Get the last message postgres - sql

Question

I'm using Laravel to build something like a chat, i'd like to get the last message from user X and Y:
I have this table called "messages"
id integer
receiver_id integer references user
sender_id integer references user
message text
created_at datetime
Here I have a the message, when and who send the message;
$user = JWTAuth::toUser();
$messages = DB::table("messages")
->select(DB::raw(
"least(sender_id, receiver_id) as user_1,
greatest(sender_id, receiver_id) as user_2,
max(created_at) as last_timestamp,
max(message) as message"))
->where("sender_id", $user->id)
->orWhere("receiver_id", $user->id)
->groupBy(DB::raw("least(sender_id, receiver_id), greatest(sender_id, receiver_id)"))
->orderBy("last_timestamp", "desc")
->get();
$message_info = array();
foreach($messages as $k => $m) {
$message_info[$k]['message'] = $m->message;
$message_info[$k]['last_message'] = $m->last_timestamp;
if($m->user_2 == $user->id){
$message_info[$k]['user_id'] = $m->user_1;
}else{
$message_info[$k]['user_id'] = $m->user_2;
}
}
Here I list the users that have messages
$listUserHaveMessage = [];
foreach ($messages as $message){
if($message->user_2 == $user->id){
$listUserHaveMessage[] = $message->user_1;
}else{
$listUserHaveMessage[] = $message->user_2;
}
}
And here the users that not have send messages
$notMessage = User::where("client_id",'=',$user->client_id)
->where("id","!=", $user->id)
->where("is_visible",'=', true)
->whereNotIn("id", $listUserHaveMessage)
->get();
foreach ($notMessage as $m){
$listUserNotHaveMessage[] = $m->id;
}
Now I make the merge of arrays and a query to get all users
$list_users = array_merge($listUserHaveMessage, $listUserNotHaveMessage);
$idsImploded = implode(',',$list_users);
$users = User::where("client_id",'=',$user->client_id)
->where("id","!=", $user->id)
->where("is_visible",'=', true)
->whereIn("id", $list_users)
->orderByRaw(DB::raw("position(id::text in '$idsImploded')"))
->get();
$outPut = array();
foreach($users as $k => $u){
$outPut['usuarios'][$k] = $u;
}
My question is:
How to merge the last message to User array??
There is a way to do it??
Thanks