authtype and rewriterule process order question

[Jeff Sherk Forerunner Ministries <jeff@xxxxxxxxxxxxxxxx>]

I have authtype basic setup on a folder (https://mydomain.com/myfolder) 
and would like to redirect the addresses below to it first and then have 
it ask for username and password:
http://mydomain.com/myfolder
http://www.mydomain.com/myfolder
https://www.mydomain.com/myfolder
(the above 3 should all be redirected to https://mydomain.com/myfolder)

Without the rewriterule, all 4 urls are accessible as is (and ask for 
username & password).

Here is my htaccess file so far, but what it appears to do is always ask 
for the username and password first and then redirect second. I want it 
to redirect first and then ask for username and password, so that you 
cannot enter your username & password with regular http but have to use 
https.

RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteCond %{REQUEST_URI} myfolder
RewriteRule ^(.*)$ https://mydomain.com/myfolder/$1 [R,L]

AuthType Basic
AuthName "AUTHORIZED ACCESS ONLY"
AuthUserFile "/home/mydomain/.htpasswds/public_html/myfolder/passwd"
require valid-user

Thanks

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