How to Create a Candlestick Pattern Detector on TradingView

// This Pine Script™ code is subject to the terms of the Mozilla Public License 2.0 at https://mozilla.org/MPL/2.0/
// © Pineify — Candlestick pattern detector (educational)

//@version=5
indicator("Candlestick Pattern Detector", shorttitle="Patterns", overlay=true)

dojiBodyPct = input.float(10.0, "Doji max body % of range", minval=1, maxval=40) / 100.0
hammerWickMult = input.float(2.0, "Hammer lower wick ≥ body ×", minval=1, step=0.1)
hammerTopPct = input.float(25.0, "Hammer body in top % of range", minval=5, maxval=45) / 100.0

body = math.abs(close - open)
rng = math.max(high - low, syminfo.mintick)
upperW = high - math.max(open, close)
lowerW = math.min(open, close) - low
isDoji = rng > 0 and body / rng <= dojiBodyPct

// Hammer (bullish bias variant at bottom of move — simplified)
bodyTop = math.max(open, close)
bodyBot = math.min(open, close)
bodyInTop = (high - bodyTop) / rng <= hammerTopPct
hammer = body > 0 and lowerW >= body * hammerWickMult and upperW <= body * 0.6 and bodyInTop

// Bullish engulfing
prevBear = close[1] < open[1]
currBull = close > open
bullEngulf = prevBear and currBull and open <= close[1] and close >= open[1] and body > body[1]

// Morning star (relaxed gaps)
c1Bear = close[2] < open[2] and (open[2] - close[2]) > rng[2] * 0.45
c2Small = body[1] / rng[1] <= 0.35
c3Bull = close > open and close > (open[2] + close[2]) / 2
morningStar = c1Bear and c2Small and c3Bull and close[1] < close[2] and low[1] < low[2]

plotshape(isDoji, title="Doji", style=shape.cross, location=location.abovebar, size=size.tiny, color=color.new(color.gray, 0))
plotshape(hammer, title="Hammer", style=shape.triangleup, location=location.belowbar, size=size.small, color=color.new(color.teal, 0))
plotshape(bullEngulf, title="Bull engulf", style=shape.circle, location=location.belowbar, size=size.small, color=color.new(color.lime, 0))
plotshape(morningStar, title="Morning star", style=shape.diamond, location=location.belowbar, size=size.normal, color=color.new(color.aqua, 0))

// Bearish engulfing for symmetry in learning
prevBull = close[1] > open[1]
currBear = close < open
bearEngulf = prevBull and currBear and open >= close[1] and close <= open[1] and body > body[1]
plotshape(bearEngulf, title="Bear engulf", style=shape.circle, location=location.abovebar, size=size.small, color=color.new(color.red, 0))

// Label last signal to reduce clutter
var string lastPat = na
if hammer
    lastPat := "Hammer"
if bullEngulf
    lastPat := "Bull Engulfing"
if bearEngulf
    lastPat := "Bear Engulfing"
if morningStar
    lastPat := "Morning Star"
if isDoji
    lastPat := "Doji"

var table patTable = table.new(position.top_right, 2, 3, border_width=1)
if barstate.islast
    table.cell(patTable, 0, 0, "Last pattern", bgcolor=color.new(color.gray, 60), text_color=color.white)
    table.cell(patTable, 1, 0, na(lastPat) ? "—" : lastPat, bgcolor=color.new(color.gray, 60), text_color=color.white)
    table.cell(patTable, 0, 1, "Body/Range", bgcolor=color.new(color.gray, 70), text_color=color.white)
    table.cell(patTable, 1, 1, str.tostring(body / rng * 100, "#.1") + "%", bgcolor=color.new(color.gray, 70), text_color=color.white)
    table.cell(patTable, 0, 2, "Range", bgcolor=color.new(color.gray, 60), text_color=color.white)
    table.cell(patTable, 1, 2, str.tostring(rng, format.mintick), bgcolor=color.new(color.gray, 60), text_color=color.white)

alertcondition(bullEngulf, title="Bullish engulfing", message="Bullish engulfing detected")
alertcondition(morningStar, title="Morning star", message="Morning star detected")
alertcondition(hammer, title="Hammer", message="Hammer detected")
alertcondition(isDoji, title="Doji", message="Doji detected")