[Owncloud] Question about IDNs

[Christian Reiner]

Hello all, 
I just took a look at this issue: https://github.com/owncloud/shorty/issues/7

It raises the question about IDNs being valid urls (which is right, 
obviously), whilst they are not accepted by the Shorty app as valid urls. 
Shorty has a builtin url validation using regexes amongst other things) for 
this. It helps to prevent entering invalid urls and also offers some 
additional protection against missuse and forgery. 

My problem (as stated in the issue tracker): 
I can modify Shorty to accept IDNs, however this also means to lower the url 
validation rules pretty far, so far to make them more or less useless. 

My question: 
Does anyone here have experience with handling IDNs? 
Any suggestion to how to accept and validate such urls without accepting more 
or less any string that has some scheme notation and a '://' at the beginning? 

Thanks, 
Christian Reiner (arkascha)