Rewrite URL from plural to singular

Question

How can all URLs that are plural and followed by /<integer> be redirected to the singular name along with the integer as a parameter. See below for examples. Ideally "users" need not be hardcoded, and "vendors" would redirect to "vendor" the same way. Note that I am not using any server code (i.e. PHP, etc).

users.html (not that this page is plural)

<a href="/users/1">John Doe</a>  <!-- should redirect to user.html?id=1 -->
<a href="/users/2">Jan Doe</a>   <!-- should redirect to user.html?id=2 -->
<a href="/users/3">Baby Doe</a>  <!-- should redirect to user.html?id=3 -->

Current configuration is as follows.

<IfModule mod_ssl.c>
    <VirtualHost *:443>
        ServerName admin.facdocs.example.net
        DocumentRoot /var/www/facdocs/frontends/admin/public
        <Directory "/var/www/facdocs/frontends/admin/public">
            #Options Indexes FollowSymLinks MultiViews
            Options Indexes FollowSymLinks
            AllowOverride All
            Order allow,deny
            allow from all
            RewriteEngine On
            LogLevel info rewrite:trace3
            RewriteBase /

            RewriteCond %{REQUEST_FILENAME} !-f
            RewriteCond %{REQUEST_FILENAME} !-d
            RewriteRule ^([A-Za-z]+)s/(\d+)/?$ $1.html?id=$2 [L]
            RewriteBase /

            RewriteCond %{REQUEST_URI} !^.*\.html$
            RewriteCond %{REQUEST_FILENAME} !-f
            RewriteCond %{REQUEST_FILENAME} !-d
            RewriteRule ^(.*)$ %{REQUEST_FILENAME}.html
        </Directory>
        Include /etc/letsencrypt/options-ssl-apache.conf
        SSLCertificateFile /etc/letsencrypt/live/api.example.net/cert.pem
        SSLCertificateKeyFile /etc/letsencrypt/live/api.example.net/privkey.pem
        SSLCertificateChainFile /etc/letsencrypt/live/api.example.net/chain.pem
    </VirtualHost>
</IfModule>

Answer 1

To handle plurals only as words ending in s and only if a corresponding .html exists, you may match as:

RewriteEngine On
# The actual file does not exist already as a file or directory
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# Alpha excluding final `s` captures in $1
# Numeric value in $2 with optional trailing slash
RewriteRule ^([A-Za-z]+)s/(\d+)/?$ $1.html?id=$2 [L]

A plural word (ending in s) without a corresponding singular .html will resutl in a 404.

Note: The above assumes a <Directory> or .htaccess context. If you put this in a server-level or <Location>, use a leading slash

RewriteRule ^/([A-Za-z]+)s...

And this also assumes case-sensitivity between the input plural and corresponding .html.