Recipe: x402 server email-fulfillment

import express from "express"
import { createX402bServerExpress } from "@bosonprotocol/x402-server-express"
import { ChannelRegistry, type FulfillmentChannel } from "@bosonprotocol/x402-fulfillment"
import { Resend } from "resend"
import { ethers } from "ethers"
 
const resend = new Resend(process.env.RESEND_API_KEY)
const wallet = new ethers.Wallet(process.env.SELLER_PRIVATE_KEY!)
 
const emailChannel: FulfillmentChannel = {
  id: "email",
  async fulfill({ buyer, exchangeId, deliveryInfo }) {
    const licenseKey = await mintLicenseKey(exchangeId)
    await resend.emails.send({
      from: "licenses@example.com",
      to: deliveryInfo!.email,
      subject: "Your license key",
      text: `Thanks! Your key: ${licenseKey}`,
    })
  },
}
 
const x402 = createX402bServerExpress({
  network: "polygon",
  chainId: 137,
  escrow: {
    configId: "production-137-0",
    sellerId: "12",
    productUuid: "ec00f1a5-2c96-4d22-9d80-2a7c12345678",
    fulfillment: { channels: ["email"] },
  },
  signer: wallet,
  facilitator: { url: "https://facilitator.bosonprotocol.io" },
  channelRegistry: new ChannelRegistry([emailChannel]),
})
 
const app = express()
app.get("/api/license", x402.middleware(), async (_, res) => {
  // Middleware already fulfilled via the email channel.
  res.json({ ok: true, exchangeId: req.x402!.exchangeId })
})
 
app.listen(3000)

await fetchWithPayment("https://api.example.com/license", {
  headers: {
    "x402-fulfillment": JSON.stringify({ channel: "email", email: "buyer@example.com" }),
  },
})