/**
 * 
 * @param source 
 * @param period 
 * @param lookback_period 
 * @param size 
 * @returns 
 */
export async function rmi(
    source: Array<number>, period: number,
    lookback_period: number, size: number = source.length
) {

    const output: Array<number> = []

    // if (period < 1) throw new Error("Invalid Options")
    // if (lookback_period < 1) throw new Error("Invalid Options")
    // if (size <= lookback_period) throw new Error("Out of range")

    let gains_ema
    let losses_ema

    let i = lookback_period
    gains_ema = ((0) > (source[i] - source[i - lookback_period]) ? (0) : (source[i] - source[i - lookback_period]))
    losses_ema = ((0) > (source[i - lookback_period] - source[i]) ? (0) : (source[i - lookback_period] - source[i]))
    ++i

    output.push(gains_ema / (gains_ema + losses_ema) * 100)

    for (; i < size; ++i) {
        gains_ema = ((0) > (source[i] - source[i - lookback_period]) ? (0) : (source[i] - source[i - lookback_period]) - gains_ema) * 2. / (1 + period) + gains_ema
        losses_ema = ((0) > (source[i - lookback_period] - source[i]) ? (0) : (source[i - lookback_period] - source[i]) - losses_ema) * 2. / (1 + period) + losses_ema
        output.push(gains_ema / (gains_ema + losses_ema) * 100)
    }

    return output
}