I am going to try and sum up what I am trying to achieve. I have custom post type named "item" and there are also registered taxonomy named "item_category". I need now to rewrite url, to remove "item" completly from url and instead of that to put "item_category".
"item_category", of course can have different values like food or sport and example would be:
http:sitename.com/item/post_name - > http:sitename.com/food/post_name
http:sitename.com/item/post_name - > http:sitename.com/sport/post_name
So I should check taxonomy (value of "item_category") and replace name of custom post type ("item" in this case) with that taxonomy. I can't register different post types or do any larger code changes because client has theme installed and a lot of content inside, so that option is off.
Is this at all possible?