sync

internal/types/downsample.go

@@ -0,0 +1,63 @@
+package types
+
+// Downsampler implements the Largest-Triangle-Three-Buckets algorithm
+type Downsampler struct{}
+
+// NewDownsampler creates a new Downsampler instance
+func NewDownsampler() *Downsampler {
+	return &Downsampler{}
+}
+
+// Process downsamples data using Largest-Triangle-Three-Buckets algorithm
+func (d *Downsampler) Process(data []float64, threshold int) []float64 {
+	if len(data) <= threshold || threshold <= 0 {
+		return data
+	}
+
+	sampled := make([]float64, 0, threshold)
+	sampled = append(sampled, data[0]) // First point
+
+	bucketSize := float64(len(data)-2) / float64(threshold-2)
+
+	for i := 1; i < threshold-1; i++ {
+		bucketStart := int(float64(i-1)*bucketSize) + 1
+		bucketEnd := int(float64(i)*bucketSize) + 1
+
+		if bucketEnd >= len(data) {
+			bucketEnd = len(data) - 1
+		}
+
+		maxArea := -1.0
+		selectedPoint := data[bucketStart]
+
+		for j := bucketStart; j < bucketEnd; j++ {
+			area := triangleArea(
+				data[bucketStart-1],
+				data[j],
+				data[bucketEnd],
+			)
+
+			if area > maxArea {
+				maxArea = area
+				selectedPoint = data[j]
+			}
+		}
+
+		sampled = append(sampled, selectedPoint)
+	}
+
+	sampled = append(sampled, data[len(data)-1]) // Last point
+	return sampled
+}
+
+// triangleArea calculates the area of a triangle formed by three points
+func triangleArea(a, b, c float64) float64 {
+	return abs((a-b)*(c-b)-(b-c)*(a-c)) / 2
+}
+
+func abs(x float64) float64 {
+	if x < 0 {
+		return -x
+	}
+	return x
+}