Apache mod_rewrite query string without specific order - apache

Question

I have a rule that translates old-style urls into new style. It works ok as long as I use the same order of parameters in the query:
RewriteCond %{QUERY_STRING} ^country=([a-z]{2})&id=([0-9]+)$ [NC]
RewriteRule ^(.*)$ http://%1.localhost/%2? [R=301,L]
So url localhost/index.php?country=us&id=1234 would go to us.localhost/1234
But the problem is that using localhost/index.php?id=1234&country=us (note that arguments are now swapped in order) then the rule of course doesn't apply.
I thought about changing the rule to handle arguments separately, like this:
RewriteCond %{QUERY_STRING} country=([a-z]{2}) [NC]
RewriteCond %{QUERY_STRING} id=([0-9]+) [NC]
RewriteRule ^(.*)$ http://%1.localhost/%2? [R=301,L]
But when entering localhost/index.php?id=1234&country=us I get 1234.localhost/us which is not what I expect (I'd expect first cond to give me %1 and second cond %2 but it seems the order isn't determined this way)
Is there any easy way to achieve this? Of course I could write two separate rules each handling each case, but was wondering if some generic approach could be used (think if we had 3 parameters then permutations would make this unmanageable)

Answer 1

From the documentation, it looks like you can only reference rules from the last match:
RewriteCond backreferences: These are backreferences of the form %N (0 <= N <= 9). %1 to %9 provide access to the grouped parts (again, in parentheses) of the pattern, from the last matched RewriteCond in the current set of conditions. %0 provides access to the whole string matched by that pattern.
I've been racking my brains on a good way to do this and the best I can come up with is to use multiple rules to extract the data into environment variables and then reference those at the end for your final rewrite.
Something like this:
RewriteCond %{QUERY_STRING} country=([a-z]{2}) [NC]
RewriteRule ^(.*)$ - [E=URL_COUNTRY:%1]
RewriteCond %{QUERY_STRING} id=([0-9]+) [NC]
RewriteRule ^(.*)$ - [E=URL_ID:%1]
RewriteRule ^(.*)$ http://%{ENV:URL_COUNTRY}.localhost/%{ENV:URL_ID}? [R=301,L]