//@version=6
indicator("Martingale Lab", overlay = true)

// 1. Settings
fastLen  = input.int(20, "Fast average")
slowLen  = input.int(50, "Slow average")
atrMult  = input.float(2.0, "Stop = ATR x", step = 0.5)
rr       = input.float(2.0, "Target = R x", step = 0.5)
baseRisk = input.float(1.0, "Base risk per trade (%)", step = 0.25) / 100
maxSteps = input.int(6, "How many doublings a rule may take", minval = 1)
sims     = input.int(300, "Alternative orderings to test", minval = 50, maxval = 800)
seed     = input.int(11, "Random seed")

// 2. The strategy. It is ordinary on purpose: the sizing rule is the experiment.
// ta.* calls stay at the top level so they run on every bar.
atr  = ta.atr(14)
fast = ta.ema(close, fastLen)
slow = ta.ema(close, slowLen)
long = ta.crossover(fast, slow)
plot(fast, "Fast", color.aqua)
plot(slow, "Slow", color.orange)

// 3. Record every trade as an R multiple, keeping the books by hand.
// One open trade at a time: a loser is -1 R, a winner is +rr R, so the
// history is a clean list of R values with no engine assumptions in it.
var float entry = na
var float stop  = na
var float targ  = na
var array<float> rs = array.new<float>()
opened  = false
hitStop = false
hitTarg = false
if na(entry)
    if long and atr > 0
        entry := close
        stop  := close - atrMult * atr
        targ  := close + atrMult * atr * rr
        opened := true
else
    if low <= stop
        array.push(rs, -1.0)
        entry := na
        hitStop := true
    else if high >= targ
        array.push(rs, rr)
        entry := na
        hitTarg := true
plotshape(opened, "Entry", shape.triangleup, location.belowbar, color.teal)
plotshape(hitTarg, "Target", shape.triangledown, location.abovebar, color.green)
plotshape(hitStop, "Stop", shape.xcross, location.abovebar, color.red)

// 4. Random numbers, so we can reorder the same trades (state in a one-slot array)
var array<int> rngBox = array.new_int(1, seed)
nextRand() =>
    st = (1103515245 * array.get(rngBox, 0) + 12345) % 2147483648
    array.set(rngBox, 0, st)
    math.abs(st) / 2147483648.0

// 5. THE EXPERIMENT. One function, three rules, identical trades.
// rule 0 = flat, 1 = martingale (double after a loss),
// 2 = anti-martingale (double after a win).
// Returns where the account finished, its worst drawdown, and whether it was ruined.
replay(src, rule) =>
    eq   = 1.0
    peak = 1.0
    dd   = 0.0
    mult = 1.0
    ruined = false
    for i = 0 to array.size(src) - 1
        r = array.get(src, i)
        stake = math.min(baseRisk * mult, 1.0)
        eq := eq * (1 + stake * r)
        peak := math.max(peak, eq)
        dd := math.max(dd, 1 - eq / peak)
        if eq <= 0.2 and not ruined
            ruined := true
        mult := rule == 0 ? 1.0 :
          rule == 1 ? (r < 0 ? math.min(mult * 2, math.pow(2, maxSteps)) : 1.0) :
          (r > 0 ? math.min(mult * 2, math.pow(2, maxSteps)) : 1.0)
    [eq, dd, ruined]

// 6. A shuffled copy of the trade list (Fisher-Yates)
shuffled(src) =>
    work = array.copy(src)
    for i = array.size(work) - 1 to 1
        j = math.floor(nextRand() * (i + 1))
        tmp = array.get(work, i)
        array.set(work, i, array.get(work, j))
        array.set(work, j, tmp)
    work

// 7. The two tables
var table t = table.new(position.bottom_left, 4, 5, border_width = 1)
head(c, s) =>
    table.cell(t, c, 0, s, text_color = color.white, text_size = size.normal,
      bgcolor = color.new(color.blue, 20))
var table h = table.new(position.middle_right, 3, 5, border_width = 1)
blocks(v, pk) =>
    w = int(math.round(22.0 * v / math.max(pk, 0.0001)))
    s = ""
    // a Pine for-loop with a start above its end counts DOWNWARDS,
    // so an empty bin would print two blocks instead of none
    if w > 0
        for i = 1 to w
            s += "█"
    s

