"""외국인 N일 누적 순매수 강도 (시총 대비)."""

import pandas as pd

from .base import ScoreNode, percentile_rank


class ForeignBuy(ScoreNode):
    name  = "foreign_buy"
    label = "외국인 누적 순매수"
    default_params = {"window_days": 5}
    param_schema = {
        "type": "object",
        "properties": {
            "window_days": {"type": "integer", "minimum": 1, "maximum": 60, "default": 5}
        },
    }

    def compute(self, ctx, params: dict) -> pd.Series:
        window = int(params.get("window_days", 5))
        flow = ctx.flow
        if flow.empty:
            return pd.Series(dtype=float)

        last_dates = (
            flow.sort_values("date").groupby("ticker").tail(window)
        )
        net_sum = last_dates.groupby("ticker")["foreign_net"].sum()

        market_cap = ctx.master["market_cap"].fillna(0).reindex(net_sum.index)
        raw = (net_sum / market_cap.replace(0, pd.NA)).astype(float)

        return percentile_rank(raw).fillna(50.0)