Validating user input with debconf

[Yurkao <yurkao@gmail.com>]

Hello mentors

I have the following question: I want to validate user input while configuring the package and if user provides incorrect input - reprompt question until valid value is provided.
Is it a good practice to do that with debconf? 
If it is - where should I do this ?
In config script?
Postinst?

The naive asnwer is: prompt user in config script until user provides valid input. 

This would work fine, but on the other hand the debconf frontend could be non interactive. In this case, if wrong answer was preseeded, looping really doesn't help - because debconf just spinning in the loop without getting any input from user. 

Any ideas/suggestions for correct solution?


Best regards,
Yurii Oleynikov