refactoring post

initial_implementation.rb

class ApplyProductStateOrder
  def initialize(status_change_order)
    @status_change_order = status_change_order
  end

  def call
    ActiveRecord::Base.transaction do
      state_change = update_product

      status_change_order.update_timestamps(state_change)

      status_change_order.save!
    end
  end

  private

  attr_reader :status_change_order

  def update_product
    product = status_change_order.product

    state_change = product_state_change

    unless state_change == :none
      product.send(state_change)
      product.save!
    end

    state_change
  end

  def product_state_change
    product = status_change_order.product

    if status_change_order.missed?
      Rails.logger.warn do
        "Not applying product state order #{status_change_order.id} because it has already ended."
      end

      return :none
    end

    transition = status_change_order.product_transition

    unless can_transition?(status_change_order.product, transition)
      Rails.logger.warn do
        "Cancelling product_state_order #{status_change_order.id}->#{status_change_order.order_type}. Current state is #{product.state}"
      end

      return :none
    end

    transition
  end

  def can_transition?(product, transition)
    product.aasm.may_fire_event?(transition)
  end
end

refactored_version.rb

class ApplyProductStateOrder
  def initialize(status_change_order)
    @status_change_order = status_change_order
  end

  def call
    with_valid_state_change do
      ActiveRecord::Base.transaction do
        product.send(transition)
        product.save!

        update_order(transition)
      end
    end
  end

  private

  attr_reader :status_change_order

  def with_valid_state_change
    if status_change_order.missed?
      Rails.logger.warn do
        "Not applying product state order #{status_change_order.id} because it has already ended."
      end
      update_order(:none) and return
    end

    unless can_transition?
      Rails.logger.warn do
        "Cancelling product_state_order #{status_change_order.id}->#{status_change_order.order_type}. Current state is #{product.state}"
      end
      update_order(:none) and return
    end

    yield
  end

  def update_order(state_change)
    status_change_order.update_timestamps(state_change)
    status_change_order.save!
  end

  def transition
    @transition ||= status_change_order.product_transition
  end

  def can_transition?
    product.aasm.may_fire_event?(transition)
  end

  def product
    status_change_order.product
  end
end