const COOKIE_NAME = "fs_session";

export function readSessionCookie(req: Request): string | null {
  const header = req.headers.get("cookie");
  if (!header) return null;
  for (const part of header.split(";")) {
    const idx = part.indexOf("=");
    if (idx === -1) continue;
    const name  = part.slice(0, idx).trim();
    const value = part.slice(idx + 1).trim();
    if (name === COOKIE_NAME && value) return decodeURIComponent(value);
  }
  return null;
}

export function setSessionCookieHeader(token: string, expiresAt: number): string {
  const maxAge = Math.max(0, Math.floor((expiresAt - Date.now()) / 1000));
  return `${COOKIE_NAME}=${encodeURIComponent(token)}; Path=/; Max-Age=${maxAge}; HttpOnly; SameSite=Lax`;
}

export function clearSessionCookieHeader(): string {
  return `${COOKIE_NAME}=; Path=/; Max-Age=0; HttpOnly; SameSite=Lax`;
}