inbound-parse-multipart-parser

A javascript/nodejs multipart/form-data parser which operates on data from SendGrid's Inbound Parse Webhook.

For example, a SendGrid Inbound Parse webhook pointing to an Azure Function

author

Cristian Salazar was the author of the original parser. You can find the original [here][https://github.com/freesoftwarefactory/parse-multipart#readme]. I, Allistair Vilakazi, just adapted the code to be able to parse the specific multipart/form-data format of SendGrid's Inbound Parse Webhook.

Background

Sometimes you only have access to the raw multipart payload and it needs to be parsed in order to extract the data contained on it. As an example: an Azure Function, which will operate as a facade between the http client (SendGrid Inbound Parse Webhook) and your response (sending a dynamic email using the SendGrid bindings and it's dynamic template).

The raw payload formatted as multipart/form-data will looks like this one:

...
--xYzZy
Content-Disposition: form-data; name="html"

<div dir=\"ltr\">This is the message body sent from an email.</div>
--xYzZY
Content-Disposition: form-data; name="from"

Allistair Vilakazi <[e-mail]>
--xYzZY
Content-Disposition: form-data; name="text"

This is the message body sent from an email.
--xYzZY--

The lines above represents a raw multipart/form-data payload sent by the SendGrid Inbound Parse Webhook via email. We need to extract the all data contained inside it.

Usage

In the next lines you can see a implementation. In this case two key values needs to be present:

• body, which can be:

--xYzZY
Content-Disposition: form-data; name="text"

This is the message body sent from an email.
--xYzZY--

• boundary, the string which serve as a 'separator' between parts, it normally comes to you via headers. In this case, the boundary is:

    xYzZY

Now, having this two key values then you can implement it:

    var multipart = require('multipart.js');

    var body = Buffer.from(req.rawBody),'utf-8');
    
    var boundary = multipart.getBoundary(req.headers['content-type']);
    var parts = multipart.Parse(body,boundary);
    
    for(var i=0;i<parts.length;i++){
        var part = parts[i];
        // will be:
        // { name: 'text', data: 'This is the message body sent from an email.' }
    }

The returned data is an array of parts, each one described by a name and a data, this latter being a String.