// strip-reorder.mjs's drop rule: where a dragged slide lands, as the
// `after` a move_slide wants, and when a drop changes nothing.
import test from 'node:test'
import assert from 'node:assert/strict'
import { dropTarget, dropOp } from './strip-reorder.mjs'

const ids = ['a', 'b', 'c', 'd']

test('dropTarget: before puts it ahead of the item, after behind it, null means first', () => {
  assert.equal(dropTarget(ids, 'c', 'a', 'before'), null)
  assert.equal(dropTarget(ids, 'c', 'a', 'after'), 'a')
  assert.equal(dropTarget(ids, 'a', 'd', 'after'), 'd')
  assert.equal(dropTarget(ids, 'a', 'd', 'before'), 'c')
  assert.equal(dropTarget(ids, 'd', 'b', 'before'), 'a')
})

test('a drop that leaves the order as it is is no move', () => {
  assert.equal(dropTarget(ids, 'a', 'a', 'before'), undefined)
  assert.equal(dropTarget(ids, 'b', 'a', 'after'), undefined)
  assert.equal(dropTarget(ids, 'b', 'c', 'before'), undefined)
  assert.equal(dropTarget(ids, 'a', 'b', 'before'), undefined)
  assert.equal(dropTarget(ids, 'a', 'zz', 'before'), undefined)
  assert.equal(dropOp(ids, 'b', 'a', 'after'), null)
})

test('dropOp is the move_slide', () => {
  assert.deepEqual(dropOp(ids, 'c', 'a', 'before'), { op: 'move_slide', id: 'c' })
  assert.deepEqual(dropOp(ids, 'a', 'c', 'after'), { op: 'move_slide', id: 'a', after: 'c' })
})