Accept Payments with Paystack in Firebase Cloud Functions

# Initialize Cloud Functions if not already done
firebase init functions
# Choose TypeScript, Node 18

# Store Paystack secret key as a Firebase secret
firebase functions:secrets:set PAYSTACK_SECRET_KEY

# Install dependencies
cd functions
npm install cors
npm install --save-dev @types/cors

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

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

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

      const secretKey = paystackSecretKey.value();
      const { email, amount } = req.body;

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

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

      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,
              amount: Math.round(Number(amount) * 100),
              reference,
            }),
          }
        );

        const data = await paystackRes.json();

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

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

# Deploy the function
firebase deploy --only functions:initializePayment

# Get the function URL from the console or CLI output:
# https://<region>-<project-id>.cloudfunctions.net/initializePayment

// Frontend call
async function initializePayment(email: string, amount: number) {
  var response = await fetch(
    "https://<region>-<project-id>.cloudfunctions.net/initializePayment",
    {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ email, amount }),
    }
  )

  var data = await response.json()
  // data.authorization_url — redirect or open in WebView
  window.location.href = data.authorization_url
}

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

Next: Verify Paystack Payments in Firebase Cloud Functions

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