// The MIT License (MIT)
// © mihakralj
//@version=6
indicator("Volume Weighted Moving Average (VWMA)", "VWMA", overlay=true)

//@function Calculates VWMA using circular buffer for efficient computation
//@doc https://github.com/mihakralj/pinescript/blob/main/indicators/volume/vwma.md
//@param src Source price series
//@param vol Volume series
//@param period Lookback period for VWMA calculation
//@returns VWMA value representing volume-weighted moving average
//@optimized for performance and dirty data
vwma(series float src, series float vol, simple int period) =>
    if period <= 0
        runtime.error("Period must be greater than 0")
    var int p = math.max(1, period), var int head = 0, var int count = 0
    var array<float> price_buffer = array.new_float(p, na)
    var array<float> vol_buffer = array.new_float(p, na)
    var float sum_pv = 0.0, var float sum_vol = 0.0
    float old_price = array.get(price_buffer, head), float old_vol = array.get(vol_buffer, head)
    if not na(old_price) and not na(old_vol)
        sum_pv -= old_price * old_vol
        sum_vol -= old_vol
        count -= 1
    float current_price = nz(src), float current_vol = nz(vol, 0.0)
    if current_vol > 0.0
        sum_pv += current_price * current_vol
        sum_vol += current_vol
        count += 1
    array.set(price_buffer, head, current_price)
    array.set(vol_buffer, head, current_vol)
    head := (head + 1) % p
    sum_vol > 0.0 ? sum_pv / sum_vol : src

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

// Inputs
i_period = input.int(20, "Period", minval=1)
i_source = input.source(close, "Source")

// Calculation
vwma_value = vwma(i_source, volume, i_period)

// Plot
plot(vwma_value, "VWMA", color=color.yellow, linewidth=2)