public IProcessStep NavigateForward(IWorkSession session)
{
try
{
if (!this.CanNavigateForward(session))
{
throw TransactionException.BuildException(TransactionException.ErrorCode.ActionNotAvailable);
}
// If the navigation gets blocked by a validation issue then the navigation process must fall back to the step
// it started on.
var fallbackStepId = this.CurrentStepId;
IProcessStep startingStep = this.CurrentStep;
IProcessStep nextStep = null;
bool isBlocked = false;
while (true)
{
// Get the step history record for the starting step. This record should always exist.
IStepHistory stepHistory = this.TransactionHistory.GetHistoryForStep(startingStep);
if (stepHistory is null)
{
throw TransactionException.BuildException(TransactionException.ErrorCode.StepHistoryNotFound);
}
bool hasExecuted = stepHistory.CompletedOn.HasValue;
if (!hasExecuted)
{
ExecutionContext.Trace("Getting next step by executing current step.");
// When the step has not been executed we need to execute it to find out what the next step in the
// processes is because steps with conditional branching do not know the next step until execution.
//
// Additionally, any validation requirements associated with the step will be evaluated and this could
// result in blocking forward navigation. In this case we still update the step history to show that the
// step was executed.
var executionResult = startingStep.Execute(ExecutionContext, session, this, RequirementEvaluator);
nextStep = executionResult.NextStep;
isBlocked = executionResult.StepIsBlocked; //validation requirements may block further advancement.
this.TransactionHistory.AddToHistory(this.ExecutionContext, session, nextStep, true);
}
else
{
ExecutionContext.Trace("Getting next step from step history");
if (stepHistory.NextStepId is null)
{
throw TransactionException.BuildException(TransactionException.ErrorCode.StepHistoryInvalid);
}
var nextStepId = this.TransactionHistory.GetHistoryById(stepHistory.NextStepId).ProcessStepId;
// When the step has executed then we just get the next step based on history.
nextStep = this.CurrentProcess.ProcessSteps.Where(r => Id == nextStepId.Id).FirstOrDefault();
}
// Stop moving forward when a UI step is found or when the step represents the last step in the process or
// when additional execution is blocked.
if (isBlocked || nextStep is null || nextStep.IsLastStep() || nextStep.Type.IsUIStep)
{
break;
}
// advance to the next process step and run through the loop again
startingStep = nextStep;
}
// When any execution in this step is blocked because of validation then the process falls back to
// the step that was current before we started. However any items that were completed in the above loop
if (isBlocked)
{
this.CurrentStepId = fallbackStepId;
return(this.CurrentStep);
}
// save the current step to the data base.
this.CurrentStepId = nextStep;
this.TransactionService.SaveTransactionCurrentStep(this.ExecutionContext, this, this.CurrentStepId);
return(this.CurrentStep);
}
catch (Exception ex)
{
throw TransactionException.BuildException(TransactionException.ErrorCode.ProcessNavigationError, ex);
}
}