prism/test/test_orm_list_position.rb

require 'minitest/autorun'
require 'prism'
require 'tmpdir'
require 'fileutils'

class OrmListPositionTest < Minitest::Test
  def setup
    @dir = Dir.mktmpdir('prism-list-position-store')
    @store = Prism::Orm::Store.new(File.join(@dir, 'test.pstore'))
    @store.create_table(:tasks, %w[id title position deleted_at])
    @store.create_table(:cards, %w[id title position board_id])

    task_class = Class.new(Prism::Orm::Model) do
      table_name :tasks
      acts_as_paranoid
      acts_as_list column: :position
    end
    card_class = Class.new(Prism::Orm::Model) do
      table_name :cards
      acts_as_list column: :position, scope: :board_id
    end
    plain_class = Class.new(Prism::Orm::Model) { table_name :tasks }

    [task_class, card_class].each { |klass| klass.store = @store }
    plain_class.store = @store
    Object.const_set(:Task, task_class)
    Object.const_set(:Card, card_class)
    Object.const_set(:PlainTask, plain_class)
  end

  def teardown
    FileUtils.remove_entry(@dir)
    %i[Task Card PlainTask].each { |name| Object.send(:remove_const, name) if Object.const_defined?(name) }
  end

  def test_a_model_that_never_called_acts_as_list_is_unaffected
    refute PlainTask.acts_as_list?
    assert Task.acts_as_list?
  end

  def test_fresh_records_are_appended_to_the_bottom_in_creation_order
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    c = Task.create!(title: 'c')
    assert_equal [1, 2, 3], [a, b, c].map(&:list_position)
  end

  def test_move_higher_swaps_with_the_previous_item_and_is_a_noop_at_the_top
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    b.move_higher
    assert_equal 1, b.list_position
    assert_equal 2, a.reload.list_position

    b.reload.move_higher # b is already first - nothing above it to swap with
    assert_equal 1, b.list_position
    assert_equal 2, a.reload.list_position
  end

  def test_move_lower_swaps_with_the_next_item_and_is_a_noop_at_the_bottom
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    a.move_lower
    assert_equal 2, a.list_position
    assert_equal 1, b.reload.list_position

    b.reload.move_lower # b is now first (pos 1), a is last (pos 2) - moving b lower swaps back
    assert_equal 2, b.list_position
    assert_equal 1, a.reload.list_position
  end

  def test_move_lower_on_the_last_item_is_a_noop
    a = Task.create!(title: 'a')
    Task.create!(title: 'b')
    b2 = Task.find_by!(title: 'b')
    b2.move_lower
    assert_equal 2, b2.list_position
    assert_equal 1, a.reload.list_position
  end

  def test_move_higher_on_the_first_item_is_a_noop
    a = Task.create!(title: 'a')
    Task.create!(title: 'b')
    a.move_higher
    assert_equal 1, a.list_position
  end

  def test_first_and_last_in_list_predicates
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    c = Task.create!(title: 'c')
    assert a.first_in_list?
    refute a.last_in_list?
    assert c.last_in_list?
    refute c.first_in_list?
    refute b.first_in_list?
    refute b.last_in_list?
  end

  def test_move_to_top_and_move_to_bottom_reposition_and_shift_everyone_between
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    c = Task.create!(title: 'c')
    d = Task.create!(title: 'd')

    c.move_to_top
    assert_equal [1, 2, 3, 4], [c, a, b, d].map { |t| t.reload.list_position }

    a.reload.move_to_bottom
    assert_equal [1, 2, 3, 4], [c, b, d, a].map { |t| t.reload.list_position }
  end

  def test_insert_at_moves_an_item_to_an_arbitrary_middle_slot
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    c = Task.create!(title: 'c')
    d = Task.create!(title: 'd')

    d.insert_at(2)
    assert_equal [1, 2, 3, 4], [a, d, b, c].map { |t| t.reload.list_position }
  end

  def test_insert_at_on_a_record_that_is_not_persisted_raises
    task = Task.new(title: 'unsaved')
    assert_raises(Prism::Orm::RecordNotFound) { task.insert_at(1) }
  end

  def test_destroying_an_item_closes_the_gap_for_everyone_below_it
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    c = Task.create!(title: 'c')
    b.destroy
    assert_equal 1, a.reload.list_position
    assert_equal 2, c.reload.list_position
  end

  def test_soft_deleting_a_paranoid_item_also_closes_the_gap
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    c = Task.create!(title: 'c')
    b.destroy # paranoid: soft-delete, not a real row removal
    assert b.deleted?
    assert_equal 1, a.reload.list_position
    assert_equal 2, c.reload.list_position
  end

  def test_restoring_a_soft_deleted_item_reappends_it_to_the_bottom_not_its_old_slot
    a = Task.create!(title: 'a')
    b = Task.create!(title: 'b')
    c = Task.create!(title: 'c')
    b.destroy
    d = Task.create!(title: 'd')
    assert_equal [1, 2, 3], [a.reload, c.reload, d.reload].map(&:list_position)

    restored = Task.only_deleted.find_by!(title: 'b')
    restored.restore
    assert_equal 4, restored.list_position
    # nobody else collides with the reappended slot
    assert_equal [1, 2, 3, 4], [a.reload, c.reload, d.reload, restored.reload].map(&:list_position).sort
  end