Initial commit

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01F22Ms5Cxam5UHyxaCrtZzu

shared/buyer-ip.ts

@@ -0,0 +1,15 @@
+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`);
+}