create-farcaster-mini-app/src/app/api/webhook/route.ts

import { NextRequest } from 'next/server';
import {
  ParseWebhookEvent,
  parseWebhookEvent,
  verifyAppKeyWithNeynar,
} from '@farcaster/miniapp-node';
import { APP_NAME } from '~/lib/constants';
import {
  deleteUserNotificationDetails,
  setUserNotificationDetails,
} from '~/lib/kv';
import { sendMiniAppNotification } from '~/lib/notifs';

export async function POST(request: NextRequest) {
  // If Neynar is enabled, we don't need to handle webhooks here
  // as they will be handled by Neynar's webhook endpoint
  const neynarEnabled =
    process.env.NEYNAR_API_KEY && process.env.NEYNAR_CLIENT_ID;
  if (neynarEnabled) {
    return Response.json({ success: true });
  }

  const requestJson = await request.json();

  let data;
  try {
    data = await parseWebhookEvent(requestJson, verifyAppKeyWithNeynar);
  } catch (e: unknown) {
    const error = e as ParseWebhookEvent.ErrorType;

    switch (error.name) {
      case 'VerifyJsonFarcasterSignature.InvalidDataError':
      case 'VerifyJsonFarcasterSignature.InvalidEventDataError':
        // The request data is invalid
        return Response.json(
          { success: false, error: error.message },
          { status: 400 },
        );
      case 'VerifyJsonFarcasterSignature.InvalidAppKeyError':
        // The app key is invalid
        return Response.json(
          { success: false, error: error.message },
          { status: 401 },
        );
      case 'VerifyJsonFarcasterSignature.VerifyAppKeyError':
        // Internal error verifying the app key (caller may want to try again)
        return Response.json(
          { success: false, error: error.message },
          { status: 500 },
        );
    }
  }

  const fid = data.fid;
  const event = data.event;

  // Only handle notifications if Neynar is not enabled
  // When Neynar is enabled, notifications are handled through their webhook
  switch (event.event) {
    case 'frame_added':
      if (event.notificationDetails) {
        await setUserNotificationDetails(fid, event.notificationDetails);
        await sendMiniAppNotification({
          fid,
          title: `Welcome to ${APP_NAME}`,
          body: 'Mini app is now added to your client',
        });
      } else {
        await deleteUserNotificationDetails(fid);
      }
      break;

    case 'frame_removed':
      await deleteUserNotificationDetails(fid);
      break;

    case 'notifications_enabled':
      await setUserNotificationDetails(fid, event.notificationDetails);
      await sendMiniAppNotification({
        fid,
        title: `Welcome to ${APP_NAME}`,
        body: 'Notifications are now enabled',
      });
      break;

    case 'notifications_disabled':
      await deleteUserNotificationDetails(fid);
      break;
  }

  return Response.json({ success: true });
}