Handling Authentication

Handling Authentication in StickerNest

This skill covers implementing authentication flows, protecting routes, managing sessions, and providing auth context to widgets.

Architecture Overview

┌─────────────────────────────────────────────────────────────┐
│                     Supabase Auth                            │
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐          │
│  │   Email     │  │   OAuth     │  │   Magic     │          │
│  │  Password   │  │   (Google)  │  │   Link      │          │
│  └──────┬──────┘  └──────┬──────┘  └──────┬──────┘          │
└─────────┼────────────────┼────────────────┼─────────────────┘
          │                │                │
          └────────────────┼────────────────┘
                           ▼
┌─────────────────────────────────────────────────────────────┐
│                     AuthContext                              │
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐          │
│  │    user     │  │   session   │  │  isLoading  │          │
│  │   profile   │  │   tokens    │  │   isLocal   │          │
│  └─────────────┘  └─────────────┘  └─────────────┘          │
└─────────────────────────┬───────────────────────────────────┘
                          │
        ┌─────────────────┼─────────────────┐
        ▼                 ▼                 ▼
  Components         Widgets          Services
  (useAuth)       (WidgetAuth)      (API calls)

AuthContext Implementation

Location: src/contexts/AuthContext.tsx

import React, { createContext, useContext, useEffect, useState } from 'react';
import { createClient, SupabaseClient, User, Session } from '@supabase/supabase-js';

interface Profile {
  id: string;
  username: string | null;
  display_name: string | null;
  avatar_url: string | null;
  bio: string | null;
}

interface AuthContextType {
  user: User | null;
  profile: Profile | null;
  session: Session | null;
  isLoading: boolean;
  isAuthenticated: boolean;
  isLocalDevMode: boolean;
  signUp: (email: string, password: string) => Promise<{ error: Error | null }>;
  signIn: (email: string, password: string) => Promise<{ error: Error | null }>;
  signInWithOAuth: (provider: 'google' | 'github') => Promise<void>;
  signOut: () => Promise<void>;
  updateProfile: (updates: Partial<Profile>) => Promise<{ error: Error | null }>;
}

const AuthContext = createContext<AuthContextType | undefined>(undefined);

// Supabase client singleton
let supabaseClient: SupabaseClient | null = null;

export function getSupabaseClient(): SupabaseClient | null {
  if (!supabaseClient && import.meta.env.VITE_SUPABASE_URL) {
    supabaseClient = createClient(
      import.meta.env.VITE_SUPABASE_URL,
      import.meta.env.VITE_SUPABASE_ANON_KEY
    );
  }
  return supabaseClient;
}

export function AuthProvider({ children }: { children: React.ReactNode }) {
  const [user, setUser] = useState<User | null>(null);
  const [profile, setProfile] = useState<Profile | null>(null);
  const [session, setSession] = useState<Session | null>(null);
  const [isLoading, setIsLoading] = useState(true);

  const isLocalDevMode = !import.meta.env.VITE_SUPABASE_URL;

  useEffect(() => {
    if (isLocalDevMode) {
      // Local dev mode - use demo user
      setUser({ id: 'demo-user', email: 'demo@local.dev' } as User);
      setProfile({
        id: 'demo-user',
        username: 'demo',
        display_name: 'Demo User',
        avatar_url: null,
        bio: 'Local development user',
      });
      setIsLoading(false);
      return;
    }

    const supabase = getSupabaseClient();
    if (!supabase) return;

    // Get initial session
    supabase.auth.getSession().then(({ data: { session } }) => {
      setSession(session);
      setUser(session?.user ?? null);
      if (session?.user) {
        fetchProfile(session.user.id);
      }
      setIsLoading(false);
    });

