// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Ulcer Index (UI)", shorttitle="UI", format=format.price, precision=2, overlay=false)

//@function Calculates the Ulcer Index (UI).
//@param src The source series. Default is `close`.
//@param period The lookback period. Default is 14.
//@returns float The Ulcer Index value.
ui(series float src, int period) =>
    var deque = array.new_int(0)
    var src_buffer = array.new_float(period, na)
    var int current_index = 0
    float current_val = nz(src)
    array.set(src_buffer, current_index, current_val)
    while array.size(deque) > 0 and array.get(deque, 0) <= bar_index - period
        array.shift(deque)
    while array.size(deque) > 0
        int last_index_in_deque = array.get(deque, array.size(deque) - 1)
        int buffer_lookup_index = last_index_in_deque % period
        if array.get(src_buffer, buffer_lookup_index) <= current_val
            array.pop(deque)
        else
            break
    array.push(deque, bar_index)
    int highest_index = array.get(deque, 0)
    int highest_buffer_index = highest_index % period
    highestClose = array.get(src_buffer, highest_buffer_index)
    current_index := (current_index + 1) % period
    percentDrawdown = ((src - highestClose) / highestClose) * 100.0
    squaredDrawdown = math.pow(percentDrawdown, 2)
    sumSquaredDrawdown = math.sum(squaredDrawdown, period)
    averageSquaredDrawdown = sumSquaredDrawdown / period
    ui = math.sqrt(averageSquaredDrawdown)
    ui

// Inputs
i_src_ui = input.source(close, "Source")
i_period_ui = input.int(14, "Period", minval=1, tooltip="Lookback period for calculating the Ulcer Index.")

// Calculation
uiValue = ui(i_src_ui, i_period_ui)

// Plot
plot(uiValue, "UI", color=color.yellow, linewidth=2)