Refactoring for drivy.engineering blog (Ruby 2.5)

## after.rb
class ConfirmOrder < Command
  def initialize(order, payment_token, notify: true)
    @order = order
    @payment_token = payment_token
    @notify = notify
  end

  validate do
    payment_token_must_be_valid
    payment_amount_must_match_sales_quote
  end

  perform do
    capture_payment!
    create_invoice_and_update_status
    send_notifications

  rescue Payment::CaptureError
    add_error(:payment_capture_error)
  end

  private

  def payment
    @payment ||= @order.payments.new(token: @payment_token)
  end

  def payment_token_must_be_valid
    add_error(:payment_token_invalid) unless payment.valid?
  end

  def payment_amount_must_match_sales_quote
    add_error(:payment_amount_mismatch) unless payment_amount_match_sales_quote?
  end

  def payment_amount_match_sales_quote?
    payment.amount == @order.sales_quote.amount &&
    payment.currency == @order.sales_quote.currency
  end

  def capture_payment!
    payment.save!
    payment.capture!
  end

  def create_invoice_and_update_status
    Order.transaction do
      create_invoice
      update_status
    end
  end

  def create_invoice
    invoice = @order.invoices.create!({
      amount: @order.sales_quote.amount,
      currency: @order.sales_quote.currency,
    })

    @order.sales_quote.items.find_each do |item|
      invoice.items.create!({
        product_id: item.product_id,
        quantity: item.quantity,
        unit_price: item.unit_price,
      })
    end
  end

  def update_order_status
    @order.update(status: :confirmed)
  end

  def send_notifications
    return unless @notify
    OrderMailer.preparation_details(@order).deliver_async
    OrderMailer.confirmation(@order).deliver_async
    OrderMailer.available_invoice(@order).deliver_async
  end
end

## before.rb
class ConfirmOrder < Command
  def initialize(order, payment_token, notify: true)
    @order = order
    @payment_token = payment_token
    @notify = notify
  end

  validate do
    payment = @order.payments.new(token: @payment_token)

    if !payment.valid?
      add_error(:payment_token_invalid)
    end

    if payment.amount != @order.sales_quote.amount || payment.currency != @order.sales_quote.currency
      add_error(:payment_amount_mismatch)
    end
  end

  perform do
    @order.payments.create!(token: @payment_token).capture!

    Order.transaction do
      invoice = @order.invoices.create!({
        amount: @order.sales_quote.amount,
        currency: @order.sales_quote.currency,
      })

      sales_quote.items.find_each do |item|
        invoice.items.create!({
          product_id: item.product_id,
          quantity: item.quantity,
          unit_price: item.unit_price,
        })
      end

      @order.update(status: :confirmed)
    end

    if @notify
      OrderMailer.preparation_details(@order).deliver_async
      OrderMailer.confirmation(@order).deliver_async
      OrderMailer.available_invoice(@order).deliver_async
    end

  rescue Payment::CaptureError => error
    add_error(:payment_capture_error)
  end
end