Chapter7

cmd/web/handlers.go

@@ -57,9 +57,10 @@ func (app *Application) SnippetView(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	app.render(w, r, http.StatusOK, "view.tmpl", templateData{
-		Snippet: snippet,
-	})
+	data := app.NewTemplateData(r)
+	data.Snippet = snippet
+
+	app.render(w, r, http.StatusOK, "view.tmpl", *data)
 
 }
 
@@ -122,6 +123,8 @@ func (app *Application) SnippetCreatePost(w http.ResponseWriter, r *http.Request
 		app.serverError(w, r, err)
 		return
 	}
+	// Saving message flash
+	app.sessionManager.Put(r.Context(), "flash", "Snippet created successfully!")
 
 	http.Redirect(w, r, fmt.Sprintf("/snippet/view/%d", id), http.StatusSeeOther)
 }

cmd/web/handlers_test.go

@@ -9,6 +9,8 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/alexedwards/scs/v2"
+	"github.com/alexedwards/scs/v2/memstore"
 	"snippetbox.tonidefez.net/internal/models"
 )
 
@@ -85,13 +87,19 @@ func TestSnippetView(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	// Create fake session manager
+	sessionManager := scs.New()
+	sessionManager.Store = memstore.New()
+
 	app := &Application{
-		logger:        dummyLogger,
-		snippets:      &models.MockSnippetModel{},
-		templateCache: templateCache,
+		logger:         dummyLogger,
+		snippets:       &models.MockSnippetModel{},
+		templateCache:  templateCache,
+		sessionManager: sessionManager,
 	}
 
-	router := app.routes()
+	//Be sure to manage session for each route
+	router := app.sessionManager.LoadAndSave(app.routes())
 	router.ServeHTTP(rr, req)
 
 	// verify status
@@ -115,18 +123,22 @@ func TestSnippetCreateGet(t *testing.T) {
 	dummyLogger := slog.New(slog.NewTextHandler(io.Discard, nil))
 	dummyDB := &models.SnippetModel{DB: nil}
 	templateCache, err := newTemplateCache()
+	// Create fake session manager
+	sessionManager := scs.New()
+	sessionManager.Store = memstore.New()
 
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	app := &Application{
-		logger:        dummyLogger,
-		snippets:      dummyDB,
-		templateCache: templateCache,
+		logger:         dummyLogger,
+		snippets:       dummyDB,
+		templateCache:  templateCache,
+		sessionManager: sessionManager,
 	}
 
-	router := app.routes()
+	router := app.sessionManager.LoadAndSave(app.routes())
 	router.ServeHTTP(rr, req)
 
 	// verify status
@@ -144,13 +156,18 @@ func TestSnippetCreatePost(t *testing.T) {
 
 	dummyLogger := slog.New(slog.NewTextHandler(io.Discard, nil))
 
+	// Create fake session manager
+	sessionManager := scs.New()
+	sessionManager.Store = memstore.New()
+
 	// simulate dependencies
 	app := &Application{
-		logger:   dummyLogger,
-		snippets: &models.MockSnippetModel{},
+		logger:         dummyLogger,
+		snippets:       &models.MockSnippetModel{},
+		sessionManager: sessionManager,
 	}
 
-	router := app.routes()
+	router := app.sessionManager.LoadAndSave(app.routes())
 	router.ServeHTTP(rr, req)
 
 	// Verificar redirección
@@ -172,8 +189,14 @@ func TestSnippetCreatePost_InvalidData(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
+	// Create fake session manager
+	sessionManager := scs.New()
+	sessionManager.Store = memstore.New()
+
 	app := &Application{
-		templateCache: templateCache,
+		templateCache:  templateCache,
+		sessionManager: sessionManager,
 	}
 
 	form := url.Values{}
@@ -186,7 +209,7 @@ func TestSnippetCreatePost_InvalidData(t *testing.T) {
 
 	rr := httptest.NewRecorder()
 
-	app.SnippetCreatePost(rr, req)
+	app.sessionManager.LoadAndSave(http.HandlerFunc(app.SnippetCreatePost)).ServeHTTP(rr, req)
 
 	res := rr.Result()
 	defer res.Body.Close()

cmd/web/helper.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net/http"
 	"runtime/debug"
+	"time"
 
 	"snippetbox.tonidefez.net/internal/models"
 )
@@ -54,7 +55,14 @@ func (app *Application) render(w http.ResponseWriter, r *http.Request, status in
 
 func (app *Application) NewTemplateData(r *http.Request) *templateData {
 	return &templateData{
-		Snippet:  models.Snippet{},
-		Snippets: []models.Snippet{},
+		Snippet:     models.Snippet{},
+		Snippets:    []models.Snippet{},
+		CurrentYear: time.Now().Year(),
+		// Use the PopString() method to retrieve the value for the "flash" key.
+		// PopString() also deletes the key and value from the session data, so it
+		// acts like a one-time fetch. If there is no matching key in the session
+		// data this will return the empty string.
+
+		Flash: app.sessionManager.PopString(r.Context(), "flash"),
 	}
 }

cmd/web/main.go

@@ -7,7 +7,10 @@ import (
 	"net/http"
 	"os"
 	"text/template"
+	"time"
 
