build(vercel): Add script that should run before vercel starts the app

Author: OliverDudgeon

package.json

@@ -10,6 +10,7 @@
     "dev:debug": "NODE_OPTIONS='--inspect' next dev",
     "build": "next build",
     "start": "next start",
+    "start:vercel": "node vercel.prestart.js && next start",
     "tsc": "tsc --pretty --noEmit",
     "lint": "eslint lint --max-warnings=0",
     "format": "eslint --fix --max-warnings=0",

vercel.prestart.js

@@ -0,0 +1,23 @@
+const fs = require('fs');
+
+const ENV = process.env.VERCEL_ENV;
+const URL = process.env.VERCEL_URL;
+const REPO_SLUG = process.env.VERCEL_GIT_REPO_SLUG;
+const REPO_OWNER = process.env.VERCEL_GIT_REPO_OWNER;
+const COMMIT_REF = process.env.VERCEL_GIT_COMMIT_REF;
+
+const domain = 'vercel.app';
+
+const url = () => {
+  if (ENV === 'production' && REPO_SLUG) {
+    return `${REPO_SLUG}.${domain}`;
+  }
+
+  if (COMMIT_REF !== 'master' && COMMIT_REF !== 'main' && REPO_SLUG && COMMIT_REF && REPO_OWNER) {
+    return `${REPO_SLUG}-git-${COMMIT_REF}-${REPO_OWNER}.${domain}`;
+  }
+
+  return URL ?? '';
+};
+
+fs.appendFileSync('.env', `\nVERCEL_URL="${url()}"\n`);