From f7d46752e1a31ec706040a0695803010ed9ea768 Mon Sep 17 00:00:00 2001
From: Hongbo Wu <hongbo@omnivore.app>
Date: Fri, 14 Apr 2023 18:40:38 +0800
Subject: [PATCH] Forward subscription confirmation email

---
 packages/inbound-email-handler/src/index.ts   | 17 +++++++----
 .../inbound-email-handler/src/newsletter.ts   | 30 +++++++++++++------
 2 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/packages/inbound-email-handler/src/index.ts b/packages/inbound-email-handler/src/index.ts
index f14b94f9c..42d86f9eb 100644
--- a/packages/inbound-email-handler/src/index.ts
+++ b/packages/inbound-email-handler/src/index.ts
@@ -13,8 +13,9 @@ import parseHeaders from 'parse-headers'
 import * as multipart from 'parse-multipart-data'
 import { promisify } from 'util'
 import {
-  handleConfirmation,
-  isConfirmationEmail,
+  handleGoogleConfirmationEmail,
+  isGoogleConfirmationEmail,
+  isSubscriptionConfirmationEmail,
   parseUnsubscribe,
 } from './newsletter'
 import { handlePdfAttachment } from './pdf'
@@ -132,10 +133,13 @@ export const inboundEmailHandler = Sentry.GCPFunction.wrapHttpFunction(
       })
 
       try {
-        // check if it is a confirmation email or forwarding newsletter
-        if (isConfirmationEmail(from, subject)) {
-          console.log('handleConfirmation', from)
-          await handleConfirmation(to, subject)
+        // check if it is a subscription google confirmation email
+        const isGoogleConfirmation = isGoogleConfirmationEmail(from, subject)
+        if (isGoogleConfirmation || isSubscriptionConfirmationEmail(subject)) {
+          console.debug('handleConfirmation', from, subject)
+          // we need to parse the confirmation code from the email
+          isGoogleConfirmation &&
+            (await handleGoogleConfirmationEmail(to, subject))
           // queue non-newsletter emails
           await pubsub.topic(NON_NEWSLETTER_EMAIL_TOPIC).publishMessage({
             json: {
@@ -163,6 +167,7 @@ export const inboundEmailHandler = Sentry.GCPFunction.wrapHttpFunction(
           )
           return res.send('ok')
         }
+        // all other emails are considered newsletters
         const newsletterMessage = await handleNewsletter({
           from,
           to,
diff --git a/packages/inbound-email-handler/src/newsletter.ts b/packages/inbound-email-handler/src/newsletter.ts
index b3239f55d..b3686b20e 100644
--- a/packages/inbound-email-handler/src/newsletter.ts
+++ b/packages/inbound-email-handler/src/newsletter.ts
@@ -7,12 +7,14 @@ interface Unsubscribe {
   httpUrl?: string
 }
 
-const EMAIL_CONFIRMATION_CODE_RECEIVED_TOPIC = 'emailConfirmationCodeReceived'
-const CONFIRMATION_EMAIL_SENDER_ADDRESS = 'forwarding-noreply@google.com'
+const GOOGLE_CONFIRMATION_CODE_RECEIVED_TOPIC = 'emailConfirmationCodeReceived'
+const GOOGLE_CONFIRMATION_EMAIL_SENDER_ADDRESS = 'forwarding-noreply@google.com'
 // check unicode parentheses too
-const CONFIRMATION_CODE_PATTERN = /\d+/u
+const GOOGLE_CONFIRMATION_CODE_PATTERN = /\d+/u
 const UNSUBSCRIBE_HTTP_URL_PATTERN = /<(https?:\/\/[^>]*)>/
 const UNSUBSCRIBE_MAIL_TO_PATTERN = /<mailto:([^>]*)>/
+const CONFIRMATION_EMAIL_SUBJECT_PATTERN =
+  /(confirm|verify).*(newsletter(s)*|subscription(s)*|sign\s*up)/i
 
 export const parseUnsubscribe = (unSubHeader: string): Unsubscribe => {
   // parse list-unsubscribe header
@@ -32,7 +34,10 @@ const parseAddress = (address: string): string => {
   return ''
 }
 
-export const handleConfirmation = async (email: string, subject: string) => {
+export const handleGoogleConfirmationEmail = async (
+  email: string,
+  subject: string
+) => {
   console.log('confirmation email', email, subject)
 
   const confirmationCode = getConfirmationCode(subject)
@@ -47,11 +52,11 @@ export const handleConfirmation = async (email: string, subject: string) => {
   }
 
   const message = { emailAddress: email, confirmationCode: confirmationCode }
-  return publishMessage(EMAIL_CONFIRMATION_CODE_RECEIVED_TOPIC, message)
+  return publishMessage(GOOGLE_CONFIRMATION_CODE_RECEIVED_TOPIC, message)
 }
 
 export const getConfirmationCode = (subject: string): string | undefined => {
-  const matches = subject.match(CONFIRMATION_CODE_PATTERN)
+  const matches = subject.match(GOOGLE_CONFIRMATION_CODE_PATTERN)
   if (matches) {
     // get the number code only
     // e.g. (#123456) => 123456
@@ -60,9 +65,16 @@ export const getConfirmationCode = (subject: string): string | undefined => {
   return undefined
 }
 
-export const isConfirmationEmail = (from: string, subject: string): boolean => {
+export const isGoogleConfirmationEmail = (
+  from: string,
+  subject: string
+): boolean => {
   return (
-    parseAddress(from) === CONFIRMATION_EMAIL_SENDER_ADDRESS &&
-    CONFIRMATION_CODE_PATTERN.test(subject)
+    parseAddress(from) === GOOGLE_CONFIRMATION_EMAIL_SENDER_ADDRESS &&
+    GOOGLE_CONFIRMATION_CODE_PATTERN.test(subject)
   )
 }
+
+export const isSubscriptionConfirmationEmail = (subject: string): boolean => {
+  return CONFIRMATION_EMAIL_SUBJECT_PATTERN.test(subject)
+}