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param("band_len", 60, { min: 10, max: 500, description: "Bars in the volatility band" });
// The chart's own candles are the grid every other input lines up on.
input("close", ohlcv.close);
input("buy", trades.volume, { side: "BUY", missing: "zero", description: "Aggressive buy volume" });
input("sell", trades.volume, { side: "SELL", missing: "zero", description: "Aggressive sell volume" });
output("cvd", line, lower, {
  width: 2,
  color_by: "sign",
  colors: ["#ff5b7f", "#22d3a5"],
  description: "Cumulative volume delta on the chart's market",
});
output("upper_band", line, lower, { color: "#22d3a5", opacity: 0.35, description: "CVD plus one standard deviation" });
output("lower_band", line, lower, { color: "#ff5b7f", opacity: 0.35, description: "CVD minus one standard deviation" });
output("sign", none, lower);

let stdev = new Stdev(60);
let cvd: f64 = 0.0;

function onStart(): void {
  stdev = new Stdev(i32(p_band_len()));
}

function onBar(): void {
  // A module-level variable is the accumulator: it survives from bar to bar.
  cvd += in_buy() - in_sell();
  const band = stdev.update(cvd);
  const width = isNaN(band) ? 0.0 : band;
  out_cvd(cvd);
  out_upper_band(cvd + width);
  out_lower_band(cvd - width);
  out_sign(cvd >= 0.0 ? 1.0 : 0.0);
}