feat: add transport-neutral request metrics

metrics/metrics_test.go

@@ -0,0 +1,67 @@
+package metrics_test
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http/httptest"
+	"testing"
+
+	apierrors "git.yuntuo.hk/k2safe/go-omni/errors"
+	"git.yuntuo.hk/k2safe/go-omni/httpx"
+	"git.yuntuo.hk/k2safe/go-omni/metrics"
+)
+
+func TestMiddlewareCollectsStatusesAndErrors(t *testing.T) {
+	collector := metrics.New()
+	request := httptest.NewRequest("GET", "/health", nil)
+	first := httptest.NewRecorder()
+	ctx := httpx.NewContext(request, first, nil)
+	if err := collector.Middleware()(func(c *httpx.Context) error { return c.OK("ok") })(ctx); err != nil {
+		t.Fatal(err)
+	}
+
+	second := httptest.NewRecorder()
+	ctx = httpx.NewContext(request, second, nil)
+	handled := collector.Middleware()(func(*httpx.Context) error {
+		return apierrors.NotFound("MISSING", "missing")
+	})
+	if err := handled(ctx); err == nil {
+		t.Fatal("expected handler error")
+	}
+
+	snapshot := collector.Snapshot()
+	if snapshot.Requests != 2 || snapshot.Errors != 1 || snapshot.InFlight != 0 || snapshot.StatusCounts["200"] != 1 || snapshot.StatusCounts["404"] != 1 {
+		t.Fatalf("unexpected snapshot: %+v", snapshot)
+	}
+}
+
+func TestHandlerReturnsJSONSnapshot(t *testing.T) {
+	collector := metrics.New()
+	request := httptest.NewRequest("GET", "/metrics", nil)
+	recorder := httptest.NewRecorder()
+	ctx := httpx.NewContext(request, recorder, nil)
+	if err := collector.Handler()(ctx); err != nil {
+		t.Fatal(err)
+	}
+	var envelope struct {
+		Code string           `json:"code"`
+		Data metrics.Snapshot `json:"data"`
+	}
+	if err := json.Unmarshal(recorder.Body.Bytes(), &envelope); err != nil {
+		t.Fatal(err)
+	}
+	if envelope.Code != "OK" || envelope.Data.StatusCounts == nil {
+		t.Fatalf("unexpected metrics response: %s", recorder.Body)
+	}
+}
+
+func TestMiddlewarePreservesApplicationErrors(t *testing.T) {
+	collector := metrics.New()
+	request := httptest.NewRequest("GET", "/", nil)
+	ctx := httpx.NewContext(request, httptest.NewRecorder(), nil)
+	want := errors.New("database unavailable")
+	got := collector.Middleware()(func(*httpx.Context) error { return want })(ctx)
+	if !errors.Is(got, want) {
+		t.Fatalf("middleware replaced error: %v", got)
+	}
+}