more validation on credit card info; change smoke test for payment service to have a valid credit card

src/paymentservice/charge.js

@@ -0,0 +1,64 @@
+const cardValidator = require('simple-card-validator');
+
+class CreditCardError extends Error {
+  constructor(message) {
+    super(message);
+    this.code = 400; // Invalid argument error
+  }
+}
+
+class InvalidCreditCard extends CreditCardError {
+  constructor(cardType) {
+    super(`Credit card info is invalid`);
+  }
+}
+
+class UnacceptedCreditCard extends CreditCardError {
+  constructor(cardType) {
+    super(`Sorry, we cannot process ${cardType} credit cards. Only VISA or MasterCard is accepted.`);
+  }
+}
+
+class ExpiredCreditCard extends CreditCardError {
+  constructor(number, month, year) {
+    super(`Your credit card (ending ${number.substr(-4)}) expired on ${month}/${year}`);
+  }
+}
+
+/**
+ * Verifies the credit card number and (pretend) charges the card.
+ *
+ * @param {*} request
+ * @return transaction_id - a random number.
+ */
+module.exports = function charge(request) {
+  const { amount, credit_card: creditCard } = request;
+  const cardNumber = creditCard.credit_card_number;
+  const cardInfo = cardValidator(cardNumber);
+  const {
+    card_type: cardType,
+    valid,
+    cvv_length: cvvLength,
+  } = cardInfo.getCardDetails();
+
+  if (!valid)
+    throw new InvalidCreditCard();
+
+  // Only VISA and mastercard is accepted, other card types (AMEX, dinersclub) will
+  // throw UnacceptedCreditCard error.
+  if (!(cardType === 'visa' || cardType == 'mastercard'))
+    throw new UnacceptedCreditCard(cardType);
+
+  // Also validate expiration is > today.
+  const currentMonth = new Date().getMonth() + 1;
+  const currentYear = new Date().getFullYear();
+  const { credit_card_expiration_year: year, credit_card_expiration_month: month } = creditCard;
+  if ((currentYear * 12 + currentMonth) > (year * 12 + month))
+    throw new ExpiredCreditCard(cardNumber.replace('-', ''), month, year);
+
+  console.log(`Transaction processed: ${cardType} ending ${cardNumber.substr(-4)} \
+    Amount: ${amount.currency_code}${amount.amount.decimal}.${amount.amount.fractional}`)
+
+  return { transaction_id: -1 }
+}
+