Build a newsletter signup form in React Router

app/
  root.tsx
  routes.ts
  routes/
    home.tsx
    newsletter.tsx
    api.ikiform.ts
  components/newsletter-form.tsx
react-router.config.ts
.env

import { type RouteConfig, index, route } from "@react-router/dev/routes";

export default [
  index("routes/home.tsx"),
  route("newsletter", "routes/newsletter.tsx"),
  route("api/ikiform", "routes/api.ikiform.ts"),
] satisfies RouteConfig;

IKIFORM_SECRET_KEY=ik_sk_your_secret_key
IKIFORM_WEBHOOK_SECRET=whsec_your_webhook_secret
MAILERLITE_API_KEY=your_mailerlite_token
MAILERLITE_GROUP_ID=123456789

import { data } from "react-router";
import { NewsletterForm } from "~/components/newsletter-form";
import type { Route } from "./+types/newsletter";

const PLACEMENTS = ["footer", "post", "newsletter-page"];

export async function action({ request }: Route.ActionArgs) {
  const form = await request.formData();
  if (form.get("consent") !== "true") {
    return data(
      { ok: false as const, field: "consent", message: "Tick the box so we know you want the emails." },
      { status: 422 },
    );
  }

  const source = String(form.get("source") ?? "");
  const response = await fetch("https://ikiform.com/f/frm_xxxxxxxxxxxxxxxx", {
    method: "POST",
    headers: {
      Accept: "application/json",
      "Content-Type": "application/json",
      Authorization: `Bearer ${process.env.IKIFORM_SECRET_KEY}`,
      Origin: request.headers.get("origin") ?? "",
    },
    body: JSON.stringify({
      email: String(form.get("email") ?? "").trim(),
      first_name: String(form.get("first_name") ?? "").trim().slice(0, 80) || undefined,
      consent: true,
      source: PLACEMENTS.includes(source) ? source : "footer",
      _gotcha: String(form.get("_gotcha") ?? ""),
    }),
    signal: AbortSignal.timeout(8000),
  }).catch(() => null);

  const result = await response?.json().catch(() => null);
  if (result?.ok) return { ok: true as const };
  const email = result?.error?.fields?.email?.[0];
  return data(
    {
      ok: false as const,
      field: email ? "email" : "form",
      message: String(email ?? result?.error?.message ?? "We couldn't reach the list. Try again."),
    },
    { status: response?.status ?? 502 },
  );
}

export function meta() {
  return [{ title: "Newsletter" }];
}

export default function Newsletter({ actionData }: Route.ComponentProps) {
  return (
    <main>
      <h1>The monthly newsletter</h1>
      <NewsletterForm source="newsletter-page" initial={actionData} />
    </main>
  );
}

import { useFetcher } from "react-router";
import type { Route } from "../routes/+types/newsletter";
import type { action } from "../routes/newsletter";

interface Props {
  source: "footer" | "post" | "newsletter-page";
  initial?: Route.ComponentProps["actionData"];
}

export function NewsletterForm({ source, initial }: Props) {
  const fetcher = useFetcher<typeof action>({ key: `newsletter-${source}` });
  const result = fetcher.data ?? initial;
  const busy = fetcher.state !== "idle";

  if (result?.ok) return <p role="status">Almost done. Open the email we sent you and confirm your address.</p>;
  const error = result?.ok === false ? result : null;

  return (
    <fetcher.Form method="post" action="/newsletter">
      <label>
        Email
        <input name="email" type="email" required autoComplete="email" aria-invalid={error?.field === "email"} />
      </label>
      <label>
        First name (optional)
        <input name="first_name" maxLength={80} autoComplete="given-name" />
      </label>
      <label>
        <input name="consent" type="checkbox" value="true" required aria-invalid={error?.field === "consent"} />
        Email me the newsletter. I can unsubscribe at any time.
      </label>
      <input type="hidden" name="source" value={source} />
      <input name="_gotcha" type="text" tabIndex={-1} autoComplete="off" hidden />
      {error ? <p role="alert">{error.message}</p> : null}
      <button disabled={busy}>{busy ? "Subscribing" : "Subscribe"}</button>
    </fetcher.Form>
  );
}

import type { ShouldRevalidateFunctionArgs } from "react-router";
import { Outlet } from "react-router";
import { NewsletterForm } from "~/components/newsletter-form";

export function shouldRevalidate({ formAction, defaultShouldRevalidate }: ShouldRevalidateFunctionArgs) {
  if (formAction === "/newsletter") return false;
  return defaultShouldRevalidate;
}

export default function App() {
  return (
    <>
      <Outlet />
      <footer>
        <p>One email a month. Unsubscribe from any issue.</p>
        <NewsletterForm source="footer" />
      </footer>
    </>
  );
}

import { verifyWebhook, WebhookVerificationError } from "@ikiform/sdk/webhooks";
import type { Route } from "./+types/api.ikiform";

export async function action({ request }: Route.ActionArgs) {
  let event;
  try {
    event = await verifyWebhook({
      payload: await request.text(),
      headers: request.headers,
      secret: process.env.IKIFORM_WEBHOOK_SECRET ?? "",
    });
  } catch (error) {
    if (error instanceof WebhookVerificationError) return new Response(error.reason, { status: 400 });
    throw error;
  }
  if (event.type !== "submission.created") return new Response(null, { status: 204 });

  const { email, first_name, consent } = event.data.fields;
  if (consent !== true || typeof email !== "string") return new Response("Skipped", { status: 200 });

  const answer = await fetch("https://connect.mailerlite.com/api/subscribers", {
    method: "POST",
    headers: {
      Authorization: `Bearer ${process.env.MAILERLITE_API_KEY}`,
      "Content-Type": "application/json",
      Accept: "application/json",
    },
    body: JSON.stringify({
      email,
      fields: typeof first_name === "string" && first_name ? { name: first_name } : {},
      groups: [process.env.MAILERLITE_GROUP_ID],
      status: "unconfirmed",
    }),
  });

  if (answer.status === 429) return new Response("MailerLite rate limit", { status: 503, headers: { "retry-after": "60" } });
  if (!answer.ok) return new Response(`MailerLite answered ${answer.status}`, { status: 502 });
  return new Response(null, { status: 204 });
}