Convert the login variables to a struct with parsing and validation

It is a lot of code having to check the login variables inside the POST
handler, and i could not mark each input field individually as invalid
because the generic errors array i was using did no identify which field
had the error.

Thus, i use more or less the same technique as with Numerus: a struct
with the value and the error message.  This time the input field does
not have the label and extra attributes because i believe this belongs
to the template: if i want do reuse the same form template, i should
create a common template rather than defining everything in Go.

The name is a bit different, however, because it has meaning both to the
front and back ends, as it needs to be exactly the same.  Writing it
twice is error-prone, as with a rename i could easily forget to change
one or the other, and here i see value in having that in Go, because
it is also used in code.

pkg/app/app.go

@@ -6,23 +6,14 @@
 package app
 
 import (
-	"errors"
+	"golang.org/x/text/language"
 	"net/http"
-	"net/mail"
 	"path"
 	"strings"
-	"time"
-
-	"golang.org/x/text/language"
 
 	"dev.tandem.ws/tandem/camper/pkg/database"
 	httplib "dev.tandem.ws/tandem/camper/pkg/http"
 	"dev.tandem.ws/tandem/camper/pkg/locale"
-	"dev.tandem.ws/tandem/camper/pkg/template"
-)
-
-const (
-	sessionCookie = "camper-session"
 )
 
 func shiftPath(p string) (head, tail string) {
@@ -87,60 +78,3 @@ func (h *App) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		http.NotFound(w, r)
 	}
 }
-
-func (h *App) handleGet(w http.ResponseWriter, r *http.Request) {
-	l := h.matchLocale(r)
-	template.MustRender(w, l, "login.gohtml", nil)
-}
-
-func (h *App) matchLocale(r *http.Request) *locale.Locale {
-	return locale.Match(r, h.locales, h.defaultLocale, h.languageMatcher)
-}
-
-func (h *App) handleLogin(w http.ResponseWriter, r *http.Request) {
-	if err := r.ParseForm(); err != nil {
-		http.Error(w, err.Error(), http.StatusBadRequest)
-		return
-	}
-	var errs []error
-	l := h.matchLocale(r)
-	email := strings.TrimSpace(r.FormValue("email"))
-	if email == "" {
-		errs = append(errs, errors.New(l.Get("Email can not be empty.")))
-	} else if _, err := mail.ParseAddress(email); err != nil {
-		errs = append(errs, errors.New(l.Get("This email is not valid. It should be like name@domain.com.")))
-	}
-	password := strings.TrimSpace(r.FormValue("password"))
-	if password == "" {
-		errs = append(errs, errors.New(l.Get("Password can not be empty.")))
-	}
-	if errs == nil {
-		conn := h.db.MustAcquire(r.Context())
-		cookie := conn.MustGetText(r.Context(), "select login($1, $2, $3)", email, password, httplib.RemoteAddr(r))
-		if cookie != "" {
-			setSessionCookie(w, cookie)
-			http.Redirect(w, r, "/", http.StatusSeeOther)
-			return
-		}
-		errs = append(errs, errors.New(l.Get("Invalid user or password.")))
-		w.WriteHeader(http.StatusUnauthorized)
-	} else {
-		w.WriteHeader(http.StatusUnprocessableEntity)
-	}
-	template.MustRender(w, l, "login.gohtml", errs)
-}
-
-func setSessionCookie(w http.ResponseWriter, cookie string) {
-	http.SetCookie(w, createSessionCookie(cookie, 8766*24*time.Hour))
-}
-
-func createSessionCookie(value string, duration time.Duration) *http.Cookie {
-	return &http.Cookie{
-		Name:     sessionCookie,
-		Value:    value,
-		Path:     "/",
-		Expires:  time.Now().Add(duration),
-		HttpOnly: true,
-		SameSite: http.SameSiteLaxMode,
-	}
-}

