Nginx Question about redirects

I am merging 2 websites into 1, a.com and b.com.
I want to set up the redirect for a.com and b.com to go to a.com and all http to go to https.
I also have to mass redirect all the url. Is the code below the best way to implement this?
Thank you.

Code:

map $request_uri $new_uri {
   default "";
   /old/a.com-url /new/b.com-url;
   /old/b.com-url /new/b.com-url;
   ...
}
 server {
   server_name a.com www.a.com b.com www.b.com;
   return 301 https://a.com$request_uri;
   include /usr/local/nginx/conf/staticfiles.conf;
 }

server {
  listen 443 ssl http2;
  server_name a.com www.a.com;
   if ($new_uri != "") {
       rewrite ^(.*)$ $new_uri permanent;
   }
}

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