Implement Credits::ProgressiveBillingService and add it to Invoices::…

…CalculateFeesService (#2443)

## Context

AI companies want their users to pay before the end of a period if usage
skyrockets. The problem being that self-serve companies can overuse
their API without paying, triggering lots of costs on their side.

## Description

Adds a service for calculating how much to deduct from the subscription
invoice based on previously billed progressive invoices.

app/models/invoice.rb

@@ -403,42 +403,43 @@ def status_changed_to_finalized?
 #
 # Table name: invoices
 #
-#  id                                     :uuid             not null, primary key
-#  coupons_amount_cents                   :bigint           default(0), not null
-#  credit_notes_amount_cents              :bigint           default(0), not null
-#  currency                               :string
-#  fees_amount_cents                      :bigint           default(0), not null
-#  file                                   :string
-#  invoice_type                           :integer          default("subscription"), not null
-#  issuing_date                           :date
-#  negative_amount_cents                  :bigint           default(0), not null
-#  net_payment_term                       :integer          default(0), not null
-#  number                                 :string           default(""), not null
-#  payment_attempts                       :integer          default(0), not null
-#  payment_dispute_lost_at                :datetime
-#  payment_due_date                       :date
-#  payment_overdue                        :boolean          default(FALSE)
-#  payment_status                         :integer          default("pending"), not null
-#  prepaid_credit_amount_cents            :bigint           default(0), not null
-#  ready_for_payment_processing           :boolean          default(TRUE), not null
-#  ready_to_be_refreshed                  :boolean          default(FALSE), not null
-#  skip_charges                           :boolean          default(FALSE), not null
-#  status                                 :integer          default("finalized"), not null
-#  sub_total_excluding_taxes_amount_cents :bigint           default(0), not null
-#  sub_total_including_taxes_amount_cents :bigint           default(0), not null
-#  taxes_amount_cents                     :bigint           default(0), not null
-#  taxes_rate                             :float            default(0.0), not null
-#  timezone                               :string           default("UTC"), not null
-#  total_amount_cents                     :bigint           default(0), not null
-#  version_number                         :integer          default(4), not null
-#  voided_at                              :datetime
-#  created_at                             :datetime         not null
-#  updated_at                             :datetime         not null
-#  customer_id                            :uuid
-#  organization_id                        :uuid             not null
-#  organization_sequential_id             :integer          default(0), not null
-#  payable_group_id                       :uuid
-#  sequential_id                          :integer
+#  id                                      :uuid             not null, primary key
+#  coupons_amount_cents                    :bigint           default(0), not null
+#  credit_notes_amount_cents               :bigint           default(0), not null
+#  currency                                :string
+#  fees_amount_cents                       :bigint           default(0), not null
+#  file                                    :string
+#  invoice_type                            :integer          default("subscription"), not null
+#  issuing_date                            :date
+#  negative_amount_cents                   :bigint           default(0), not null
+#  net_payment_term                        :integer          default(0), not null
+#  number                                  :string           default(""), not null
+#  payment_attempts                        :integer          default(0), not null
+#  payment_dispute_lost_at                 :datetime
+#  payment_due_date                        :date
+#  payment_overdue                         :boolean          default(FALSE)
+#  payment_status                          :integer          default("pending"), not null
+#  prepaid_credit_amount_cents             :bigint           default(0), not null
+#  progressive_billing_credit_amount_cents :bigint           default(0), not null
+#  ready_for_payment_processing            :boolean          default(TRUE), not null
+#  ready_to_be_refreshed                   :boolean          default(FALSE), not null
+#  skip_charges                            :boolean          default(FALSE), not null
+#  status                                  :integer          default("finalized"), not null
+#  sub_total_excluding_taxes_amount_cents  :bigint           default(0), not null
+#  sub_total_including_taxes_amount_cents  :bigint           default(0), not null
+#  taxes_amount_cents                      :bigint           default(0), not null
+#  taxes_rate                              :float            default(0.0), not null
+#  timezone                                :string           default("UTC"), not null
+#  total_amount_cents                      :bigint           default(0), not null
+#  version_number                          :integer          default(4), not null
+#  voided_at                               :datetime
+#  created_at                              :datetime         not null
+#  updated_at                              :datetime         not null
+#  customer_id                             :uuid
+#  organization_id                         :uuid             not null
+#  organization_sequential_id              :integer          default(0), not null
+#  payable_group_id                        :uuid
+#  sequential_id                           :integer
 #
 # Indexes
 #

