from __future__ import annotations

import json
import time
from pathlib import Path


class Tracker:
    def __init__(self, path: Path):
        self.path = Path(path); self.path.parent.mkdir(parents=True, exist_ok=True)
        self.t0 = time.time()

    def log(self, **kw) -> None:
        kw["elapsed_s"] = round(time.time() - self.t0, 1)
        with open(self.path, "a") as fh:
            fh.write(json.dumps(kw, default=float) + "\n")