/**
 * Browser-side client for the user's roaming reading preferences.
 *
 * The BFF stores prefs as opaque JSONB keyed off the user. This module
 * just round-trips that blob — it makes no claim about its shape (that
 * contract is owned by components/reading-settings.tsx). All calls run
 * with `credentials: "include"` so the auth cookie comes along.
 */

const BFF_BASE =
  process.env.NEXT_PUBLIC_BFF_URL || "http://localhost:8080";

type Envelope<T> = {
  success?: boolean;
  data?: T;
  error?: { code: number; message: string };
};

async function call<T>(path: string, init?: RequestInit): Promise<T | null> {
  const res = await fetch(`${BFF_BASE}/api/v1${path}`, {
    credentials: "include",
    headers: { "Content-Type": "application/json", ...(init?.headers ?? {}) },
    ...init,
  });
  if (res.status === 401 || res.status === 403) return null;
  if (!res.ok) {
    throw new Error(`reading-prefs ${path}: ${res.status}`);
  }
  const body = (await res.json().catch(() => ({}))) as Envelope<T>;
  return (body.data ?? null) as T | null;
}

export const readingPrefsApi = {
  /** Fetches the caller's reading prefs blob. Returns `null` if the
   *  request is unauthenticated (treat as "no remote prefs"). The blob
   *  is the raw JSON object the frontend wrote last; an empty object
   *  on first load. */
  async get(): Promise<Record<string, unknown> | null> {
    const data = await call<Record<string, unknown>>("/users/me/reading-prefs");
    return data ?? null;
  },

  /** Overwrites the caller's reading prefs blob. The server stores the
   *  payload verbatim (after canonicalising via re-marshal) — schema is
   *  client-owned. Errors are swallowed by the caller; reading prefs
   *  should never block a UI interaction. */
  async put(prefs: Record<string, unknown>): Promise<void> {
    await call<Record<string, unknown>>("/users/me/reading-prefs", {
      method: "PUT",
      body: JSON.stringify(prefs),
    });
  },
};