Scary Reorder Service

scary_service.rb

module Services
  module Column
    class Reorder
      attr_reader :column_to_move, :column_before, :column_set

      def initialize(column_to_move_id, column_before_id = nil)
        @column_to_move = ::Column.find(column_to_move_id)
        @column_before  = ::Column.find(column_before_id) if column_before_id.present?
        @column_set     = @column_to_move.column_set
      end

      def reorder
        if column_before
          if column_before.position > column_to_move.position
            columns_to_reorder = column_set.columns.where('position <= ?', column_before.position)
                                     .where('position > ?', column_to_move.position)
                                     .where('id != ?', column_to_move)
                                     .pluck(:id)

            ActiveRecord::Base.transaction do
              column_to_move.update_attributes!(position: column_before.position)
              ::Column.where(id: columns_to_reorder).each do |column|
                column.update_attributes!(position: column.position - 1)
              end
            end
          else
            columns_to_reorder = column_set.columns.where('position > ?', column_before.try(:position) || 0)
                                     .where('position < ?', column_to_move.position)
                                     .where('id != ?', column_to_move)
                                     .pluck(:id)

            ActiveRecord::Base.transaction do
              column_to_move.update_attributes!(position: column_before.position + 1)
              ::Column.where(id: columns_to_reorder).each do |column|
                column.update_attributes!(position: column.position + 1)
              end
            end
          end
        else
          columns_to_reorder = column_set.columns.where('position >= ?', column_before.try(:position) || 0)
                                   .where('position < ?', column_to_move.position)
                                   .where('id != ?', column_to_move)
                                   .pluck(:id)

          ActiveRecord::Base.transaction do
            column_to_move.update_attributes!(position: 0)
            ::Column.where(id: columns_to_reorder).each do |column|
              column.update_attributes!(position: column.position + 1)
            end
          end
        end
      end
    end
  end
end

scary_service_spec.rb

require 'spec_helper'

describe Services::Column::Reorder do
  let(:user) { users(:jane) }
  let(:column_set) { create_column_set(user: user) }
  let!(:column0) { create_column(column_set: column_set, position: 0) }
  let!(:column1) { create_column(column_set: column_set, position: 1) }
  let!(:column2) { create_column(column_set: column_set, position: 2) }
  let!(:column3) { create_column(column_set: column_set, position: 3) }

  describe "moving a column to the top of the set" do
    let(:subject) { Services::Column::Reorder.new(column2.id, "") }

    it "does not move column3" do
      expect { subject.reorder }.to_not change { column3.reload.position }
    end

    it "moves column2 to position 0" do
      expect { subject.reorder }.to change { column2.reload.position }.from(2).to(0)
    end

    it "moves column0 down 1 position" do
      expect { subject.reorder }.to change { column0.reload.position }.from(0).to(1)
    end

    it "moves column1 down 1 position" do
      expect { subject.reorder }.to change { column1.reload.position }.from(1).to(2)
    end
  end

  describe "moving a column up within the set" do
    let(:subject) { Services::Column::Reorder.new(column2.id, column0.id) }

    it "does not move column3" do
      expect { subject.reorder }.to_not change { column3.reload.position }
    end

    it "moves column2 to position 1" do
      expect { subject.reorder }.to change { column2.reload.position }.from(2).to(1)
    end

    it "does not move column0" do
      expect { subject.reorder }.to_not change { column0.reload.position }
    end

    it "moves column1 down 1 position" do
      expect { subject.reorder }.to change { column1.reload.position }.from(1).to(2)
    end
  end

  describe "moving a column down within the set" do
    let(:subject) { Services::Column::Reorder.new(column1.id, column2.id) }

    it "does not move column3" do
      expect { subject.reorder }.to_not change { column3.reload.position }
    end

    it "moves column2 to position 1" do
      expect { subject.reorder }.to change { column2.reload.position }.from(2).to(1)
    end

    it "does not move column0" do
      expect { subject.reorder }.to_not change { column0.reload.position }
    end

    it "moves column1 to position 2" do
      expect { subject.reorder }.to change { column1.reload.position }.from(1).to(2)
    end
  end

  describe "moving a column to the bottom of the set" do
    let(:subject) { Services::Column::Reorder.new(column1.id, column3.id) }

    it "moves column3 to position 2" do
      expect { subject.reorder }.to change { column3.reload.position }.from(3).to(2)
    end

    it "moves column2 to position 1" do
      expect { subject.reorder }.to change { column2.reload.position }.from(2).to(1)
    end

    it "does not move column0" do
      expect { subject.reorder }.to_not change { column0.reload.position }
    end

    it "moves column1 to position 3" do
      expect { subject.reorder }.to change { column1.reload.position }.from(1).to(3)
    end
  end
end