gmail api - Where to find body of email depending of mimeType

Question

I am making a request to the User.messages endpoint. All objects returned (the emails) have a mimeType property which I'm struggling to understand.

More specifically, I want to be able to extract the body of the email depending of the mimeType since I've been able to notice that depending on the mimeType, the body will be inside the body property in payload, or in the parts array. What are the different mimeTypes that can be returned, and where can I find the body of the email for each one of them?

Answer 1

I think it will make sense if you think of the payload as a part in of itself. Let's say I send a message with just a subject and a plain message text:

From: emtholin@gmail.com
To: emtholin@gmail.com
Subject: Example Subject

This is the plain text message

This will result in the following parsed message:

{
 "id": "154ecb53c10b74d8",
 "threadId": "154ecb53c10b74d8",
 "labelIds": [
  "INBOX",
  "SENT"
 ],
 "snippet": "This is the plain text message",
 "historyId": "38877",
 "internalDate": "1464260181000",
 "payload": {
  "partId": "",
  "mimeType": "text/plain",
  "filename": "",
  "headers": [
   ...
  ],
  "body": {
   "size": 31,
   "data": "VGhpcyBpcyB0aGUgcGxhaW4gdGV4dCBtZXNzYWdlCg=="
  }
 },
 "sizeEstimate": 355
}

If I send a message with a plain text part, a html part and an image, it will look like this when parsed:

{
 "id": "154ed5ccaa12f3df",
 "threadId": "154ed5ccaa12f3df",
 "labelIds": [
  "SENT",
  "INBOX",
  "IMPORTANT"
 ],
 "snippet": "This is a plain/html message with an image.",
 "historyId": "841379",
 "internalDate": "1464271162000",
 "payload": {
  "mimeType": "multipart/mixed",
  "filename": "",
  "headers": [
     ...
  ],
  "body": {
   "size": 0
  },
  "parts": [
   {
    "mimeType": "multipart/alternative",
    "filename": "",
    "headers": [
     {
      "name": "Content-Type",
      "value": "multipart/alternative; boundary=089e0122896c7c80d80533bf3205"
     }
    ],
    "body": {
     "size": 0
    },
    "parts": [
     {
      "partId": "0.0",
      "mimeType": "text/plain",
      "filename": "",
      "headers": [
       {
        "name": "Content-Type",
        "value": "text/plain; charset=UTF-8"
       }
      ],
      "body": {
       "size": 47,
       "data": "VGhpcyBpcyBhIHBsYWluL2h0bWwgKm1lc3NhZ2UqIHdpdGggYW4gaW1hZ2UuDQo="
      }
     },
     {
      "partId": "0.1",
      "mimeType": "text/html",
      "filename": "",
      "headers": [
       {
        "name": "Content-Type",
        "value": "text/html; charset=UTF-8"
       }
      ],
      "body": {
       "size": 73,
       "data": "PGRpdiBkaXI9Imx0ciI-VGhpcyBpcyBhIHBsYWluL2h0bWwgPGI-bWVzc2FnZTwvYj4gd2l0aCBhbiBpbWFnZS48L2Rpdj4NCg=="
      }
     }
    ]
   },
   {
    "partId": "1",
    "mimeType": "image/png",
    "filename": "smile.png",
    "headers": [
       ...
    ],
    "body": {
     "attachmentId": "ANGjdJ-OrSy7VAYL-UbRyNtmySbZLlV-fV43zJF0_neNGZ8yKugsZAxb32eSb-CrbYIhF9NvjGwBVEjSkRrUWoCS7aDpgoQnt9WR7f2sa17qVEyOg_JVSbrGrunirvQw2dY-SxxB3Y0JP3aYDHSBXpNO6fFCByVFWQDw1et5Mh9di7bGO4AWOLKFVe_Yb2RmdDwuazGXGb8zA88TTMaiEPIacPTNiVtBrIWG0EKGxHBhep9j8ujyWeCS5P9X80dBHvBNj4T9XjUwcrN6FvwegRewRMM9cBupY7jQESR7915OcbhCNyi5l64x6vVh1ZU",
     "size": 2002
    }
   }
  ]
 },
 "sizeEstimate": 3077
}

You will see it's just the RFC822-message parsed to JSON. If you just traverse the parts, and treat the payload as a part itself, you will find what you are looking for.

var parts = [response.payload];

while (parts.length) {
  var part = parts.shift();
  if (part.parts) {
    parts = parts.concat(part.parts);
  }

  if(part.mimeType === 'text/html') {
    var decodedPart = decodeURIComponent(escape(atob(part.body.data.replace(/-/g, '+').replace(/\_/g, '/'))));
    console.log(decodedPart);
  }
}