feat(auth): wire login and signup pages to backend API

.env.example

@@ -0,0 +1,4 @@
+# Base URL of the MyFans NestJS backend
+# Development default: http://localhost:3000
+# Must be prefixed with NEXT_PUBLIC_ so it is inlined into the browser bundle.
+NEXT_PUBLIC_API_URL=http://localhost:3000

src/app/login/login-form.tsx

@@ -4,7 +4,8 @@ import { useState } from "react";
 import { useForm } from "react-hook-form";
 import { zodResolver } from "@hookform/resolvers/zod";
 import { useRouter, useSearchParams } from "next/navigation";
-import { api } from "@/lib/api/client";
+import { login, extractApiErrorMessage } from "@/lib/api/auth";
+import { ApiError } from "@/lib/api/errors";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import {
@@ -16,31 +17,29 @@ import {
   FormMessage,
 } from "@/components/ui/form";
 import { loginSchema, type LoginFormValues } from "@/lib/validations/auth";
-import type { AuthResponse } from "@/types/api";
 
 export function LoginForm() {
   const router = useRouter();
   const searchParams = useSearchParams();
   const redirectTo = searchParams.get("redirect") || "/dashboard";
   const [serverError, setServerError] = useState<string | null>(null);
 
-  // useForm wires up RHF with our Zod schema as the validator.
-  // zodResolver translates Zod errors into the format RHF expects.
   const form = useForm<LoginFormValues>({
     resolver: zodResolver(loginSchema),
     defaultValues: { email: "", password: "" },
   });
 
-  // This function only runs when ALL fields pass Zod validation.
   async function onSubmit(values: LoginFormValues) {
     setServerError(null);
     try {
-      const response = await api.post<AuthResponse>("/auth/login", values);
-      api.setToken(response.access_token);
-      api.setCurrentUser(response.user);
+      await login(values);
       router.replace(redirectTo);
-    } catch {
-      setServerError("Login failed. Check your credentials and try again.");
+    } catch (error) {
+      if (error instanceof ApiError && error.statusCode === 401) {
+        setServerError("Invalid email or password.");
+      } else {
+        setServerError(extractApiErrorMessage(error));
+      }
     }
   }
 
@@ -49,21 +48,17 @@ export function LoginForm() {
       <div className="w-full max-w-md space-y-4 rounded-lg border p-6">
         <h1 className="text-2xl font-semibold">Log in</h1>
 
-        {/* Form spreads the RHF context so all FormField children can access it */}
         <Form {...form}>
           <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-4">
-
             <FormField
               control={form.control}
               name="email"
               render={({ field }) => (
                 <FormItem>
                   <FormLabel>Email</FormLabel>
-                  {/* FormControl merges id + aria-invalid onto the Input */}
                   <FormControl>
                     <Input type="email" placeholder="you@example.com" {...field} />
                   </FormControl>
-                  {/* Renders the Zod error message, or nothing when valid */}
                   <FormMessage />
                 </FormItem>
               )}
@@ -84,7 +79,9 @@ export function LoginForm() {
             />
 
             {serverError ? (
-              <p className="text-sm text-destructive">{serverError}</p>
+              <p role="alert" className="text-sm text-destructive">
+                {serverError}
+              </p>
             ) : null}
 
             <Button

src/app/signup/signup-form.tsx

@@ -4,7 +4,8 @@ import { useState } from "react";
 import { useForm } from "react-hook-form";
 import { zodResolver } from "@hookform/resolvers/zod";
 import { useRouter } from "next/navigation";
-import { api } from "@/lib/api/client";
+import { signup, extractApiErrorMessage } from "@/lib/api/auth";
+import { ApiError } from "@/lib/api/errors";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import {
@@ -16,7 +17,6 @@ import {
   FormMessage,
 } from "@/components/ui/form";
 import { signupSchema, type SignupFormValues } from "@/lib/validations/auth";
-import type { AuthResponse } from "@/types/api";
 
 export function SignupForm() {
   const router = useRouter();
@@ -30,14 +30,14 @@ export function SignupForm() {
   async function onSubmit(values: SignupFormValues) {
     setServerError(null);
     try {
-      const response = await api.post<AuthResponse>("/auth/signup", {
-        email: values.email,
-        password: values.password,
-      });
-      api.setToken(response.access_token);
+      await signup({ email: values.email, password: values.password });
       router.replace("/dashboard");
-    } catch {
-      setServerError("Sign up failed. This email may already be in use.");
+    } catch (error) {
+      if (error instanceof ApiError && error.statusCode === 409) {
+        setServerError("An account with this email already exists.");
+      } else {
+        setServerError(extractApiErrorMessage(error));
+      }
     }
   }
 
@@ -48,7 +48,6 @@ export function SignupForm() {
 
         <Form {...form}>
           <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-4">
-
             <FormField
               control={form.control}
               name="email"
@@ -86,14 +85,15 @@ export function SignupForm() {
                   <FormControl>
                     <Input type="password" placeholder="••••••••" {...field} />
                   </FormControl>
-                  {/* This message comes from the .refine() cross-field check */}
                   <FormMessage />
                 </FormItem>
               )}
             />
 
             {serverError ? (
-              <p className="text-sm text-destructive">{serverError}</p>
+              <p role="alert" className="text-sm text-destructive">
+                {serverError}
+              </p>
             ) : null}
 
             <Button

src/lib/api/auth.ts

@@ -0,0 +1,46 @@
+import { api } from "./client";
+import { ApiError, NetworkError } from "./errors";
+import type { AuthResponse } from "@/types/api";
+import type { LoginFormValues, SignupFormValues } from "@/lib/validations/auth";
+
+export async function login(credentials: LoginFormValues): Promise<AuthResponse> {
+  const response = await api.post<AuthResponse>("/auth/login", credentials);
+  api.setToken(response.access_token);
+  api.setCurrentUser(response.user);
+  return response;
+}
+
+export async function signup(
+  values: Pick<SignupFormValues, "email" | "password">
+): Promise<AuthResponse> {
+  const response = await api.post<AuthResponse>("/auth/signup", values);
+  api.setToken(response.access_token);
+  api.setCurrentUser(response.user);
+  return response;
+}
+
+export function logout(): void {
+  api.clearToken();
+  api.clearCurrentUser();
+}
+
+/**
+ * Extracts a human-readable message from an API or network error.
+ * NestJS validation errors arrive as message arrays; credential/conflict
+ * errors arrive as a single string.
+ */
+export function extractApiErrorMessage(error: unknown): string {
+  if (error instanceof ApiError) {
+    const data = error.data as { message?: string | string[] } | null;
+    if (data?.message) {
+      return Array.isArray(data.message)
+        ? data.message.join(". ")
+        : data.message;
+    }
+    return error.message;
+  }
+  if (error instanceof NetworkError) {
+    return "Could not reach the server. Check your connection and try again.";
+  }
+  return "An unexpected error occurred. Please try again.";
+}