Function createPayment

src/services/x402/client.ts:294–328

(
  requirement: PaymentRequirement,
  fromAddress: string,
  privateKeyHex: string,
)

 * Create a signed x402 payment payload for a given requirement.
 */
export function createPayment(
  requirement: PaymentRequirement,
  fromAddress: string,
  privateKeyHex: string,
): PaymentPayload {
  const nonce = '0x' + randomBytes(32).toString('hex')
  const validAfter = '0'
  const validBefore = String(
    Math.floor(Date.now() / 1000) + requirement.maxTimeoutSeconds,
  )

  const authorization = {
    from: fromAddress,
    to: requirement.payTo,
    value: requirement.maxAmountRequired,
    validAfter,
    validBefore,
    nonce,
  }

  const domain = getEIP712Domain(requirement)
  const domainSeparator = computeDomainSeparator(domain)
  const structHash = computeStructHash(authorization)
  const signature = signEIP712(domainSeparator, structHash, privateKeyHex)

  return {
    x402Version: 1,
    scheme: requirement.scheme,
    network: requirement.network,
    payload: {
      signature,
      authorization,
    },
  }
}

/**
 * Encode a payment payload as a base64 string for the X-Payment header.