import { authService } from './auth/auth.service';
import {
  NavigationService,
  navigationService,
} from './navigation/navigation.interface';

// Mock OAuth configuration
const GOOGLE_CLIENT_ID = 'mock_google_client_id';
const GITHUB_CLIENT_ID = 'mock_github_client_id';

// Mock OAuth endpoints
const GOOGLE_AUTH_URL = 'https://accounts.google.com/o/oauth2/v2/auth';
const GITHUB_AUTH_URL = 'https://github.com/login/oauth/authorize';

// Mock OAuth scopes
const GOOGLE_SCOPES = 'openid email profile';
const GITHUB_SCOPES = 'user:email';

// Mock redirect URI
const REDIRECT_URI = 'http://localhost:3000/auth/callback';

// Mock OAuth state generation
const generateState = () => crypto.randomUUID();

/**
 * OAuth Service Class
 *
 * Handles OAuth authentication flows with dependency injection for navigation,
 * making it more testable and maintainable.
 */
export class OAuthService {
  constructor(private navigation: NavigationService = navigationService) {}

  /**
   * Initiates Google OAuth authentication flow
   */
  googleAuth(): void {
    const state = generateState();
    const url = new URL(GOOGLE_AUTH_URL);
    url.searchParams.append('client_id', GOOGLE_CLIENT_ID);
    url.searchParams.append('response_type', 'code');
    url.searchParams.append('scope', GOOGLE_SCOPES);
    url.searchParams.append('redirect_uri', REDIRECT_URI);
    url.searchParams.append('state', state);

    // Store state for CSRF protection
    localStorage.setItem('oauth_state', state);

    // Redirect to Google's auth endpoint
    this.navigation.redirectTo(url.toString());
  }

  /**
   * Initiates GitHub OAuth authentication flow
   */
  githubAuth(): void {
    const state = generateState();
    const url = new URL(GITHUB_AUTH_URL);
    url.searchParams.append('client_id', GITHUB_CLIENT_ID);
    url.searchParams.append('response_type', 'code');
    url.searchParams.append('scope', GITHUB_SCOPES);
    url.searchParams.append('redirect_uri', REDIRECT_URI);
    url.searchParams.append('state', state);

    // Store state for CSRF protection
    localStorage.setItem('oauth_state', state);

    // Redirect to GitHub's auth endpoint
    this.navigation.redirectTo(url.toString());
  }

  /**
   * Handles Google OAuth callback
   */
  async handleGoogleCallback() {
    const params = this.navigation.getSearchParams();
    const code = params.get('code');
    const state = params.get('state');
    const storedState = localStorage.getItem('oauth_state');

    // Verify state to prevent CSRF attacks
    if (state !== storedState) {
      throw new Error('Invalid OAuth state');
    }

    // Clear stored state
    localStorage.removeItem('oauth_state');

    // Exchange code for token
    const accessToken = await this.mockExchangeCodeForToken('google', code);

    // Get user info
    const userInfo = await this.mockGetUserInfo('google', accessToken);

    // Register or login the user
    return authService.loginWithOAuth('google', {
      email: userInfo.email,
      username: userInfo.name,
    });
  }

  /**
   * Handles GitHub OAuth callback
   */
  async handleGithubCallback() {
    const params = this.navigation.getSearchParams();
    const code = params.get('code');
    const state = params.get('state');
    const storedState = localStorage.getItem('oauth_state');

    // Verify state to prevent CSRF attacks
    if (state !== storedState) {
      throw new Error('Invalid OAuth state');
    }

    // Clear stored state
    localStorage.removeItem('oauth_state');

    // Exchange code for token
    const accessToken = await this.mockExchangeCodeForToken('github', code);

    // Get user info
    const userInfo = await this.mockGetUserInfo('github', accessToken);

    // Register or login the user
    return authService.loginWithOAuth('github', {
      email: userInfo.email,
      username: userInfo.name,
    });
  }

  /**
   * Mock token exchange
   * In a real implementation, this would make a POST request to the token endpoint
   */
  private async mockExchangeCodeForToken(
    provider: 'google' | 'github',
    _code: string | null
  ): Promise<string> {
    // For this mock, we'll just return a mock access token
    return `mock_${provider}_access_token_${crypto.randomUUID()}`;
  }

  /**
   * Mock user info retrieval
   * In a real implementation, this would make a GET request to the user info endpoint
   */
  private async mockGetUserInfo(
    provider: 'google' | 'github',
    _accessToken: string
  ): Promise<{ email: string; name: string }> {
    // For this mock, we'll return mock user info
    return {
      email: `mock_${provider}_user_${crypto.randomUUID()}@example.com`,
      name: `Mock ${provider.charAt(0).toUpperCase() + provider.slice(1)} User`,
    };
  }
}

// Default instance for production use
const oauthService = new OAuthService();

// Export both the class and convenience functions for backward compatibility
export const googleAuth = () => oauthService.googleAuth();
export const githubAuth = () => oauthService.githubAuth();
export const handleGoogleCallback = () => oauthService.handleGoogleCallback();
export const handleGithubCallback = () => oauthService.handleGithubCallback();

// Export the service instance for direct use
export { oauthService };
export default oauthService;