Hiding multiple dynamically-named subdirectories with mod_rewrite in .htaccess - .htaccess

Question

I am having difficulty configuring a mod_rewrite rule in my .htaccess file to hide certain subdirectories.
Input:
https://example.com/hidden_sub1/hidden_sub2/additional_sub/file.php?lang=en-US
Desired output:
https://example.com/en-US/additional_sub/file
I had code that allowed me to hide something if I specifically name it:
RewriteEngine On
RewriteBase /
RewriteCond %{THE_REQUEST} ^GET\ /hidden_sub1/hidden_sub2/ [NC]
RewriteRule ^hidden_sub1/hidden_sub2/(.*) /$1 [L,R=301]
RewriteRule !^hidden_sub1/hidden_sub2/ hidden_sub1/hidden_sub2%{REQUEST_URI} [L]
However, it stopped working once I added in the following language subdirectory code:
RewriteRule ^([a-z]{2}(-[A-Z]{2})?)/(.*) $3?lang=$1 [L,QSA]
Besides, the name of the subdirectory is dynamic. "hidden_sub1" might be "random_name243". However, they would always be the first two subdirectories.
So how do I take out the first two randomly-named subdirectories while still keeping the language subdirectory?
I appreciate any help.

Answer 1

To change your url from the form
https://example.com/hidden_sub1/hidden_sub2/additional_sub/file.php?lang=en-US
To the form :
https://example.com/en-US/additional_sub/file
You can use the following Rewrite rule
RewriteEngine On
RewriteBase /
#1)externally redirect "/hidden_sub1/hidden_sub2/foo.php?lang=bar" to "/bar/foo"
RewriteCond %{THE_REQUEST} /hidden_sub1/hidden_sub2/([^.]+)\.php\?lang=(.+)\sHTTP [NC]
RewriteRule ^ /%2/%1? [L,R=301]
#2)internally rewrite "/bar/foo" to "/hidden_sub1/hidden_sub2/foo.php?lang=bar"
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/([^/]+)/?$ /hidden_sub1/hidden_sub2/$2.php?lang=$1 [NC,L]
Tested on apache 2.2. and 2.4.