rvi

//version=4
study("HalfTrend", overlay=true)

amplitude = input(title="Amplitude", defval=1)
channelDeviation = input(title="Channel Deviation", defval=2)
showArrows = input(title="Show Arrows", defval=true)
showChannels = input(title="Show Channels", defval=false)

var int trend = 0
var int nextTrend = 0
var float maxLowPrice = nz(low[1], low)
var float minHighPrice = nz(high[1], high)

var float up = 0.0
var float down = 0.0
float atrHigh = 0.0
float atrLow = 0.0
float arrowUp = na
float arrowDown = na

atr2 = atr(100) / 2
dev = channelDeviation * atr2

highPrice = high[abs(highestbars(amplitude))]
lowPrice = low[abs(lowestbars(amplitude))]
highma = sma(high, amplitude)
lowma = sma(low, amplitude)

if nextTrend == 1
maxLowPrice := max(lowPrice, maxLowPrice)

if highma < maxLowPrice and close < nz(low[1], low)
trend := 1
nextTrend := 0
minHighPrice := highPrice
else
minHighPrice := min(highPrice, minHighPrice)

if lowma > minHighPrice and close > nz(high[1], high)
trend := 0
nextTrend := 1
maxLowPrice := lowPrice

if trend == 0
if not na(trend[1]) and trend[1] != 0
up := na(down[1]) ? down : down[1]
arrowUp := up - atr2
else
up := na(up[1]) ? maxLowPrice : max(maxLowPrice, up[1])
atrHigh := up + dev
atrLow := up - dev
else
if not na(trend[1]) and trend[1] != 1
down := na(up[1]) ? up : up[1]
arrowDown := down + atr2
else
down := na(down[1]) ? minHighPrice : min(minHighPrice, down[1])
atrHigh := down + dev
atrLow := down - dev

ht = trend == 0 ? up : down

var color buyColor = color.blue
var color sellColor = color.red

htColor = trend == 0 ? buyColor : sellColor
htPlot = plot(ht, title="HalfTrend", linewidth=2, color=htColor)

atrHighPlot = plot(showChannels ? atrHigh : na, title="ATR High", style=plot.style_circles, color=sellColor)
atrLowPlot = plot(showChannels ? atrLow : na, title="ATR Low", style=plot.style_circles, color=buyColor)

fill(htPlot, atrHighPlot, title="ATR High Ribbon", color=sellColor)
fill(htPlot, atrLowPlot, title="ATR Low Ribbon", color=buyColor)

buySignal = not na(arrowUp) and (trend == 0 and trend[1] == 1)
sellSignal = not na(arrowDown) and (trend == 1 and trend[1] == 0)

plotshape(showArrows and buySignal ? atrLow : na, title="Arrow Up", style=shape.labelup, location=location.absolute, size=size.tiny, color=color.lime, textcolor=color.white, text="Buy")
plotshape(showArrows and sellSignal ? atrHigh : na, title="Arrow Down", style=shape.labeldown, location=location.absolute, size=size.tiny, color=sellColor, textcolor=color.white, text="Sell")

alertcondition(buySignal, title="Alert: HalfTrend Buy", message="HalfTrend Buy")
alertcondition(sellSignal, title="Alert: HalfTrend Sell", message="HalfTrend Sell")