Get gmail attachment's downloading URL?

Question

I am fetching Gmail Attachment through Gmail API using the get_user_message_attachment method , but the data it sends is in Base64 encoded form. I want to get the attachment's downloadable URL, which I can store and send to the frontend of my application. Is it possible to get the URL of the attachment in some way? I do not want to convert the Base64 string to a file on my server and then upload it somewhere and send that upload's link to the front-end.

@gmail_service = Google::Apis::GmailV1::GmailService.new
#authorization stuff is done and then I fetch the attachment which is received as a Google::Apis::GmailV1::MessagePartBody response
resp = @gmail_service.get_user_message_attachment("[email protected]", message_id, attachment_id)
# resp.data contains the base64 encoded string

I want the attachment as a downloadable URL, so that I don't have to do the manual file conversion and uploading stuff.

Answer 1

The message.get method returns a Message object

This object contains the body of the message base64 encoded.

If you want a downloadable url I suggest that you convert the Base64 string to a file on your server and then upload it somewhere and send that upload's link to the front-end.

There is no other option this is the data the API returns.

Answer 2

You may want to consider providing a proxy endpoint on your server for your frontend. Then give your frontend a link to this endpoint with a messageId, and make your server download the Gmail message and stream it to your client.

This is Aqueduct(Dart) sample code:

1. Have a dedicated route for attachments (tempToken&fileName is optional, also contentType can be derived from attachment data):

..route('/attachments/:tempToken/:msgId/:attachmentId/:fileName').link(() => AttachmentsController(ctx))

2. The controller essentially loads an attachment by msgId&attachmentId and gives its content to a client:

@Operation.get('tempToken', 'msgId', 'attachmentId', 'fileName') Future<Response> getAttachment(
  @Bind.path('tempToken') String tempToken, //
  @Bind.path('msgId') int msgId,
  @Bind.path('attachmentId') String attachmentId,
  @Bind.query('contentType') String contentType) async {

...

final attachment = await mailbox.readAttachment(messageId,attachmentId);

return Response.ok(attachment)
  ..encodeBody = false
  ..contentType = ContentType.parse(contentType);   }

3. We use Google provided Gmail API library. This is mailbox.readAttachment:

@override
Future<List<int>> readAttachment(String messageId, String attachmentId) async => (await _gmail.users.messages.attachments.get('me', messageId, attachmentId)).dataAsBytes;