ch9.3

cmd/web/handlers.go

@@ -6,18 +6,17 @@ import (
 	"fmt"
 	"net/http"
 	"strconv"
-	"strings"
-	"unicode/utf8"
 
 	"gitea.local.lab/Lbenedar/snippetbox/internal/models"
+	"gitea.local.lab/Lbenedar/snippetbox/internal/validator"
 	"github.com/julienschmidt/httprouter"
 )
 
 type snippetCreateForm struct {
-	Title       string
-	Content     string
-	Expires     int
-	FieldErrors map[string]string
+	Title               string `form:"title"`
+	Content             string `form:"content"`
+	Expires             int    `form:"expires"`
+	validator.Validator `form:"-"`
 }
 
 func (app *application) render(w http.ResponseWriter, status int, page string, data *templateData) {
@@ -89,40 +88,19 @@ func (app *application) snippetCreate(w http.ResponseWriter, r *http.Request) {
 }
 
 func (app *application) snippetCreatePost(w http.ResponseWriter, r *http.Request) {
-	err := r.ParseForm()
+	var form snippetCreateForm
+	err := app.decodePostForm(r, &form)
 	if err != nil {
 		app.clientError(w, http.StatusBadRequest)
 		return
 	}
 
-	expires, err := strconv.Atoi(r.PostForm.Get("expires"))
-	if err != nil {
-		app.clientError(w, http.StatusBadRequest)
-		return
-	}
+	form.CheckField(validator.NotBlank(form.Title), "title", "This field cannot be blank")
+	form.CheckField(validator.MaxChars(form.Title, 100), "title", "This field cannot be more than 100 character long")
+	form.CheckField(validator.NotBlank(form.Content), "content", "This field cannot be blank")
+	form.CheckField(validator.PermittedInt(form.Expires, 1, 7, 365), "expires", "This field must equal 1, 7 and 365")
 
-	form := snippetCreateForm{
-		Title:       r.PostForm.Get("title"),
-		Content:     r.PostForm.Get("content"),
-		Expires:     expires,
-		FieldErrors: map[string]string{},
-	}
-
-	if strings.TrimSpace(form.Title) == "" {
-		form.FieldErrors["title"] = "This field cannot be blank"
-	} else if utf8.RuneCountInString(form.Title) > 100 {
-		form.FieldErrors["title"] = "This field cannot be more than 100 character long"
-	}
-
-	if strings.TrimSpace(form.Content) == "" {
-		form.FieldErrors["content"] = "This field cannot be blank"
-	}
-
-	if form.Expires != 1 && form.Expires != 7 && form.Expires != 365 {
-		form.FieldErrors["expires"] = "This field must equal 1, 7 and 365"
-	}
-
-	if len(form.FieldErrors) > 0 {
+	if !form.Valid() {
 		data := app.newTemplateData(r)
 		data.Form = form
 		app.render(w, http.StatusUnprocessableEntity, "create.tmpl", data)
@@ -135,5 +113,7 @@ func (app *application) snippetCreatePost(w http.ResponseWriter, r *http.Request
 		return
 	}
 
+	app.sessionManager.Put(r.Context(), "flash", "Snippet successfully created!")
+
 	http.Redirect(w, r, fmt.Sprintf("/snippet/view/%d", id), http.StatusSeeOther)
 }

cmd/web/helpers.go

@@ -1,9 +1,12 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"runtime/debug"
+
+	"github.com/go-playground/form/v4"
 )
 
 func (app *application) serverError(w http.ResponseWriter, err error) {
@@ -20,3 +23,20 @@ func (app *application) clientError(w http.ResponseWriter, status int) {
 func (app *application) notFound(w http.ResponseWriter) {
 	app.clientError(w, http.StatusNotFound)
 }
+
+func (app *application) decodePostForm(r *http.Request, snippetForm *snippetCreateForm) error {
+	err := r.ParseForm()
+	if err != nil {
+		return err
+	}
+
+	err = app.formDecoder.Decode(&snippetForm, r.PostForm)
+	if err != nil {
+		var invalidDecoderError *form.InvalidDecoderError
+		if errors.As(err, &invalidDecoderError) {
+			panic("Invalid decoder error")
+		}
+		return err
+	}
+	return nil
+}

cmd/web/main.go

@@ -7,17 +7,23 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"time"
 
