"""In-process sliding-window rate limiting for single-process deployments."""

from __future__ import annotations

import time
from collections import deque
from typing import Callable


class SlidingWindowRateLimiter:
    """Allow at most ``limit`` requests per key during a sliding time window."""

    def __init__(
        self,
        *,
        limit: int,
        window_seconds: float,
        clock: Callable[[], float] = time.monotonic,
    ) -> None:
        if limit < 1:
            raise ValueError("limit must be positive")
        if window_seconds <= 0:
            raise ValueError("window_seconds must be positive")
        self.limit = limit
        self.window_seconds = window_seconds
        self.clock = clock
        self._hits: dict[str, deque[float]] = {}

    def allow(self, key: str) -> bool:
        now = self.clock()
        hits = self._hits.setdefault(key, deque())
        while hits and now - hits[0] >= self.window_seconds:
            hits.popleft()
        if len(hits) >= self.limit:
            return False
        hits.append(now)
        return True