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

import { dropIndex, neighborsForMove } from './reorder';

const ids = ['A', 'B', 'C', 'D'];

describe('neighborsForMove (issue #45)', () => {
  it('moves up one: D between B and C', () => {
    // D at index 3 → newIndex 2 in the without-array [A, B, C].
    expect(neighborsForMove(ids, 'D', 2)).toEqual({ afterId: 'B', beforeId: 'C' });
  });

  it('moves to the top: afterId null', () => {
    expect(neighborsForMove(ids, 'C', 0)).toEqual({ afterId: null, beforeId: 'A' });
  });

  it('moves to the bottom: beforeId null', () => {
    expect(neighborsForMove(ids, 'A', 3)).toEqual({ afterId: 'D', beforeId: null });
  });

  it('clamps an out-of-range index', () => {
    expect(neighborsForMove(ids, 'A', 99)).toEqual({ afterId: 'D', beforeId: null });
    expect(neighborsForMove(ids, 'A', -5)).toEqual({ afterId: null, beforeId: 'B' });
  });
});

describe('dropIndex (issue #45)', () => {
  it('drops before the target by default', () => {
    // Drop A onto C (upper half) → before C. without = [B, C, D], C at 1.
    expect(dropIndex(ids, 'A', 'C', false)).toBe(1);
  });

  it('drops after the target on the lower half — reaches the bottom', () => {
    // Drop A onto D lower half → after D. without = [B, C, D], D at 2 → 3 (end).
    expect(dropIndex(ids, 'A', 'D', true)).toBe(3);
  });
});