import { act, renderHook } from "@testing-library/react";
import { describe, it, expect } from "vitest";
import { useClientPagination } from "./line-pagination-footer";

describe("useClientPagination", () => {
  it("defaults to page 0 with the given size and derives slice bounds", () => {
    const { result } = renderHook(() => useClientPagination(250, 100));
    expect(result.current.page).toBe(0);
    expect(result.current.pageSize).toBe(100);
    expect(result.current.pageCount).toBe(3);
    expect(result.current.start).toBe(0);
    expect(result.current.end).toBe(100);
  });

  it("moves between pages and exposes the right slice bounds", () => {
    const { result } = renderHook(() => useClientPagination(250, 100));
    act(() => result.current.setPage(2));
    expect(result.current.page).toBe(2);
    expect(result.current.start).toBe(200);
    expect(result.current.end).toBe(300);
  });

  it("clamps an out-of-range page to the last page during render", () => {
    const { result } = renderHook(() => useClientPagination(250, 100));
    act(() => result.current.setPage(99));
    expect(result.current.page).toBe(2); // pageCount - 1
  });

  it("resets to the first page when the page size changes", () => {
    const { result } = renderHook(() => useClientPagination(250, 100));
    act(() => result.current.setPage(2));
    act(() => result.current.setPageSize(50));
    expect(result.current.pageSize).toBe(50);
    expect(result.current.page).toBe(0);
    expect(result.current.pageCount).toBe(5);
  });

  it("clamps to a single page when there are no rows", () => {
    const { result } = renderHook(() => useClientPagination(0, 100));
    expect(result.current.pageCount).toBe(1);
    expect(result.current.page).toBe(0);
    expect(result.current.start).toBe(0);
  });

  it("re-clamps the page when the row total shrinks below it", () => {
    const { result, rerender } = renderHook(({ total }) => useClientPagination(total, 100), {
      initialProps: { total: 250 },
    });
    act(() => result.current.setPage(2));
    expect(result.current.page).toBe(2);
    // The set dropped to one page worth of rows — the stored page is now out of
    // range and must clamp on the next render without any effect.
    rerender({ total: 100 });
    expect(result.current.pageCount).toBe(1);
    expect(result.current.page).toBe(0);
  });
});