from pathlib import Path
from hashlib import sha256

datadir = Path('data')

def get_df_from_bq(sql: str, **opt):
    hashed = sha256(sql.encode("utf-8")).hexdigest()
    cache = datadir / "cache"
    cache.mkdir(exist_ok=True)
    fname = cache / f"{hashed}.csv"
    if fname.exists():
        return pd.read_csv(fname, **opt)
    else:
        client = bigquery.Client()
        df = client.query(sql).to_dataframe()
        df.to_csv(fname, index=False)
        return df