import { atom } from 'jotai';
import { atomWithStorage, createJSONStorage } from 'jotai/utils';

export type RecentGif = {
  url: string;
  width: number;
  height: number;
  /** A small still image used for the picker thumbnail (so recents don't all autoplay). */
  previewUrl?: string;
};

const STORAGE_KEY = 'cinny_recent_gifs_v1';
const MAX_RECENT_GIFS = 16;

// getOnInit reads localStorage synchronously so the Recent row is present on the
// first render of the GIF picker (no flash of the empty default).
const internalAtom = atomWithStorage<RecentGif[]>(
  STORAGE_KEY,
  [],
  createJSONStorage(() => localStorage),
  { getOnInit: true },
);

/**
 * Global atom: the most recently sent GIFs, newest first, deduped by url, capped
 * at MAX_RECENT_GIFS. Backed by localStorage (device-local convenience).
 */
export const recentGifsAtom = atom(
  (get): RecentGif[] => get(internalAtom),
  (_get, set, updater: RecentGif[] | ((prev: RecentGif[]) => RecentGif[])) => {
    set(internalAtom, (prev) => {
      const prevList = Array.isArray(prev) ? prev : [];
      return typeof updater === 'function' ? updater(prevList) : updater;
    });
  },
);

/**
 * Prepend a GIF: ignores an empty url, de-dupes by url (moving an existing entry
 * to the front), and caps the list at `max`. Pure — returns a new array.
 */
export const addRecentGif = (
  prev: RecentGif[],
  gif: RecentGif,
  max = MAX_RECENT_GIFS,
): RecentGif[] => {
  if (!gif.url) return prev;
  const withoutDupe = prev.filter((g) => g.url !== gif.url);
  return [gif, ...withoutDupe].slice(0, max);
};

/**
 * Wipe persisted recent GIFs. Called on logout — these are media the user sent
 * (can be personally sensitive) and must not surface under "Recent" to the next
 * person on a shared device.
 */
export const clearRecentGifs = (): void => {
  try {
    localStorage.removeItem(STORAGE_KEY);
  } catch {
    /* localStorage unavailable — nothing to clear */
  }
};
