export const STARTER_PASSWORD = "mega2026";
export const SESSION_COOKIE = "mega_session";

const validEmail = (email: string) => /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email) && email.length <= 254;

export function validateLogin(email: string, password: string): string | null {
  if (!validEmail(email.trim()) || !password) return "Enter your email and password.";
  return null;
}

export function validateNewPassword(password: string, confirmation: string): string | null {
  if (password.length < 8) return "Choose a password with at least 8 characters.";
  if (password === STARTER_PASSWORD) return "Choose a password different from the starter password.";
  if (password !== confirmation) return "The passwords do not match.";
  return null;
}

export function validateNewUser(name: string, email: string): string | null {
  if (!name.trim()) return "Enter the person's name.";
  if (!validEmail(email.trim())) return "Enter a valid email address.";
  return null;
}

export function authDestination(session: { passwordChanged: boolean } | null): string {
  return !session ? "/login" : session.passwordChanged ? "/" : "/change-password";
}