from typing import Tuple
import pandas as pd
from datetime import datetime


def time_based_split(
    df: pd.DataFrame,
    timestamp_col: str = "timestamp",
    train_pct: float = 0.70,
    val_pct: float = 0.85,
) -> Tuple[pd.DataFrame, pd.DataFrame, pd.DataFrame]:
    df_sorted = df.sort_values(timestamp_col)

    n_total = len(df_sorted)
    n_train = int(n_total * train_pct)
    n_val = int(n_total * val_pct)

    train = df_sorted.iloc[:n_train]
    val = df_sorted.iloc[n_train:n_val]
    test = df_sorted.iloc[n_val:]

    return train, val, test


__all__ = ["time_based_split"]