import { useCallback, useEffect, useState } from "react";
import { useTranslation } from "react-i18next";
import { CARD_PAGE_SIZES, parseCardSize } from "./channelLayout";
import { readAccount, writeAccount } from "./storage";

// Client-side pagination for the channel manager's card layout, owned once instead of twice. Both
// manager tabs page an in-memory list the same way, and keeping two copies meant every fix landed
// twice (and the day one copy was missed, the tabs would page differently). The caller keeps only
// what genuinely differs: which rows, which storage key, and when to jump back to page one.
//
// The page size persists per account; the page itself is transient. `enabled` is the card layout
// flag — in table mode DataTable does its own paging, so this does no work and holds still.
export function useCardPager<T>(rows: T[], sizeKey: string, enabled: boolean) {
  const { t } = useTranslation();
  const [size, setSize] = useState(() => parseCardSize(readAccount(sizeKey, null)));
  const [page, setPage] = useState(0);

  const totalPages = size <= 0 ? 1 : Math.max(1, Math.ceil(rows.length / size));
  const safePage = Math.min(page, totalPages - 1);

  // A list that shrank under you (an unsubscribe, a refetch) leaves `page` out of range: the clamp
  // above only HIDES that, so commit it or it springs back the moment the list grows again. Only
  // fires when the page you are on stopped existing, so it never costs you your place otherwise.
  useEffect(() => {
    if (enabled && page > totalPages - 1) setPage(totalPages - 1);
  }, [enabled, page, totalPages]);

  const paged = !enabled || size <= 0 ? rows : rows.slice(safePage * size, safePage * size + size);

  return {
    paged,
    /** Spread onto <Pager/>. */
    pagerProps: {
      page: safePage,
      size,
      total: rows.length,
      pageSizeOptions: CARD_PAGE_SIZES,
      onPageChange: setPage,
      onSizeChange: (s: number) => {
        setSize(s);
        writeAccount(sizeKey, s);
        setPage(0);
      },
      sizeLabel: t("channels.cardsPerPage"),
    },
    /** Call when the caller's own filters change — a different list starts at page one. */
    resetPage: useCallback(() => setPage(0), []),
  };
}