Go-Mail multiple recipients and attachment - go

I am trying to make an email service using go-mail library and made it working. However there are few challenges that i am unable to solve
I have the struct for form data-
type SendMailBody struct {
EmailTo []string `form:"sendTo"`
Subject string `form:"subject"`
Body string `form:"body"`
}
The form data that i am sending to the API is
subject: Notification
sendTo:["abc#gmail.com", "xyz#gmail.com"]
body:You have been notified
Challenges-
If I pass a single email in "sendTO", It is working fine. But after passing the slice of emails, it is unable to send emails to the recepients. How can i make it work?
If I pass the attachment through Form data, how can I attach it with the mail. In documentation, it is mentioned that we can do it like that "m.Attach("/tmp/image.jpg")" . But how should i do it if i pass the attachment via form data in API
Please guide me through that.

Some more details are needed to help here. In particular which go-mail are you using?
For 1.)
If you refer to https://github.com/wneessen/go-mail, using Msg.To() should work fine with multiple recipient. See the documentation at: https://pkg.go.dev/github.com/wneessen/go-mail#Msg.To
If you refer to https://github.com/go-mail/mail, there is Message.SetAddressHeader() (https://pkg.go.dev/github.com/go-mail/mail?utm_source=godoc#Message.SetAddressHeader) which does not support multiple recipient addresses. You would need to use Message.SetHeaders() for the "To"-header instead (https://pkg.go.dev/github.com/go-mail/mail?utm_source=godoc#Message.SetHeaders).
For 2.)
This totally depends on how you read the attachment data (and again also on the go-mail library you are using). https://github.com/wneessen/go-mail has different ways of attaching and embedding files (i. e. from a local file, from embedFS, from an io.Reader...)

Related

Attach meta data / custom data to slack messages sent through the API

I am developing a series of Slack apps for my workspace, and some of them are meant to interact with the content (messages) delivered by the other apps : extracting content IDs that may be referred to by other messages
A concrete example :
Suppose I have an app A "FindUser" that is capable of giving me the user profile when a slack user types find me#example.com, and it replies in the thread with a formatted view of the user profile
I am developing an app B "EditTags", which basically gives me a right click option with "edit tags" (see Slack's Interactive Components/Actions), the idea being that a user could first ask app A to find a user, and then right click on the reply from App A and click the "edit tags" action given by the other app. What this app B does it actually retrieve the tags for the user mentionned by the previous message from app A, and in another reply to the thread it gives some controls to either delete an existing tag OR it shows a select with autocomplete to add new tags.
The B app needs to retrieve the user ID that the A app mentionned previously. So I need some way to pass that data directly in the slack message. When looking at the examples, slack does not seem to provide a way to add arbitrary "metadata" to a message, am I wrong ? Do you have workaround for this ? I mean I could totally send the user ID say, in the footer, so I can just read the footer, but I was planning to use the footer for something else... Is there a way to pass metadata hrough properties that would be hidden to the end user ?
Although this does not feel relevant, I am building a slack nodeJS app using the node slack sdk (and especially the #slack/interactive-messages package)
For the most part the Slack API does not provide any official means to attach custom data / meta data to messages. But with some simple "hacks" it is still possible. Here is how:
Approach
The basic approach is to use an existing field of the message as container for your data. Obviously you want to pick a field that is not directly linked to Slack functionality.
Some field are not always needed, so you can just use that field as data container. Or if its needed, you can include the functional value of that field along with your custom data in the data container.
For example for message buttons you could use the value field of a button and structure your code in a way that you do not need it in its original function. Usually its sufficient to know which button the user client (via the name field), so the value field is free to be used for your custom data. Or you can include the functional value of your button along with the custom data in a data container (e.g. a JSON string) in that field.
Serialization
All messages are transported through HTTP and mostly encoded as UTF-8 in JSON. So you want to serialize / de-serialize your data accordingly, especially if its binary data. If possible I would recommend to use JSON.
Length
The maximum allowed length of most fields is documented in the official Slack API documentation. e.g. for the value field for message buttons can contain up to 2.000 characters. Keep in mind that you need to consider the length of your data after serialization. e.g. if you convert binary data into Base64 so it can be transported with HTTP you will end up with about 1.33 characters for every byte.
Contents
In general I would recommend to keep your data container as small as possible and not include the actual data, but only IDs. Here are two common approaches:
Include IDs of your data objects and load the actual objects
from a data store when the request is later processed.
Include the ID of server session and when processing the request you
can restore the corresponding server session which contains all data
objects.
In addition you might need to include functional values so that the functionality of the field you are using still works (e.g. value of a menu option, see below)
Implementation
Dialogs
Dialogs provide an official field for custom data called state. Up to 3.000 characters.
Message buttons
For Message buttons you can use the message action fields / value. Up to 2.000 characters. Its also possible to use the name field, but I would advise against it, because the maximum allowed length of that field is not documented.
Message menus
For Message menus you can use the value field of an option or the name field of the menu action.
Usually the value field is the better approach, since you have a documented max length of 2.000 and it gives you more flexibility. However, you will need to combine you custom data with the actual functional value for each option. Also, this will not work for dynamic select elements (like users), where you can not control the value field.
When using the name field note, keep in mind that the maximum allowed length of name is not documented, so you want to keep you data as short as possible. Also, if you want to use more than one menu per attachment you need to include the actual name of the menu into your data container.
Normal message attachments
Normal message attachments do not contain any suitable field to be used as container for custom data, since all fields are linked to Slack functionality.
Technically you could use the fallback field, but only if you are 100% sure that your app is never used on a client that can not display attachments. Otherwise your data will be displayed to the user.

