// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Stochastic Oscillator (STOCH)", "STOCH", overlay=false)

//@function Calculates the Stochastic Oscillator (%K and %D). %K = 100 * (close - lowest_low(kLength)) / (highest_high(kLength) - lowest_low(kLength)). %D = SMA(%K, dPeriod). Uses efficient deque implementation for min/max and buffer-based SMA.
//@param kLength `simple int` The lookback period for calculating highest high and lowest low.
//@param dPeriod `simple int` The smoothing period for the %D line (SMA of %K).
//@returns `[float, float]` A tuple containing the %K value and the %D value.
stoch(simple int kLength,simple int dPeriod)=>
    if kLength<=0 or dPeriod<=0
        runtime.error("Both periods must be positive")
    var float kVal=0.0, var float dVal=0.0
    var int dHead=0, var float dSum=0.0
    var array<int>lowestDeque=array.new_int(0)
    var array<float>lowestBuffer=array.new_float(kLength,na)
    var array<int>highestDeque=array.new_int(0)
    var array<float>highestBuffer=array.new_float(kLength,na)
    var array<float>dBuffer=array.new_float(dPeriod,0.0)
    int idx=bar_index%kLength
    float lv=nz(low), float hv=nz(high)
    array.set(lowestBuffer,idx,lv)
    array.set(highestBuffer,idx,hv)
    while array.size(lowestDeque)>0
        if array.get(lowestDeque,0)<=bar_index-kLength
            array.shift(lowestDeque)
        else
            break
    while array.size(lowestDeque)>0
        if array.get(lowestBuffer,array.get(lowestDeque,array.size(lowestDeque)-1)%kLength)>=lv
            array.pop(lowestDeque)
        else
            break
    array.push(lowestDeque,bar_index)
    while array.size(highestDeque)>0
        if array.get(highestDeque,0)<=bar_index-kLength
            array.shift(highestDeque)
        else
            break
    while array.size(highestDeque)>0
        if array.get(highestBuffer,array.get(highestDeque,array.size(highestDeque)-1)%kLength)<=hv
            array.pop(highestDeque)
        else
            break
    array.push(highestDeque,bar_index)
    int li=array.get(lowestDeque,0)
    int hi=array.get(highestDeque,0)
    float lowestLow=array.get(lowestBuffer,li%kLength)
    float highestHigh=array.get(highestBuffer,hi%kLength)
    float rnge=highestHigh-lowestLow
    kVal:=rnge>0?100*(close-lowestLow)/rnge:0.0
    if bar_index==0
        dSum:=kVal*dPeriod
        array.fill(dBuffer,kVal)
    else
        float oldVal=array.get(dBuffer,dHead)
        dSum:=dSum-oldVal+kVal
        array.set(dBuffer,dHead,kVal)
        dHead:=(dHead+1)%dPeriod
    dVal:=dSum/dPeriod
    [kVal,dVal]


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

// Inputs
kPeriod = input.int(14, "K Length", minval=1)
dPeriod = input.int(3, "D Smooth", minval=1)

// Calculation
[kValue, dValue] = stoch(kPeriod, dPeriod)

// Plot
plot(kValue, "Stochastic %K", color=color.green, linewidth=2)
plot(dValue, "Stochastic %D", color=color.red, linewidth=2)