import time
import asyncio
from collections import deque

from attr import dataclass, ib


@dataclass(slots=True, frozen=True)
class AsyncThrottler:
    rate_limit: int
    period: float
    interval: float = 0.01

    tasks_times: deque = ib(factory=deque, init=False)

    def wait(self) -> None:
        now = time.time()

        while self.tasks_times:
            task_wait_time = now - self.tasks_times[0]

            if task_wait_time > self.period:
                self.tasks_times.popleft()
                continue

            break

    async def acquire(self) -> None:
        while True:
            self.wait()

            if len(self.tasks_times) < self.rate_limit:
                break

            await asyncio.sleep(self.interval)

        self.tasks_times.append(time.time())

    async def __aenter__(self) -> None:
        await self.acquire()

    async def __aexit__(self, exc_type, exc, tb) -> None:
        pass