// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Williams %R (WILLR)", "WILLR", overlay=false)

//@function Calculates Williams %R oscillator
//@param period Lookback period for highest high and lowest low calculation
//@returns Williams %R value (-100 to 0 scale)
willr(simple int period) =>
    if period <= 0
        runtime.error("Period must be positive")
    var array<float> high_buffer = array.new_float(period, na)
    var array<float> low_buffer = array.new_float(period, na)
    var int head = 0, var int count = 0
    idx = head % period
    old_high = array.get(high_buffer, idx)
    if not na(old_high)
        count := count - 1
    array.set(high_buffer, idx, high)
    array.set(low_buffer, idx, low)
    count := count + 1
    head := head + 1
    highest_high = array.max(high_buffer)
    lowest_low = array.min(low_buffer)
    range_val = highest_high - lowest_low
    range_val > 0 ? -100 * (highest_high - close) / range_val : -50


// ---------- Main loop ----------

// Inputs
i_period = input.int(14, "Period", minval=1, maxval=100, tooltip="Lookback period for highest high and lowest low calculation")

// Calculation
willr_value = willr(i_period)

// Plots
plot(willr_value, "Williams %R", color=color.yellow, linewidth=2)