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function sleep(ms: number): Promise<void> {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve();
    }, ms);
  });
}

type UserId = string & { __userId: never };

export interface User {
  id: UserId;

  displayName: string;
}

const usersData = new Map<UserId, Omit<User, "id">>([
  ["alice" as UserId, { displayName: "Alice" }],
  ["bob" as UserId, { displayName: "Bob" }],
  ["carol" as UserId, { displayName: "Carol" }],
]);

export async function fetchUserInfo(
  req: Request,
  abortSignal: AbortSignal,
): Promise<User> {
  await sleep(Math.random() * 500 + 1000);
  if (abortSignal.aborted) {
    throw new Error("Operation was aborted.");
  }

  const url = new URL(req.url);

  const id = url.searchParams.get("id") as UserId | null;

  if (!id) {
    throw new Error("UserId is required.");
  }

  const user = usersData.get(id);
  if (!user) {
    throw new Error(`User with UserId("${id}") does not exist.`);
  }

  return {
    id,
    ...user,
  };
}