Personal Catalogue: React & Firebase — Chapter 10, Exercise 2
=====================================================================

TASK
Configure the nginx location /catalogue/ block against a real,
deployed Firebase Hosting site (a second local nginx config is fine
for testing), including the Host header override and
proxy_ssl_server_name. Confirm the page loads correctly, then
temporarily remove just the Host header line and observe what happens.

SOLUTION

Full config, as given in the chapter:

server {
    listen 443 ssl;
    server_name existing-site.com;

    location /catalogue/ {
        proxy_pass https://catalogue-prod.web.app/;
        proxy_set_header Host catalogue-prod.web.app;
        proxy_ssl_server_name on;
    }
}

After `nginx -s reload`, visiting https://existing-site.com/catalogue/
loads the real, working catalogue app — the page renders correctly,
and its own assets (already built with the /catalogue/ base prefix
from Exercise 1) load without any 404s.

Temporary change — remove the Host header override:

location /catalogue/ {
    proxy_pass https://catalogue-prod.web.app/;
    # proxy_set_header Host catalogue-prod.web.app;  (commented out)
    proxy_ssl_server_name on;
}

Reloading nginx and revisiting https://existing-site.com/catalogue/
now: nginx forwards the request with its own real default Host header
value, Host: existing-site.com, unchanged from what the original
browser request carried. Firebase Hosting's own routing has no project
registered under that hostname, so the request either fails outright
(a connection-level error) or returns Firebase's own generic
"Site Not Found" page rather than the real catalogue app — confirming
that the Host header override isn't a defensive extra, it's the one
thing that actually tells Firebase's shared infrastructure which real
project's content to serve.

WHY THIS WORKS AS AN ANSWER
----------------------------
It configures and tests the real, working setup first, then
deliberately isolates exactly one line (the Host header override) to
confirm it's genuinely load-bearing by observing the real failure that
results from removing only that piece, rather than assuming its
purpose without checking.