    // Listen for auth changes
    const { data: { subscription } } = supabase.auth.onAuthStateChange(
      async (event, session) => {
        setSession(session);
        setUser(session?.user ?? null);

        if (event === 'SIGNED_IN' && session?.user) {
          await fetchProfile(session.user.id);
        } else if (event === 'SIGNED_OUT') {
          setProfile(null);
        }
      }
    );

    return () => subscription.unsubscribe();
  }, [isLocalDevMode]);

  async function fetchProfile(userId: string) {
    const supabase = getSupabaseClient();
    if (!supabase) return;

    const { data, error } = await supabase
      .from('profiles')
      .select('*')
      .eq('id', userId)
      .single();

    if (!error && data) {
      setProfile(data);
    }
  }

  async function signUp(email: string, password: string) {
    const supabase = getSupabaseClient();
    if (!supabase) return { error: new Error('Supabase not configured') };

    const { error } = await supabase.auth.signUp({ email, password });
    return { error };
  }

  async function signIn(email: string, password: string) {
    const supabase = getSupabaseClient();
    if (!supabase) return { error: new Error('Supabase not configured') };

    const { error } = await supabase.auth.signInWithPassword({ email, password });
    return { error };
  }

  async function signInWithOAuth(provider: 'google' | 'github') {
    const supabase = getSupabaseClient();
    if (!supabase) return;

    await supabase.auth.signInWithOAuth({
      provider,
      options: {
        redirectTo: `${window.location.origin}/auth/callback`,
      },
    });
  }

  async function signOut() {
    const supabase = getSupabaseClient();
    if (!supabase) return;

    await supabase.auth.signOut();
  }

  async function updateProfile(updates: Partial<Profile>) {
    const supabase = getSupabaseClient();
    if (!supabase || !user) return { error: new Error('Not authenticated') };

    const { error } = await supabase
      .from('profiles')
      .update(updates)
      .eq('id', user.id);

    if (!error) {
      setProfile((prev) => prev ? { ...prev, ...updates } : null);
    }

    return { error };
  }

  const value: AuthContextType = {
    user,
    profile,
    session,
    isLoading,
    isAuthenticated: !!user,
    isLocalDevMode,
    signUp,
    signIn,
    signInWithOAuth,
    signOut,
    updateProfile,
  };

  return (
    <AuthContext.Provider value={value}>
      {children}
    </AuthContext.Provider>
  );
}

export function useAuth() {
  const context = useContext(AuthContext);
  if (context === undefined) {
    throw new Error('useAuth must be used within an AuthProvider');
  }
  return context;
}

Protected Routes

ProtectedRoute Component

// src/components/ProtectedRoute.tsx

import { Navigate, useLocation } from 'react-router-dom';
import { useAuth } from '@/contexts/AuthContext';

interface ProtectedRouteProps {
  children: React.ReactNode;
  requireProfile?: boolean;
}

export function ProtectedRoute({ children, requireProfile = false }: ProtectedRouteProps) {
  const { isAuthenticated, isLoading, profile, isLocalDevMode } = useAuth();
  const location = useLocation();

  // Show loading while checking auth
  if (isLoading) {
    return <LoadingSpinner />;
  }

  // Local dev mode - always authenticated
  if (isLocalDevMode) {
    return <>{children}</>;
  }

  // Not authenticated - redirect to login
  if (!isAuthenticated) {
    return <Navigate to="/login" state={{ from: location }} replace />;
  }

  // Need profile but don't have one - redirect to onboarding
  if (requireProfile && !profile?.username) {
    return <Navigate to="/onboarding" state={{ from: location }} replace />;
  }

  return <>{children}</>;
}

Route Setup

// src/App.tsx or routes.tsx

import { Routes, Route } from 'react-router-dom';
import { ProtectedRoute } from '@/components/ProtectedRoute';

function AppRoutes() {
  return (
    <Routes>
      {/* Public routes */}
      <Route path="/login" element={<LoginPage />} />
      <Route path="/signup" element={<SignupPage />} />
      <Route path="/auth/callback" element={<AuthCallback />} />

      {/* Protected routes */}
      <Route
        path="/dashboard"
        element={
          <ProtectedRoute>
            <DashboardPage />
          </ProtectedRoute>
        }
      />

