Implementing Recurring Payments

  <form action="https://www.myservice.com/subscription/issue-billing" method="post">
    <div>
        <label for="card_number">Card number XXXX-XXXX-XXXX-XXXX</label>
        <input id="card_number" type="text" name="card_number">
    </div>
    <div>
        <label for="expiry">Card expiration date YYYY-MM</label>
        <input id="expiry" type="text" name="expiry">
    </div>
    <div>
        <label for="birth">Date of birth YYMMDD</label>
        <input id="birth" type="text" name="birth">
    </div>
    <div>
        <label for="pwd_2digit">First 2 digits of card password XX</label>
        <input id="pwd_2digit" type="text" name="pwd_2digit">
    </div>
    <input hidden type="text" value="johndoe_0001_1234" name="customer_uid">
    <input type="submit" value="Pay">
  </form>

  // Handle POST request to "/subscription/issue-billing"
  app.post("/subscriptions/issue-billing", async (req, res) => {
    try {
      const {
        card_number, // Card number
        expiry, // Card expiration date
        birth, // Date of birth
        pwd_2digit, // First 2 digits of card password
        customer_uid, // The id that corresponds 1:1 to the card (billing key)
      } = req.body; // Extract the card information from the request body
      ...
    } catch (e) {
      res.status(400).send(e);
    }
  });

  // Handle POST request to "/subscription/issue-billing"
  app.post("/subscriptions/issue-billing", async (req, res) => {
    try {
      const {
        card_number, // Card number
        expiry, // Card expiration date
        birth, // Date of birth
        pwd_2digit, // First 2 digits of card password
        customer_uid, // The id that corresponds 1:1 to the card (billing key)
      } = req.body; // Extract the card information from the request body
      ...
      // Acquire access token
      const getToken = await axios({
        url: "https://api.iamport.kr/users/getToken",
        method: "post", // POST method
        headers: { "Content-Type": "application/json" }, // "Content-Type": "application/json"
        data: {
          imp_key: "imp_apikey", // REST API key
          imp_secret: "ekKoeW8RyKuT0zgaZsUtXXTLQ4AhPFW3ZGseDA6bkA5lamv9OqDMnxyeB9wqOsuO9W3Mx9YSJ4dTqJ3f" // REST API Secret
        }
      });
      const { access_token } = getToken.data.response; // Authentication token
      ...
      // Request a billing key
      const issueBilling = await axios({
        url: \`https://api.iamport.kr/subscribe/customers/\${customer_uid}\`,
        method: "post",
        headers: { "Authorization": access_token }, // Append the authentication token to Authorization header
        data: {
          card_number, // Card number
          expiry, // Card expiration date
          birth, // Date of birth
          pwd_2digit, // First 2 digits of card password
        }
      });
      ...
      const { code, message } = issueBilling.data;
      if (code === 0) { // Billing key was issued successfully
        res.send({ status: "success", message: "Billing has successfully issued" });
      } else { // Failed to acquire a billing key
        res.send({ status: "failed", message });
      }
    } catch (e) {
      res.status(400).send(e);
    }
  });

  // Call IMP.request_pay(param, callback)
  IMP.request_pay({ // param
    pg: "html5_inicis",
    pay_method: "card", // Only "card" is supported
    merchant_uid: "issue_billingkey_monthly_0001", // The order number to acquire the billing key
    customer_uid: "johndoe_0001_1234", // The id that corresponds 1:1 to the card (billing key)
    name: "The initial authenticated payment",
    amount: 0, // Set to 0 to acquire only the billing key
    buyer_email: "johndoe@gmail.com",
    buyer_name: "John Doe",
    buyer_tel: "010-4242-4242",
    buyer_addr: "Shinsa-dong, Gangnam-gu, Seoul",
    buyer_postcode: "01181"
  }, function (rsp) { // callback
    if (rsp.success) {
      // Billing key was issued successfully
    } else {
      // Failed to acquire a billing key
    }
  });

  // Call IMP.request_pay(param, callback)
  IMP.request_pay({ // param
    /* ...code omitted here... */
  }, function (rsp) { // callback
    if (rsp.success) {
      // Billing key was issued successfully
      // HTTP request using jQuery
      jQuery.ajax({
        url: "https://www.myservice.com/billings/", // URL of the web service
        method: "POST",
        headers: { "Content-Type": "application/json" },
        data: {
          customer_uid: "johndoe_0001_1234", // The id that corresponds 1:1 to the card (billing key)
        }
      });
    } else {
      // Failed to acquire a billing key
    }
  });

  // Handle POST request for "/billings"
  app.post("/billings", async (req, res) => {
    try {
      const { customer_uid } = req.body; // Extract customer_uid from req body
        ...
    } catch (e) {
      res.status(400).send(e);
    }
  });