+	"github.com/alexedwards/scs/mysqlstore"
+	"github.com/alexedwards/scs/v2"
 	_ "github.com/go-sql-driver/mysql"
 	"snippetbox.tonidefez.net/internal/models"
 )
@@ -16,10 +19,10 @@ import (
 // web application. For now we'll only include the structured logger, but we'll
 // add more to this as the build progresses.
 type Application struct {
-	logger *slog.Logger
-	// implemeting an interfaz we can make with differents dependencies DIP
-	snippets      models.SnippetModeler
-	templateCache map[string]*template.Template
+	logger         *slog.Logger
+	snippets       models.SnippetModeler
+	templateCache  map[string]*template.Template
+	sessionManager *scs.SessionManager
 }
 
 func main() {
@@ -43,6 +46,14 @@ func main() {
 	// before the main() function exits.
 	defer db.Close()
 
+	// Use the scs.New() function to initialize a new session manager. Then we
+	// configure it to use our MySQL database as the session store, and set a
+	// lifetime of 12 hours (so that sessions automatically expire 12 hours
+	// after first being created).
+	sessionManager := scs.New()
+	sessionManager.Store = mysqlstore.New(db)
+	sessionManager.Lifetime = 12 * time.Hour
+
 	// Initialize a new template cache...
 	templateCache, err := newTemplateCache()
 	if err != nil {
@@ -51,17 +62,18 @@ func main() {
 	}
 
 	app := &Application{
-		logger:        logger,
-		snippets:      &models.SnippetModel{DB: db},
-		templateCache: templateCache,
+		logger:         logger,
+		snippets:       &models.SnippetModel{DB: db},
+		templateCache:  templateCache,
+		sessionManager: sessionManager,
 	}
 
 	logger.Info("starting server", "addr", *addr)
 
 	// Because the err variable is now already declared in the code above, we need
 	// to use the assignment operator = here, instead of the := 'declare and assign'
 	// operator.
-	err = http.ListenAndServe(*addr, app.routes())
+	err = http.ListenAndServe(*addr, app.sessionManager.LoadAndSave(app.routes()))
 	logger.Error(err.Error())
 	os.Exit(1)
 }

cmd/web/templates.go

@@ -17,6 +17,7 @@ type templateData struct {
 	Snippet     models.Snippet
 	Snippets    []models.Snippet
 	Form        any
+	Flash       string
 }
 
 func newTemplateCache() (map[string]*template.Template, error) {

docker/mysql/docker/mysql/init.sql

@@ -34,3 +34,8 @@ INSERT INTO snippets (title, content, created, expires) VALUES (
 );
 
 
+CREATE TABLE sessions (
+    token CHAR(43) PRIMARY KEY,
+    data BLOB NOT NULL,
+    expiry TIMESTAMP(6) NOT NULL
+);

go.mod

@@ -4,5 +4,7 @@ go 1.24.1
 
 require (
 	filippo.io/edwards25519 v1.1.0 // indirect
+	github.com/alexedwards/scs/mysqlstore v0.0.0-20250417082927-ab20b3feb5e9 // indirect
+	github.com/alexedwards/scs/v2 v2.8.0 // indirect
 	github.com/go-sql-driver/mysql v1.9.1 // indirect
 )

go.sum

@@ -1,4 +1,9 @@
 filippo.io/edwards25519 v1.1.0 h1:FNf4tywRC1HmFuKW5xopWpigGjJKiJSV0Cqo0cJWDaA=
 filippo.io/edwards25519 v1.1.0/go.mod h1:BxyFTGdWcka3PhytdK4V28tE5sGfRvvvRV7EaN4VDT4=
+github.com/alexedwards/scs/mysqlstore v0.0.0-20250417082927-ab20b3feb5e9 h1:HsYYLdEqKkjHrnt77Tiu8hnD4TIswIa+czpnlJldIJs=
+github.com/alexedwards/scs/mysqlstore v0.0.0-20250417082927-ab20b3feb5e9/go.mod h1:p8jK3D80sw1PFrCSdlcJF1O75bp55HqbgDyyCLM0FrE=
+github.com/alexedwards/scs/v2 v2.8.0 h1:h31yUYoycPuL0zt14c0gd+oqxfRwIj6SOjHdKRZxhEw=
+github.com/alexedwards/scs/v2 v2.8.0/go.mod h1:ToaROZxyKukJKT/xLcVQAChi5k6+Pn1Gvmdl7h3RRj8=
+github.com/go-sql-driver/mysql v1.7.1/go.mod h1:OXbVy3sEdcQ2Doequ6Z5BW6fXNQTmx+9S1MCJN5yJMI=
 github.com/go-sql-driver/mysql v1.9.1 h1:FrjNGn/BsJQjVRuSa8CBrM5BWA9BWoXXat3KrtSb/iI=
 github.com/go-sql-driver/mysql v1.9.1/go.mod h1:qn46aNg1333BRMNU69Lq93t8du/dwxI64Gl8i5p1WMU=

ui/html/base.tmpl

@@ -16,6 +16,10 @@
         </header>
         {{template "nav" .}}
         <main>
+          <!-- Display the flash message if one exists -->
+            {{with .Flash}}
+                <div class='flash'>{{.}}</div>
+            {{end}}
             {{template "main" .}}
         </main>
         <footer>Powered by <a href='https://golang.org/'>Go</a></footer>