abandoned mail-listener2 rewrite.js

import Imap from 'imap'
import { simpleParser } from 'mailparser'
import util from 'util'

// Modernized verison, with modern JS, async/await, util.promisify, etc.
class MailListener {
  constructor({
    username,
    password,
    host,
    port,
    tls,
    tlsOptions = {},
    connTimeout = null,
    authTimeout = null,
    debug = null,
    xoauth2,
    mailbox = 'INBOX',
    searchFilter = ['UNSEEN'],
    markSeen,
    fetchUnreadOnStart,
    attachments = false,
    attachmentOptions = {},
    mailParserOptions = {},
  }) {
    this.markSeen = markSeen
    this.mailbox = mailbox
    if ('string' === typeof searchFilter) {
      this.searchFilter = [searchFilter]
    } else {
      this.searchFilter = searchFilter
    }
    this.fetchUnreadOnStart = fetchUnreadOnStart
    this.mailParserOptions = mailParserOptions
    if (attachments && attachmentOptions && attachmentOptions.stream) {
      this.mailParserOptions.streamAttachments = true
    }
    this.attachmentOptions = attachmentOptions
    this.attachments = attachments
    this.attachmentOptions.directory = this.attachmentOptions.directory ?? ''
    this.imap = new Imap({
      xoauth2,
      user: username,
      password,
      host,
      port,
      tls,
      tlsOptions,
      connTimeout,
      authTimeout,
      debug,
    })

    this.imap.once('ready', this.imapReady)
    this.imap.once('close', this.imapClose)
    this.imap.on('error', this.imapError)
  }

  start() {
    this.imap.connect()
  }

  stop() {
    this.imap.end()
  }

  imapReady() {
    this.imap.openBox(this.mailbox, false, (err, mailbox) => {
      if (err) {
        this.emit('error', err)
      } else {
        this.emit('server:connected')
        if (this.fetchUnreadOnStart) {
          this.parseUnread()
        }
        this.imap.on('mail', this.imapMail)
        this.imap.on('update', this.imapMail)
      }
    })
  }

  imapClose() {
    this.emit('server:disconnected')
  }

  imapError(err) {
    this.emit('error', err)
  }

  imapMail() {
    this.parseUnread()
  }

  async parseUnread() {
    // modern version without async library, using modern async/await syntax instead (with util.promisify to convert imap functions to promises)

    const search = util.promisify(this.imap.search).bind(this.imap)
    const fetch = util.promisify(this.imap.fetch).bind(this.imap)

    const results = await search(this.searchFilter)
    if (results.length === 0) return

    for (const result of results) {
      const fetchResult = await fetch(result, {
        bodies: '',
        markSeen: this.markSeen,
      })
      fetchResult.on('message', async (message, sequenceNumber) => {
        let attributes = null
        let emailBuffer = Buffer.from('')

        message.on('attributes', (attrs) => {
          attributes = attrs
        })

        const parsed = await simpleParser(emailBuffer)

        this.emit('mail', parsed, sequenceNumber, attributes)
      })
    }
  }
}