Build Paystack Subscriptions in Firebase Cloud Functions

// functions/src/index.ts
import { onRequest } from "firebase-functions/v2/https";
import { defineSecret } from "firebase-functions/params";
import { getFirestore } from "firebase-admin/firestore";
import { initializeApp } from "firebase-admin/app";
import * as cors from "cors";

initializeApp();

const paystackSecretKey = defineSecret("PAYSTACK_SECRET_KEY");
const corsHandler = cors({ origin: true });

export const subscribe = onRequest(
  { secrets: [paystackSecretKey] },
  async (req, res) => {
    corsHandler(req, res, async () => {
      if (req.method !== "POST") {
        res.status(405).send("Method not allowed");
        return;
      }

      const { email, planCode } = req.body;

      if (!email || !planCode) {
        res.status(400).json({ error: "email and planCode are required" });
        return;
      }

      const reference = "sub_" + Date.now() + "_" + Math.random().toString(36).slice(2, 8);
      const secretKey = paystackSecretKey.value();

      try {
        const paystackRes = await fetch(
          "https://api.paystack.co/transaction/initialize",
          {
            method: "POST",
            headers: {
              Authorization: "Bearer " + secretKey,
              "Content-Type": "application/json",
            },
            body: JSON.stringify({ email, plan: planCode, reference }),
          }
        );

        const data = await paystackRes.json();

        if (!data.status) {
          res.status(400).json({ error: data.message });
          return;
        }

        // Store pending subscription in Firestore
        const db = getFirestore();
        await db.collection("subscriptions").doc(email).set({
          email,
          plan_code: planCode,
          reference,
          status: "pending",
          created_at: new Date().toISOString(),
        }, { merge: true });

        res.json({
          authorization_url: data.data.authorization_url,
          reference: data.data.reference,
        });
      } catch {
        res.status(500).json({ error: "Failed to initialize subscription" });
      }
    });
  }
);

// In your paystackWebhook Cloud Function, add subscription event handling:

case "subscription.create": {
  const sub = event.data;
  const db = getFirestore();
  await db.collection("subscriptions").doc(sub.customer.email).set({
    status: "active",
    subscription_code: sub.subscription_code,
    email_token: sub.email_token,
    plan_name: sub.plan?.name,
    next_billing_date: sub.next_payment_date,
    activated_at: new Date().toISOString(),
  }, { merge: true });
  break;
}

case "charge.success": {
  // Recurring billing charge on an active subscription
  if (event.data.plan) {
    const db = getFirestore();
    await db.collection("subscriptions").doc(event.data.customer.email).update({
      status: "active",
      last_paid_at: new Date().toISOString(),
    });
  }
  break;
}

case "invoice.payment_failed": {
  const db = getFirestore();
  await db.collection("subscriptions").doc(event.data.customer.email).update({
    status: "past_due",
    last_failed_at: new Date().toISOString(),
  });
  break;
}

case "subscription.disable": {
  const db = getFirestore();
  const snapshot = await db.collection("subscriptions")
    .where("subscription_code", "==", event.data.subscription_code)
    .get();
  snapshot.forEach(doc => doc.ref.update({ status: "cancelled" }));
  break;
}

export const cancelSubscription = onRequest(
  { secrets: [paystackSecretKey] },
  async (req, res) => {
    corsHandler(req, res, async () => {
      const { email } = req.body;
      const db = getFirestore();

      const subDoc = await db.collection("subscriptions").doc(email).get();
      const sub = subDoc.data();

      if (!sub || sub.status !== "active") {
        res.status(404).json({ error: "No active subscription found" });
        return;
      }

      const secretKey = paystackSecretKey.value();

      const paystackRes = await fetch(
        "https://api.paystack.co/subscription/disable",
        {
          method: "POST",
          headers: {
            Authorization: "Bearer " + secretKey,
            "Content-Type": "application/json",
          },
          body: JSON.stringify({
            code: sub.subscription_code,
            token: sub.email_token,
          }),
        }
      );

      const data = await paystackRes.json();

      if (!data.status) {
        res.status(400).json({ error: data.message });
        return;
      }

      await db.collection("subscriptions").doc(email).update({
        status: "cancelled",
        cancelled_at: new Date().toISOString(),
      });

      res.json({ cancelled: true });
    });
  }
);

This guide is part of the Paystack integration guides by language and framework series.

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