Schaff Trend Cycle

// This source code is subject to the terms of the Mozilla Public License 2.0 at https://mozilla.org/MPL/2.0/
// @version=5
// Schaff Trend Cycle Indicator
 

indicator(title='Schaff Trend Cycle', shorttitle='STC', overlay=false)
var GRP1 = "Input Parameters"
var GRP2 = "Over Bought/Sold Zones"
length = input(10, 'Length',group=GRP1)
fastLength = input(23, 'Fast Length',group=GRP1)
slowLength = input(50, 'Slow Length',group=GRP1)

calculateMADiff(src,fastLength, slowLength) =>
    fastMA = ta.ema(src,fastLength)
    slowMA = ta.ema(src,slowLength)
    MADiff = fastMA - slowMA
    MADiff

calculateSTC(length, fastLength, slowLength) =>
    smoothingFactor = input(0.5,group=GRP1)
    var stcPercent = 0.0
    var stcValue = 0.0
    var stcPer =0.0
    var STC= 0.0
    MADiff = calculateMADiff(close,fastLength,slowLength)
    lowestSTC = ta.lowest(MADiff, length)
    highestSTC = ta.highest(MADiff, length) - lowestSTC
    stcPercent := highestSTC > 0 ? (MADiff - lowestSTC) / highestSTC * 100 : nz(stcPercent[1])
    stcValue := na(stcValue[1]) ? stcPercent : stcValue[1] + smoothingFactor * (stcPercent - stcValue[1])
    lowestValue = ta.lowest(stcValue, length)
    highestValue = ta.highest(stcValue, length) - lowestValue
    stcPer := highestValue > 0 ? (stcValue - lowestValue) / highestValue * 100 : nz(stcPer[1])
    STC:= na(STC[1]) ? stcPer: STC[1] + smoothingFactor * (stcPer - STC[1])
    STC

stcline = calculateSTC(length, fastLength, slowLength)
stcColor = (stcline > stcline[1] ) ? color.new(#03ec0b, 20) : color.new(#f81b1b, 20)

var float HighClose = na
var float LowClose=na
var T=0.0
var R=0.0

HighClose := T == 0 ? close : ta.highest(close,T)
LowClose := R == 0 ? close : ta.highest(close,R)
rg=HighClose-LowClose

divid=100/rg
stcline2=stcline*divid+LowClose

plot(stcline2, color=stcColor, title='STC', linewidth=2)
ShowZones=input.bool(true, "Show OverBought/OverSold",   inline = "01",group=GRP2)
var clrtop=color.new(#1e65ff, 20)
var clrbot=color.new(#ff2929, 27)
var fillcolor=color.new(#919cc4, 50)

if (ShowZones==false)
    clrtop:=color.new(#6645f8, 100)
    clrbot:=color.new(#ff2929, 100)
    fillcolor:=color.new(#7d91db, 100)
    
LowHL=input(25,"Over Bought",group=GRP2)
HiHL=input(75,"Over Sold",group=GRP2)
upperLevel = plot(LowHL, title="OverBought",color=clrbot)
lowerLevel = plot(HiHL, title="OverSold",color=clrtop)
fill(upperLevel, lowerLevel,title="Area OverBought/Sell Zone", color=fillcolor)