pkg/app/login.go

@@ -0,0 +1,104 @@
+/*
+ * SPDX-FileCopyrightText: 2023 jordi fita mas <jfita@peritasoft.com>
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package app
+
+import (
+	"errors"
+	"net/http"
+	"time"
+
+	"dev.tandem.ws/tandem/camper/pkg/form"
+	httplib "dev.tandem.ws/tandem/camper/pkg/http"
+	"dev.tandem.ws/tandem/camper/pkg/locale"
+	"dev.tandem.ws/tandem/camper/pkg/template"
+)
+
+const (
+	sessionCookie = "camper-session"
+)
+
+type loginForm struct {
+	Email    *form.Input
+	Password *form.Input
+	Error    error
+}
+
+func newLoginForm() *loginForm {
+	return &loginForm{
+		Email: &form.Input{
+			Name: "email",
+		},
+		Password: &form.Input{
+			Name: "password",
+		},
+	}
+}
+
+func (f *loginForm) Parse(r *http.Request) error {
+	if err := r.ParseForm(); err != nil {
+		return err
+	}
+	f.Email.FillValue(r)
+	f.Password.FillValue(r)
+	return nil
+}
+
+func (f *loginForm) Valid(l *locale.Locale) bool {
+	v := form.NewValidator(l)
+	if v.CheckRequired(f.Email, l.GettextNoop("Email can not be empty.")) {
+		v.CheckValidEmail(f.Email, l.GettextNoop("This email is not valid. It should be like name@domain.com."))
+	}
+	v.CheckRequired(f.Password, l.GettextNoop("Password can not be empty."))
+	return v.AllOK
+}
+
+func (h *App) handleGet(w http.ResponseWriter, r *http.Request) {
+	l := h.matchLocale(r)
+	login := newLoginForm()
+	template.MustRender(w, l, "login.gohtml", login)
+}
+
+func (h *App) matchLocale(r *http.Request) *locale.Locale {
+	return locale.Match(r, h.locales, h.defaultLocale, h.languageMatcher)
+}
+
+func (h *App) handleLogin(w http.ResponseWriter, r *http.Request) {
+	login := newLoginForm()
+	if err := login.Parse(r); err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+	l := h.matchLocale(r)
+	if login.Valid(l) {
+		conn := h.db.MustAcquire(r.Context())
+		cookie := conn.MustGetText(r.Context(), "select login($1, $2, $3)", login.Email, login.Password, httplib.RemoteAddr(r))
+		if cookie != "" {
+			setSessionCookie(w, cookie)
+			http.Redirect(w, r, "/", http.StatusSeeOther)
+			return
+		}
+		login.Error = errors.New(l.Gettext("Invalid user or password."))
+		w.WriteHeader(http.StatusUnauthorized)
+	} else {
+		w.WriteHeader(http.StatusUnprocessableEntity)
+	}
+	template.MustRender(w, l, "login.gohtml", login)
+}
+
+func setSessionCookie(w http.ResponseWriter, cookie string) {
+	http.SetCookie(w, createSessionCookie(cookie, 8766*24*time.Hour))
+}
+
+func createSessionCookie(value string, duration time.Duration) *http.Cookie {
+	return &http.Cookie{
+		Name:     sessionCookie,
+		Value:    value,
+		Path:     "/",
+		Expires:  time.Now().Add(duration),
+		HttpOnly: true,
+		SameSite: http.SameSiteLaxMode,
+	}
+}

pkg/form/input.go

@@ -0,0 +1,25 @@
+/*
+ * SPDX-FileCopyrightText: 2023 jordi fita mas <jfita@peritasoft.com>
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package form
+
+import (
+	"database/sql/driver"
+	"net/http"
+	"strings"
+)
+
+type Input struct {
+	Name  string
+	Val   string
+	Error error
+}
+
+func (input *Input) FillValue(r *http.Request) {
+	input.Val = strings.TrimSpace(r.FormValue(input.Name))
+}
+func (input *Input) Value() (driver.Value, error) {
+	return input.Val, nil
+}

