sync

fitness-tui/internal/analysis/downsample.go

@@ -0,0 +1,95 @@
+package analysis
+
+import (
+	"time"
+)
+
+// DownsampledPoint represents a single data point in a downsampled metric series
+type DownsampledPoint struct {
+	TimeOffset int     `json:"time_offset"` // Seconds from activity start
+	Value      float64 `json:"value"`       // Average value during this segment
+	Min        float64 `json:"min,omitempty"`
+	Max        float64 `json:"max,omitempty"`
+}
+
+// DownsampleMetric downsamples a metric array to the specified number of points
+func DownsampleMetric(data []float64, duration time.Duration, targetPoints int) []DownsampledPoint {
+	if len(data) == 0 || targetPoints <= 0 {
+		return nil
+	}
+
+	totalSeconds := int(duration.Seconds())
+	if totalSeconds <= 0 {
+		return nil
+	}
+
+	// Calculate segment duration in seconds (floating point for accuracy)
+	segmentDuration := float64(totalSeconds) / float64(targetPoints)
+	if segmentDuration < 1 {
+		segmentDuration = 1
+	}
+
+	// Preallocate segments array
+	segments := make([]struct {
+		sum   float64
+		count int
+		min   float64
+		max   float64
+	}, targetPoints)
+
+	// Initialize min/max with zero values - we'll update them when we see data
+
+	// Assign data points to segments
+	for i, value := range data {
+		// Calculate time offset for this data point
+		timeOffset := float64(i) * float64(totalSeconds) / float64(len(data))
+		segmentIndex := int(timeOffset / segmentDuration)
+
+		// Clamp to valid segment range
+		if segmentIndex >= targetPoints {
+			segmentIndex = targetPoints - 1
+		}
+
+		seg := &segments[segmentIndex]
+		seg.sum += value
+		seg.count++
+
+		// Initialize min/max on first value in segment
+		if seg.count == 1 {
+			seg.min = value
+			seg.max = value
+		} else {
+			if value < seg.min {
+				seg.min = value
+			}
+			if value > seg.max {
+				seg.max = value
+			}
+		}
+	}
+
+	// Build results array
+	results := make([]DownsampledPoint, targetPoints)
+	for j := 0; j < targetPoints; j++ {
+		seg := &segments[j]
+		timeOffset := int(float64(j) * segmentDuration)
+
+		if seg.count == 0 {
+			// For empty segments, omit min/max
+			results[j] = DownsampledPoint{
+				TimeOffset: timeOffset,
+				Value:      0,
+			}
+		} else {
+			avg := seg.sum / float64(seg.count)
+			results[j] = DownsampledPoint{
+				TimeOffset: timeOffset,
+				Value:      avg,
+				Min:        seg.min,
+				Max:        seg.max,
+			}
+		}
+	}
+
+	return results
+}