pages/api/auth/google.js

export default function handler(req, res) {
  const clientId = process.env.NEXT_PUBLIC_GOOGLE_CLIENT_ID;
  const redirectUri = `${process.env.NEXTAUTH_URL || 'http://localhost:3000'}/api/auth/callback/google`;
  const scope = 'openid email profile';
  
  const authUrl = `https://accounts.google.com/o/oauth2/v2/auth?` +
    `client_id=${clientId}&` +
    `redirect_uri=${encodeURIComponent(redirectUri)}&` +
    `response_type=code&` +
    `scope=${encodeURIComponent(scope)}&` +
    `access_type=offline&` +
    `prompt=consent`;

  res.redirect(authUrl);
}