Refactor code structure and remove redundant changes

lib/services/auth/oauthService.ts

@@ -0,0 +1,174 @@
+/**
+ * OAuth Service
+ * 
+ * Handles OAuth authentication flow with Google and Discord providers.
+ * Works with django-allauth backend for seamless OAuth integration.
+ */
+
+import { apiClient } from '@/lib/api/client';
+import { AuthResponse } from '@/lib/types/auth';
+import { tokenStorage } from './tokenStorage';
+
+export type OAuthProvider = 'google' | 'discord';
+
+/**
+ * OAuth state management for CSRF protection
+ */
+const OAUTH_STATE_KEY = 'oauth_state';
+const OAUTH_REDIRECT_KEY = 'oauth_redirect';
+
+/**
+ * Generate random state for OAuth CSRF protection
+ */
+function generateState(): string {
+  const array = new Uint8Array(32);
+  crypto.getRandomValues(array);
+  return Array.from(array, byte => byte.toString(16).padStart(2, '0')).join('');
+}
+
+/**
+ * Store OAuth state in sessionStorage
+ */
+function storeState(state: string, redirectUrl?: string): void {
+  if (typeof window === 'undefined') return;
+  
+  sessionStorage.setItem(OAUTH_STATE_KEY, state);
+  if (redirectUrl) {
+    sessionStorage.setItem(OAUTH_REDIRECT_KEY, redirectUrl);
+  }
+}
+
+/**
+ * Retrieve and validate OAuth state
+ */
+function validateState(state: string): boolean {
+  if (typeof window === 'undefined') return false;
+  
+  const storedState = sessionStorage.getItem(OAUTH_STATE_KEY);
+  sessionStorage.removeItem(OAUTH_STATE_KEY);
+  
+  return storedState === state;
+}
+
+/**
+ * Get stored redirect URL
+ */
+function getRedirectUrl(): string | null {
+  if (typeof window === 'undefined') return null;
+  
+  const redirectUrl = sessionStorage.getItem(OAUTH_REDIRECT_KEY);
+  sessionStorage.removeItem(OAUTH_REDIRECT_KEY);
+  
+  return redirectUrl;
+}
+
+/**
+ * Initiate OAuth flow for a provider
+ * 
+ * @param provider - OAuth provider ('google' or 'discord')
+ * @param redirectUrl - Optional URL to redirect to after successful OAuth
+ */
+export async function initiateOAuth(
+  provider: OAuthProvider,
+  redirectUrl?: string
+): Promise<void> {
+  // Generate state for CSRF protection
+  const state = generateState();
+  storeState(state, redirectUrl);
+  
+  // Build OAuth initiation URL
+  const callbackUrl = `${window.location.origin}/auth/oauth/callback`;
+  const params = new URLSearchParams({
+    state,
+    redirect_uri: callbackUrl,
+  });
+  
+  // Redirect to OAuth provider via Django backend
+  const oauthUrl = `${process.env.NEXT_PUBLIC_DJANGO_API_URL}/api/v1/auth/oauth/${provider}/?${params}`;
+  window.location.href = oauthUrl;
+}
+
+/**
+ * Handle OAuth callback after provider authentication
+ * 
+ * @param provider - OAuth provider
+ * @param code - Authorization code from provider
+ * @param state - State parameter for CSRF validation
+ * @returns Auth response with JWT tokens and user info
+ */
+export async function handleOAuthCallback(
+  provider: OAuthProvider,
+  code: string,
+  state: string
+): Promise<{ authResponse: AuthResponse; redirectUrl: string | null }> {
+  // Validate state to prevent CSRF attacks
+  if (!validateState(state)) {
+    throw new Error('Invalid OAuth state - possible CSRF attack');
+  }
+  
+  // Exchange code for JWT tokens
+  const response = await apiClient.post<AuthResponse>(
+    `/api/v1/auth/oauth/${provider}/callback`,
+    { code, state }
+  );
+  
+  // Store tokens
+  tokenStorage.setAccessToken(response.data.access);
+  tokenStorage.setRefreshToken(response.data.refresh);
+  
+  // Get redirect URL if stored
+  const redirectUrl = getRedirectUrl();
+  
+  return {
+    authResponse: response.data,
+    redirectUrl,
+  };
+}
+
+/**
+ * Link OAuth provider to existing account
+ * 
+ * @param provider - OAuth provider to link
+ */
+export async function linkOAuthProvider(provider: OAuthProvider): Promise<void> {
+  const state = generateState();
+  storeState(state);
+  
+  const callbackUrl = `${window.location.origin}/auth/oauth/link/callback`;
+  const params = new URLSearchParams({
+    state,
+    redirect_uri: callbackUrl,
+    link: 'true',
+  });
+  
+  const oauthUrl = `${process.env.NEXT_PUBLIC_DJANGO_API_URL}/api/v1/auth/oauth/${provider}/?${params}`;
+  window.location.href = oauthUrl;
+}
+
+/**
+ * Unlink OAuth provider from account
+ * 
+ * @param provider - OAuth provider to unlink
+ */
+export async function unlinkOAuthProvider(provider: OAuthProvider): Promise<void> {
+  await apiClient.post(`/api/v1/auth/oauth/${provider}/unlink`);
+}
+
+/**
+ * Get list of linked OAuth providers
+ */
+export async function getLinkedProviders(): Promise<OAuthProvider[]> {
+  const response = await apiClient.get<{ providers: OAuthProvider[] }>(
+    '/api/v1/auth/oauth/linked'
+  );
+  return response.data.providers;
+}
+
+// Export all functions as a service object
+export const oauthService = {
+  initiateOAuth,
+  handleOAuthCallback,
+  linkOAuthProvider,
+  unlinkOAuthProvider,
+  getLinkedProviders,
+};