pkg/form/validator.go

@@ -0,0 +1,41 @@
+/*
+ * SPDX-FileCopyrightText: 2023 jordi fita mas <jfita@peritasoft.com>
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package form
+
+import (
+	"dev.tandem.ws/tandem/camper/pkg/locale"
+	"errors"
+	"net/mail"
+)
+
+type Validator struct {
+	l     *locale.Locale
+	AllOK bool
+}
+
+func NewValidator(l *locale.Locale) *Validator {
+	return &Validator{
+		l:     l,
+		AllOK: true,
+	}
+}
+
+func (v *Validator) CheckRequired(input *Input, message string) bool {
+	return v.check(input, input.Val != "", message)
+}
+
+func (v *Validator) CheckValidEmail(input *Input, message string) bool {
+	_, err := mail.ParseAddress(input.Val)
+	return v.check(input, err == nil, message)
+}
+
+func (v *Validator) check(field *Input, ok bool, message string) bool {
+	if !ok {
+		field.Error = errors.New(v.l.Get(message))
+		v.AllOK = false
+	}
+	return ok
+}

po/ca.po

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: camper\n"
 "Report-Msgid-Bugs-To: jordi@tandem.blog\n"
-"POT-Creation-Date: 2023-07-22 23:45+0200\n"
+"POT-Creation-Date: 2023-07-24 17:04+0200\n"
 "PO-Revision-Date: 2023-07-22 23:45+0200\n"
 "Last-Translator: jordi fita mas <jordi@tandem.blog>\n"
 "Language-Team: Catalan <ca@dodds.net>\n"
@@ -18,22 +18,22 @@ msgstr ""
 "Content-Transfer-Encoding: 8bit\n"
 "Plural-Forms: nplurals=2; plural=(n != 1);\n"
 
-#: web/templates/login.gohtml:2 web/templates/login.gohtml:7
+#: web/templates/login.gohtml:2 web/templates/login.gohtml:8
 msgctxt "title"
 msgid "Login"
 msgstr "Entrada"
 
-#: web/templates/login.gohtml:9
+#: web/templates/login.gohtml:17
 msgctxt "input"
 msgid "Email"
 msgstr "Correu-e"
 
-#: web/templates/login.gohtml:12
+#: web/templates/login.gohtml:26
 msgctxt "input"
 msgid "Password"
 msgstr "Contrasenya"
 
-#: web/templates/login.gohtml:15
+#: web/templates/login.gohtml:35
 msgctxt "action"
 msgid "Login"
 msgstr "Entra"
@@ -41,3 +41,19 @@ msgstr "Entra"
 #: web/templates/layout.gohtml:15
 msgid "Skip to main content"
 msgstr "Salta al contingut principal"
+
+#: pkg/app/login.go:50
+msgid "Email can not be empty."
+msgstr "No podeu deixar el correu en blanc."
+
+#: pkg/app/login.go:51
+msgid "This email is not valid. It should be like name@domain.com."
+msgstr "Aquest correu-e no és vàlid. Hauria de ser similar a nom@domini.com."
+
+#: pkg/app/login.go:53
+msgid "Password can not be empty."
+msgstr "No podeu deixar la contrasenya en blanc."
+
+#: pkg/app/login.go:82
+msgid "Invalid user or password."
+msgstr "Nom d’usuari o contrasenya incorrectes."

po/es.po

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: camper\n"
 "Report-Msgid-Bugs-To: jordi@tandem.blog\n"
-"POT-Creation-Date: 2023-07-22 23:45+0200\n"
+"POT-Creation-Date: 2023-07-24 17:04+0200\n"
 "PO-Revision-Date: 2023-07-22 23:46+0200\n"
 "Last-Translator: jordi fita mas <jordi@tandem.blog>\n"
 "Language-Team: Spanish <es@tp.org.es>\n"
@@ -18,22 +18,22 @@ msgstr ""
 "Content-Transfer-Encoding: 8bit\n"
 "Plural-Forms: nplurals=2; plural=(n != 1);\n"
 
