set immutable cache-headers to files matching hash regex

packages/ilmomasiina-backend/src/app.ts

@@ -85,11 +85,18 @@ export default async function initApp(): Promise<FastifyInstance> {
   // but this helps run a low-effort server.
   // frontend files should not be gzipped on the fly, rather done on the build step.
   if (config.frontendFilesPath) {
+    const javascriptHashRegex = /.*[.-][0-9a-fA-F]+[..*]+/;
     console.info(`Serving frontend files from '${config.frontendFilesPath}'`);
     server.register(fastifyStatic, {
       root: path.resolve(config.frontendFilesPath),
       preCompressed: true,
       wildcard: false, // Disable wildcard matching, so that own index.html is served
+      setHeaders: (res, filePath) => {
+        // set immutable cache for javascript files with hash in the name
+        if (javascriptHashRegex.test(filePath)) {
+          res.setHeader('Cache-Control', 'public, max-age=31536000, immutable');
+        }
+      },
     });
     server.get('*', (_req, reply) => {
       reply.sendFile('index.html');