feat: separate routes from main.go and create an app struct

Author: anandg112

cmd/web/handlers.go

@@ -3,14 +3,12 @@ package main
 import (
 	"fmt"
 	"html/template"
-	"log"
 	"net/http"
 	"strconv"
 )
 
-// Define a home handler function which writes a byte slice containing
-// "Hello from Snippetbox" as the response body.
-func home(w http.ResponseWriter, r *http.Request) {
+// change the signature of the home handler so it is defined as a method against *application
+func (app *application) home(w http.ResponseWriter, r *http.Request) {
 
 	if r.URL.Path != "/" {
 		http.NotFound(w, r)
@@ -26,39 +24,39 @@ func home(w http.ResponseWriter, r *http.Request) {
 	ts, err := template.ParseFiles(files...)
 
 	if err != nil {
-		log.Print(err.Error())
-		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		app.logger.Error(err.Error(), "method", r.Method, "uri", r.URL.RequestURI())
+		app.serverError(w, r, err)
 		return
 	}
 
 	err = ts.ExecuteTemplate(w, "base", nil)
 
 	if err != nil {
-		log.Print(err.Error())
-		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		app.logger.Error(err.Error(), "method", r.Method, "uri", r.URL.RequestURI())
+		app.serverError(w, r, err)
 	}
 
 }
 
 // Add a snippetView handler function.
-func snippetView(w http.ResponseWriter, r *http.Request) {
+func (app *application) snippetView(w http.ResponseWriter, r *http.Request) {
 
 	id, err := strconv.Atoi(r.URL.Query().Get("id"))
 
 	if err != nil || id < 1 {
-		http.NotFound(w, r)
+		app.notFound(w)
 		return
 	}
 
 	fmt.Fprintf(w, "Display a specific snippet with ID %d...", id)
 }
 
 // Add a snippetCreate handler function.
-func snippetCreate(w http.ResponseWriter, r *http.Request) {
+func (app *application) snippetCreate(w http.ResponseWriter, r *http.Request) {
 
 	if r.Method != http.MethodPost {
 		w.Header().Set("Allow", http.MethodPost)
-		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
+		app.clientError(w, http.StatusMethodNotAllowed)
 		return
 	}
 

cmd/web/helpers.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"net/http"
+	"runtime/debug"
+)
+
+func (app *application) serverError(w http.ResponseWriter, r *http.Request, err error) {
+
+	var (
+		method = r.Method
+		uri    = r.URL.RequestURI()
+		trace  = string(debug.Stack())
+	)
+	app.logger.Error(err.Error(), "method", method, "uri", uri, "trace", trace)
+	http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+}
+
+func (app *application) clientError(w http.ResponseWriter, status int) {
+	http.Error(w, http.StatusText(status), status)
+}
+
+func (app *application) notFound(w http.ResponseWriter) {
+	app.clientError(w, http.StatusNotFound)
+}

cmd/web/main.go

@@ -2,8 +2,9 @@ package main
 
 import (
 	"flag"
-	"log"
+	"log/slog"
 	"net/http"
+	"os"
 )
 
 func main() {
@@ -14,20 +15,19 @@ func main() {
 	flag.StringVar(&cfg.staticDir, "static-dir", "./ui/static", "Path to static assets")
 
 	flag.Parse()
-	// Register the two new handler functions and corresponding URL patterns with
-	// the servemux, in exactly the same way that we did before.
-	mux := http.NewServeMux()
 
-	fileServer := http.FileServer(http.Dir(cfg.staticDir))
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
 
-	mux.Handle("/static/", http.StripPrefix("/static/", fileServer))
+	// Intialize a new instance of our application struct, containing the
+	//dependencies
+	app := &application{
+		logger: logger,
+	}
 
-	mux.HandleFunc("/", home)
-	mux.HandleFunc("/snippet/view", snippetView)
-	mux.HandleFunc("/snippet/create", snippetCreate)
+	logger.Info("Starting server", slog.String("addr", cfg.addr))
 
-	log.Printf("starting server on %s", cfg.addr)
+	err := http.ListenAndServe(cfg.addr, app.routes())
 
-	err := http.ListenAndServe(cfg.addr, mux)
-	log.Fatal(err)
+	logger.Error(err.Error())
+	os.Exit(1)
 }

cmd/web/routes.go

@@ -0,0 +1,20 @@
+package main
+
+import "net/http"
+
+func (app *application) routes() *http.ServeMux {
+
+	var cfg config
+
+	mux := http.NewServeMux()
+
+	fileServer := http.FileServer(http.Dir(cfg.staticDir))
+
+	mux.Handle("/static/", http.StripPrefix("/static/", fileServer))
+
+	mux.HandleFunc("/", app.home)
+	mux.HandleFunc("/snippet/view", app.snippetView)
+	mux.HandleFunc("/snippet/create", app.snippetCreate)
+
+	return mux
+}

cmd/web/interfaces.go renamed to cmd/web/types.go

@@ -1,6 +1,12 @@
 package main
 
+import "log/slog"
+
 type config struct {
 	addr      string
 	staticDir string
 }
+
+type application struct {
+	logger *slog.Logger
+}