const FIRST_FORWARDED_IP_INDEX = 0;

export const BUYER_IP_HEADERS = ["oxygen-buyer-ip", "cf-connecting-ip", "x-forwarded-for"] as const;
export const DEVELOPMENT_BUYER_IP = "127.0.0.1";

export function getBuyerIp(headers: Pick<Headers, "get">): string {
  for (const header of BUYER_IP_HEADERS) {
    const buyerIp = headers.get(header)?.split(",")[FIRST_FORWARDED_IP_INDEX]?.trim();
    if (buyerIp) return buyerIp;
  }

  if (process.env.NODE_ENV !== "production") return DEVELOPMENT_BUYER_IP;

  throw new Error(`${BUYER_IP_HEADERS.join(", ")} is required for private Storefront API clients`);
}