SparkPost relay webhooks sample

extractRelayAttachments.js

'use strict';

/* Receive and extract email attachments using SparkPost relay webhooks.
 *
 * Prerequisites:
 *  - An inbound domain: https://developers.sparkpost.com/api/inbound-domains.html
 *  - A relay webhook: https://developers.sparkpost.com/api/relay-webhooks.html
 */

/*
  "dependencies": {
    "body-parser": "^1.15.2",
    "express": "^4.14.0",
    "mailparser": "^0.6.1"
  }
 */
let express = require('express')
  , bodyParser = require('body-parser')
  , fs = require('fs')
  , MailParser = require('mailparser').MailParser
  , port = process.env.PORT || 3000
  , app = express();
  
app.use(bodyParser.json({limit: '25mb'}));

app.post('/', (req, res) => {
  req.body.forEach(msg => {
    let content = msg.msys.relay_message.content
      , body = content.email_rfc822
      , parser = new MailParser({
        streamAttachments: true
      });

    if (content.email_rfc822_is_base64) {
      body = Buffer.from(body, 'base64');
    } 

    parser.on('attachment', (attachment, mail) => {
      console.log(`Writing ${attachment.fileName}...`);
      attachment.stream.pipe(fs.createWriteStream(attachment.generatedFileName));
    });

    parser.on('end', mail => {
      res.status(200).end();
    });

    parser.write(body);
    parser.end();
  });
});

app.listen(port, () => {
  console.log(`Listening on port ${port}`);
});