feat: add peerstat package with Sink interface and NoopSink

peerstat/sink.go

@@ -0,0 +1,19 @@
+// Package peerstat defines the contract for collecting peer-level statistics.
+package peerstat
+
+// Sink 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 Sink interface {
+	// Record reports a statistic event for a given peer.
+	// The event parameter contains the domain-specific details.
+	Record(peerID string, event any)
+}
+
+// NoopSink is a null implementation of Sink that does nothing.
+// It is used when no actual statistics collector is wired in.
+type NoopSink struct{}
+
+// Record implements Sink for NoopSink, doing nothing.
+func (NoopSink) Record(_ string, _ any) {}

peerstat/sink_test.go

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