RewriteEngine On

# Rewrite to html cache if it exists and the request is off a static page (no url query params and only get requests)
RewriteCond %{REQUEST_METHOD} GET
RewriteCond %{QUERY_STRING} !.*=.*
RewriteCond %{DOCUMENT_ROOT}/cache/static%{REQUEST_URI}.html -f
RewriteRule ^(.*)$  /cache/static%{REQUEST_URI}.html [L]

# This is specific to cache the index when it' accesed vie /
RewriteCond %{REQUEST_METHOD} GET
RewriteCond %{QUERY_STRING} !.*=.*
RewriteCond %{DOCUMENT_ROOT}/cache/static/index.html -f
RewriteCond %{REQUEST_URI} ^/$
RewriteRule .* /cache/static/index.html [L]