mailing: grouped emails

app.yml

@@ -38,7 +38,7 @@ wwMeta:
 
 mail:
   enabled: false
-  frequency: 10000 # 10"
+  frequency: 3000 # 10"
   host: smtp.sparkpostmail.com
   port: 587
   auth: LOGIN

src/lib/mail.ts

@@ -4,7 +4,7 @@ import * as nodemailer from 'nodemailer'
 import * as os from 'os'
 
 const DEFAULT_FREQUENCY = 5 * 60 * 1000 // 5'
-const queue: EmailContent[] = []
+const queue: MailContent[] = []
 let conf: ConfMail|undefined
 
 export function initConfMail(confMail: ConfMail) {
@@ -26,16 +26,52 @@ export async function queueEmail(subject: string, html: string, cc?: string) {
   console.log(`[mail] added 1 mail to queue`)
 }
 
+function consumeMessages(cc: string): MailContent[] {
+  const mails: MailContent[] = []
+  for (let i = 0; i < queue.length; i++) {
+    const mail = queue[i]
+    if (mail.cc === (cc || undefined)) {
+      mails.push(queue[i])
+      queue.splice(i, 1)
+      i--
+    }
+  }
+  return mails
+}
+
 async function consumeQueue() {
   console.log(`[mail] consuming mailing queue: ${queue.length} messages to be sent`)
   while (queue.length) {
-    const mail = queue.shift()
-    if (mail) {
+    if (queue.length > 1) {
+      const ccs = queue.reduce((ccs, mail) => {
+        const cc = getGroup(mail)
+        if (ccs.indexOf(cc) === -1) {
+          ccs.push(cc)
+        }
+        return ccs
+      }, [] as string[])
+      console.log(`[mail] grouping messages into ${ccs.length} group(s)`)
+      for (const cc of ccs) {
+        const messages: MailContent[] = consumeMessages(cc)
+        const subject = `[dw] [${os.hostname}] ${messages.length} notifications`
+        let body = ''
+        for (const message of messages) {
+          body += `<h1>${message.subject}</h1>\n`
+          body += `<div>${message.body}</div>\n`
+        }
+        await sendEmail(subject, body, cc || undefined)
+      }
+    } else {
+      const mail = queue.shift() as MailContent
       await sendEmail(mail.subject, mail.body, mail.cc)
     }
   }
 }
 
+function getGroup(mail: MailContent) {
+  return mail.cc || ''
+}
+
 async function sendEmail(subject: string, html: string, cc?: string) {
 
   if (!conf) {
@@ -111,7 +147,7 @@ export const mail = {
   },
 }
 
-interface EmailContent {
+interface MailContent {
   subject: string
   body: string
   cc?: string