Transmission api setting wrong To header when specify header_to with multiple recipients

I'm trying to send an email to multiple people(multiple to addresses) and have them all listed in the email clients like a regular email. When I set the header_to field on all recipients to email1#foo.com, email2#foo.com I end up with emails that have a to header set to "First Name" <email1#foo.com, email2#foo.com> which is incorrect.
This shows up as a single person with multiple email addresses in most clients and the header is wrong.
Why is the sparkpost transmission api messing with the header_to field? It's docs say that it uses this in place of generating a To header for you.
After going through every page of docs I could find to try and figure out how sparkpost's backend works I've found that you must omit the Name field on all recipients.
https://developers.sparkpost.com/api/recipient-lists/#header-recipient-object

Is there a way to fetch the attachments of an email message?

I'm using the default net/pop class in order to fetch emails from a specific email account. From each message, I need to read all attachments and extract some data from them. But I can't find any way to achieve that! Seems like the POPMail class doesn't have a specific method to get the message's attachments.

Returning custom contact fields via the Google contacts api

I have been unable to return any UserDefined/custom fields for a contact. I'm not even wanting to create or update an existing entry as per Programatically adding "New Custom Field" To Google Contacts using Google contact API
I have followed the guide here https://developers.google.com/google-apps/contacts/v3/reference, but still to no avail.
I've called both
https://www.google.com/m8/feeds/contacts/default/full?alt=json
and
https://www.google.com/m8/feeds/contacts/default/full/DEADBEEF?alt=json
in an attempt to get ALL of the values returned. I thought I might have to call each contact id specifically to get the full details, but that doesn't work either.
DEADBEEF is clearly replaced with a valid contact id in my scenario.
/contacts/default determines that request should return contacts for the current auth'd user, which is myself in this case.
Has anyone managed to return custom values, is this even possible?
Thanks
I found the answer, add the ?v=3.0 to the url string eg
https://www.google.com/m8/feeds/contacts/default/full/DEADBEEF?alt=json&v=3.0
However, you should use the preferred method of adding a GData-Version header.

How can I use Parse to send data to specific user

I'm creating an online game which have to send data between users. I chose Parse as the backend service. How can I use Parse to do this task?
Query for the user that you want to send data to and send data
Take a look a the Parse Docs. What you want to do is documented very well there.
https://parse.com/docs/android_guide
Take a look at saving and retrieving objects.
Also make sure your console (where you can see the "User" class and all your other classes) is set up with the objects you need.

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