.htaccess rule, rewrite key in url - .htaccess

Question

Let's say we have an url like this:
http://domain.com/?theme_of_site=parameter_value
http://domain.com/?type_of_site=parameter_value
domain.com - stable/static, always the same
theme_of_site & type_of_site - stable/static, the same when choosen
parameter_value - dynamic
It's like to have always the url's like:
http://domain.com/?theme=parameter_value
http://domain.com/?type=parameter_value
How can I write this in .htaccess?
For the below discussion:
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
# Start by redirecting the original links from type_of_site= to type=
# Only if the browser's original request contains the strings
RewriteCond %{THE_REQUEST} theme_of_site=([^&]+)
RewriteCond %{THE_REQUEST} type_of_site=([^&]+)
RewriteRule (.*) $1?theme=%1&type=%2 [L,R=301]
RewriteCond %{THE_REQUEST} theme_of_site=([^&]+)
RewriteRule (.*) $1?theme=%1 [L,R=301]
RewriteCond %{THE_REQUEST} type_of_site=([^&]+)
RewriteRule (.*) $1?type=%1 [L,R=301]
# Then, after performing the initial redirects to change the browser
# URL, rewrite the parameters internally
# Match both present:
RewriteCond %{QUERY_STRING} theme=([^&]+)
RewriteCond %{QUERY_STRING} type=([^&]+)
RewriteRule (.*) $1?theme_of_site=%1&type_of_site=%2 [L]
# Then match each individually
RewriteCond %{QUERY_STRING} theme=([^&]+)
RewriteRule (.*) $1?theme_of_site=%1 [L]
RewriteCond %{QUERY_STRING} type=([^&]+)
RewriteRule (.*) $1?type_of_site=%1 [L]
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

Answer 1

Query string parameters need to be captured in RewriteCond. You can match (theme|type) and capture the value, then rewrite it internally using the (theme|type)_of_site in a RewriteRule.
RewriteEngine On
# Match the theme or type paramater in `%1` and capture its value in `%2`
RewriteCond %{QUERY_STRING} (theme|type)=([^&]+)
# Rewrite The parameter name to include _of_site using the values captured above
# for all URLs as captured in $1
RewriteRule (.*) $1?%1_of_site=%2 [L]
The simple example above works only if either of the parameters is specified. If you need to be able to handle both at once like example.com/?type=abc&theme=123 it gets a little more complex:
# Start by redirecting the original links from type_of_site= to type=
# Only if the browser's original request contains the strings
RewriteCond %{THE_REQUEST} theme_of_site=([^&]+)
RewriteCond %{THE_REQUEST} type_of_site=([^&]+)
RewriteRule (.*) $1?theme=%1&type=%2 [L,R=301]
RewriteCond %{THE_REQUEST} theme_of_site=([^&]+)
RewriteRule (.*) $1?theme=%1 [L,R=301]
RewriteCond %{THE_REQUEST} type_of_site=([^&]+)
RewriteRule (.*) $1?type=%1 [L,R=301]
# Then, after performing the initial redirects to change the browser
# URL, rewrite the parameters internally
# Match both present:
RewriteCond %{QUERY_STRING} theme=([^&]+)
RewriteCond %{QUERY_STRING} type=([^&]+)
RewriteRule (.*) $1?theme_of_site=%1&type_of_site=%2 [L]
# Then match each individually
RewriteCond %{QUERY_STRING} theme=([^&]+)
RewriteRule (.*) $1?theme_of_site=%1 [L]
RewriteCond %{QUERY_STRING} type=([^&]+)
RewriteRule (.*) $1?type_of_site=%1 [L]