feat: add single player mode

packages/lib/server-only/feature-flags/all.ts

@@ -0,0 +1,39 @@
+import { NextRequest, NextResponse } from 'next/server';
+
+import { getToken } from 'next-auth/jwt';
+
+import { LOCAL_FEATURE_FLAGS } from '@documenso/lib/constants/feature-flags';
+import PostHogServerClient from '@documenso/lib/server-only/feature-flags/get-post-hog-server-client';
+
+import { extractDistinctUserId, mapJwtToFlagProperties } from './get';
+
+/**
+ * Get all the evaluated feature flags based on the current user if possible.
+ */
+export default async function handlerFeatureFlagAll(req: Request) {
+  const requestHeaders = Object.fromEntries(req.headers.entries());
+
+  const nextReq = new NextRequest(req, {
+    headers: requestHeaders,
+  });
+
+  const token = await getToken({ req: nextReq });
+
+  const postHog = PostHogServerClient();
+
+  // Return the local feature flags if PostHog is not enabled, true by default.
+  // The front end should not call this API if PostHog is not enabled to reduce network requests.
+  if (!postHog) {
+    return NextResponse.json(LOCAL_FEATURE_FLAGS);
+  }
+
+  const distinctId = extractDistinctUserId(token, nextReq);
+
+  const featureFlags = await postHog.getAllFlags(distinctId, mapJwtToFlagProperties(token));
+
+  const res = NextResponse.json(featureFlags);
+
+  res.headers.set('Cache-Control', 'public, s-maxage=60, stale-while-revalidate=300');
+
+  return res;
+}