// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Volume Oscillator (VO)", "VO", overlay=false)

//@function Calculates Volume Oscillator
//@param short_period Period for short-term volume moving average
//@param long_period Period for long-term volume moving average
//@param signal_period Period for signal line moving average
//@param vol Volume series
//@returns Volume Oscillator value
//@optimized for performance and dirty data
vo(simple int short_period, simple int long_period, simple int signal_period, series float vol=volume) =>
    volume_val = math.max(nz(vol, 0.0), 1.0)
    var p_short = short_period
    var buffer_short = array.new_float(p_short, na)
    var head_short = 0, var sum_short = 0.0, var valid_count_short = 0
    oldest_short = array.get(buffer_short, head_short)
    sum_short := not na(oldest_short) ? sum_short - oldest_short : sum_short
    valid_count_short := not na(oldest_short) ? valid_count_short - 1 : valid_count_short
    sum_short := not na(volume_val) ? sum_short + volume_val : sum_short
    valid_count_short := not na(volume_val) ? valid_count_short + 1 : valid_count_short
    array.set(buffer_short, head_short, volume_val)
    head_short := (head_short + 1) % p_short
    short_ma = valid_count_short > 0 ? sum_short / valid_count_short : volume_val
    var p_long = long_period
    var buffer_long = array.new_float(p_long, na)
    var head_long = 0, var sum_long = 0.0, var valid_count_long = 0
    oldest_long = array.get(buffer_long, head_long)
    sum_long := not na(oldest_long) ? sum_long - oldest_long : sum_long
    valid_count_long := not na(oldest_long) ? valid_count_long - 1 : valid_count_long
    sum_long := not na(volume_val) ? sum_long + volume_val : sum_long
    valid_count_long := not na(volume_val) ? valid_count_long + 1 : valid_count_long
    array.set(buffer_long, head_long, volume_val)
    head_long := (head_long + 1) % p_long
    long_ma = valid_count_long > 0 ? sum_long / valid_count_long : volume_val
    vo_value = long_ma > 0 ? ((short_ma - long_ma) / long_ma) * 100 : 0.0
    var p_signal = signal_period
    var buffer_signal = array.new_float(p_signal, na)
    var head_signal = 0, var sum_signal = 0.0, var valid_count_signal = 0
    oldest_signal = array.get(buffer_signal, head_signal)
    sum_signal := not na(oldest_signal) ? sum_signal - oldest_signal : sum_signal
    valid_count_signal := not na(oldest_signal) ? valid_count_signal - 1 : valid_count_signal
    sum_signal := not na(vo_value) ? sum_signal + vo_value : sum_signal
    valid_count_signal := not na(vo_value) ? valid_count_signal + 1 : valid_count_signal
    array.set(buffer_signal, head_signal, vo_value)
    head_signal := (head_signal + 1) % p_signal
    signal_line = valid_count_signal > 0 ? sum_signal / valid_count_signal : vo_value
    [vo_value, signal_line]

short_period = input.int(5, "Short Period", minval=1, maxval=50, tooltip="Period for short-term volume moving average")
long_period = input.int(10, "Long Period", minval=2, maxval=100, tooltip="Period for long-term volume moving average")
signal_period = input.int(10, "Signal Period", minval=1, maxval=50, tooltip="Period for signal line moving average")

[vo_value, signal_line] = vo(short_period, long_period, signal_period)

plot(vo_value, "Volume Oscillator", color=color.yellow, linewidth=2)
plot(signal_line, "Signal Line", color=color.blue, linewidth=2)