Zig Zag

//@version=4
study("Zig Zag", overlay=true)

dev_threshold = input(title="Deviation (%)", type=input.float, defval=5, minval=1, maxval=100)
depth = input(title="Depth", type=input.integer, defval=10, minval=1)

pivots(src, length, isHigh) =>
    p = nz(src[length])

    if length == 0
        [bar_index, p]
    else
        isFound = true
        for i = 0 to length - 1
            if isHigh and src[i] > p
                isFound := false
            if not isHigh and src[i] < p
                isFound := false

        for i = length + 1 to 2 * length
            if isHigh and src[i] >= p
                isFound := false
            if not isHigh and src[i] <= p
                isFound := false

        if isFound and length * 2 <= bar_index
            [bar_index[length], p]
        else
            [int(na), float(na)]

[iH, pH] = pivots(high, floor(depth / 2), true)
[iL, pL] = pivots(low, floor(depth / 2), false)

calc_dev(base_price, price) =>
    100 * (price - base_price) / base_price

var line lineLast = na
var int iLast = 0
var float pLast = 0
var bool isHighLast = true // otherwise the last pivot is a low pivot
var int linesCount = 0

pivotFound(dev, isHigh, index, price) =>
    if isHighLast == isHigh and not na(lineLast)
        // same direction
        if isHighLast ? price > pLast : price < pLast
            if linesCount <= 1
                line.set_xy1(lineLast, index, price)
            line.set_xy2(lineLast, index, price)
            [lineLast, isHighLast, false]
        else
            [line(na), bool(na), false]
    else // reverse the direction (or create the very first line)
        if na(lineLast)
            id = line.new(index, price, index, price, color=color.red, width=2)
            [id, isHigh, true]
        else
            // price move is significant
            if abs(dev) >= dev_threshold
                id = line.new(iLast, pLast, index, price, color=color.red, width=2)
                [id, isHigh, true]
            else
                [line(na), bool(na), false]

if not na(iH) and not na(iL) and iH == iL
    dev1 = calc_dev(pLast, pH)
    [id2, isHigh2, isNew2] = pivotFound(dev1, true, iH, pH)
    if isNew2
        linesCount := linesCount + 1
    if not na(id2)
        lineLast := id2
        isHighLast := isHigh2
        iLast := iH
        pLast := pH

    dev2 = calc_dev(pLast, pL)
    [id1, isHigh1, isNew1] = pivotFound(dev2, false, iL, pL)
    if isNew1
        linesCount := linesCount + 1
    if not na(id1)
        lineLast := id1
        isHighLast := isHigh1
        iLast := iL
        pLast := pL

else
    if not na(iH)
        dev1 = calc_dev(pLast, pH)
        [id, isHigh, isNew] = pivotFound(dev1, true, iH, pH)
        if isNew
            linesCount := linesCount + 1
        if not na(id)
            lineLast := id
            isHighLast := isHigh
            iLast := iH
            pLast := pH
    else
        if not na(iL)
            dev2 = calc_dev(pLast, pL)
            [id, isHigh, isNew] = pivotFound(dev2, false, iL, pL)
            if isNew
                linesCount := linesCount + 1
            if not na(id)
                lineLast := id
                isHighLast := isHigh
                iLast := iL
                pLast := pL