// BFF → external backend wiring. Two surfaces, one upstream:
//
//   • `backend`  — typed JSON client (`backend.get<T>("/widgets")`). Use
//     this from server components, route handlers, and any code that
//     calls the backend with a typed response.
//
//   • `proxyToBackend` — raw `Response` passthrough used by the
//     `app/api/backend/[...path]/route.ts` proxy. Necessary because the
//     proxy streams the body untouched; the typed client buffers it.
//
// Configure `BACKEND_URL` in your env. Tokens, retry/timeout, and auth
// header injection live in this file — that's the one place that talks
// to the upstream service.

import { createFetchHttpClient, type HttpClient } from "@raredays/core";

const BACKEND_URL = process.env.BACKEND_URL ?? "";

// Lazy-initialized: warn once, on first actual use of the backend client,
// rather than at module-import time. This keeps `next build` quiet for
// apps that don't (yet) use backend calls, while still surfacing a clear
// signal the first time a missing config bites.
let warnedMissingBackendUrl = false;
function warnIfMissingBackendUrl(): void {
  if (warnedMissingBackendUrl) return;
  if (BACKEND_URL) return;
  if (process.env.NODE_ENV !== "production") return;
  warnedMissingBackendUrl = true;
  // eslint-disable-next-line no-console
  console.warn("[backend-client] BACKEND_URL is not set — backend calls will fail.");
}

export const backend: HttpClient = createFetchHttpClient({
  // `baseUrl` is read at call time by the underlying client, so the lazy
  // warning above is sufficient — no module-load side effect needed.
  baseUrl: BACKEND_URL,
  // Default retry: 2 attempts on 5xx/network errors with 100ms backoff.
  // Tune per-call via `backend.get(path, { retry: { ... } })` when you need
  // different semantics (e.g. webhooks shouldn't retry, batch jobs should).
  retry: { maxAttempts: 2 },
});

/**
 * Raw passthrough for the `[...path]` proxy route. Keeps the streaming
 * semantics that `fetch` provides — the typed `backend` client buffers
 * the body and isn't appropriate for proxying.
 */
export async function proxyToBackend(path: string, init: RequestInit): Promise<Response> {
  warnIfMissingBackendUrl();
  if (!BACKEND_URL) {
    return new Response("BACKEND_URL not configured", { status: 502 });
  }
  const url = `${BACKEND_URL.replace(/\/$/, "")}/${path.replace(/^\//, "")}`;
  return fetch(url, init);
}