      {/* Protected + requires profile */}
      <Route
        path="/canvas/:id"
        element={
          <ProtectedRoute requireProfile>
            <EditorPage />
          </ProtectedRoute>
        }
      />

      {/* Public canvas viewing */}
      <Route path="/c/:slug" element={<PublicCanvasPage />} />
    </Routes>
  );
}

Auth Components

Login Form

// src/components/auth/LoginForm.tsx

import { useState } from 'react';
import { useAuth } from '@/contexts/AuthContext';
import { useNavigate, useLocation } from 'react-router-dom';

export function LoginForm() {
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [error, setError] = useState('');
  const [isSubmitting, setIsSubmitting] = useState(false);

  const { signIn, signInWithOAuth } = useAuth();
  const navigate = useNavigate();
  const location = useLocation();

  const from = location.state?.from?.pathname || '/dashboard';

  async function handleSubmit(e: React.FormEvent) {
    e.preventDefault();
    setError('');
    setIsSubmitting(true);

    const { error } = await signIn(email, password);

    if (error) {
      setError(error.message);
      setIsSubmitting(false);
    } else {
      navigate(from, { replace: true });
    }
  }

  return (
    <form
      {error && <div className="error">{error}</div>}

      <input
        type="email"
        value={email}
        => setEmail(e.target.value)}
        placeholder="Email"
        required
      />

      <input
        type="password"
        value={password}
        => setPassword(e.target.value)}
        placeholder="Password"
        required
      />

      <button type="submit" disabled={isSubmitting}>
        {isSubmitting ? 'Signing in...' : 'Sign In'}
      </button>

      <div className="oauth-buttons">
        <button type="button" => signInWithOAuth('google')}>
          Continue with Google
        </button>
        <button type="button" => signInWithOAuth('github')}>
          Continue with GitHub
        </button>
      </div>
    </form>
  );
}

OAuth Callback Handler

// src/pages/AuthCallback.tsx

import { useEffect } from 'react';
import { useNavigate } from 'react-router-dom';
import { getSupabaseClient } from '@/contexts/AuthContext';

export function AuthCallback() {
  const navigate = useNavigate();

  useEffect(() => {
    const supabase = getSupabaseClient();
    if (!supabase) {
      navigate('/login');
      return;
    }

    // Handle OAuth callback
    supabase.auth.getSession().then(({ data: { session } }) => {
      if (session) {
        // Check if profile exists
        supabase
          .from('profiles')
          .select('username')
          .eq('id', session.user.id)
          .single()
          .then(({ data }) => {
            if (data?.username) {
              navigate('/dashboard');
            } else {
              navigate('/onboarding');
            }
          });
      } else {
        navigate('/login');
      }
    });
  }, [navigate]);

  return <LoadingSpinner />;
}

Widget Authentication

Providing Auth to Widgets

// src/runtime/WidgetHost.ts

class WidgetHost {
  private sendAuthInfo() {
    const { user, profile, isAuthenticated } = this.authContext;

    // Only send safe, read-only info to widget
    this.sendMessage('widget:auth', {
      isAuthenticated,
      userId: user?.id || null,
      username: profile?.username || null,
      displayName: profile?.display_name || null,
      avatarUrl: profile?.avatar_url || null,
      // Never send: email, tokens, session
    });
  }

  // Handle auth-requiring requests from widgets
  private handleWidgetRequest(action: string, data: any) {
    if (!this.authContext.isAuthenticated) {
      return { error: 'Not authenticated' };
    }

    switch (action) {
      case 'social:follow':
        return SocialGraphService.followUser(data.userId);
      case 'social:sendMessage':
        return ChatService.sendMessage(data.channelId, data.content);
      // ... other authenticated actions
    }
  }
}

