import asyncio,time
BASE,MAX,STEP,CALM,CAP=0.5,2.0,0.25,5.0,20
class State:
    __slots__=("slot","interval","last","tasks")
    def __init__(s):s.slot=0.0;s.interval=BASE;s.last=0.0;s.tasks=set()
class Limiter:
    def __init__(s):s.users={}
    def admit(s,uid):
        now=time.monotonic();st=s.users.get(uid)
        if st is None:st=s.users[uid]=State()
        if len(st.tasks)>=CAP:return st,None,True
        if now-st.last>CALM:st.interval=BASE
        wait=max(0.0,st.slot-now)
        if wait>0:st.interval=min(MAX,st.interval+STEP)
        st.slot=max(now,st.slot)+st.interval;st.last=now
        return st,wait,False
    def flush(s,st):
        n=len(st.tasks)
        for t in list(st.tasks):t.cancel()
        st.tasks.clear();st.slot=0.0;st.interval=BASE;return n
    def track(s,uid,st,task):
        st.tasks.add(task)
        def done(t):
            st.tasks.discard(t)
            if not st.tasks and time.monotonic()-st.last>CALM*2 and s.users.get(uid) is st:s.users.pop(uid,None)
        task.add_done_callback(done)