@aryanbansal-launch/edge-utils

Edge Utils for Contentstack Launch

A production-ready toolkit for Contentstack Launch Edge Functions — security, auth, routing, Next.js fixes, and geo-awareness, plus a full local dev/test setup so you can try everything before you deploy.

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Try it in one command

npm install @aryanbansal-launch/edge-utils
npx launch-edge-quickstart

That's it. This one command scaffolds an edge function, sets up a local KV store to simulate Launch's redirect/rewrite/cache-priming config, seeds it with sample data, and starts a local dev server — printing exactly what's configured and what URL to try for each feature:

Ready — here's what's configured

  ✔ Redirects  2 rule(s) configured
      curl -i http://localhost:8787/legacy/about  → 301 to /about
  ✔ Rewrites  2 rule(s) configured
      curl --compressed http://localhost:8787/home  → serves /, URL unchanged
  ✔ Cache priming  2 URL(s), auto-primed on startup
      curl -i http://localhost:8787/  → X-Cache: HIT once warmed

Run it again any time — it never overwrites files you already have (your handler, your launch.json), it only fills in what's missing. See Local testing for the full picture, or jump to Table of contents.

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Table of contents

• Try it in one command — the fastest path
• Features
• Use this in production — add utilities to your real edge handler
• Local testing — quickstart, step-by-step, and how KV/cache simulation works
• Config-driven redirects (launch.json)
• Writing a handler
• API Reference
• CLI Commands
• Platform Support

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Features

• Security — block AI crawlers, IP allow/deny lists, block default Launch domains
• Edge Auth — Basic Auth for specific hostnames (e.g. staging)
• Geo-Aware — read country/region/city from Launch's geo headers
• Next.js Ready — fixes for RSC header issues on Launch proxies
• Routing — code-level conditional redirects, plus config-driven redirects/rewrites via launch.json
• Full local dev setup — run your edge function and simulate Launch's redirect/rewrite/cache-priming config, entirely offline (Wrangler + Miniflare, no Cloudflare account)
• Lean — no runtime deps in the code you import at the edge; Wrangler is bundled so local testing needs no separate install

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Use this in production

Add one or more helpers to your real Contentstack Launch edge handler.

npm install @aryanbansal-launch/edge-utils
npx create-launch-edge          # scaffolds functions/[proxy].edge.js if it doesn't exist

Then import what you need and wire it into your handler — each utility returns a Response on match (return it immediately) or null (fall through to the next check):

import { blockAICrawlers, redirectIfMatch, passThrough } from "@aryanbansal-launch/edge-utils";

export default async function handler(request, context) {
  const botCheck = blockAICrawlers(request);
  if (botCheck) return botCheck;

  const redirect = redirectIfMatch(request, { path: "/old-page", to: "/new-page", status: 301 });
  if (redirect) return redirect;

  return passThrough(request);
}

Deploy through Contentstack Launch as usual — it runs functions/[proxy].edge.js at the edge before traffic reaches your app. See Writing a handler for a fuller example and the API Reference for every utility.

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Local testing

Test redirects, rewrites, cache priming, and your handler's own logic on your machine, without deploying. Wrangler's dev server runs on Miniflare, a Workers-compatible runtime — no Cloudflare account, no network calls.

The fast way

npx launch-edge-quickstart

Non-interactively creates whatever's missing — functions/[proxy].edge.js (a self-contained demo handler, if you don't have one yet), functions/dev-worker.edge.js (the local KV-aware shim), wrangler.toml, and a sample launch.json — never overwrites an existing handler or config, seeds the local KV, prints a status report with copy-pasteable curl commands per feature, then starts the dev server (which auto-primes the cache once ready).

Pass through wrangler dev args as usual: npx launch-edge-quickstart --port 8788. Add --no-prime to skip the automatic startup cache warm-up. Edit launch.json and re-run the same command any time to pick up changes.

Try it:

curl -i http://localhost:8787/legacy/about        # redirect: 301 -> /about
curl -i http://localhost:8787/old-shop/tees/blue  # wildcard redirect: 301 -> /shop/tees/blue
curl    http://localhost:8787/home                # rewrite: serves /, URL unchanged
curl -i http://localhost:8787/about                # X-Cache: HIT (auto-primed on startup)

If you want your own edge function's logic instead

Already have functions/[proxy].edge.js with your own code (auth, geo, bot-block, etc.)? Quickstart leaves it completely untouched — it only adds the KV plumbing around it. If you'd rather test only your handler, with no KV/redirect/rewrite/cache involved at all, remove the [[kv_namespaces]] block from wrangler.toml — with no KV bound, dev-worker.edge.js becomes a pure passthrough to your handler, no cache headers, no KV reads.

