commit for version used in evaluation of thesis

internal/detect/copod.go

@@ -0,0 +1,98 @@
+// Package detect provides anomaly detection algorithms and ensemble logic.
+package detect
+
+import (
+	"fmt"
+	"log"
+
+	"codeberg.org/pata1704/copod"
+	"codeberg.org/pata1704/guenther/pkg/types"
+)
+
+// COPODDetector implements the AnomalyDetector interface by wrapping the
+// external codeberg.org/pata1704/copod package.
+//
+// Streaming mode: Score calls Update internally, so the sliding-window buffer
+// stays current without requiring a separate Update call. Callers (like SEAD)
+// only need to call Score per time step.
+//
+// Fit seeds the buffer with a batch of normal vectors. If Fit is not called
+// the detector starts cold and returns score=0 until the buffer has enough
+// points (controlled by bufferSize in the underlying library).
+type COPODDetector struct {
+	detector *copod.Detector
+}
+
+// NewCOPODDetector initialises the streaming COPOD detector wrapper.
+//
+//   - bufferSize: sliding-window capacity. Recommended: 100–200.
+//   - threshold:  score cutoff for standalone IsAnomaly. When used inside
+//     SEAD the threshold is ignored (SEAD applies its own adaptive threshold).
+func NewCOPODDetector(bufferSize int, threshold float64) (*COPODDetector, error) {
+	det, err := copod.NewDetector(bufferSize, threshold)
+	if err != nil {
+		return nil, fmt.Errorf("copod: initialize wrapped detector: %w", err)
+	}
+	return &COPODDetector{
+		detector: det,
+	}, nil
+}
+
+// Fit seeds the COPOD history buffer with a slice of labelled-normal vectors.
+func (c *COPODDetector) Fit(vectors []types.FeatureVector) error {
+	for _, v := range vectors {
+		if err := c.update(v); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Update adds a single observation to the sliding window.
+// Safe to call concurrently with Score.
+func (c *COPODDetector) Update(vector types.FeatureVector) error {
+	return c.update(vector)
+}
+
+// Score computes the COPOD anomaly score for the given vector and
+// simultaneously updates the internal sliding window with the scored vector.
+//
+// The self-update ensures COPOD's buffer reflects the current data stream
+// without requiring a separate Update call after every Score. This is
+// consistent with the RRCF and IsolationForest detectors which also
+// update themselves inside Score.
+func (c *COPODDetector) Score(vector types.FeatureVector) (types.AnomalyResult, error) {
+	vec := copod.FeatureVector{
+		NormalizedVector: vector.NormalizedVector,
+		Timestamp:        vector.Timestamp,
+	}
+
+	// Score first, then append to the buffer so the scored point does not
+	// bias its own copula calculation (score-then-insert, same as RRCF).
+	res, err := c.detector.Score(vec)
+	if err != nil {
+		return types.AnomalyResult{}, fmt.Errorf("copod: score: %w", err)
+	}
+
+	if err := c.update(vector); err != nil {
+		// Log but don't fail: the score is already computed.
+		log.Printf("copod: update after score: %v", err)
+	}
+
+	return types.AnomalyResult{
+		Timestamp:  res.Timestamp,
+		Score:      res.Score,
+		IsAnomaly:  res.IsAnomaly,
+		Confidence: res.Confidence,
+		Method:     res.Method,
+	}, nil
+}
+
+// update is the internal helper that adds vector to the copod sliding window.
+func (c *COPODDetector) update(vector types.FeatureVector) error {
+	vec := copod.FeatureVector{
+		NormalizedVector: vector.NormalizedVector,
+		Timestamp:        vector.Timestamp,
+	}
+	return c.detector.Update(vec)
+}