Widget-Side Auth Handling

// In widget code
const WidgetAPI = {
  auth: null,

  handleMessage(event) {
    if (event.data.type === 'widget:auth') {
      this.auth = event.data.payload;
      this.onAuthChange?.(this.auth);
    }
  },

  isAuthenticated() {
    return this.auth?.isAuthenticated ?? false;
  },

  getCurrentUser() {
    return this.auth;
  },

  // Request that requires auth
  async sendMessage(content) {
    if (!this.isAuthenticated()) {
      throw new Error('Authentication required');
    }
    return this.request('social:sendMessage', { content });
  }
};

Session Management

Token Refresh

// Supabase handles token refresh automatically
// But you can listen for refresh events:

supabase.auth.onAuthStateChange((event, session) => {
  if (event === 'TOKEN_REFRESHED') {
    console.log('Token refreshed');
    // Update any cached tokens
  }
});

Session Persistence

// Configure session persistence (default is localStorage)
const supabase = createClient(url, key, {
  auth: {
    persistSession: true,
    storageKey: 'stickernest-auth',
    storage: window.localStorage,
  },
});

Permission Checks

Service-Level Authorization

// In services, always verify user can perform action

export async function deleteCanvas(canvasId: string): Promise<void> {
  const supabase = getSupabaseClient();
  const user = (await supabase.auth.getUser()).data.user;

  if (!user) {
    throw new Error('Not authenticated');
  }

  // RLS will also enforce this, but explicit check is good practice
  const { data: canvas } = await supabase
    .from('canvases')
    .select('user_id')
    .eq('id', canvasId)
    .single();

  if (canvas?.user_id !== user.id) {
    throw new Error('Not authorized');
  }

  await supabase.from('canvases').delete().eq('id', canvasId);
}

Hook for Permission Checks

// src/hooks/usePermission.ts

export function usePermission() {
  const { user, profile } = useAuth();

  return {
    canEditCanvas: (canvas: Canvas) => canvas.user_id === user?.id,
    canDeleteWidget: (widget: Widget, canvas: Canvas) => canvas.user_id === user?.id,
    canFollow: (targetUserId: string) => user?.id !== targetUserId,
    canSendDM: (targetUserId: string) => user?.id !== targetUserId,
    isOwner: (resource: { user_id: string }) => resource.user_id === user?.id,
  };
}

Local Development Mode

Demo User Setup

// When VITE_SUPABASE_URL is not set, use local mode

const isLocalDevMode = !import.meta.env.VITE_SUPABASE_URL;

if (isLocalDevMode) {
  // Use demo user
  const demoUser = {
    id: 'demo-user-id',
    email: 'demo@local.dev',
  };

  const demoProfile = {
    id: 'demo-user-id',
    username: 'demo',
    display_name: 'Demo User',
    avatar_url: null,
  };

  // Store in localStorage
  localStorage.setItem('demo-user', JSON.stringify(demoUser));
  localStorage.setItem('demo-profile', JSON.stringify(demoProfile));
}

Error Handling

Auth Error Types

type AuthError =
  | 'invalid_credentials'
  | 'email_not_confirmed'
  | 'user_not_found'
  | 'email_taken'
  | 'weak_password'
  | 'rate_limited'
  | 'network_error';

function getAuthErrorMessage(error: any): string {
  const message = error?.message?.toLowerCase() || '';

  if (message.includes('invalid login')) return 'Invalid email or password';
  if (message.includes('email not confirmed')) return 'Please confirm your email';
  if (message.includes('already registered')) return 'Email already registered';
  if (message.includes('password')) return 'Password must be at least 6 characters';
  if (message.includes('rate limit')) return 'Too many attempts. Please wait.';

  return 'An error occurred. Please try again.';
}

Reference Files

Best Practices

1. Never expose tokens to widgets - Only send user ID and profile info
2. Use RLS as primary security - Service checks are secondary
3. Handle loading states - Show spinners during auth checks
4. Redirect after login - Return to original destination
5. Support local dev mode - Demo user for offline development
6. Validate on server - Never trust client-side checks alone
7. Use secure cookies - For session persistence in production
8. Implement rate limiting - Prevent brute force attacks