I am having serious problems decoding the message body of the emails I get using the Gmail API. I want to grab the message content and put the content in a div. I am using a base64 decoder, which I know won't decode emails encoded differently, but I am not sure how to check an email to decide which decoder to use -- emails that say they are utf-8 encoded are successfully decoded by the base64 decoder, but not be a utf-8 decoder.
I've been researching email decoding for several days now, and I've learned that I am a little out of my league here. I haven't done much work with coding around email before. Here is the code I am using to get the emails:
gapi.client.load('gmail', 'v1', function() {
var request = gapi.client.gmail.users.messages.list({
labelIds: ['INBOX']
});
request.execute(function(resp) {
document.getElementById('email-announcement').innerHTML = '<i>Hello! I am reading your <b>inbox</b> emails.</i><br><br>------<br>';
var content = document.getElementById("message-list");
if (resp.messages == null) {
content.innerHTML = "<b>Your inbox is empty.</b>";
} else {
var encodings = 0;
content.innerHTML = "";
angular.forEach(resp.messages, function(message) {
var email = gapi.client.gmail.users.messages.get({
'id': message.id
});
email.execute(function(stuff) {
if (stuff.payload == null) {
console.log("Payload null: " + message.id);
}
var header = "";
var sender = "";
angular.forEach(stuff.payload.headers, function(item) {
if (item.name == "Subject") {
header = item.value;
}
if (item.name == "From") {
sender = item.value;
}
})
try {
var contents = "";
if (stuff.payload.parts == null) {
contents = base64.decode(stuff.payload.body.data);
} else {
contents = base64.decode(stuff.payload.parts[0].body.data);
}
content.innerHTML += '<b>Subject: ' + header + '</b><br>';
content.innerHTML += '<b>From: ' + sender + '</b><br>';
content.innerHTML += contents + "<br><br>";
} catch (err) {
console.log("Encoding error: " + encodings++);
}
})
})
}
});
});
I was performing some checks and debugging, so there's leftover console.log
's and some other things that are only there for testing. Still, you can see here what I am trying to do.
What is the best way to decode the emails I pull from the Gmail API? Should I try to put the emails into <script>
's with charset
and type
attributes matching the encoding content of the email? I believe I remember charset only works with a src
attribute, which I wouldn't have here. Any suggestions?
For a prototype app I'm writing, the following code is working for me:
var base64 = require('js-base64').Base64;
// js-base64 is working fine for me.
var bodyData = message.payload.body.data;
// Simplified code: you'd need to check for multipart.
base64.decode(bodyData.replace(/-/g, '+').replace(/_/g, '/'));
// If you're going to use a different library other than js-base64,
// you may need to replace some characters before passing it to the decoder.
Caution: these points are not explicitly documented and could be wrong:
The users.messages: get
API returns "parsed body content" by default. This data seems to be always encoded in UTF-8 and Base64, regardless of the Content-Type
and Content-Transfer-Encoding
header.
For example, my code had no problem parsing an email with these headers: Content-Type: text/plain; charset=ISO-2022-JP
, Content-Transfer-Encoding: 7bit
.
The mapping table of the Base64 encoding varies among various implementations. Gmail API uses -
and _
as the last two characters of the table, as defined by RFC 4648's "URL and Filename safe Alphabet"1.
Check if your Base64 library is using a different mapping table. If so, replace those characters with the ones your library accepts before passing the body to the decoder.
1 There is one supportive line in the documentation: the "raw" format returns "body content as a base64url encoded string". (Thanks Eric!)