// Node.js 示例导入了 node-rsa
const NodeRSA = require('node-rsa')

function getPayload(){
    payload['version'] = '1.0'
    payload['autoRedirect'] = false
    payload['transactionId'] = ORDER_ID_IN_YOUR_SYSTEM
    payload['transactionType'] = 'pay'
    payload['transactionExpirationTime'] = 14400
    payload['appId'] = YOUR_APP_ID
    payload['amount'] = 1234
    payload['currency'] = 'USD'
    
    const userInfo = {
        userId: USER_ID_IN_YOUR_SYSTEM,
        phoneNo: USER'S_PHONE_NO,
        email: USER'S_EMAIL,
        IP: USER'S_IP
    }
    const billingAddress = {}
    billingAddress['houseNo'] = CUSTOMER'S_HOUSE_NO
    billingAddress['email'] = CUSTOMER'S_EMAIL
    billingAddress['phoneNo'] = CUSTOMER'S_PHONE_NO
    billingAddress['firstName'] = CUSTOMER'S_FIRST_NAME
    billingAddress['lastName'] = CUSTOMER'S_LAST_NAME
    billingAddress['street'] = CUSTOMER'S_STREET
    billingAddress['postalCode'] = CUSTOMER'S_POSTAL_CODE
    billingAddress['city'] = CUSTOMER'S_CITY
    billingAddress['state'] = CUSTOMER'S_STATE
    billingAddress['country'] = CUSTOMER'S_COUNTRY // ISO 3166-1-alpha-2
    payerInfo['billingAddress'] = billingAddress
    payload['userInfo'] = JSON.stringify(userInfo)
    
    const payerInfo = {
        paymentMethod: 'credit_card',
        authorizationMethod: 'cvv'
    }
    payload['payerInfo'] = JSON.stringify(payerInfo)
    
    const orderInfo = {
        subject: ORDER_SUBJECT_IN_YOUR_SYSTEM,
    }
    const goodsInfo = Array()
    goodsInfo.push(
      {
        id: SKU_ID_IN_YOUR_SYSTEM,
        name: PRODUCT_NAME,
        price: PRICE,
        quantity: QUANTITY,
        url: PRODUCT_LINK,
        image: IMAGE_OF_PRODUCT
      },
      {    
        id: SKU_ID_IN_YOUR_SYSTEM,
        name: PRODUCT_NAME,
        price: PRICE,
        quantity: QUANTITY,
        url: PRODUCT_LINK,
        image: IMAGE_OF_PRODUCT
      },
    )
    const shippingAddress = {}
    shippingAddress['houseNo'] = CUSTOMER'S_HOUSE_NO
    shippingAddress['email'] = CUSTOMER'S_EMAIL
    shippingAddress['phoneNo'] = CUSTOMER'S_PHONE_NO
    shippingAddress['firstName'] = CUSTOMER'S_FIRST_NAME
    shippingAddress['lastName'] = CUSTOMER'S_LAST_NAME
    shippingAddress['street'] = CUSTOMER'S_STREET
    shippingAddress['postalCode'] = CUSTOMER'S_POSTAL_CODE
    shippingAddress['city'] = CUSTOMER'S_CITY
    shippingAddress['state'] = CUSTOMER'S_STATE
    shippingAddress['country'] = CUSTOMER'S_COUNTRY // ISO 3166-1-alpha-2
    orderInfo['goodsInfo'] = goodsInfo
    orderInfo['shippingAddress'] = shippingAddress
    payload['orderInfo'] = JSON.stringify(orderInfo)
    
    payload['signType'] = 'RSA'
    payload['merchantNo'] = YOUR_MERCHANT_NO
    payload['notifyUrl'] = ASYNC_NOTIFY_URL
    payload['echoParam'] = ECHO_PARAM
    payload['sign'] = calcRSA(payload)

}

function calcRSA(payload) {
  const data = Object.keys(payload)
    .sort()
    .reduce((obj, key) => {
      obj[key] = payload[key]
      return obj
    }, {})
  var str = ''
  Object.keys(data).forEach((key) => {
    if (data[key] != '' && key != 'sign') {
      str = str + key + '=' + data[key] + '&'
    }
  })
  str = str.substr(0, str.length - 1)
  return new NodeRSA(YOUR_RSA_PRIVATE_KEY, 'pkcs8-private').sign(
    Buffer.from(str),
    'base64',
  )
}