Laravel orderby joining 2 tables without eloquent relationship

Question

I have 2 tables for a chatting system

"users" table structure:

id	name

"messages" table structure:

id	sender_id	receiver_id	message

I want to return friend users ordered by when there was chatting between you and friend last time. Note: id works same as timestamp

Suppose,

id	sender_id	receiver_id	message
1	$userA->id	$userB->id	abc
2	$userC->id	$userA->id	xyz

So, If $userA is the logged in user - I want users to be returned like:

[
    0 => $userC,
    1 => $userB,
    2 => $userD,
    3 => $userE,
    4 => $userF,
    ...
]

(where $userD, $userE, $userF has no messages with user $userA)

Basically I want to return all the friend users sorted using if user has any message with logged in user.

My current code giving me some unexpected result -

return DB::table('users')->leftJoin('messages', function ($join) {
    $join->on('users.id', '=', 'messages.sender_id')
        ->where('messages.sender_id', auth()->id())
        ->orOn('users.id', '=', 'messages.receiver_id')
        ->where('messages.receiver_id', auth()->id());
})
->select('users.*')
->where('users.id', '!=', auth()->id())
->orderBy('messages.id', 'asc')
->get();

Answer 1

Honestly I can't be sure if this will work as I can't testi it, but I think code should be something like:

$messagesSent = DB::table('messages')
    ->select('sender_id as other_user', DB::raw('MAX(id) as last_message_id'))
    ->where('receiver_id', auth()->id())
    ->groupBy('sender_id');

$messagesSentOrReceived = DB::table('messages')
    ->select('receiver_id as other_user', DB::raw('MAX(id) as last_message_id'))
    ->where('sender_id', auth()->id())
    ->groupBy('receiver_id')
    ->union($messagesSent);

$usersWithCommunication = DB::table('users')
    ->select('other_user', DB::raw('MAX(last_message_id) as last_message_id'))
    ->joinSub($messagesSentOrReceived, 'latest_messages', function ($join) {
        $join->on('users.id', '=', 'latest_messages.other_user');
    })
    ->groupBy('other_user');
    

return DB::table('users')
    ->leftJoinSub($usersWithCommunication, 'latest_communications', function ($join) {
        $join->on('users.id', '=', 'latest_communications.other_user');
    })
    ->select('users.*')
    ->orderBy('latest_communications.last_message_id', 'asc')
    ->get();