init

logic/evaluator.go

@@ -0,0 +1,66 @@
+package logic
+
+import (
+	"math"
+	"sort"
+)
+
+func CalculateCardValue(baseSales, exactSales []float64, factors map[string]float64) float64 {
+	bpRaw := calculateBasePrice(baseSales)
+	emp := 0.0
+	if len(exactSales) > 0 {
+		emp = calculateBasePrice(exactSales)
+	}
+	bpFinal := calculateFinalBasePrice(bpRaw, emp, len(exactSales))
+	value := (bpFinal * factors["GF"] * factors["RF"] * factors["EF"] * factors["ST"] * factors["DF"] * factors["AF"] * factors["MF"]) + factors["TAF"]
+	return math.Round(value*100) / 100
+}
+
+func calculateBasePrice(sales []float64) float64 {
+	cleanSales := removeOutliers(sales)
+	median := calculateMedian(cleanSales)
+	stdDev := calculateStdDev(cleanSales, median)
+	vaf := 1 + (stdDev/median)*0.1
+	return median * vaf
+}
+
+func calculateFinalBasePrice(bp, emp float64, exactCount int) float64 {
+	weight := 0.0
+	switch {
+	case exactCount >= 10:
+		weight = 0.8
+	case exactCount >= 5:
+		weight = 0.6
+	case exactCount >= 2:
+		weight = 0.4
+	}
+	return (bp * (1 - weight)) + (emp * weight)
+}
+
+func removeOutliers(sales []float64) []float64 {
+	median := calculateMedian(sales)
+	var filtered []float64
+	for _, s := range sales {
+		if s >= median*0.7 && s <= median*1.3 {
+			filtered = append(filtered, s)
+		}
+	}
+	return filtered
+}
+
+func calculateMedian(sales []float64) float64 {
+	sort.Float64s(sales)
+	n := len(sales)
+	if n%2 == 0 {
+		return (sales[n/2-1] + sales[n/2]) / 2
+	}
+	return sales[n/2]
+}
+
+func calculateStdDev(sales []float64, mean float64) float64 {
+	var sum float64
+	for _, s := range sales {
+		sum += math.Pow(s-mean, 2)
+	}
+	return math.Sqrt(sum / float64(len(sales)))
+}