  // The controller to handle POST request for "/billings"
  app.post("/billings", async (req, res) => {
    try {
      const { customer_uid } = req.body; // Extract customer_uid from req body
      // Acquire access token
      const getToken = await axios({
        url: "https://api.iamport.kr/users/getToken",
        method: "post", // POST method
        headers: { "Content-Type": "application/json" }, // "Content-Type": "application/json"
        data: {
          imp_key: "imp_apikey", // REST API key
          imp_secret: "ekKoeW8RyKuT0zgaZsUtXXTLQ4AhPFW3ZGseDA6bkA5lamv9OqDMnxyeB9wqOsuO9W3Mx9YSJ4dTqJ3f" // REST API Secret
        }
      });
      const { access_token } = getToken.data.response; // Authentication token
      ...
      // Request (re)payment
      const paymentResult = await axios({
        url: \`https://api.iamport.kr/subscribe/payments/again\`,
        method: "post",
        headers: { "Authorization": access_token }, // Append the authentication token to Authorization header
        data: {
          customer_uid,
          merchant_uid: "order_monthly_0001", // The order number for the newly created (re)payment
          amount: 8900,
          name: "Recurring payments for monthly subscription"
        }
      });
      ...
      const { code, message } = paymentResult;
      if (code === 0) { // Successful communication with the card company (additional check is required to confirm whether the payment was successful)
        if ( paymentResult.status === "paid" ) { // The payment was approved
          res.send({ ... });
        } else { // Failed to approve the payment (e.g. Customer card limit exceeded, suspended card, insufficient balance, etc.)
          // paymentResult.status: failed is returned
          res.send({ ... });
        }
        res.send({ ... });
      } else { // The payment was not approved by the card company (paymentResult is null)
        res.send({ ... });
      }
    } catch (e) {
      res.status(400).send(e);
    }
  });

  // Schedule a payment
  axios({
    url: \`https://api.iamport.kr/subscribe/payments/schedule\`,
    method: "post",
    headers: { "Authorization": access_token }, // Append the authentication token to Authorization header
    data: {
      customer_uid: "johndoe_0001_1234", // The id that corresponds 1:1 to the card (billing key)
      schedules: [
        {
          merchant_uid: "order_monthly_0001", // order number
          schedule_at: 1519862400, // Time of payment attempt in Unix timestamp. e.g. The 1st of the next month
          amount: 8900,
          name: "Recurring payments for monthly subscription",
          buyer_name: "John Doe",
          buyer_tel: "01012345678",
          buyer_email: "johndoe@gmail.com"
        }
      ]
    }
  });

  // Handle POST request for "/iamport-callback/schedule"
  app.post("/iamport-callback/schedule", async (req, res) => {
    try {
      const { imp_uid, merchant_uid } = req.body;
      ...
    } catch (e) {
      res.status(400).send(e);
    }
  });

  // Handle POST request for "/iamport-callback/schedule"
  app.post("/iamport-callback/schedule", async (req, res) => {
    try {
      const { imp_uid, merchant_uid } = req.body;
      // Acquire access token
      const getToken = await axios({
        url: "https://api.iamport.kr/users/getToken",
        method: "post", // POST method
        headers: { "Content-Type": "application/json" }, // "Content-Type": "application/json"
        data: {
          imp_key: "imp_apikey", // REST API key
          imp_secret: "ekKoeW8RyKuT0zgaZsUtXXTLQ4AhPFW3ZGseDA6bkA5lamv9OqDMnxyeB9wqOsuO9W3Mx9YSJ4dTqJ3f" // REST API Secret
        }
      });
      const { access_token } = getToken.data.response; // Authentication token
      // Query payment information from Iamport with imp_uid
      const getPaymentData = await axios({
        url: \`https://api.iamport.kr/payments/\${imp_uid}\`, // pass imp_uid
        method: "get", // GET method
        headers: { "Authorization": access_token } // Append the authentication token to Authorization header
      });
      const paymentData = getPaymentData.data.response; // Query result
      const { status } = paymentData;
      if (status === "paid) { // Payment complete
        // Store the payment information in the database
        await Orders.findByIdAndUpdate(merchant_uid, { $set: paymentData }); // Mongoose
        ...
      } else {
        // Reattempt the payment
      }
    } catch (e) {
      res.status(400).send(e);
    }
  });

  // Handle POST request for "/iamport-callback/schedule"
  app.post("/iamport-callback/schedule", async (req, res) => {
    try {
      const { imp_uid, merchant_uid } = req.body;
      // Acquire access token
      /* ...code omitted here ... */
      // Query payment information from Iamport with imp_uid
      /* ...code omitted here ... */
      const paymentData = getPaymentData.data.response; // Query result
      const { status } = paymentData;
      if (status === "paid) { // Payment complete
        // Store the payment information in the database
        await Orders.findByIdAndUpdate(merchant_uid, { $set: paymentData }); // Mongoose
        ...
        // Schedule a new payment
        axios({
          url: \`https://api.iamport.kr/subscribe/payments/schedule\`,
          method: "post",
          headers: { "Authorization": access_token }, // Append the authentication token to Authorization header
          data: {
            customer_uid: "johndoe_0001_1234", // The id that corresponds 1:1 to the card (billing key)
            schedules: [
              {
                merchant_uid: "order_monthly_0001", // order number
                schedule_at: 1519516800, // Time of payment attempt in Unix timestamp. e.g. The 1st of the next month
                amount: 8900,
                name: "Recurring payments for monthly subscription",
                ...
              }
            ]
          }
        });
      } else {
        // Reattempt the payment
      }
    } catch (e) {
      res.status(400).send(e);
    }
  });