// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/
// © Venture Lab – https://venturelab-bots.pages.dev/pine/
//
// ATR trailing stop.
// What it does: draws a stop line at "ATR multiplier" x ATR away from the close. In an up phase the line
// only moves up; when a bar closes below it, the phase flips to down and the line starts above price
// (and only moves down) until a bar closes above it again. Flips are marked and can trigger alerts.
// What it does NOT do: it places no orders, it does not guarantee fills at the line (gaps and slippage),
// it is not a trading system and it is not financial advice. On the open bar the line and the phase can
// still change until the bar closes.

//@version=6
indicator("ATR Trailing Stop [Venture Lab]", shorttitle = "ATR Trail", overlay = true)

// ---- Inputs
int   atrLen = input.int(14, "ATR length", minval = 1)
float mult   = input.float(3.0, "ATR multiplier", minval = 0.1, step = 0.1)

// ---- Calculation
float atr  = ta.atr(atrLen)
float dist = mult * atr

var float trail = na
var int   dir   = 1   // 1 = up phase (stop below price), -1 = down phase (stop above price)

if na(atr)
    trail := na
else if na(trail)
    trail := close - dist
    dir   := 1
else if dir == 1
    if close < trail
        dir   := -1
        trail := close + dist
    else
        trail := math.max(trail, close - dist)
else
    if close > trail
        dir   := 1
        trail := close - dist
    else
        trail := math.min(trail, close + dist)

int  prevDir  = nz(dir[1], dir)
bool flipUp   = dir == 1 and prevDir == -1
bool flipDown = dir == -1 and prevDir == 1

// ---- Plots
plot(dir == 1 ? trail : na, "Stop (up phase)", color = color.teal, linewidth = 2, style = plot.style_linebr)
plot(dir == -1 ? trail : na, "Stop (down phase)", color = color.red, linewidth = 2, style = plot.style_linebr)
plotshape(flipUp, "Flip to up", shape.circle, location.belowbar, color.teal, size = size.tiny)
plotshape(flipDown, "Flip to down", shape.circle, location.abovebar, color.red, size = size.tiny)

// ---- Alerts
alertcondition(flipUp, "ATR stop flip up", "Close crossed above the ATR trailing stop on {{ticker}} ({{interval}})")
alertcondition(flipDown, "ATR stop flip down", "Close crossed below the ATR trailing stop on {{ticker}} ({{interval}})")