 	"gitea.local.lab/Lbenedar/snippetbox/internal/models"
 
+	"github.com/alexedwards/scs/mysqlstore"
+	"github.com/alexedwards/scs/v2"
+	"github.com/go-playground/form/v4"
 	_ "github.com/go-sql-driver/mysql"
 )
 
 type application struct {
-	errorLog      *log.Logger
-	infoLog       *log.Logger
-	snippets      *models.SnippetModel
-	templateCache map[string]*template.Template
+	errorLog       *log.Logger
+	infoLog        *log.Logger
+	snippets       *models.SnippetModel
+	templateCache  map[string]*template.Template
+	formDecoder    *form.Decoder
+	sessionManager *scs.SessionManager
 }
 
 type config struct {
@@ -47,11 +53,18 @@ func main() {
 		errorLog.Fatal(err)
 	}
 
+	formDecoder := form.NewDecoder()
+	sessionManager := scs.New()
+	sessionManager.Store = mysqlstore.New(db)
+	sessionManager.Lifetime = 12 * time.Hour
+
 	app := &application{
-		errorLog:      errorLog,
-		infoLog:       infoLog,
-		snippets:      &models.SnippetModel{DB: db},
-		templateCache: templateCache,
+		errorLog:       errorLog,
+		infoLog:        infoLog,
+		snippets:       &models.SnippetModel{DB: db},
+		templateCache:  templateCache,
+		formDecoder:    formDecoder,
+		sessionManager: sessionManager,
 	}
 
 	srv := &http.Server{

cmd/web/routes.go

@@ -17,12 +17,13 @@ func (app *application) routes() http.Handler {
 	fileServer := http.FileServer(http.Dir("./ui/static/"))
 	router.Handler(http.MethodGet, "/static/", http.StripPrefix("/static", fileServer))
 
-	router.HandlerFunc(http.MethodGet, "/", app.home)
-	router.HandlerFunc(http.MethodGet, "/snippet/view/:id", app.snippetView)
-	router.HandlerFunc(http.MethodGet, "/snippet/create", app.snippetCreate)
-	router.HandlerFunc(http.MethodPost, "/snippet/create", app.snippetCreatePost)
+	dynamic := alice.New(app.sessionManager.LoadAndSave)
+
+	router.Handler(http.MethodGet, "/", dynamic.ThenFunc(app.home))
+	router.Handler(http.MethodGet, "/snippet/view/:id", dynamic.ThenFunc(app.snippetView))
+	router.Handler(http.MethodGet, "/snippet/create", dynamic.ThenFunc(app.snippetCreate))
+	router.Handler(http.MethodPost, "/snippet/create", dynamic.ThenFunc(app.snippetCreatePost))
 
 	standard := alice.New(app.recoverPanic, app.logRequest, secureHeaders)
-
 	return standard.Then(router)
 }

cmd/web/templates.go

@@ -14,6 +14,7 @@ type templateData struct {
 	Snippet     *models.Snippet
 	Snippets    []*models.Snippet
 	Form        any
+	Flash       string
 }
 
 func humanDate(t time.Time) string {
@@ -27,6 +28,7 @@ var functions = template.FuncMap{
 func (app *application) newTemplateData(r *http.Request) *templateData {
 	return &templateData{
 		CurrentYear: time.Now().Year(),
+		Flash:       app.sessionManager.PopString(r.Context(), "flash"),
 	}
 }
 

go.mod

@@ -4,6 +4,9 @@ go 1.25.0
 
 require (
 	filippo.io/edwards25519 v1.1.0 // indirect
+	github.com/alexedwards/scs/mysqlstore v0.0.0-20251002162104-209de6e426de // indirect
+	github.com/alexedwards/scs/v2 v2.9.0 // indirect
+	github.com/go-playground/form/v4 v4.3.0 // indirect
 	github.com/go-sql-driver/mysql v1.9.3 // indirect
 	github.com/julienschmidt/httprouter v1.3.0 // indirect
 	github.com/justinas/alice v1.2.0 // indirect

