"""Minimum idle gap between RF/KISS frame sends (host-side pacing)."""
from __future__ import annotations

import threading
import time

MIN_TX_GAP_SEC = 1.5

_lock = threading.Lock()
_last_tx = 0.0


def tx_pace_before_send() -> None:
    """Sleep until at least MIN_TX_GAP_SEC since the previous send."""
    global _last_tx
    with _lock:
        now = time.monotonic()
        wait = MIN_TX_GAP_SEC - (now - _last_tx)
        if wait > 0:
            time.sleep(wait)
        _last_tx = time.monotonic()