Retrieving the users first unread message ID on a channel

A common request is to get the first or 'oldest' unread message a user has in a channel. 

Since it is channels that are marked as read/unread, not specific messages, getting this message id  requires some extra steps in your implementation. Luckily, it's a fairly straightforward process. 

1. Retrieve the users unread count on the channel.

const unreadCount = channel.countUnread()

2. Query the channel messages based on this count. For this example, the unread count will be 7. 

const channelWithFirstUnreadMessage = await channel.query({messages: {offset: unreadCount - 1, limit: 1}})

Edge Case: If the unreadCount is equal to the number of channel messages, the query will not return any messages. To account for this, set the offset to unreadCount - 1. If the unreadCount is zero, exit the function as there will be no need to retrieve an ID. 

The query will return a channel instance with the messages array offset to the number you provided. So - in this case, the first message returned will be 7 messages before the most recent message (the oldest timestamped unread message) 

Set the limit to 1 as only one message ID is required for this. 

3. Lastly, extract the message id from the response

const firstUnreadMessageId = channelWithFirstUnreadMessage.messages[0].id

Now the ID can be used to render a message list near that message ID. 

The SDKs have built-in methods to support this:

React - jumpToMessage docs

React Native - loadChannelAroundMessage docs

iOS - ChannelController.loadPageAroundMessageId()