import { describe, expect, it } from 'vitest';

import {
  decodeKeysetCursor,
  encodeKeysetCursor,
  paginateByKeyset,
} from '../src/platforms/xiaoheihe/cursor.js';

describe('xhh keyset cursor', () => {
  it('encodes and decodes cursor payload', () => {
    const encoded = encodeKeysetCursor({ key: 'abc-123' });
    const decoded = decodeKeysetCursor(encoded);
    expect(decoded).toEqual({ key: 'abc-123' });
  });

  it('throws on invalid cursor payload', () => {
    expect(() => decodeKeysetCursor('not-base64')).toThrow();
  });

  it('paginates deterministically without duplicates', () => {
    const items = [
      { id: 'a' },
      { id: 'b' },
      { id: 'c' },
      { id: 'd' },
      { id: 'e' },
    ];

    const page1 = paginateByKeyset(items, 2, undefined, (item) => item.id);
    expect(page1.items.map((i) => i.id)).toEqual(['a', 'b']);
    expect(page1.nextCursor).toBeTruthy();

    const page2 = paginateByKeyset(items, 2, decodeKeysetCursor(page1.nextCursor), (item) => item.id);
    expect(page2.items.map((i) => i.id)).toEqual(['c', 'd']);
    expect(page2.nextCursor).toBeTruthy();

    const page3 = paginateByKeyset(items, 2, decodeKeysetCursor(page2.nextCursor), (item) => item.id);
    expect(page3.items.map((i) => i.id)).toEqual(['e']);
    expect(page3.hasMore).toBe(false);

    const combined = [...page1.items, ...page2.items, ...page3.items].map((i) => i.id);
    expect(combined).toEqual(['a', 'b', 'c', 'd', 'e']);
  });
});