import numpy as np

from pandas import DataFrame, Series

def calculate_moving_average(data: DataFrame, window: int = 200) -> Series:
    """
    Calculate the moving average and return it as a Series.
    """
    return data['Close'].rolling(window=window).mean()

def calculate_rsi(data: DataFrame, period: int = 4) -> Series:
    """
    Calculate the RSI and return it as a Series.
    """
    delta = data['Close'].diff()
    gain = np.where(delta > 0, delta, 0)
    loss = np.where(delta < 0, -delta, 0)

    alpha = 1 / period
    avg_gain = Series(gain).ewm(alpha=alpha, adjust=False).mean()
    avg_loss = Series(loss).ewm(alpha=alpha, adjust=False).mean()

    rs = avg_gain / avg_loss
    return 100 - (100 / (1 + rs))

def signals(data: DataFrame) -> Series:
    """
    Calculate signals for the RSI PowerZones strategy.
    Returns a Series with 'L' for long signals and 'N' otherwise.
    """
    ma_200 = calculate_moving_average(data, window = 200)
    rsi_4 = calculate_rsi(data, period = 4)

    above_ma_200 = data['Close'] > ma_200
    rsi_below_30 = rsi_4 < 30

    conditions = above_ma_200 & rsi_below_30
    return Series(np.where(conditions, 'L', 'N'), index = data.index)