An example of a terrible service object

bad_service.rb

class UserSubscriberService < ServiceBase
  def call(user:, subscription_plan_name:, discount_code:, cadence_months: 1)
    @user = user
    @subscription_plan = SubscriptionPlan.active.where(name: subscription_plan_name).take
    @discount = Discount.find_by(code: discount_code)

    if @subscription_plan.name == 'free'
      @user.subscriptions.create!(
        plan: @subscription_plan,
        cadence_months: cadence_months,
        payment_amount: 0.0
      )
      5.times { @user.free_credits.create! }
      WelcomeEmailMailer.welcome_to_free_plan(user).deliver_later
      @user.enter_ab_test('starter-upsell')

    elsif @subscription_plan.name == 'starter'
      @user.subscriptions.create!(
        plan: @subscription_plan,
        cadence_months: cadence_months,
        payment_amount: calculate_discount(@subscription_plan.amount, @discount)
      )
      50.times { @user.free_credits.create! }
      WelcomeEmailMailer.welcome_to_starter_plan(user).deliver_later
      @user.enter_ab_test('premium-upsell')

    elsif @subscription_plan.name == 'premium'
      @user.subscriptions.create!(
        plan: @subscription_plan,
        cadence_months: cadence_months,
        payment_amount: calculate_discount(@subscription_plan.amount, @discount)
      )
      250.times { @user.free_credits.create! }
      WelcomeEmailMailer.welcome_to_premium_plan(user).deliver_later
    end
    EventPublishing.event(
      name: 'subscription_created',
      user_id: @user.id,
      discount_code: discount_code
    )
  end

  private

  def calculate_discount(amount, discount)
    amount * Rational(discount.percentage, 100)
  end
end