//@version=5
indicator("Concretum Bands",overlay = true,max_bars_back = 5000,max_lines_count = 500)

k=input.int(10,"Length")
vm=input.float(1,"Volatility Multiplier")
ncol=input.color(color.rgb(255, 235, 59, 70),"NoiseArea color")
ucol=input.color(color.rgb(1, 1, 1, 70),"Upperbound color")
lcol=input.color(color.rgb(1, 1, 1, 70),"Lowerbound color")
extend=input.int(30,"Extend Plotting",maxval=250,inline = "one")
useext=input.bool(true,"",inline="one")
if useext==false
    extend:=0
var n=0 // n is number of bars in the current timeframe
var bool first=true


if first
    n:=n+1

if session.islastbar and first
    first:=false

var bool skipper=true
var skipper_counter=0
if skipper
    skipper_counter:=skipper_counter+1

if skipper_counter==k*n+1
    skipper:=false
//----------------------------------------------
var candle_counter=0
var float upperbound=0
var float lowerbound=0
var float firstconstant=0
var float secondconstant=0

candle_counter:=candle_counter+1
if session.isfirstbar
    candle_counter:=0
    firstconstant:=open>close[1]?open:close[1]
    secondconstant:=open<close[1]?open:close[1]
    upperbound:=open
    lowerbound:=open
if skipper==false and candle_counter!=0
    //                       num             deno                        -1
    j=1
    sigma=0.0
    while j<=k
        move=math.abs(       (  close[n*j]/open[j*n+candle_counter] )   -1          )
        sigma:=sigma+move
        j:=j+1
    sigma:=sigma/k
    upperbound:=firstconstant*(1+vm*sigma)
    lowerbound:=secondconstant*(1-vm*sigma)

u=plot(upperbound,color=ucol)
l=plot(lowerbound,color =lcol)
fill(u,l,color=ncol)

// plotting forward
prevuy=upperbound
prevlt=lowerbound

if skipper==false  and  barstate.isrealtime
    
    lm=1
    while lm<=(n-candle_counter)
        j=1
        sigma=0.0
        while j<=k
            move=math.abs(       (  close[(n*j)-lm]/open[j*n+candle_counter] )   -1          )
            sigma:=sigma+move
            j:=j+1
            
        sigma:=sigma/k
        extu=firstconstant*(1+vm*sigma)
        extl=secondconstant*(1-vm*sigma)
        //log.info(str.tostring(extu)+" ----- "+str.tostring(extl))
        line.new(bar_index+lm-1,prevuy,bar_index+lm,extu,color = ucol)
        line.new(bar_index+lm-1,prevlt,bar_index+lm,extl,color= lcol)
        prevuy:=extu
        prevlt:=extl
        lm:=lm+1
        if lm>extend
            break