Enter TOP:

join() default channel
if failed, join() personal channel
if failed, exit() with error

Join channel:

check() ban/invite, if fails then don't move
unjoin() current channel
join() new channel
if failed, join() default channel
if failed, join() personal channel
if failed, exit() with error

Banned/uninvited from current channel:

unjoin() current channel
join() default channel
if failed, join() personal channel
if failed, exit() with error