htaccess rewrite rules to remove multiple subfolders from a URL - apache

Question

Due file system sub-directory constraints I will most likely reach I want to separate the /users folder into /users/a/username, /users/b/username, /users/c/username, etc.
So the data on the server for a user would be in:
www.domain.com/users/a/username/, www.domain.com/users/b/username/, etc
I want the URL to be:
www.domain.com/users/username/
Optionally to avoid duplicate content a 301 redirect from www.domain.com/users/a/username/ to www.domain.com/users/username/ would also be good.
Currently I have a rewrite for a single sub-directory (see below) but I'm confused how this can be done efficiently for all of the alphabetical sub-directories.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^users/(.*)$ users/a/$1 [L,NC]
I have checked this site and all seem to hide the first sub-directory e.g. domain.com/folder1/filename.html => domain.com/filename.html but nothing in more depth.

Answer 1

Put this code in your htaccess (which has to be in root folder)
Options -Indexes -MultiViews
RewriteMap lowercase int:tolower # this line in your apache file configuration
RewriteEngine On
RewriteCond %{THE_REQUEST} \s/users/[a-z]/([^/\s]+)\s
RewriteRule . /users/%1/? [R=301,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^users/([A-Za-z])([^/]+)/$ /users/${lowercase:$1}/$1$2/ [L]