incorporate observer interface into components

observer/observer.go

@@ -0,0 +1,19 @@
+// Package observer defines the contract for collecting peer-level statistics.
+package observer
+
+// Observer is the interface through which add-ons report statistics.
+// Add-ons should call Record() with a peer ID and a typed event when
+// significant events occur. The event parameter is expected to be a
+// domain-specific struct defined in the add-on's package.
+type Observer interface {
+	// Record reports a statistic event for a given peer.
+	// The event parameter contains the domain-specific details.
+	Record(peerID string, event any)
+}
+
+// NullObserver is a null implementation of Observer that does nothing.
+// It is used when no actual statistics collector is wired in.
+type NullObserver struct{}
+
+// Record implements Observer for NullObserver, doing nothing.
+func (NullObserver) Record(_ string, _ any) {}

observer/observer_test.go

@@ -0,0 +1,17 @@
+package observer
+
+import (
+	"testing"
+)
+
+func TestNullObserver(t *testing.T) {
+	// Test that NullObserver implements the Observer interface
+	var _ Observer = NullObserver{}
+
+	// Test that calling Record doesn't panic or crash
+	sink := NullObserver{}
+	sink.Record("peer1", "test event")
+	sink.Record("", nil)
+
+	// Test that it's a no-op (no assertions needed since it does nothing)
+}