package indicators

// MACDResult contient MACD line, signal line et histogramme.
type MACDResult struct {
	MACD      float64
	Signal    float64
	Histogram float64
}

// MACD calcule le Moving Average Convergence Divergence (12/26/9 standard).
// Retourne zéro-value si pas assez de données.
func MACD(closes []float64) MACDResult {
	return MACDCustom(closes, 12, 26, 9)
}

func MACDCustom(closes []float64, fast, slow, signal int) MACDResult {
	if len(closes) < slow+signal {
		return MACDResult{}
	}

	emaFast := emaSlice(closes, fast)
	emaSlow := emaSlice(closes, slow)

	// Aligner les deux séries (emaSlow est plus courte)
	offset := len(emaFast) - len(emaSlow)
	macdLine := make([]float64, len(emaSlow))
	for i := range emaSlow {
		macdLine[i] = emaFast[offset+i] - emaSlow[i]
	}

	if len(macdLine) < signal {
		return MACDResult{}
	}

	signalLine := emaSlice(macdLine, signal)
	last := macdLine[len(macdLine)-1]
	sig := signalLine[len(signalLine)-1]

	return MACDResult{
		MACD:      last,
		Signal:    sig,
		Histogram: last - sig,
	}
}

// SMA calcule la moyenne mobile simple sur les n dernières valeurs.
func SMA(closes []float64, period int) float64 {
	if len(closes) < period {
		return 0
	}
	slice := closes[len(closes)-period:]
	sum := 0.0
	for _, v := range slice {
		sum += v
	}
	return sum / float64(period)
}

// AvgVolume calcule le volume moyen sur les n dernières barres.
func AvgVolume(volumes []int64, period int) int64 {
	if len(volumes) < period {
		period = len(volumes)
	}
	if period == 0 {
		return 0
	}
	slice := volumes[len(volumes)-period:]
	var sum int64
	for _, v := range slice {
		sum += v
	}
	return sum / int64(period)
}

func emaSlice(data []float64, period int) []float64 {
	if len(data) < period {
		return nil
	}
	k := 2.0 / float64(period+1)

	// Première valeur = SMA des `period` premières
	sum := 0.0
	for i := 0; i < period; i++ {
		sum += data[i]
	}
	ema := make([]float64, 0, len(data)-period+1)
	ema = append(ema, sum/float64(period))

	for i := period; i < len(data); i++ {
		ema = append(ema, data[i]*k+ema[len(ema)-1]*(1-k))
	}
	return ema
}