsed += OnTakeOffOperationComplete;
ParkingStand parkingStand = GetParkingStandByAircraftId(token.aircraftId);
parkingStand.aircraftId = Guid.Empty;
parkingStand.state = ParkingStand.ParkingStandState.Available;
token.Dispose();
runway.Operate();
return(PerformResult.Success);
}
else // Token has expired
{
if (!token.hasExpired) // If the token's expiration date has passed but the elapsed event hasn't fired yet, then release the resources
{
ReleaseTakeOffResources(token);
}
return(PerformResult.ExpiredToken);
}
}
// Release resources resereved by a takeoff request token that will not be used.
private void ReleaseTakeOffResources(TakeOffRequestToken token)
{
Runway runway = GetRunwayById(token.runwayId);
runway.state = Runway.RunwayState.Available;
runway.aircraftId = Guid.Empty;
token.Dispose();
}
// Releases resources when the takeoff token's timer elapses.
private void OnExpiredTakeOffToken(object source, ElapsedEventArgs e)
{
TakeOffRequestToken token = (TakeOffRequestToken)source;
// Unsubscribe from the token's timer.
token.Elapsed -= OnExpiredTakeOffToken;
// Release the token's resources.
ReleaseTakeOffResources(token);
}
/* After a successful call, the resources necessary to perform the operation
* should be reserved for the time of the returned authorization. */
public RequestResult RequestTakeOff(Guid aircraftId)
{
mutex.WaitOne();
// A runway is available.
if (NumberOfAvailableRunways() > 0)
{
Guid runwayId = ReserveAvailableRunway();
// Create the takeoff request token
TakeOffRequestToken token = new TakeOffRequestToken(TokenValiditySeconds, aircraftId, runwayId);
// Subscribe for token's expiration to ensure reserved resources can be released.
token.Elapsed += OnExpiredTakeOffToken;
mutex.ReleaseMutex();
return(new RequestResult(RequestResult.RequestState.Proceed, token));
}
else
{
mutex.ReleaseMutex();
return(new RequestResult(RequestResult.RequestState.Hold, null));
}
}