How to save protocol during redirect?

Question

htaccess

The task is seemingly simple, to save the protocol when redirecting. But there is no standard method.
Given:

RewriteCond %{HTTP_HOST} !^www\.(.*) [NC]
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]

The problem is that there is no server response htttp or https can be off on true false but this is not to be sewn to the point.
There is Vary: HTTPS
but it does not return http at all.
Alternatively, something like

RewriteCond %{HTTP:X-Forwarded-Proto} http(s) [NC]
#RewriteCond %{HTTP_HOST} ^www\.(.*) [NC]
RewriteRule ^331/$ /best/http%1/%2/3 [L,R=301]

%1 works with the comment, but not with the second cond ;(

Answer 1

RewriteCond %{ENV:HTTPS} on
RewriteRule .* - [E=SSL:s]
RewriteCond %{HTTP_HOST} !^www\.(.*) [NC]
RewriteRule ^(.*)$ http%{ENV:SSL}://www.%{HTTP_HOST}/$1 [R=301,L]

Thanks everyone, I found the solution myself.
If someone suggests something better, we'll look.

Answer 2

Alternatively, something like

RewriteCond %{HTTP:X-Forwarded-Proto} http(s) [NC]
#RewriteCond %{HTTP_HOST} ^www\.(.*) [NC]
RewriteRule ^331/$ /best/http%1/%2/3 [L,R=301]

%1 works with the comment, but not with the second cond ;(

The result in %1-%9 is overwritten by the last successful pattern match.
Those. condition with a prefix !will not overwrite the results of the previous one.

RewriteCond %{HTTP:X-Forwarded-Proto} http(s)| [NC]
RewriteCond %{HTTP_HOST} !^www\.(.*) [NC]
RewriteRule ^(.*)$  http%1://www.%{HTTP_HOST}/$1 [R=301,L]

Another way is to cram both conditions into one RewriteCond.
Then the variants of the string to be checked can be as follows:

s on site.ru
s on www.site.ru
s off site.ru
s off www.site.ru

RewriteCond "s-%{HTTPS} %{HTTP_HOST}"  "^(?:(s)-on|\S+) (?!www\.)(.*)" [NC]
RewriteRule ^(.*)$ http%1://www.%2/$1  [R=301,L]

RewriteCond "s-%{HTTPS} %{HTTP_HOST}"  "^(?:(s)-on|\S+) www\.(.*)" [NC]
RewriteRule ^(.*)$     http%1://%2/$1  [R=301,L]