# pipeline_v2.py
import os
import re
import pandas as pd

try:
    import yfinance as yf
except Exception as e:
    raise ImportError(
        "yfinance is not installed. Add `yfinance>=0.2.40` to requirements.txt."
    ) from e


def _ensure_dir(path: str) -> None:
    os.makedirs(path, exist_ok=True)


def _ticker_for_query(t: str) -> str:
    """
    Prepare ticker for yfinance:
    - strip spaces
    - uppercase
    - DO NOT alter '.' or '-' (yfinance relies on them, e.g. NESN.SW, BRK-B)
    """
    return t.strip().upper()


def _ticker_for_filename(t: str) -> str:
    """
    Prepare a safe filename:
    - replace any char not [A-Za-z0-9] with '_'
    """
    return re.sub(r"[^A-Za-z0-9]", "_", t)


def update_ticker_csv(
    ticker: str,
    start: str = "2015-01-01",
    interval: str = "1d",
    dst_dir: str = "/mnt/data"
) -> str:
    """
    Download OHLCV for `ticker` using yfinance and save as CSV.
    Returns the CSV file path.
    """
    _ensure_dir(dst_dir)

    tkr_query = _ticker_for_query(ticker)
    tkr_file = _ticker_for_filename(tkr_query)

    df = yf.download(
        tkr_query,
        start=start,
        interval=interval,
        auto_adjust=False,
        progress=False,
        threads=True,
    )

    if df is None or df.empty:
        raise ValueError(
            f"No data returned for ticker '{tkr_query}' (start={start}, interval={interval}). "
            "Check the symbol and exchange suffix (e.g., NESN.SW, BMW.DE, VOD.L)."
        )

    # Ensure a clean Date index
    if not isinstance(df.index, pd.DatetimeIndex):
        df = df.reset_index()
        if "Date" in df.columns:
            df = df.set_index("Date")
        else:
            df.columns = ["Date"] + list(df.columns[1:])
            df = df.set_index("Date")

    df.index.name = "Date"

    csv_path = os.path.join(dst_dir, f"{tkr_file}_{interval}.csv")
    df.to_csv(csv_path)
    return csv_path