export function calculateSMA(prices: number[], period: number = 20): number {
  if (prices.length < period) return 0;
  const slice = prices.slice(-period);
  const sum = slice.reduce((a, b) => a + b, 0);
  return sum / period;
}

export function calculateEMA(prices: number[], period: number = 20): number {
  if (prices.length < period) return 0;
  const multiplier = 2 / (period + 1);
  let ema = prices.slice(0, period).reduce((a, b) => a + b, 0) / period;
  for (let i = period; i < prices.length; i++) {
    ema = prices[i] * multiplier + ema * (1 - multiplier);
  }
  return ema;
}

export function calculateRSI(prices: number[], period: number = 14): number {
  if (prices.length < period + 1) return 50;
  let gains = 0;
  let losses = 0;
  for (let i = prices.length - period; i < prices.length; i++) {
    const diff = prices[i] - prices[i - 1];
    if (diff > 0) gains += diff;
    else losses -= diff;
  }
  const avgGain = gains / period;
  const avgLoss = losses / period;
  if (avgLoss === 0) return 100;
  const rs = avgGain / avgLoss;
  return 100 - (100 / (1 + rs));
}

export function calculateMACD(
  prices: number[],
  fastPeriod: number = 12,
  slowPeriod: number = 26,
  signalPeriod: number = 9
): { macdLine: number; signal: number; histogram: number } {
  if (prices.length < slowPeriod + signalPeriod) return { macdLine: 0, signal: 0, histogram: 0 };
  const emaFast = calculateEMA(prices, fastPeriod);
  const emaSlow = calculateEMA(prices, slowPeriod);
  const macdLine = emaFast - emaSlow;
  // Simplified signal: use recent MACD values approximation
  const signal = macdLine * 0.8; // Simplified
  return { macdLine, signal, histogram: macdLine - signal };
}

export function calculateBollingerBands(prices: number[], period: number = 20, stdDevMult: number = 2): { upper: number; middle: number; lower: number } {
  if (prices.length < period) return { upper: 0, middle: 0, lower: 0 };
  const slice = prices.slice(-period);
  const sma = slice.reduce((a, b) => a + b, 0) / period;
  const variance = slice.reduce((sum, p) => sum + Math.pow(p - sma, 2), 0) / period;
  const stdDev = Math.sqrt(variance);
  return {
    upper: sma + stdDevMult * stdDev,
    middle: sma,
    lower: sma - stdDevMult * stdDev,
  };
}

export function calculateATR(highs: number[], lows: number[], closes: number[], period: number = 14): number {
  if (highs.length < period || lows.length < period || closes.length < period) return 0;
  const len = Math.min(highs.length, lows.length, closes.length);
  const trueRanges: number[] = [];
  for (let i = len - period; i < len; i++) {
    const highLow = highs[i] - lows[i];
    const highClose = i > 0 ? Math.abs(highs[i] - closes[i - 1]) : 0;
    const lowClose = i > 0 ? Math.abs(lows[i] - closes[i - 1]) : 0;
    trueRanges.push(Math.max(highLow, highClose, lowClose));
  }
  return trueRanges.reduce((a, b) => a + b, 0) / period;
}

export function calculateVolumeAvg(volumes: number[], period: number = 20): number {
  if (volumes.length < period) return 0;
  const slice = volumes.slice(-period);
  return slice.reduce((a, b) => a + b, 0) / period;
}