From bb8922f4292f95457ba9b7039ea4bc540bb622c2 Mon Sep 17 00:00:00 2001
From: lbenedar <lbenedar@local.lab>
Date: Tue, 24 Mar 2026 16:58:19 +0300
Subject: [PATCH] ch19.4

---
 cmd/api/middleware.go | 20 ++++++++++++++++++++
 cmd/api/routes.go     |  2 +-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/cmd/api/middleware.go b/cmd/api/middleware.go
index d09e7ad..07f0bd5 100644
--- a/cmd/api/middleware.go
+++ b/cmd/api/middleware.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"errors"
+	"expvar"
 	"fmt"
 	"net"
 	"net/http"
@@ -199,3 +200,22 @@ func (app *application) enableCORS(next http.Handler) http.Handler {
 		next.ServeHTTP(w, r)
 	})
 }
+
+func (app *application) metrics(next http.Handler) http.Handler {
+	var (
+		totalRequestsReceived           = expvar.NewInt("total_requests_received")
+		totalResponseSent               = expvar.NewInt("total_responses_sent")
+		totalProcessingTimeMicroseconds = expvar.NewInt("total_processing_time_μs")
+	)
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+
+		totalRequestsReceived.Add(1)
+		next.ServeHTTP(w, r)
+		totalResponseSent.Add(1)
+
+		duration := time.Since(start).Microseconds()
+		totalProcessingTimeMicroseconds.Add(duration)
+	})
+}
diff --git a/cmd/api/routes.go b/cmd/api/routes.go
index c6a67ed..a112c81 100644
--- a/cmd/api/routes.go
+++ b/cmd/api/routes.go
@@ -28,5 +28,5 @@ func (app *application) routes() http.Handler {
 
 	router.Handler(http.MethodGet, "/debug/vars", expvar.Handler())
 
-	return app.recoverPanic(app.enableCORS(app.rateLimit(app.authenticate(router))))
+	return app.metrics(app.recoverPanic(app.enableCORS(app.rateLimit(app.authenticate(router)))))
 }