const parseTeacherEmails = (source: string | undefined): string[] =>
  (source ?? "")
    .split(",")
    .map((email) => email.trim().toLowerCase())
    .filter(Boolean);

export const readTeacherEmailsServer = (): string[] => parseTeacherEmails(process.env.TEACHER_EMAILS);

export const readTeacherEmailsBrowser = (): string[] =>
  parseTeacherEmails(process.env.NEXT_PUBLIC_TEACHER_EMAILS);

export const isTeacherEmailAllowed = (email: string | null, allowed: string[]): boolean => {
  if (!email) return false;
  if (allowed.length === 0) return false;
  return allowed.includes(email.toLowerCase());
};