import re

def format_currency(amount: float, symbol: str = "€", is_german: bool = True) -> str:
    """Formats a numeric amount to a currency string representation."""
    if is_german:
        return f"{amount:.2f}".replace(".", ",") + f" {symbol}"
    else:
        return f"{symbol}{amount:.2f}"

def format_date(iso_timestamp: str) -> str:
    """Converts ISO timestamp to German date format DD.MM.YYYY."""
    try:
        date_part = iso_timestamp.split("T")[0]
        parts = date_part.split("-")
        if len(parts) == 3 and all(p.isdigit() for p in parts) and len(parts[0]) == 4:
            return f"{parts[2]}.{parts[1]}.{parts[0]}"
    except Exception:
        pass
    return iso_timestamp[:10]


def validate_pin(pin: str) -> bool:
    """Validates that a PIN consists of at least 4 numeric digits."""
    return bool(re.match(r"^\d{4,}$", pin))

def parse_price(price_str: str) -> float:
    """Parses a string containing a price (handling comma and dot) to a float.
    Raises ValueError if invalid.
    """
    clean_str = price_str.replace(",", ".").strip()
    price = float(clean_str)
    if price < 0:
        raise ValueError("Price cannot be negative")
    return price