import { backendBaseUrl as BASE, joinBackendPath } from "./runtime-config";

/**
 * Error thrown for non-2xx responses. `.message` stays "<status> <body>" for
 * backward compatibility; `.status` and `.payload` (parsed JSON body, if any)
 * let callers branch on a specific failure — e.g. a `code: "dwh_unreachable"`.
 */
export class ApiError extends Error {
  constructor(readonly status: number, readonly bodyText: string, readonly payload: unknown) {
    super(`${status} ${bodyText}`);
    this.name = "ApiError";
  }
}

function requestHeaders(init: RequestInit | undefined): Headers {
  const headers = new Headers(init?.headers);
  // Fetch supplies the multipart boundary for FormData. Declaring JSON here
  // would prevent Fastify from parsing an imported workspace bundle.
  if (
    init?.body != null
    && !(typeof FormData !== "undefined" && init.body instanceof FormData)
    && !headers.has("content-type")
  ) {
    headers.set("content-type", "application/json");
  }
  return headers;
}

async function request(path: string, init?: RequestInit): Promise<Response> {
  const res = await fetch(joinBackendPath(BASE, path), { ...init, headers: requestHeaders(init) });
  if (!res.ok) {
    const bodyText = await res.text().catch(() => "");
    let payload: unknown;
    try { payload = bodyText ? JSON.parse(bodyText) : undefined; } catch { payload = undefined; }
    throw new ApiError(res.status, bodyText, payload);
  }
  return res;
}

export async function apiFetch<T>(path: string, init?: RequestInit): Promise<T> {
  // Only declare a JSON content-type when we actually send a body. Body-less
  // POSTs (resume, close) would otherwise make Fastify reject the empty body
  // with FST_ERR_CTP_EMPTY_JSON_BODY (400).
  const res = await request(path, init);
  if (res.status === 204) return undefined as T;
  // Accepted fire-and-forget endpoints may legitimately return 202 with no
  // representation. Keep apiFetch useful for both 202 and 204 contracts.
  const body = await res.text();
  return body ? (JSON.parse(body) as T) : (undefined as T);
}

/** Download registry bundles without attempting to parse their ZIP body as JSON. */
export async function apiFetchBlob(path: string, init?: RequestInit): Promise<Blob> {
  return (await request(path, init)).blob();
}

export { BASE };