switch rails page cache by user agent

nginx.conf

http {
    ...
    server {
        listen       8080;
        server_name  localhost;

        #
        # Set User Agent type
        #
        set $ua_type "pc";
        if ($http_user_agent ~* '(iPhone|iPod|Opera Mini|Android.*Mobile|NetFront|PSP|BlackBerry|Windows Phone)') {
          set $ua_type "mobile";
        }

        location / {
            root /var/www/app/public;

            # Rewrite for page cache
            #
            # e.g.)
            #   pc: public/pc/xxx.html
            #   mobile: public/mobile/xxx.html
            #
            if (-f $realpath_root/$ua_type$uri) {
                rewrite (.*) /$ua_type$1 break;
            }
            if (-f $realpath_root/$ua_type$uri/index.html) {
                rewrite (.*) /$ua_type$1/index.html break;
            }
            if (-f $realpath_root/$ua_type$uri.html) {
                rewrite (.*) /$ua_type$1.html break;
            }

            proxy_pass http://127.0.0.1:3000;
        }
    }
}