public async Task Join(GroupChangeEvent evt)
{
//todo add all user connections to group(s)
var userId = await _userStore.GetUserIdForConnectionAsync(Context.ConnectionId);
var connections = await _userStore.GetUserConnectionsAsync(userId);
var tasks = evt.Groups
.Select(group => Groups.AddToGroupAsync(Context.ConnectionId, group));
await Task.WhenAll(tasks);
await _userStore.AddUserToGroupsAsync(userId, evt.Groups);
// send presence event
var presenceEvents = evt.Groups.Select(g => new PresenceEvent
{
Action = PresenceAction.Join,
Group = g,
Uuid = userId
});
var presenceTasks = presenceEvents.Select(e => Clients.GroupExcept(e.Group, connections).Presence(e));
await Task.WhenAll(presenceTasks);
}