import time
from collections import deque


class HistoryStore:
    def __init__(self, maxlen: int) -> None:
        self._buf: deque[tuple[float, dict[str, float | int | None]]] = deque(maxlen=maxlen)

    def record(self, sample: dict[str, float | int | None]) -> None:
        self._buf.append((time.time(), sample))

    def snapshot(self) -> list[tuple[float, dict[str, float | int | None]]]:
        return list(self._buf)

    def latest(self) -> dict[str, float | int | None] | None:
        return self._buf[-1][1] if self._buf else None

    def __len__(self) -> int:
        return len(self._buf)