Supertrend in dart . I am trying to calculate supertrend in dart but problem is other charting platfrom have very different values than mine

Question

I am using period = 10 and multiplier = 3. Here is the code. Where might I be wrong. Because my upperband and lowerband are way off from charting platfroms such as trading view or zerodha. I am getting 5 minute candle data for 2 days and based on that calculating the ATR and supertrend. (so maybe 224 candles and 10 period).

class SupertrendCalculator {
  final List<StockDataKite> candles;
  final int period;
  final double multiplier;
  final int emaPeriod = 13; // EMA period

  SupertrendCalculator({
    required this.candles,
    this.period = 10,
    this.multiplier = 3,
  });
  List<double> calculateATR() {
    List<double> trValues = []; // True Range values
    List<double> atrValues = List.filled(candles.length, 0.0); // ATR values

    // Calculate True Range for each candle
    for (int i = 0; i < candles.length; i++) {
      double highLow = candles[i].high - candles[i].low;
      double highClosePrev =
          i == 0 ? 0 : (candles[i].high - candles[i - 1].close).abs();
      double lowClosePrev =
          i == 0 ? 0 : (candles[i].low - candles[i - 1].close).abs();
      double trueRange = max(highLow, max(highClosePrev, lowClosePrev));
      trValues.add(trueRange);
      //print('True range length ${candles.length} ${trValues}');
    }

    // Calculate ATR
    for (int i = period; i < candles.length; i++) {
      if (i == period) {
        // Initial ATR is the average of the first 'period' TR values
        double sumTR = trValues.sublist(0, period).reduce((a, b) => a + b);
        atrValues[i] = sumTR / period;
      } else {
        // Subsequent ATR values are calculated using the previous ATR value
        atrValues[i] =
            ((atrValues[i - 1] * (period - 1)) + trValues[i]) / period;
      }
    }
    return atrValues;
  }

  dynamic calculateEMA({bool single = false}) {
    List<double> emaValues = List.filled(candles.length, 0.0);
    double multiplier = 2 / (emaPeriod + 1.0);

    if (candles.isNotEmpty) {
      // Set the first EMA value to the first close price
      emaValues[0] = candles[0].close;

      for (int i = 1; i < candles.length; i++) {
        double closePrice = candles[i].close;
        // EMA formula
        emaValues[i] =
            ((closePrice - emaValues[i - 1]) * multiplier) + emaValues[i - 1];
      }
    }
    if (single == true) {
      return emaValues.last;
    } else {
      return emaValues;
    }
  }

  List calculateSupertrend() {
    List<double> atr = calculateATR();
    List<double> ema = calculateEMA(); // Calculate EMA values
    bool trend = false; // Initial trend
    double upperBand = 0.0, lowerBand = 0.0;
    for (int i = candles.length - period; i < candles.length; i++) {
      // First, calculate new bands regardless of the current trend
      var hl2 = (candles[i].high + candles[i].low) / 2;
      double newUpperBand = hl2 + (multiplier * atr[i]);
      double newLowerBand = hl2 - (multiplier * atr[i]);

         if (trend && candles[i].close < newLowerBand) {
          trend =
            false; // If current close is below the new lower band in an uptrend, switch 
           to downtrend
          } else if (!trend && candles[i].close > newUpperBand) {
           trend =
            true; // If current close is above the new upper band in a downtrend, switch 
            to uptrend
           }

           // Update bands based on the new trend direction
           if (trend) {
           upperBand = newUpperBand; // In an uptrend, always update the upper band
            lowerBand = max(
            lowerBand, newLowerBand); // Lower band doesn't decrease in uptrend
            } else {
               lowerBand =
              newLowerBand; // In a downtrend, always update the lower band
             upperBand = min(upperBand,
               newUpperBand); // Upper band doesn't increase in downtrend
             }

      bool isEMATouchingOrClose = (ema[i] - candles[i].close).abs() <=
          (candles[i].close * 0.003); // EMA is within 0.5% of the close price
      if (trend &&
          candles[i].close > candles[i].open &&
          candles[i].close > ema[i] &&
          isEMATouchingOrClose &&
          ema[i] > ema[i - 1] &&
          ema[i - 1] > ema[i - 2]) {
        candles[i].supertrendSignal = "BUY"; // Uptrend and EMA is increasing
      } else if (!trend &&
          candles[i].close < candles[i].open &&
          isEMATouchingOrClose &&
          ema[i] < ema[i - 1] &&
          candles[i].close < ema[i] &&
          ema[i - 1] < ema[i - 2]) {
        candles[i].supertrendSignal = "SELL"; // Downtrend and EMA is decreasing
      } else {
        candles[i].supertrendSignal = "HOLD";
      }
      // print(
      //     '${candles[i].timestamp} -- ${trend} -- ${candles[i].supertrendSignal}');
    }
    for (var candle in candles) {
      print(
          "Candle ${candle.timestamp}: Close=${candle.close}, Trend=${candle.supertrendSignal}, Signal=${candle.supertrendSignal}");
    }
    return [
      candles.last.supertrendSignal,
      ema.last,
      candles.last.open,
      candles.last.close
    ];
  }
}

The problem occurs when my code gives wrong signals because it things stock is in uptrend while it is in downtrend because of the messed up values of upper and lower bands. But when i change my multiplier to 1.3 or something within this range, this problems somewhat becomes less worrisome. But still I want the same upper band and lowerband values as othe r charting platforms.