import { describe, expect, it } from 'vitest';
import { dropIndex } from '../../src/editor/tile/PictureStrip';

/**
 * Reordering the pictures of a tile by dragging a row (#118). The index the move command
 * takes counts in the list without the dragged row, which is where the off-by-ones live.
 */
describe('dropping a picture row', () => {
  it('takes the place of the row it is dropped on', () => {
    expect(dropIndex(0, { at: 'onto', targetId: '1' }, 3)).toBe(1);
    expect(dropIndex(2, { at: 'onto', targetId: '0' }, 3)).toBe(0);
    // Dropping a row on itself is nothing to do – which is also what the list reports as no spot.
    expect(dropIndex(1, { at: 'onto', targetId: '1' }, 3)).toBe(1);
  });

  it('counts a gap in the list the row has already left', () => {
    // Downwards: the gap below row 1 is index 1 once row 0 is out of the way.
    expect(dropIndex(0, { at: 'after', targetId: '1' }, 3)).toBe(1);
    expect(dropIndex(0, { at: 'before', targetId: '2' }, 3)).toBe(1);
    // Upwards nothing shifts: the gap above row 0 stays index 0.
    expect(dropIndex(2, { at: 'before', targetId: '0' }, 3)).toBe(0);
    expect(dropIndex(2, { at: 'after', targetId: '0' }, 3)).toBe(1);
    expect(dropIndex(1, { at: 'end' }, 3)).toBe(2);
  });

  it('refuses a row or a target that is not in the list', () => {
    expect(dropIndex(-1, { at: 'end' }, 3)).toBe(-1);
    expect(dropIndex(3, { at: 'end' }, 3)).toBe(-1);
    expect(dropIndex(0, { at: 'onto', targetId: '9' }, 3)).toBe(-1);
    expect(dropIndex(0, { at: 'before', targetId: 'nonsense' }, 3)).toBe(-1);
  });
});