Different location for a specific path - node.js

Question

im trying to serve a different location based on a specific path structure and user agent to serve dynamic rendering to crawler.
What i needs is that every path following this structure: /user//artwork/ and with a user agent of any bot to serve a nodejs express app with reverse proxy, everything else just send to the root of a static html dir.
Here what i tried with no success:
server {
index index.html;
server_name domain.app;
location ~/user/(.*)/artwork/(.*) {
set $prerender 0;
if ($http_user_agent ~* "baiduspider|twitterbot|facebookexternalhit|rogerbot|linkedinbot|embedly|quora link preview|showyoubot|outbrain|pinterest|slackbot|vkShare|W3C_Validator") {
set $prerender 1;
}
if ($uri ~ "\.(js|css|xml|less|png|jpg|jpeg|gif|pdf|doc|txt|ico|rss|zip|mp3|rar|exe|wmv|doc|avi|ppt|mpg|mpeg|tif|wav|mov|psd|ai|xls|mp4|m4a|swf|dat|dmg|iso|flv|m4v|torrent|ttf|woff)") {
set $prerender 0;
}
#resolve using Google's DNS server to force DNS resolution and prevent caching of IPs
resolver 8.8.8.8;
if ($prerender = 1) {
set $prerender "localhost:3010";
proxy_pass http://$prerender;
}
root /home/user/domain.app/dist;
try_files $uri $uri/ /index.html;
}
location / {
root /home/user/domain.app/dist;
#try_files $uri $uri/ =404;
try_files $uri $uri/ /index.html;
}
listen [::]:443 ssl ipv6only=on; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/domain.app/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/domain.app/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
server {
if ($host = domain.app) {
return 301 https://$host$request_uri;
} # managed by Certbot
listen 80 default_server;
server_name domain.app;
return 404; # managed by Certbot
}
It doesnt seem to serve anything different when its a bot user agent (using Googlebot user agent on google chrome Network condition setting)
EDIT:
I made it this way and its working:
server {
index index.html;
server_name domain.app;
location ~*/robots.txt {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-NginX-Proxy true;
proxy_set_header Host $http_host;
proxy_cache_bypass $http_upgrade;
proxy_redirect off;
proxy_pass http://localhost:3010;
}
location ~*/user/(.*)/artwork/(.*) {
set $prerender 0;
if ($http_user_agent ~* "googlebot|bingbot|yandex|baiduspider|twitterbot|facebookexternalhit|rogerbot|linkedinbot|embedly|quora link preview|showyoubot|outbrain|pinterest\/0\.|pinterestbot|slackbot|vkShare|W3C_Validator|whatsapp>
set $prerender 1;
}
if ($args ~ "_escaped_fragment_") {
set $prerender 1;
}
if ($http_user_agent ~ "Prerender") {
set $prerender 0;
}
if ($uri ~* "\.(js|css|xml|less|png|jpg|jpeg|gif|pdf|doc|txt|ico|rss|zip|mp3|rar|exe|wmv|doc|avi|ppt|mpg|mpeg|tif|wav|mov|psd|ai|xls|mp4|m4a|swf|dat|dmg|iso|flv|m4v|torrent|ttf|woff|svg|eot)") {
set $prerender 0;
}
#resolve using Google's DNS server to force DNS resolution and prevent caching of IPs
resolver 8.8.8.8;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-NginX-Proxy true;
proxy_set_header Host $http_host;
proxy_cache_bypass $http_upgrade;
proxy_redirect off;
if ($prerender = 1) {
proxy_pass http://localhost:3010;
break;
}
root /home/user/domain.app/dist;
try_files $uri $uri/ /index.html;
}
location / {
root /home/user/domain.app/dist;
#try_files $uri $uri/ =404;
try_files $uri $uri/ /index.html;
}
listen [::]:443 ssl ipv6only=on; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/domain.app/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/domain.app/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
server {
if ($host = domain.app) {
return 301 https://$host$request_uri;
} # managed by Certbot
listen 80 default_server;
server_name domain.app;
return 404; # managed by Certbot
}
This is working but probably a bit messy.
For some reasons, set $prerender "localhost:3010"; and then using $prerender proxy_pass http://$prerender; wasn't working so i use it directly like this: proxy_pass http://localhost:3010;
If anyone have advice to make it beter i would be happy to clean it up :)