Zen Big Bar Midpoints

//@version=5
indicator("Zen Big Bar Midpoints v1.8", overlay=true, max_lines_count=500, max_boxes_count=500)
// ============================================================
// INPUTS
// ============================================================
grpDetect = "Big Bar Detection"
abrLookback   = input.int(8,    "ABR Lookback",          minval=1, group=grpDetect)
bigBarMult    = input.float(1.6,"Big Bar Threshold (x ABR)", minval=0.1, step=0.1, group=grpDetect)
showBull      = input.bool(true,"Show Bull Bars",         group=grpDetect)
showBear      = input.bool(true,"Show Bear Bars",         group=grpDetect)
grpMid = "Midpoints (H-L mid & Extreme-Close mid)"
midMode       = input.string("Lines", "Display Mode", options=["Lines", "Boxes", "Off"], group=grpMid)
midBullColor  = input.color(color.blue, "Bull Colour",       group=grpMid)
midBearColor  = input.color(color.red,  "Bear Colour",       group=grpMid)
midBoxTransp  = input.int(75, "Box Fill Transparency", minval=0, maxval=100, group=grpMid)
grpFrac = "Fractional Levels (0.33 / 0.66)"
fracMode      = input.string("Off", "Display Mode", options=["Lines", "Boxes", "Off"], group=grpFrac)
fracLow       = input.float(0.33,"Lower Fraction",  minval=0.0, maxval=1.0, step=0.01, group=grpFrac)
fracHigh      = input.float(0.66,"Upper Fraction",  minval=0.0, maxval=1.0, step=0.01, group=grpFrac)
fracBullColor = input.color(color.blue, "Bull Colour",       group=grpFrac)
fracBearColor = input.color(color.red,  "Bear Colour",       group=grpFrac)
fracBoxTransp = input.int(50, "Box Fill Transparency", minval=0, maxval=100, group=grpFrac)
grpStyle = "Line Style"
extendBars    = input.int(10,    "Extension (bars)", minval=1, group=grpStyle)
lineWidth     = input.int(2,     "Line Width",       minval=1, maxval=4, group=grpStyle)
// ============================================================
// CALCULATIONS
// ============================================================
barRange = high - low
abr      = ta.sma(barRange[1], abrLookback)
isBigBar = barRange > abr * bigBarMult
isBull   = close > open
isBear   = close < open
plotThis = isBigBar and ((isBull and showBull) or (isBear and showBear))
midLineCol  = isBull ? midBullColor  : midBearColor
midFillCol  = color.new(midLineCol, midBoxTransp)
fracLineCol = isBull ? fracBullColor : fracBearColor
fracFillCol = color.new(fracLineCol, fracBoxTransp)
// ============================================================
// HELPERS
// ============================================================
f_drawLine(_price, _col) =>
    line.new(bar_index, _price, bar_index + extendBars, _price, xloc=xloc.bar_index, extend=extend.none, color=_col, style=line.style_dotted, width=lineWidth)
f_drawBox(_top, _bot, _col, _border) =>
    box.new(bar_index, _top, bar_index + extendBars, _bot, xloc=xloc.bar_index, border_color=_border, border_width=1, border_style=line.style_dotted, bgcolor=_col)
// ============================================================
// DRAWING
// ============================================================
if plotThis
    midFull  = (high + low) / 2
    midClose = isBull ? (low + close) / 2 : (high + close) / 2
    if midMode == "Lines"
        f_drawLine(midFull,  midLineCol)
        f_drawLine(midClose, midLineCol)
    else
        if midMode == "Boxes"
            topM = math.max(midFull, midClose)
            botM = math.min(midFull, midClose)
            f_drawBox(topM, botM, midFillCol, midLineCol)
    lvlLow  = low + barRange * fracLow
    lvlHigh = low + barRange * fracHigh
    if fracMode == "Lines"
        f_drawLine(lvlLow,  fracLineCol)
        f_drawLine(lvlHigh, fracLineCol)
    else
        if fracMode == "Boxes"
            f_drawBox(lvlHigh, lvlLow, fracFillCol, fracFillCol)