feat(Apple Pay): allow for customization of event updates

Adds the ability for listeners on the various Apple Pay emitters to
accept a `complete` callback as the second argument. If the callback
names this argument, then the SDK will defer the execution to that
callback instead of resolving itself. The interface for each callback
depends on the triggering event, but this opens up the ability to fetch
custom taxes on payment method selection, update shipping costs on
shipping contact/method selection and validate email/phone addresses on
authorization.

This also enhances the `token` event to include the raw payment event as
the second argument.

lib/recurly/apple-pay/apple-pay.js

@@ -71,12 +71,20 @@ export class ApplePay extends Emitter {
     debug('Creating new Apple Pay session', paymentRequest);
 
     const session = new window.ApplePaySession(MINIMUM_SUPPORTED_VERSION, paymentRequest);
-    session.onvalidatemerchant = this.onValidateMerchant.bind(this);
-    session.onshippingcontactselected = this.onShippingContactSelected.bind(this);
-    session.onshippingmethodselected = this.onShippingMethodSelected.bind(this);
-    session.onpaymentmethodselected = this.onPaymentMethodSelected.bind(this);
-    session.onpaymentauthorized = this.onPaymentAuthorized.bind(this);
     session.oncancel = this.onCancel.bind(this);
+    session.onvalidatemerchant = this.onValidateMerchant.bind(this);
+
+    session.onpaymentmethodselected = registerEventHandler(
+      this, 'paymentMethodSelected', this.onPaymentMethodSelected.bind(this));
+
+    session.onshippingcontactselected = registerEventHandler(
+      this, 'shippingContactSelected', this.onShippingContactSelected.bind(this));
+
+    session.onshippingmethodselected = registerEventHandler(
+      this, 'shippingMethodSelected', this.onShippingMethodSelected.bind(this));
+
+    session.onpaymentauthorized = registerEventHandler(
+      this, 'paymentAuthorized', this.onPaymentAuthorized.bind(this));
 
     return this._session = session;
   }
@@ -137,7 +145,7 @@ export class ApplePay extends Emitter {
     else return this.initError = this.error('apple-pay-factory-only');
 
     if (options.form) this.config.form = options.form;
-    if (options.recurring) this.config.recurring = options.recurring;
+    if ('recurring' in options) this.config.recurring = options.recurring;
 
     this.config.i18n = {
       ...I18N,
@@ -221,7 +229,7 @@ export class ApplePay extends Emitter {
    * @private
    */
   onValidateMerchant (event) {
-    debug('Validating Apple Pay merchant session', event);
+    debug('validateMerchant', event);
 
     const validationURL = event.validationURL;
 
@@ -235,6 +243,14 @@ export class ApplePay extends Emitter {
     });
   }
 
+  /**
+   * sets the `contact` to the proper address on the pricing object.
+   *
+   * @param {string} addressType 'shippingAddress' or 'address'
+   * @param {object} contact The Apple Pay contact
+   * @param {Function} done
+   * @private
+   */
   setAddress (addressType, contact, done) {
     if (!contact || !this.config.pricing) return done?.();
 
@@ -249,16 +265,13 @@ export class ApplePay extends Emitter {
    * @param  {Event} event
    * @private
    */
-  onPaymentMethodSelected (event) {
-    debug('Payment method selected', event);
-
-    this.emit('paymentMethodSelected', event);
-
-    this.setAddress('address', event.paymentMethod.billingContact, () => {
+  onPaymentMethodSelected ({ paymentMethod: { billingContact } }, update) {
+    this.setAddress('address', billingContact, () => {
       this.session.completePaymentMethodSelection({
         newTotal: this.finalTotalLineItem,
         newLineItems: this.lineItems,
-        ...(this.recurringPaymentRequest && { newRecurringPaymentRequest: this.recurringPaymentRequest }),
+        newRecurringPaymentRequest: this.recurringPaymentRequest,
+        ...update,
       });
     });
   }
@@ -269,15 +282,13 @@ export class ApplePay extends Emitter {
    * @param  {Event} event
    * @private
    */
-  onShippingContactSelected (event) {
-    this.emit('shippingContactSelected', event);
-
-    this.setAddress('shippingAddress', event.shippingContact, () => {
+  onShippingContactSelected ({ shippingContact }, update) {
+    this.setAddress('shippingAddress', shippingContact, () => {
       this.session.completeShippingContactSelection({
         newTotal: this.finalTotalLineItem,
         newLineItems: this.lineItems,
-        newShippingMethods: [],
-        ...(this.recurringPaymentRequest && { newRecurringPaymentRequest: this.recurringPaymentRequest }),
+        newRecurringPaymentRequest: this.recurringPaymentRequest,
+        ...update,
       });
     });
   }
@@ -288,14 +299,12 @@ export class ApplePay extends Emitter {
    * @param  {Event} event
    * @private
    */
-  onShippingMethodSelected (event) {
-    this.emit('shippingMethodSelected', event);
-
+  onShippingMethodSelected (event, update) {
     this.session.completeShippingMethodSelection({
       newTotal: this.finalTotalLineItem,
       newLineItems: this.lineItems,
-      newShippingMethods: [],
-      ...(this.recurringPaymentRequest && { newRecurringPaymentRequest: this.recurringPaymentRequest }),
+      newRecurringPaymentRequest: this.recurringPaymentRequest,
+      ...update
     });
   }
 
@@ -307,12 +316,15 @@ export class ApplePay extends Emitter {
    * @emit 'token'
    * @private
    */
-  onPaymentAuthorized (event) {
-    debug('Payment authorization received', event);
+  onPaymentAuthorized (event, { errors } = {}) {
+    this.emit('authorized', event); // deprecated
 
-    this.emit('paymentAuthorized', event);
+    if (typeof errors === 'object' && errors.length > 0) {
+      this.session.completePayment({ status: this.session.STATUS_FAILURE, errors });
+      return;
+    }
 
-    return this.token(event);
+    this.token(event);
   }
 
   token (event) {
@@ -330,8 +342,7 @@ export class ApplePay extends Emitter {
         debug('Token received', token);
 
         this.session.completePayment({ status: this.session.STATUS_SUCCESS });
-        this.emit('authorized', event);
-        this.emit('token', token);
+        this.emit('token', token, event);
       }
     });
   }
@@ -383,6 +394,21 @@ export class ApplePay extends Emitter {
   }
 }
 
+function registerEventHandler (emitter, eventName, handler) {
+  return function (event) {
+    debug(eventName, event);
+
+    // listener accepts the `done` callback as an argument
+    if (!emitter.listeners(eventName).some(l => l.length >= 2)) {
+      emitter.emit(eventName, event);
+      handler(event);
+      return;
+    }
+
+    emitter.emit(eventName, event, (...args) => handler(event, ...args));
+  };
+}
+
 function restorePricing (pricing, state, done) {
   if (!pricing) return done();