ATR Trailing Stop

// This Pine Script® code is licensed under Apache-2.0
// SPDX-License-Identifier: Apache-2.0
// © PineForge contributors 2026
//
// PF probe 13 — ATR-trailing-stop with var-state direction
// Purpose: parity test for ta.atr() driven trailing stop and `var float trailStop`
// / `var bool isLong` state-machine progression on EMA crossovers.
//
//@version=6
strategy("ATR Trailing Stop", overlay=true, initial_capital=1000000, process_orders_on_close=false, pyramiding=1, commission_type=strategy.commission.percent, commission_value=0, slippage=0, default_qty_type=strategy.fixed, default_qty_value=1)

// === Inputs ===
atrLen    = input.int(14, "ATR Length", minval=1)
atrMult   = input.float(2.0, "ATR Multiplier", step=0.1)
maLen     = input.int(20, "MA Length", minval=5)

// === Indicators ===
atrVal = ta.atr(atrLen)
maVal  = ta.ema(close, maLen)

// === Trailing stop logic with var ===
var float trailStop = na
var bool isLong = false

// === Entry signals ===
longEntry  = ta.crossover(close, maVal)
shortEntry = ta.crossunder(close, maVal)

if longEntry
    strategy.entry("Long", strategy.long)
    isLong := true
    trailStop := close - atrVal * atrMult

if shortEntry
    strategy.entry("Short", strategy.short)
    isLong := false
    trailStop := close + atrVal * atrMult

// === Update trailing stop ===
if isLong and strategy.position_size > 0
    newStop = close - atrVal * atrMult
    if not na(trailStop)
        trailStop := math.max(trailStop, newStop)
    else
        trailStop := newStop
    if close < trailStop
        strategy.close("Long")
        isLong := false

if not isLong and strategy.position_size < 0
    newStop = close + atrVal * atrMult
    if not na(trailStop)
        trailStop := math.min(trailStop, newStop)
    else
        trailStop := newStop
    if close > trailStop
        strategy.close("Short")

plot(trailStop, "Trail Stop", color=isLong ? color.green : color.red, style=plot.style_stepline)
plot(maVal, "MA", color=color.blue)