export type FetchHandler = (
  req: Request,
) => Response | Promise<Response>;

export type CapturedRequest = {
  method: string;
  url: string;
  headers: Headers;
  body: string;
};

export type FetchStub = {
  calls: CapturedRequest[];
  restore: () => void;
};

export const installFetchStub = (handler: FetchHandler): FetchStub => {
  const original = globalThis.fetch;
  const calls: CapturedRequest[] = [];
  let restored = false;

  globalThis.fetch = async (input, init) => {
    const req = new Request(input as RequestInfo, init);
    const body = req.method === "GET" || req.method === "HEAD"
      ? ""
      : await req.clone().text();
    calls.push({
      method: req.method,
      url: req.url,
      headers: new Headers(req.headers),
      body,
    });
    return await handler(req);
  };

  return {
    calls,
    restore: () => {
      if (restored) throw new Error("FetchStub.restore() called twice");
      restored = true;
      globalThis.fetch = original;
    },
  };
};

export const jsonResponse = (
  body: unknown,
  init: ResponseInit = {},
): Response => {
  return new Response(JSON.stringify(body), {
    status: init.status ?? 200,
    headers: { "Content-Type": "application/json", ...(init.headers ?? {}) },
  });
};

export const errorResponse = (status: number, text = "error"): Response =>
  new Response(text, { status });