Step-by-step (more control)

Use this instead of the one-shot command if you want to pick a specific preset via a wizard, or run scaffold/seed/serve as separate steps.

npx launch-edge-local          # interactive wizard — pick a preset (see below)
npx launch-edge-seed-local     # seed the local KV from launch.json
npx launch-edge-test-local     # start the dev server

npx launch-edge-local shows a numbered menu:

#	Preset	Try
1	Redirect (code-level)	/legacy-demo → 301
2	JSON edge route	/api/edge-ping
3	Basic auth	prompts for demo/demo
4	Block AI crawlers	curl -A "GPTBot" ... → 403
5	Next.js RSC fix	strips RSC header on configured paths
6	KV redirects	/legacy/about → 301 (from launch.json)
7	KV rewrites	/docs/intro serves /blog/intro
8	Cache priming	/__prime warms the cache, then /about is X-Cache: HIT

Presets 6–8 also write a sample launch.json. If functions/[proxy].edge.js already exists you're asked before it's overwritten — say no to keep your own handler; the KV logic lives in dev-worker.edge.js regardless.

Align BACKEND_URL in wrangler.toml with your app's dev server (default http://127.0.0.1:3000) if your handler passes requests through to a real backend.

How the KV simulation works

launch.json — the same file you deploy — is the single source of truth for redirects, rewrites, and cache priming. Locally, it's seeded into a Miniflare-emulated KV namespace (EDGE_CONFIG) so your setup can read it exactly as Launch would in production:

• functions/[proxy].edge.js — your real handler. Deploys to Launch unchanged; never touched by the KV tooling.
• functions/dev-worker.edge.js — a local-dev-only shim that reads EDGE_CONFIG, applies redirects/rewrites/cache priming, then delegates everything else to your handler. It's feature-detected (if (env.EDGE_CONFIG)), so with no KV bound it's just a plain rewrite-to-origin dev worker.
• Cache priming runs automatically — on startup (once the dev server reports ready) and again in the background on the first request served, mirroring how Launch warms pages after a deploy. GET /__prime remains available to re-trigger manually.

For the full mental model (two-layer worker design, request lifecycle, KV/cache persistence, diagrams), see ARCHITECTURE.md.

Caveats

• Cacheability: the Cache API only retains responses that are cacheable per HTTP semantics — a response with no Cache-Control header is silently dropped, so cache priming won't show a HIT for it. Set Cache-Control on routes you want cached.
• Fidelity: local KV/cache is functional, not timing-accurate — it won't reproduce real KV propagation delay or edge cache tiering.
• Persist dir: launch-edge-seed-local and launch-edge-test-local both default to .wrangler-local; if you override one with --persist-to, override the other the same way.
• Hostname rules (protectWithBasicAuth): matching checks both the request URL host and the Host header, so hostnameIncludes: "localhost" works locally even though the rewritten request points at 127.0.0.1.
• Geo/IP headers: Miniflare doesn't inject Cloudflare's cf metadata, so getGeoHeaders/getClientIP may return empty values locally unless you set headers yourself.

See examples/local-dev/ for a minimal runnable project with the KV simulation wired up (npm install, then npm start).

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Config-driven redirects (launch.json)

For static, predictable redirects/rewrites/cache priming that don't need request-time logic, skip the edge function entirely — launch.json at your project root is read directly by Launch.

npx launch-config

Interactively add redirects (one-by-one or bulk import from CSV/JSON), rewrites, and cache-priming URLs. See npx launch-config bulk import formats below for the file formats. Test it locally the same way as the edge function — see Local testing above.

Config vs. edge function — use launch.json for bulk, static rules (hundreds of SEO redirects, simple path changes); use the edge function for anything that needs request data (cookies, geo, A/B tests, headers). They compose: keep static rules in launch.json, dynamic logic in functions/[proxy].edge.js.

You can also generate launch.json in code with generateLaunchConfig — see the API Reference.

