Delphi code for sanitizing a URL entered by the user

Question

I need a user to be able to enter a URL, and would like to make sure it is as wholesome as possible. Things like checking that there is http:// at the front, no double-dots, perhaps valid TLD, trailing slash (I have to add the final page).

I figure this is such a common requirement that it must exist already. Suggestions?

[edit:] To be clear, this is a run-time requirement in a Windows Service. The aim is to get the best from the URL read from the configuration, rather than validate what the user typed in. In essence, if I can adjust the URL and make it work, then that is what I'd like to do. The download will be a specific file, so if it all goes wrong it won't get the wrong thing from another server by mistake.

Answer 1

Have you had a look at "What is the best regular expression to check if a string is a valid URL"? It is not Delphi specific, but might get you started.

Answer 2

Perhaps some of the suggestions here might help.

Answer 3

How about using the PathIsURL function in the Windows API?

Update: This is already wrapped in the Delphi RTL in the ShLwApi unit.