from datetime import date, datetime

def _days_since(date_str: str | None) -> float:
                                                                                           
    if not date_str:
        return 999.0
    for fmt in ("%Y-%m-%d", "%Y-%m", "%Y"):
        try:
            d = datetime.strptime(date_str, fmt).date()
            return float(max(0, (date.today() - d).days))
        except ValueError:
            continue
    return 999.0

def score(candidate: dict) -> float:
                                    
    signals = candidate.get("redrob_signals", {}) or {}

    days_inactive   = _days_since(signals.get("last_active_date"))
    recency         = max(0.0, 1.0 - days_inactive / 180.0)
    response_rate   = float(signals.get("recruiter_response_rate") or 0.0)
    open_to_work    = 1.0 if signals.get("open_to_work_flag") else 0.0

                                                                             
    if open_to_work and days_inactive < 7:
        response_rate = max(response_rate, 0.3)

    return float(min(1.0, 0.4 * recency + 0.4 * response_rate + 0.2 * open_to_work))