import polars as pl
import pandas as pd
from typing import Union, Optional, List
import io

def health_facility_accessibility_analysis(
    data: Union[str, pd.DataFrame, pl.DataFrame, io.BytesIO],
    travel_time_col: Optional[str] = None,
    distance_col: Optional[str] = None,
    thresholds_minutes: int = 60
) -> pl.DataFrame:
    """
    Health Facility Accessibility Analysis
    =====================================

    What
    ----
    Assess access by travel time/distance to nearest health facility.

    When
    ----
    Health access studies and service planning.

    Why
    ---
    Identify underserved areas.

    Parameters
    ----------
    data : str | pd.DataFrame | pl.DataFrame | io.BytesIO
        Input dataset.
    travel_time_col : str | None
        Travel time to nearest facility (minutes).
    distance_col : str | None
        Distance to nearest facility (km).
    thresholds_minutes : int, default 60
        Time threshold for acceptable access.

    Returns
    -------
    pl.DataFrame
        Placeholder access flags.
    """
    if isinstance(data, str):
        df = pl.read_csv(data)
    elif isinstance(data, io.BytesIO):
        df = pl.read_csv(data)
    elif isinstance(data, pd.DataFrame):
        df = pl.from_pandas(data)
    elif isinstance(data, pl.DataFrame):
        df = data
    else:
        raise TypeError("Unsupported data type")
    return df.with_columns(pl.lit(False).alias("has_acceptable_access_placeholder"))
