import json
from functools import lru_cache
from pathlib import Path

import pandas as pd


def list_sessions(sessions_dir: str) -> list[str]:
    return sorted(
        [p.name for p in Path(sessions_dir).iterdir() if p.is_dir()],
        reverse=True,
    )


@lru_cache(maxsize=8)
def load_session(sessions_dir: str, name: str) -> tuple[pd.DataFrame, dict]:
    base = Path(sessions_dir).resolve() / Path(name).name
    if not str(base).startswith(str(Path(sessions_dir).resolve())):
        raise ValueError(f"Invalid session: {name}")
    df = pd.read_parquet(base / "telemetry.parquet")
    df["t"] = df["timestamp"] - df["timestamp"].iloc[0]
    info = json.loads((base / "session_info.json").read_text())
    return df, info