-#: web/templates/login.gohtml:2 web/templates/login.gohtml:7
+#: web/templates/login.gohtml:2 web/templates/login.gohtml:8
 msgctxt "title"
 msgid "Login"
 msgstr "Entrada"
 
-#: web/templates/login.gohtml:9
+#: web/templates/login.gohtml:17
 msgctxt "input"
 msgid "Email"
 msgstr "Correo-e"
 
-#: web/templates/login.gohtml:12
+#: web/templates/login.gohtml:26
 msgctxt "input"
 msgid "Password"
 msgstr "Contraseña"
 
-#: web/templates/login.gohtml:15
+#: web/templates/login.gohtml:35
 msgctxt "action"
 msgid "Login"
 msgstr "Entrar"
@@ -41,3 +41,19 @@ msgstr "Entrar"
 #: web/templates/layout.gohtml:15
 msgid "Skip to main content"
 msgstr "Saltar al contenido principal"
+
+#: pkg/app/login.go:50
+msgid "Email can not be empty."
+msgstr "No podéis dejar el correo-e en blanco."
+
+#: pkg/app/login.go:51
+msgid "This email is not valid. It should be like name@domain.com."
+msgstr "Este correo-e no es válido. Tiene que ser parecido a nombre@dominio.com."
+
+#: pkg/app/login.go:53
+msgid "Password can not be empty."
+msgstr "No podéis dejar la contraseña en blanco."
+
+#: pkg/app/login.go:82
+msgid "Invalid user or password."
+msgstr "Usuario o contraseña incorrectos."

web/templates/layout.gohtml

@@ -20,3 +20,10 @@
 </main>
 </body>
 </html>
+
+{{ define "error-attrs" }}{{ if .Error }}aria-invalid="true" aria-errormessage="{{ .Name }}-error"{{ end }}{{ end }}
+{{ define "error-message" -}}
+    {{ if .Error -}}
+        <span id="{{ .Name }}-error" class="error">{{ .Error }}</span><br>
+    {{- end }}
+{{- end }}

web/templates/login.gohtml

@@ -3,23 +3,33 @@
 {{- end }}
 
 {{ define "content" -}}
+    {{- /*gotype: dev.tandem.ws/tandem/camper/pkg/app.loginForm */ -}}
     <form method="post" action="/login">
         <h2>{{( pgettext "Login" "title" )}}</h2>
-        {{ if . -}}
+        {{ if .Error -}}
-            <div class="message" role="alert">
+            <div class="error" role="alert">
-                {{ range . -}}
+                <p>{{ .Error }}</p>
-                    <p>{{ . }}</p>
-                {{- end }}
             </div>
         {{- end }}
         <fieldset>
-            <label>
+            {{ with .Email -}}
-                {{( pgettext "Email" "input" )}}<br>
+                <label>
-                <input type="email" name="email" autocomplete="username" required autofocus><br>
+                    {{( pgettext "Email" "input" )}}<br>
-            </label><label>
+                    <input type="email" name="{{ .Name }}" value="{{ .Val }}"
-                {{( pgettext "Password" "input" )}}<br>
+                           autocomplete="username" required autofocus
-                <input type="password" name="password" autocomplete="current-password" required><br>
+                            {{ template "error-attrs" . }}><br>
-            </label>
+                </label>
+                {{ template "error-message" . }}
+            {{- end }}
+            {{ with .Password -}}
+                <label>
+                    {{( pgettext "Password" "input" )}}<br>
+                    <input type="password" name="{{ .Name }}" value="{{ .Val }}"
+                           autocomplete="current-password" required
+                            {{ template "error-attrs" . }}><br>
+                </label>
+                {{ template "error-message" . }}
+            {{- end }}
         </fieldset>
         <footer>
             <button type="submit">{{( pgettext "Login" "action" )}}</button>