single file backend, because this is not Ruby

Author: piger

backend/go.mod

@@ -1,3 +1,3 @@
 module github.com/piger/nginx-lab
 
-go 1.18
+go 1.24

backend/main.go

@@ -2,30 +2,96 @@
 package main
 
 import (
+	"encoding/json"
+	"errors"
 	"flag"
+	"fmt"
 	"log"
-
-	"github.com/piger/nginx-lab/server"
+	"log/slog"
+	"net/http"
+	"os"
+	"strings"
+	"time"
 )
 
-var (
-	listenAddress = flag.String("addr", "0.0.0.0", "Address to bind to")
-	listenPort    = flag.Int("port", 4444, "Port to listen on")
-)
+type logMiddleware struct {
+	inner  http.Handler
+	logger *slog.Logger
+}
 
-func run() error {
-	flag.Parse()
+func (l logMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	start := time.Now().UTC()
+	l.inner.ServeHTTP(w, r)
+	l.logger.Info("request", "method", r.Method, "url", r.URL.String(), "remote_addr", r.RemoteAddr, "elapsed", time.Since(start).String())
+}
+
+func withLog(h http.HandlerFunc, logger *slog.Logger) http.Handler {
+	return logMiddleware{inner: h, logger: logger}
+}
+
+type echoResponse struct {
+	Method     string            `json:"method"`
+	URL        string            `json:"url"`
+	Proto      string            `json:"proto"`
+	Headers    map[string]string `json:"headers"`
+	Host       string            `json:"host"`
+	RequestURI string            `json:"request_uri"`
+	RemoteAddr string            `json:"remote_addr"`
+}
 
-	srv := server.New(*listenAddress, *listenPort)
-	if err := srv.Run(); err != nil {
+// echoHandler is an handler that returns a JSON object containing information about the received request.
+func echoHandler(w http.ResponseWriter, r *http.Request) {
+	headers := make(map[string]string)
+	for k, v := range r.Header {
+		headers[k] = strings.Join(v, ", ")
+	}
+
+	resp := echoResponse{
+		Method:     r.Method,
+		URL:        r.URL.String(),
+		Proto:      r.Proto,
+		Headers:    headers,
+		Host:       r.Host,
+		RequestURI: r.RequestURI,
+		RemoteAddr: r.RemoteAddr,
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+
+	if err := json.NewEncoder(w).Encode(resp); err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "ERROR: %s\n", err)
+		return
+	}
+}
+
+func run(addr string, logger *slog.Logger) error {
+	mux := http.NewServeMux()
+	mux.Handle("/", withLog(echoHandler, logger))
+
+	srv := http.Server{
+		Addr:           addr,
+		Handler:        mux,
+		ReadTimeout:    10 * time.Second,
+		WriteTimeout:   10 * time.Second,
+		MaxHeaderBytes: 1 << 20, // 1 MiB
+	}
+
+	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
 		return err
 	}
 
 	return nil
 }
 
 func main() {
-	if err := run(); err != nil {
+	flagAddr := flag.String("addr", ":4444", "Address to listen to (e.g. 0.0.0.0:4444)")
+	flag.Parse()
+
+	logger := slog.New(slog.NewJSONHandler(os.Stderr, nil))
+	slog.SetDefault(logger)
+
+	if err := run(*flagAddr, logger); err != nil {
 		log.Fatalf("error: %s", err)
 	}
 }