go.sum

@@ -1,5 +1,12 @@
 filippo.io/edwards25519 v1.1.0 h1:FNf4tywRC1HmFuKW5xopWpigGjJKiJSV0Cqo0cJWDaA=
 filippo.io/edwards25519 v1.1.0/go.mod h1:BxyFTGdWcka3PhytdK4V28tE5sGfRvvvRV7EaN4VDT4=
+github.com/alexedwards/scs/mysqlstore v0.0.0-20251002162104-209de6e426de h1:/Y/iIFgV1Ofvk4Euv5gUQ74vgqFZOQ1wlJQ3yz/zYGs=
+github.com/alexedwards/scs/mysqlstore v0.0.0-20251002162104-209de6e426de/go.mod h1:p8jK3D80sw1PFrCSdlcJF1O75bp55HqbgDyyCLM0FrE=
+github.com/alexedwards/scs/v2 v2.9.0 h1:xa05mVpwTBm1iLeTMNFfAWpKUm4fXAW7CeAViqBVS90=
+github.com/alexedwards/scs/v2 v2.9.0/go.mod h1:ToaROZxyKukJKT/xLcVQAChi5k6+Pn1Gvmdl7h3RRj8=
+github.com/go-playground/form/v4 v4.3.0 h1:OVttojbQv2WNCs4P+VnjPtrt/+30Ipw4890W3OaFlvk=
+github.com/go-playground/form/v4 v4.3.0/go.mod h1:Cpe1iYJKoXb1vILRXEwxpWMGWyQuqplQ/4cvPecy+Jo=
+github.com/go-sql-driver/mysql v1.7.1/go.mod h1:OXbVy3sEdcQ2Doequ6Z5BW6fXNQTmx+9S1MCJN5yJMI=
 github.com/go-sql-driver/mysql v1.9.3 h1:U/N249h2WzJ3Ukj8SowVFjdtZKfu9vlLZxjPXV1aweo=
 github.com/go-sql-driver/mysql v1.9.3/go.mod h1:qn46aNg1333BRMNU69Lq93t8du/dwxI64Gl8i5p1WMU=
 github.com/julienschmidt/httprouter v1.3.0 h1:U0609e9tgbseu3rBINet9P48AI/D3oJs4dN7jwJOQ1U=

internal/validator/validator.go

@@ -0,0 +1,46 @@
+package validator
+
+import (
+	"strings"
+	"unicode/utf8"
+)
+
+type Validator struct {
+	FieldErrors map[string]string
+}
+
+func (v *Validator) Valid() bool {
+	return len(v.FieldErrors) == 0
+}
+
+func (v *Validator) AddFieldError(key, message string) {
+	if v.FieldErrors == nil {
+		v.FieldErrors = make(map[string]string)
+	}
+	if _, exist := v.FieldErrors[key]; !exist {
+		v.FieldErrors[key] = message
+	}
+}
+
+func (v *Validator) CheckField(ok bool, key, message string) {
+	if !ok {
+		v.AddFieldError(key, message)
+	}
+}
+
+func NotBlank(value string) bool {
+	return strings.TrimSpace(value) != ""
+}
+
+func MaxChars(value string, n int) bool {
+	return utf8.RuneCountInString(value) <= n
+}
+
+func PermittedInt(value int, permittedValues ...int) bool {
+	for i := range permittedValues {
+		if value == permittedValues[i] {
+			return true
+		}
+	}
+	return false
+}

ui/html/base.tmpl

@@ -14,6 +14,9 @@
         </header>
         {{template "nav" .}}
         <main>
+            {{with .Flash}}
+                <div class='flash'>{{.}}</div>
+            {{end}}
             {{template "main" .}}
         </main>
         <footer>