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Writing a handler

Edge Functions run as middleware before requests reach your origin: User Request → Edge Function → Your Application. Every utility follows the same pattern — call it, return its result if truthy, otherwise keep going:

import {
  blockDefaultDomains,
  handleNextJS_RSC,
  blockAICrawlers,
  ipAccessControl,
  protectWithBasicAuth,
  redirectIfMatch,
  getGeoHeaders,
  jsonResponse,
  passThrough
} from "@aryanbansal-launch/edge-utils";

export default async function handler(request, context) {
  // Security
  const domainCheck = blockDefaultDomains(request);
  if (domainCheck) return domainCheck;

  const botCheck = blockAICrawlers(request);
  if (botCheck) return botCheck;

  const ipCheck = ipAccessControl(request, { allow: ["203.0.113.10", "198.51.100.5"] });
  if (ipCheck) return ipCheck;

  // Auth
  const auth = await protectWithBasicAuth(request, {
    hostnameIncludes: "staging.myapp.com",
    username: "admin",
    password: "securepass123"
  });
  if (auth && auth.status === 401) return auth;

  // Framework fixes
  const rscCheck = await handleNextJS_RSC(request, { affectedPaths: ["/shop", "/products", "/about"] });
  if (rscCheck) return rscCheck;

  // Routing
  const redirect = redirectIfMatch(request, { path: "/old-page", to: "/new-page", status: 301 });
  if (redirect) return redirect;

  // Personalization
  const geo = getGeoHeaders(request);
  if (geo.country === "US") console.log(`US visitor from ${geo.city}, ${geo.region}`);

  // Custom API endpoint
  const url = new URL(request.url);
  if (url.pathname === "/api/health") {
    return jsonResponse({ status: "healthy", region: geo.region, timestamp: Date.now() });
  }

  // Default: pass to origin
  return passThrough(request);
}

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API Reference

Security & Access Control

blockAICrawlers(request, bots?)

Blocks common AI/SEO crawlers by user-agent. bots (string[], optional) overrides the default list (claudebot, gptbot, googlebot, bingbot, ahrefsbot, yandexbot, semrushbot, mj12bot, facebookexternalhit, twitterbot, case-insensitive). Returns 403 Response on match, null otherwise.

const response = blockAICrawlers(request);           // default list
if (response) return response;

const response = blockAICrawlers(request, ["gptbot", "my-custom-bot"]);  // custom list

blockDefaultDomains(request, options?)

Blocks access via the default Launch domain (*.contentstackapps.com) so search engines only index your custom domain. options.domainToBlock (string, optional) overrides the default. Returns 403 Response on match, null otherwise.

const response = blockDefaultDomains(request);
if (response) return response;

Learn more

ipAccessControl(request, { allow?, deny? })

IP allow/deny list. deny takes precedence over allow. Returns 403 Response if blocked, null if allowed.

const response = ipAccessControl(request, { allow: ["203.0.113.0/24"], deny: ["203.0.113.50"] });
if (response) return response;

Learn more

protectWithBasicAuth(request, { hostnameIncludes, username, password, realm? })

Basic Auth gate for a specific hostname. hostnameIncludes matches against the request URL hostname, the Host header, or X-Forwarded-Host (useful locally, since rewriteRequestToOrigin sets that header). Returns 401 Response on failed/missing auth, null if hostnameIncludes doesn't match (chain continues).

const auth = await protectWithBasicAuth(request, {
  hostnameIncludes: "staging.myapp.com",
  username: "admin",
  password: "securepass123"
});
if (auth && auth.status === 401) return auth;

Not for production-grade security — Basic Auth credentials are base64-encoded, not encrypted. Learn more

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Routing & Redirects

redirectIfMatch(request, { path, to, method?, status? })

Code-level conditional redirect. Returns a redirect Response if request matches path (and method, if given), else null. status defaults to 301.

const redirect = redirectIfMatch(request, { path: "/old-page", to: "/new-page", status: 301 });
if (redirect) return redirect;

Learn more · For bulk/static redirects without code, see launch.json.

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Next.js

handleNextJS_RSC(request, { affectedPaths })

Fixes a class of Next.js React Server Components bugs where a cache incorrectly serves RSC JSON data instead of a full page load, by stripping the offending header on the paths you list.

const rsc = await handleNextJS_RSC(request, { affectedPaths: ["/shop", "/products", "/about"] });
if (rsc) return rsc;

Learn more

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Geo-Location

getGeoHeaders(request)

Reads Launch's geo headers. Returns { country, region, city, latitude, longitude } (all string | null).

const geo = getGeoHeaders(request);
if (geo.country === "FR") return Response.redirect("https://fr.mysite.com", 302);

Learn more

getClientIP(request)

Returns the client's IP address from Launch's forwarded headers.

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Response Utilities

jsonResponse(body, init?)

Builds a Response with Content-Type: application/json. init (status/headers) merges in as usual.

return jsonResponse({ status: "ok" });
return jsonResponse({ error: "Not found" }, { status: 404 });

passThrough(request)

Forwards the request to the origin — equivalent to fetch(request). The typical default/fallback at the end of a handler chain.

