/@version=3
// Copyright (c) 2018-present, Alex Orekhov (everget)
// On Balance Volume script may be freely distributed under the MIT license.
study("On Balance Volume", shorttitle="OBV", precision=0)

showSignal = input(title="Show Signal ?", type=bool, defval=true)
signalType = input(title="Signal Smoothing Type", defval="SMA", options=["EMA", "SMA"])
signalLength = input(title="Signal Smoothing Length", type=integer, defval=21)
highlightCrossovers = input(title="Highlight Crossovers ?", type=bool, defval=false)
applyFilling = input(title="Apply Ribbon Filling ?", type=bool, defval=true)
src = input(title="Source", type=source, defval=close)

obv = cum(sign(change(src)) * volume)
signal = signalType == "EMA" ? ema(obv, signalLength) : sma(obv, signalLength)

trendColor = obv > signal ? #0ebb23 : red

obvColor = applyFilling ? trendColor : #0094ff
signalColor = applyFilling ? trendColor : #ff6a00

obvPlot = plot(obv, title="OBV", linewidth=2, color=obvColor, transp=0)
signalPlot = plot(showSignal ? signal : na, title="Signal", color=signalColor, transp=0)

transparent = color(white, 100)

fillColor = applyFilling ? trendColor : transparent
fill(obvPlot, signalPlot, color=fillColor, transp=70)

plotshape(crossover(obv, signal) and highlightCrossovers ? obv : na, title="Crossover", location=location.absolute, style=shape.circle, size=size.tiny, color=green, transp=0)
plotshape(crossunder(obv, signal) and highlightCrossovers ? obv : na, title="Crossunder", location=location.absolute, style=shape.circle, size=size.tiny, color=red, transp=0)