christophercliff · February 24, 2019 23:30 · Nov 30, 2013 · Nov 30, 2013
diff --git a/description.md b/description.md
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+# Stream email attachments to S3 using Mailgun, node.js
+
+Using:
+
+- [Mailgun](https://mailgun.com)
+- [express](http://expressjs.com/)
+- [request](https://github.com/mikeal/request)
+- [busboy](https://github.com/mscdex/busboy)
+- [s3-streaming-upload](https://github.com/apiaryio/s3-streaming-upload)
+
+## 1. Mailgun setup
+
+First define a [Mailgun Route](http://documentation.mailgun.com/user_manual.html#routes) using the [`store`](http://documentation.mailgun.com/user_manual.html#storing-and-retrieving-messages) action:
+
+```
+Filter Expression: match_recipient("save@YOUR_DOMAIN")
+Action: store(notify="YOUR_ROUTE")
+```
+
+We could forward the email directly to the handler, however this approach allows us to verify the email prior to doing anything with the attachments.
+
+## 2. Express setup
+
+See `email.js`.
diff --git a/email.js b/email.js
@@ -0,0 +1,87 @@
+var _ = require('underscore')
+var assert = require('assert')
+var async = require('async')
+var connectBusboy = require('connect-busboy')
+var express = require('express')
+var request = require('request')
+var Uploader = require('s3-streaming-upload').Uploader
+
+var server = module.exports = express()
+var parser = connectBusboy({
+    immediate: true,
+    files: 0
+})
+
+server.post(YOUR_ROUTE, [parser], postEmail)
+
+function postEmail(req, res) {
+    parse(req.busboy, function(err, _res, body){
+        if (err) throw err
+        if (_res.statusCode !== 200) throw new Error('unable to retrieve message')
+        var msg = JSON.parse(body)
+        console.log('saving work for ' + msg.sender + '...')
+        upload(msg, function(err, attachments){
+            if (err) throw err
+            console.log('work saved')
+            return res.send({ attachments: _.map(attachments, function(a){ return a.location }) })
+        })
+    })
+}
+
+function parse(busboy, callback) {
+    var url
+    busboy
+        .on('error', function(err){
+            return callback(err)
+        })
+        .on('field', function(name, value){
+            if (name !== 'message-url') return
+            url = value
+        })
+        .on('end', function(){
+            if (!url) return callback(new Error('message url does not exist'))
+            return request.get(url, callback).auth('api', YOUR_MAILGUN_API_KEY, false)
+        })
+}
+
+function upload(msg, callback) {
+    var tasks
+    try {
+        assert(_.isObject(msg), 'message must be an object')
+        assert(_.isArray(msg.attachments), 'message must have an attachments array')
+        tasks = _.map(msg.attachments, function(attachment){
+            return async.apply(uploadAttachment, attachment)
+        })
+    } catch (ex) {
+        return callback(ex)
+    }
+    return async.parallel(tasks, callback)
+}
+
+function uploadAttachment(attachment, callback) {
+    var readStream
+    var options
+    try {
+        assert(_.isObject(attachment), 'must have an attachment')
+        assert(_.isString(attachment.url), 'attachment must have a url')
+        assert(_.isString(attachment['content-type']), 'attachment must have a content type')
+        assert(_.isString(attachment.name), 'attachment must have a name')
+        readStream = request.get(attachment['url']).auth('api', YOUR_MAILGUN_API_KEY, false)
+        options = {
+            accessKey: YOUR_AWS_KEY,
+            secretKey: YOUR_AWS_SECRET,
+            bucket: YOUR_AWS_BUCKET,
+            objectName: attachment.name,
+            objectParams: {
+                ACL: 'public-read',
+                ContentType: attachment['content-type']
+            },
+            stream: readStream
+        }
+    } catch (ex) {
+        return callback(ex)
+    }
+    new Uploader(options)
+        .on('completed', callback)
+        .on('failed', callback)
+}
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