From 8c52b7828b4671dcc38f992e6b88b6912fbbb460 Mon Sep 17 00:00:00 2001
From: Michael Manganiello <adamantike@users.noreply.github.com>
Date: Sun, 31 Aug 2025 21:43:32 -0300
Subject: [PATCH] feat: Add COEP and COOP headers for EmulatorJS within Nginx
 config

The COEP (Cross-Origin Embedder Policy) and COOP (Cross-Origin Opener
Policy) headers are needed by EmulatorJS to use the `SharedArrayBuffer`
feature, and enable multi-threaded cores.

These headers are only being set by Nginx for responses to requests
made to the EmulatorJS player path. This is because cross-origin
isolation breaks other features in the application (such as YouTube
embeds), so we only want to enable it for the EmulatorJS player.

It's important to mention that this change does not work when `DEV_MODE`
is set, as we would need Vite server to also set these headers in that
case. This could be implemented separately, if needed.

These changes are not enough to enable multi-threaded cores in the
frontend. Because our application is a SPA, we also need to ensure
that navigation to the EmulatorJS player path results in a full page
reload, so that the cross-origin isolation can be applied. This will be
handled in a separate PR.
---
 docker/nginx/templates/default.conf.template | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/docker/nginx/templates/default.conf.template b/docker/nginx/templates/default.conf.template
index 914f03f3f..3705f7cdb 100644
--- a/docker/nginx/templates/default.conf.template
+++ b/docker/nginx/templates/default.conf.template
@@ -8,6 +8,18 @@ map $http_x_forwarded_proto $forwardscheme {
     https https;
 }
 
+# COEP and COOP headers for cross-origin isolation, which are set only for the
+# EmulatorJS player path, to enable SharedArrayBuffer support, which is needed
+# for multi-threaded cores.
+map $request_uri $coep_header {
+    default        "";
+    ~^/rom/.*/ejs$ "require-corp";
+}
+map $request_uri $coop_header {
+    default        "";
+    ~^/rom/.*/ejs$ "same-origin";
+}
+
 server {
     root /var/www/html;
     listen ${ROMM_PORT};
@@ -19,13 +31,14 @@ server {
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
     proxy_set_header X-Forwarded-Proto $forwardscheme;
 
-
     location / {
         try_files $uri $uri/ /index.html;
         proxy_redirect off;
         add_header Access-Control-Allow-Origin *;
         add_header Access-Control-Allow-Methods *;
         add_header Access-Control-Allow-Headers *;
+        add_header Cross-Origin-Embedder-Policy $coep_header;
+        add_header Cross-Origin-Opener-Policy $coop_header;
     }
 
     # Static files