feat: add 2FA prompt and OTP input to login flow

- Integrated 2FA verification into the login process.
- Added conditional rendering for OTP input.
- Updated UI to support dynamic switching between login and 2FA views.
- Introduced new state variables for managing 2FA logic.

frontend/src/app/(auth)/login/page.tsx

@@ -24,6 +24,12 @@ import {
 	FormMessage,
 } from "@/components/ui/form";
 import { Input } from "@/components/ui/input";
+import {
+	InputOTP,
+	InputOTPGroup,
+	InputOTPSeparator,
+	InputOTPSlot,
+} from "@/components/ui/input-otp";
 import { useAuth } from "@/providers/auth-provider";
 
 const loginSchema = z.object({
@@ -36,8 +42,11 @@ const loginSchema = z.object({
 type LoginFormValues = z.infer<typeof loginSchema>;
 
 export default function LoginPage() {
-	const { login } = useAuth();
+	const { login, verify2fa } = useAuth();
 	const [loading, setLoading] = React.useState(false);
+	const [show2fa, setShow2fa] = React.useState(false);
+	const [userId, setUserId] = React.useState<string | null>(null);
+	const [otpValue, setOtpValue] = React.useState("");
 
 	const form = useForm<LoginFormValues>({
 		resolver: zodResolver(loginSchema),
@@ -50,7 +59,11 @@ export default function LoginPage() {
 	async function onSubmit(values: LoginFormValues) {
 		setLoading(true);
 		try {
-			await login(values.email, values.password);
+			const res = await login(values.email, values.password);
+			if (res.userId && res.message === "Please provide 2FA token") {
+				setUserId(res.userId);
+				setShow2fa(true);
+			}
 		} catch (_error) {
 			// Error is handled in useAuth via toast
 		} finally {
@@ -58,6 +71,20 @@ export default function LoginPage() {
 		}
 	}
 
+	async function onOtpSubmit(e: React.FormEvent) {
+		e.preventDefault();
+		if (!userId || otpValue.length !== 6) return;
+
+		setLoading(true);
+		try {
+			await verify2fa(userId, otpValue);
+		} catch (_error) {
+			// Error handled in useAuth
+		} finally {
+			setLoading(false);
+		}
+	}
+
 	return (
 		<div className="min-h-screen flex items-center justify-center bg-zinc-50 dark:bg-zinc-950 p-4">
 			<div className="w-full max-w-md space-y-4">
@@ -70,45 +97,82 @@ export default function LoginPage() {
 				</Link>
 				<Card>
 					<CardHeader>
-						<CardTitle className="text-2xl">Connexion</CardTitle>
+						<CardTitle className="text-2xl">
+							{show2fa ? "Double Authentification" : "Connexion"}
+						</CardTitle>
 						<CardDescription>
-							Entrez vos identifiants pour accéder à votre compte MemeGoat.
+							{show2fa
+								? "Entrez le code à 6 chiffres de votre application d'authentification."
+								: "Entrez vos identifiants pour accéder à votre compte MemeGoat."}
 						</CardDescription>
 					</CardHeader>
 					<CardContent>
-						<Form {...form}>
-							<form onSubmit={form.handleSubmit(onSubmit)} className="space-y-4">
-								<FormField
-									control={form.control}
-									name="email"
-									render={({ field }) => (
-										<FormItem>
-											<FormLabel>Email</FormLabel>
-											<FormControl>
-												<Input placeholder="goat@example.com" {...field} />
-											</FormControl>
-											<FormMessage />
-										</FormItem>
-									)}
-								/>
-								<FormField
-									control={form.control}
-									name="password"
-									render={({ field }) => (
-										<FormItem>
-											<FormLabel>Mot de passe</FormLabel>
-											<FormControl>
-												<Input type="password" placeholder="••••••••" {...field} />
-											</FormControl>
-											<FormMessage />
-										</FormItem>
-									)}
-								/>
-								<Button type="submit" className="w-full" disabled={loading}>
-									{loading ? "Connexion en cours..." : "Se connecter"}
+						{show2fa ? (
+							<form onSubmit={onOtpSubmit} className="space-y-6 flex flex-col items-center">
+								<InputOTP
+									maxLength={6}
+									value={otpValue}
+									onChange={(value) => setOtpValue(value)}
+								>
+									<InputOTPGroup>
+										<InputOTPSlot index={0} />
+										<InputOTPSlot index={1} />
+										<InputOTPSlot index={2} />
+									</InputOTPGroup>
+									<InputOTPSeparator />
+									<InputOTPGroup>
+										<InputOTPSlot index={3} />
+										<InputOTPSlot index={4} />
+										<InputOTPSlot index={5} />
+									</InputOTPGroup>
+								</InputOTP>
+								<Button type="submit" className="w-full" disabled={loading || otpValue.length !== 6}>
+									{loading ? "Vérification..." : "Vérifier le code"}
+								</Button>
+								<Button
+									variant="ghost"
+									className="w-full"
+									onClick={() => setShow2fa(false)}
+									disabled={loading}
+								>
+									Retour
 								</Button>
 							</form>
-						</Form>
+						) : (
+							<Form {...form}>
+								<form onSubmit={form.handleSubmit(onSubmit)} className="space-y-4">
+									<FormField
+										control={form.control}
+										name="email"
+										render={({ field }) => (
+											<FormItem>
+												<FormLabel>Email</FormLabel>
+												<FormControl>
+													<Input placeholder="goat@example.com" {...field} />
+												</FormControl>
+												<FormMessage />
+											</FormItem>
+										)}
+									/>
+									<FormField
+										control={form.control}
+										name="password"
+										render={({ field }) => (
+											<FormItem>
+												<FormLabel>Mot de passe</FormLabel>
+												<FormControl>
+													<Input type="password" placeholder="••••••••" {...field} />
+												</FormControl>
+												<FormMessage />
+											</FormItem>
+										)}
+									/>
+									<Button type="submit" className="w-full" disabled={loading}>
+										{loading ? "Connexion en cours..." : "Se connecter"}
+									</Button>
+								</form>
+							</Form>
+						)}
 					</CardContent>
 					<CardFooter className="flex flex-col space-y-2">
 						<p className="text-sm text-center text-muted-foreground">