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

//@function Calculates Volume Force, measuring the force of volume behind price movements
//@param len Smoothing period (default: 14)
//@param src Source price for calculation (default: close)
//@param src_vol Volume data (default: volume)
//@returns float The Volume Force value
vf(simple int len, series float src = close, series float src_vol = volume) =>
    float price_change = src - nz(src[1], src)
    float raw_vf = price_change * nz(src_vol, 0.0)
    float alpha = 2.0 / (len + 1)
    var bool warmup = true
    var float e = 1.0
    var float ema_val = 0.0
    var float vf_result = raw_vf
    ema_val := alpha * (raw_vf - ema_val) + ema_val
    if warmup
        e *= (1.0 - alpha)
        float compensator = 1.0 / (1.0 - e)
        vf_result := compensator * ema_val
        warmup := e > 1e-10
    else
        vf_result := ema_val
    vf_result

// ---------- Main Calculation ----------

// Parameters
length = input.int(14, "Smoothing Period", minval=1)

// Calculation
vf_line = vf(length, close, volume)

// ---------- Plots ----------

plot(vf_line, "Volume Force", color=color.yellow, linewidth=2)
hline(0, "Zero Line", color.gray, linestyle=hline.style_dashed)

// Color zones for visual clarity
bgcolor(vf_line > 0 ? color.green : color.red)