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Configuration

generateLaunchConfig({ redirects?, rewrites?, cache? })

Builds a LaunchConfig object in code, so you can generate launch.json programmatically (e.g. from CMS data) instead of using the interactive CLI.

interface LaunchRedirect { source: string; destination: string; statusCode?: number; response?: { headers?: Record<string, string> } }
interface LaunchRewrite { source: string; destination: string }

import { generateLaunchConfig } from "@aryanbansal-launch/edge-utils";
import fs from "fs";

const config = generateLaunchConfig({
  redirects: [{ source: "/old-blog/:slug", destination: "/blog/:slug", statusCode: 301 }],
  rewrites: [{ source: "/api/:path*", destination: "https://api.mybackend.com/:path*" }],
  cache: { cachePriming: { urls: ["/", "/about", "/products"] } }
});

fs.writeFileSync("launch.json", JSON.stringify(config, null, 2));

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KV-backed config (local simulation / Workers deployment)

These read the same redirect/rewrite/cache-priming shape as launch.json, but from a KV namespace — emulated locally by Miniflare (see Local testing), or a real namespace if you deploy this pattern to Cloudflare Workers directly.

• redirectFromKV(request, { kv, key?, status? }) — reads a redirect table from KV (default key "redirects"), returns a redirect Response on match (exact path or trailing /* wildcard), else null.
• rewriteFromKV(request, { kv, key? }) — reads a rewrite table from KV (default key "rewrites"), returns a new Request with the path swapped (client URL unchanged) on match, else null.
• primeCache({ urls, cache, keyBase?, fetchBase?, fetcher? }) / primeCacheFromKV({ kv, cache, key?, ... }) — warms the Cache API by fetching a list of URLs (or the list stored in KV, default key "cache:priming") and storing cacheable responses.
• serveWithCache(request, { cache, fetcher?, waitUntil? }) — serves a GET from the Cache API when warm, else fetches and populates it; adds X-Cache: HIT | MISS.
• matchRule(pathname, rules) — the shared exact/wildcard matcher behind the two helpers above.
• loadRedirects / loadRewrites / loadCachePrimingUrls — lower-level readers returning parsed config from KV (empty array on missing/invalid keys).

Local development

• rewriteRequestToOrigin(request, backendOrigin) — builds a new Request pointed at backendOrigin, preserving path/query/body. Used internally by functions/dev-worker.edge.js so passThrough reaches your local app.

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CLI Commands

Command	Purpose
npx create-launch-edge	Scaffold functions/[proxy].edge.js (production handler) and local-dev files. Creates only what's missing.
npx launch-edge-quickstart	One command: scaffold + seed + run the whole local KV/cache setup. See Local testing.
npx launch-edge-local	Interactive wizard — pick a preset (code or KV) and scaffold for it.
npx launch-edge-seed-local	Seed the local KV namespace from launch.json.
npx launch-edge-test-local	Start the local dev server (wrangler dev), with automatic cache priming.
npx launch-config	Interactive editor for launch.json — redirects, rewrites, cache priming, with CSV/JSON bulk import.
npx launch-help	Print a full reference of methods and CLI commands.

All local-dev commands run from your project root and accept extra flags passed through to wrangler dev (e.g. --port 8788).

npx launch-config bulk import formats

CSV (redirects.csv):

source,destination,statusCode
/old-blog/post-1,/blog/post-1,301
/products/old-sku-123,/products/new-sku-456,308
/legacy/*,/new/*,301

JSON (redirects.json):

[
  { "source": "/old-blog/post-1", "destination": "/blog/post-1", "statusCode": 301 },
  { "source": "/products/old-sku-123", "destination": "/products/new-sku-456", "statusCode": 308 }
]

Ready-to-use templates: examples/redirects.csv, examples/redirects.json.

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Platform Support

Built for Contentstack Launch — assumes standard Web APIs (Request, Response, fetch), an edge runtime, and Launch's geo-location headers.

Not intended for Node.js servers, traditional hosting, or other edge platforms (Cloudflare Workers, Vercel Edge, etc.) — though the KV-backed helpers happen to work anywhere Workers-style KV/Cache APIs are available, since that's what powers the local simulation.

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Contributing

Contributions welcome — please open an issue or pull request.

Repository: https://github.com/AryanBansal-launch/launch-edge-utils

License

Distributed under the MIT License. See LICENSE for details.

Useful Links

• Contentstack Launch Documentation
• Edge Functions Guide
• NPM Package
• GitHub Repository
• Architecture: Local Edge Dev Setup — deep dive into how local testing, KV simulation, and cache priming work internally

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Made with for the Contentstack Launch community