import asyncio
import logging
import time
from typing import Optional

logger = logging.getLogger(__name__)


class RateLimiter:
    """
    Enforces minimum delay between requests to avoid throttling.
    Thread-safe for async use within a single event loop.
    """

    def __init__(self, min_interval_seconds: float = 3.0):
        self.min_interval = min_interval_seconds
        self._last_request_time: Optional[float] = None
        self._lock = asyncio.Lock()

    async def acquire(self):
        async with self._lock:
            now = time.monotonic()
            if self._last_request_time is not None:
                elapsed = now - self._last_request_time
                wait_time = self.min_interval - elapsed
                if wait_time > 0:
                    logger.info(
                        f"Rate limiter: waiting {wait_time:.1f}s "
                        f"(min interval: {self.min_interval}s)"
                    )
                    await asyncio.sleep(wait_time)
            self._last_request_time = time.monotonic()