export class ApiError extends Error {
  status: number;
  detail: unknown;
  constructor(status: number, detail: unknown) {
    super(typeof detail === "string" ? detail : `HTTP ${status}`);
    this.status = status;
    this.detail = detail;
  }
}

function redirectToLogin() {
  if (typeof window !== "undefined" && !window.location.pathname.startsWith("/login")) {
    // Full navigation on purpose: clears all client state/query cache after the session expired.
    // eslint-disable-next-line @next/next/no-location-assign-relative-destination
    window.location.href = `/login?next=${encodeURIComponent(window.location.pathname)}`;
  }
}

export async function api<T>(path: string, init?: RequestInit & { json?: unknown }): Promise<T> {
  const headers: Record<string, string> = { Accept: "application/json", ...(init?.headers as Record<string, string>) };
  let body = init?.body;
  if (init?.json !== undefined) {
    headers["Content-Type"] = "application/json";
    body = JSON.stringify(init.json);
  }
  const res = await fetch(path, { ...init, body, headers, credentials: "include" });
  if (res.status === 401) {
    redirectToLogin();
    throw new ApiError(401, "authentication required");
  }
  const text = await res.text();
  let data: unknown = text;
  try {
    data = text ? JSON.parse(text) : null;
  } catch {
    /* non-JSON */
  }
  if (!res.ok) {
    const detail = (data as { detail?: unknown })?.detail ?? data;
    throw new ApiError(res.status, typeof detail === "string" ? detail : JSON.stringify(detail));
  }
  return data as T;
}

export const qs = (params: Record<string, string | number | boolean | undefined | null>) =>
  Object.entries(params)
    .filter(([, v]) => v !== undefined && v !== null && v !== "")
    .map(([k, v]) => `${encodeURIComponent(k)}=${encodeURIComponent(String(v))}`)
    .join("&");