/// <summary>
/// Using a filter-supplied context type, block so that the one time code is only executed once regardless of how many
/// threads are pushing through the pipe at the same time.
/// </summary>
/// <typeparam name="T">The payload type, should be an interface</typeparam>
/// <param name="context">The pipe context</param>
/// <param name="setupMethod">The setup method, called once regardless of the thread count</param>
/// <param name="payloadFactory">The factory method for the payload context, optional if an interface is specified</param>
/// <returns></returns>
public static async Task OneTimeSetup <T>(this PipeContext context, Func <T, Task> setupMethod, PayloadFactory <T> payloadFactory = null)
where T : class
{
OneTime <T> newContext = null;
var existingContext = context.GetOrAddPayload <OneTimeSetupContext <T> >(() =>
{
var payload = payloadFactory?.Invoke() ?? TypeMetadataCache <T> .InitializeFromObject(new {});
newContext = new OneTime <T>(payload);
return(newContext);
});
if (newContext == existingContext)
{
try
{
await setupMethod(newContext.Payload).ConfigureAwait(false);
newContext.SetReady();
}
catch (Exception exception)
{
newContext.SetFaulted(exception);
throw;
}
}
else
{
await existingContext.Ready.ConfigureAwait(false);
}
}