From dd4c74598d2c8b7f88e31fffc1353fc46dd7d748 Mon Sep 17 00:00:00 2001
From: lbenedar <lbenedar@local.lab>
Date: Fri, 6 Mar 2026 14:01:57 +0300
Subject: [PATCH] ch11.4

---
 cmd/web/handlers.go             | 52 +++++++++++++++++++++++++++++++--
 internal/models/users.go        | 22 +++++++++++++-
 internal/validator/validator.go |  9 ++++--
 ui/html/pages/login.tmpl        | 26 +++++++++++++++++
 4 files changed, 104 insertions(+), 5 deletions(-)
 create mode 100644 ui/html/pages/login.tmpl

diff --git a/cmd/web/handlers.go b/cmd/web/handlers.go
index d7cc3e7..f32cc1c 100644
--- a/cmd/web/handlers.go
+++ b/cmd/web/handlers.go
@@ -26,6 +26,12 @@ type userSignupForm struct {
 	validator.Validator `form:"-"`
 }
 
+type userLoginForm struct {
+	Email               string `form:"email"`
+	Password            string `form:"password"`
+	validator.Validator `form:"-"`
+}
+
 func (app *application) render(w http.ResponseWriter, status int, page string, data *templateData) {
 	ts, ok := app.templateCache[page]
 	if !ok {
@@ -164,7 +170,47 @@ func (app *application) userSignupPost(w http.ResponseWriter, r *http.Request) {
 }
 
 func (app *application) userLoginPost(w http.ResponseWriter, r *http.Request) {
-	fmt.Fprintln(w, "Login the user...")
+	var form userLoginForm
+
+	err := app.decodePostForm(r, &form)
+	if err != nil {
+		app.clientError(w, http.StatusBadRequest)
+		return
+	}
+
+	form.CheckField(validator.NotBlank(form.Email), "email", "This field cannot be blank")
+	form.CheckField(validator.Matches(form.Email, validator.EmailRX), "email", "This field must be a valid email address")
+	form.CheckField(validator.NotBlank(form.Password), "password", "This field cannot be blank")
+
+	if !form.Valid() {
+		data := app.newTemplateData(r)
+		data.Form = form
+		app.render(w, http.StatusUnprocessableEntity, "login.tmpl", data)
+		return
+	}
+
+	id, err := app.users.Authenticate(form.Email, form.Password)
+	if err != nil {
+		if errors.Is(err, models.ErrInvalidCredentials) {
+			form.AddNonFieldError("Email or password is incorrect")
+
+			data := app.newTemplateData(r)
+			data.Form = form
+			app.render(w, http.StatusUnprocessableEntity, "login.tmpl", data)
+		} else {
+			app.serverError(w, err)
+		}
+		return
+	}
+	err = app.sessionManager.RenewToken(r.Context())
+	if err != nil {
+		app.serverError(w, err)
+		return
+	}
+
+	app.sessionManager.Put(r.Context(), "authenticatedUserID", id)
+
+	http.Redirect(w, r, "/snippet/create", http.StatusSeeOther)
 }
 
 func (app *application) userLogoutPost(w http.ResponseWriter, r *http.Request) {
@@ -178,5 +224,7 @@ func (app *application) userSignup(w http.ResponseWriter, r *http.Request) {
 }
 
 func (app *application) userLogin(w http.ResponseWriter, r *http.Request) {
-	fmt.Fprintln(w, "Display a HTML for log in a user...")
+	data := app.newTemplateData(r)
+	data.Form = userLoginForm{}
+	app.render(w, http.StatusOK, "login.tmpl", data)
 }
diff --git a/internal/models/users.go b/internal/models/users.go
index 295cf7d..7b6196c 100644
--- a/internal/models/users.go
+++ b/internal/models/users.go
@@ -45,7 +45,27 @@ func (m *UserModel) Insert(name, email, password string) error {
 }
 
 func (m *UserModel) Authenticate(email, password string) (int, error) {
-	return 0, nil
+	var id int
+	var hashedPassword []byte
+
+	stmt := `SELECT id, hashed_password FROM users WHERE email = ?`
+
+	err := m.DB.QueryRow(stmt, email).Scan(&id, &hashedPassword)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return 0, ErrInvalidCredentials
+		}
+		return 0, err
+	}
+	err = bcrypt.CompareHashAndPassword(hashedPassword, []byte(password))
+	if err != nil {
+		if errors.Is(err, bcrypt.ErrMismatchedHashAndPassword) {
+			return 0, ErrInvalidCredentials
+		}
+		return 0, err
+	}
+
+	return id, nil
 }
 
 func (m *UserModel) Exists(id int) (bool, error) {
diff --git a/internal/validator/validator.go b/internal/validator/validator.go
index 5d3956a..2bcb7e1 100644
--- a/internal/validator/validator.go
+++ b/internal/validator/validator.go
@@ -7,11 +7,12 @@ import (
 )
 
 type Validator struct {
-	FieldErrors map[string]string
+	NonFieldErrors []string
+	FieldErrors    map[string]string
 }
 
 func (v *Validator) Valid() bool {
-	return len(v.FieldErrors) == 0
+	return len(v.FieldErrors) == 0 && len(v.NonFieldErrors) == 0
 }
 
 func (v *Validator) AddFieldError(key, message string) {
@@ -23,6 +24,10 @@ func (v *Validator) AddFieldError(key, message string) {
 	}
 }
 
+func (v *Validator) AddNonFieldError(message string) {
+	v.NonFieldErrors = append(v.NonFieldErrors, message)
+}
+
 func (v *Validator) CheckField(ok bool, key, message string) {
 	if !ok {
 		v.AddFieldError(key, message)
diff --git a/ui/html/pages/login.tmpl b/ui/html/pages/login.tmpl
new file mode 100644
index 0000000..c7d6e22
--- /dev/null
+++ b/ui/html/pages/login.tmpl
@@ -0,0 +1,26 @@
+{{define "title"}}Login{{end}}
+
+{{define "main"}}
+<form action='/user/login' method='POST' novalidate>
+    {{range .Form.NonFieldErrors}}
+        <div class='error'>{{.}}</div>
+    {{end}}
+    <div>
+        <label>Email:</label>
+        {{with .Form.FieldErrors.email}}
+            <label class='error'>{{.}}</label>
+        {{end}}
+        <input type='email' name='email' value='{{.Form.Email}}'>
+    </div>
+    <div>
+        <label>Password:</label>
+        {{with .Form.FieldErrors.password}}
+            <label class='error'>{{.}}</label>
+        {{end}}
+        <input type='password' name='password'>
+    </div>
+    <div>
+        <input type='submit' value='Login'>
+    </div>
+</form>
+{{end}}
\ No newline at end of file