Time Series Momentum

//@version=6
// Time Series Momentum — sort.finance. Fills at the signal bar's close, 0.02% fee a side,
// whole account per trade, as the backtest. History and indicator warm-up
// differ from the site's, so expect close to the same trades, not identical.
strategy("Time Series Momentum", overlay=false,
     initial_capital=100, default_qty_type=strategy.percent_of_equity,
     default_qty_value=100, commission_type=strategy.commission.percent,
     commission_value=0.02, process_orders_on_close=true, pyramiding=0)

// The bar the current position opened on, and the bar the last one closed on.
var int entryBar = na
var int exitBar = -1

// ── Signals ──────────────────────────────────────────────────────────────
momentum = (close / close[90] - 1) * 100
above = momentum > 0
enterNow = above and not above[1]
exitNow = not above and above[1]

// ── Orders ───────────────────────────────────────────────────────────────
// Open on the first bar the entry holds while flat; close on the first
// later bar the exit holds; never reopen on the bar a position closed.
inTrade = strategy.position_size != 0
if inTrade and bar_index > entryBar and exitNow
    strategy.close("Long")
    exitBar := bar_index
else if not inTrade and bar_index > exitBar and enterNow
    strategy.entry("Long", strategy.long)
    entryBar := bar_index

// ── Drawing ──────────────────────────────────────────────────────────────
plot(momentum, "Momentum", color=#4d8dff)
hline(0, "Zero", color=color.new(#8a92a0, 40), linestyle=hline.style_dashed)