import _thread

class SafeQueue:
    """A lightweight, thread-safe FIFO queue for MicroPython."""
    def __init__(self, maxsize=20):
        self._queue = []
        self._lock = _thread.allocate_lock()
        self.maxsize = maxsize

    def put(self, item) -> bool:
        """Push an item to the end of the queue. Returns False if queue is full."""
        with self._lock:
            if len(self._queue) < self.maxsize:
                self._queue.append(item)
                return True
            else:
                print("[Queue Warning] Buffer full, dropping oldest message.")
                self._queue.pop(0)  # Drop oldest to make room
                self._queue.append(item)
                return False

    def get(self):
        """Pop and return the oldest item from the queue, or None if empty."""
        with self._lock:
            if self._queue:
                return self._queue.pop(0)
        return None

    def empty(self) -> bool:
        """Check if the queue has no items."""
        with self._lock:
            return len(self._queue) == 0

    def size(self) -> int:
        """Return current number of queued items."""
        with self._lock:
            return len(self._queue)