RSI divergence

// overlay = false
const rsiLen   = input.int("RSI Length", 14, { min: 2 });
const pivotLen = input.int("Pivot lookback", 5, { min: 2, max: 20 });

hline(70, { color: "#ef4444FF", style: "dashed" });
hline(50, { color: "#6b728050" });
hline(30, { color: "#22c55eFF", style: "dashed" });

plot("RSI",  null, { color: "#a78bfaFF" });
plot("Div",  null, { style: "arrowdown", colorUp: "#ef4444FF", size: 10 });

// Store prior pivot RSI and price highs
const lastPivotRsi   = Series("last-pivot-rsi");
const lastPivotPrice = Series("last-pivot-price");

onBar(() => {
  const rsi = ta.rsi(ctx.close, rsiLen);
  if (na(rsi)) return;

  plot("RSI", rsi);

  // Check for a pivot high in price (lagged by pivotLen bars)
  const priceHigh = ta.pivothigh(ctx.high, pivotLen, pivotLen);
  const rsiAtPivot = na(priceHigh) ? NaN : ta.rsi(ctx.close, rsiLen);

  // Update last-seen pivot values
  if (!na(priceHigh)) {
    lastPivotPrice.set(priceHigh);
    lastPivotRsi.set(nz(rsiAtPivot, rsi));
  } else {
    lastPivotPrice.set(lastPivotPrice.get(1));
    lastPivotRsi.set(lastPivotRsi.get(1));
  }

  // Bearish divergence: price higher high, RSI lower high
  if (!na(priceHigh) && !na(lastPivotPrice.get(1))) {
    const priceDiverge = priceHigh > lastPivotPrice.get(1);
    const rsiDiverge   = nz(rsiAtPivot, rsi) < lastPivotRsi.get(1);

    if (priceDiverge && rsiDiverge) {
      plot("Div", rsi + 5); // marker above RSI value
    } else {
      plot("Div", NaN);
    }
  } else {
    plot("Div", NaN);
  }
});