// 8. Run all three rules on the real order, then on hundreds of reorderings
if barstate.islast and array.size(rs) > 20
    n = array.size(rs)
    // the longest losing streak in the real history: this is what kills a martingale
    streak = 0
    longest = 0
    for i = 0 to n - 1
        streak := array.get(rs, i) < 0 ? streak + 1 : 0
        longest := math.max(longest, streak)
    ruin = array.new_float(3, 0.0)
    for s = 0 to sims - 1
        order = shuffled(rs)
        for rule = 0 to 2
            [_e, _d, wiped] = replay(order, rule)
            if wiped
                array.set(ruin, rule, array.get(ruin, rule) + 1)

    // 9. The comparison table: same trades, three rules
    head(0, "SAME " + str.tostring(n) + " TRADES")
    head(1, "ends at")
    head(2, "worst drawdown")
    head(3, "ruined in " + str.tostring(sims) + " orders")
    names = array.from("flat size", "martingale", "anti-martingale")
    for rule = 0 to 2
        [e, d, _w] = replay(rs, rule)
        pctRuin = 100.0 * array.get(ruin, rule) / sims
        table.cell(t, 0, rule + 1, array.get(names, rule), text_color = color.white,
          bgcolor = color.new(color.gray, 20), text_halign = text.align_left,
          text_size = size.normal)
        table.cell(t, 1, rule + 1, str.tostring(e, "#.00") + "x",
          text_color = color.white, text_size = size.normal,
          bgcolor = e < 1 ? color.new(color.red, 25) : color.new(color.teal, 25))
        table.cell(t, 2, rule + 1, str.tostring(100 * d, "#.0") + "%",
          text_color = color.white, text_size = size.normal,
          bgcolor = d > 0.5 ? color.new(color.red, 25) : color.new(color.gray, 25))
        table.cell(t, 3, rule + 1, str.tostring(pctRuin, "#.0") + "%",
          text_color = color.white, text_size = size.normal,
          bgcolor = pctRuin > 0 ? color.new(color.red, 20) :
            color.new(color.green, 30))
    table.cell(t, 0, 4, "longest losing streak", text_color = color.white,
      bgcolor = color.new(color.gray, 20), text_halign = text.align_left)
    table.cell(t, 1, 4, str.tostring(longest) + " in a row",
      text_color = color.white,
      bgcolor = color.new(color.orange, 25))
    table.cell(t, 2, 4, "a martingale needs", text_color = color.white,
      bgcolor = color.new(color.gray, 20))
    table.cell(t, 3, 4, str.tostring(math.pow(2, longest - 1), "#") + "x stake",
      text_color = color.white, bgcolor = color.new(color.red, 20))

    // 10. Risk of ruin, drawn as a bar so the difference is impossible to miss
    table.cell(h, 0, 0, "rule", text_color = color.white, text_size = size.small,
      bgcolor = color.new(color.blue, 20))
    table.cell(h, 1, 0, "RISK OF RUIN", text_color = color.white,
      text_size = size.small,
      bgcolor = color.new(color.blue, 20))
    table.cell(h, 2, 0, "", bgcolor = color.new(color.blue, 20))
    for rule = 0 to 2
        p = 100.0 * array.get(ruin, rule) / sims
        table.cell(h, 0, rule + 1, array.get(names, rule), text_color = color.white,
          bgcolor = color.new(color.gray, 30), text_size = size.tiny,
          text_halign = text.align_left)
        table.cell(h, 1, rule + 1, blocks(p, 100), text_color = color.red,
          bgcolor = color.new(color.black, 0), text_size = size.tiny,
          text_halign = text.align_left)
        table.cell(h, 2, rule + 1, str.tostring(p, "#.0") + "%",
          text_color = color.white,
          bgcolor = color.new(color.black, 0), text_size = size.tiny)