app/services/credits/progressive_billing_service.rb

@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+module Credits
+  class ProgressiveBillingService < BaseService
+    def initialize(invoice:)
+      @invoice = invoice
+      super
+    end
+
+    def call
+      result.credits = []
+      return result unless should_create_progressive_billing_credit?
+
+      invoice.invoice_subscriptions.each do |invoice_subscription|
+        subscription = invoice_subscription.subscription
+        progressive_billing_invoices = subscription
+          .invoices
+          .progressive_billing
+          .finalized
+          .where(issuing_date: invoice_subscription.charges_from_datetime...invoice_subscription.charges_to_datetime)
+          .order(issuing_date: :asc)
+
+        total_subscription_amount = invoice.fees.charge.where(subscription: subscription).sum(:amount_cents)
+
+        remaining_to_credit = total_subscription_amount
+
+        progressive_billing_invoices.each do |progressive_billing_invoice|
+          amount_to_credit = progressive_billing_invoice.fees.progressive_billing.sum(:amount_cents)
+
+          if amount_to_credit > remaining_to_credit
+            # TODO: create credit note for (amount_to_credit - remaining_credit)
+            invoice.negative_amount_cents -= (amount_to_credit - remaining_to_credit)
+            amount_to_credit = remaining_to_credit
+          end
+
+          if amount_to_credit.positive?
+            credit = Credit.create!(
+              invoice:,
+              progressive_billing_invoice:,
+              amount_cents: amount_to_credit,
+              amount_currency: invoice.currency,
+              before_taxes: true
+            )
+
+            invoice.sub_total_excluding_taxes_amount_cents -= credit.amount_cents
+            invoice.progressive_billing_credit_amount_cents += credit.amount_cents
+            result.credits << credit
+
+            remaining_to_credit -= amount_to_credit
+          end
+        end
+      end
+      result
+    end
+
+    private
+
+    def should_create_progressive_billing_credit?
+      invoice.invoice_subscriptions.any? do |invoice_subscription|
+        invoice_subscription.subscription.invoices.progressive_billing
+          .finalized
+          .where(issuing_date: invoice_subscription.charges_from_datetime...invoice_subscription.charges_to_datetime)
+          .exists?
+      end
+    end
+
+    attr_reader :invoice
+  end
+end

app/services/invoices/calculate_fees_service.rb

@@ -44,6 +44,7 @@ def call
         invoice.sub_total_excluding_taxes_amount_cents = invoice.fees.sum(:amount_cents) -
           invoice.coupons_amount_cents
 
+        Credits::ProgressiveBillingService.call(invoice:)
         Credits::AppliedCouponsService.call(invoice:) if should_create_coupon_credit?
         Invoices::ComputeAmountsFromFees.call(invoice:)
 

app/services/lifetime_usages/recalculate_and_check_service.rb

@@ -16,8 +16,10 @@ def call
         usage_thresholds.each do |usage_threshold|
           SendWebhookJob.perform_later('subscription.usage_threshold_reached', subscription, usage_threshold:)
         end
-        Invoices::ProgressiveBillingService.call(usage_thresholds:, lifetime_usage:).raise_if_error!
+        invoice_result = Invoices::ProgressiveBillingService.call(usage_thresholds:, lifetime_usage:).raise_if_error!
+        result.invoice = invoice_result.invoice
       end
+      result
     end
 
     private

db/migrate/20240820125840_add_progressive_billing_credit_amount_cents_to_invoices.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddProgressiveBillingCreditAmountCentsToInvoices < ActiveRecord::Migration[7.1]
+  def change
+    add_column :invoices, :progressive_billing_credit_amount_cents, :bigint, default: 0, null: false
+  end
+end