feat (plan-changes): Adjust boundaries upon subscription upgrade

app/models/subscription.rb

@@ -135,4 +135,20 @@ def display_name
   def invoice_name
     name.presence || plan.invoice_name
   end
+
+  # When upgrade, we want to bill one day less since date of the upgrade will be
+  # included in the first invoice for the new plan
+  def date_diff_with_timezone(from_datetime, to_datetime)
+    number_od_days = Utils::DatetimeService.date_diff_with_timezone(
+      from_datetime,
+      to_datetime,
+      customer.applicable_timezone,
+    )
+
+    return number_od_days unless terminated? && upgraded?
+
+    number_od_days -= 1
+
+    number_od_days.negative? ? 0 : number_od_days
+  end
 end

app/services/billable_metrics/prorated_aggregations/base_service.rb

@@ -102,11 +102,7 @@ def period_duration
       #       we want to bill the persisted metrics at prorata of the full period duration.
       #       ie: the number of day of the terminated period divided by number of days without termination
       def persisted_pro_rata
-        Utils::DatetimeService.date_diff_with_timezone(
-          from_datetime,
-          to_datetime,
-          subscription.customer.applicable_timezone,
-        ).fdiv(period_duration)
+        subscription.date_diff_with_timezone(from_datetime, to_datetime).fdiv(period_duration)
       end
 
       attr_accessor :options

app/services/billable_metrics/prorated_aggregations/sum_service.rb

@@ -139,11 +139,7 @@ def compute_event_aggregation
       def persisted_sum
         persisted_event_store_instante.prorated_sum(
           period_duration:,
-          persisted_duration: Utils::DatetimeService.date_diff_with_timezone(
-            from_datetime,
-            to_datetime,
-            subscription.customer.applicable_timezone,
-          ),
+          persisted_duration: subscription.date_diff_with_timezone(from_datetime, to_datetime),
         )
       end
 
@@ -180,11 +176,7 @@ def compute_grouped_event_aggregation
       def grouped_persisted_sums
         persisted_event_store_instante.grouped_prorated_sum(
           period_duration:,
-          persisted_duration: Utils::DatetimeService.date_diff_with_timezone(
-            from_datetime,
-            to_datetime,
-            subscription.customer.applicable_timezone,
-          ),
+          persisted_duration: subscription.date_diff_with_timezone(from_datetime, to_datetime),
         )
       end
     end

app/services/credit_notes/create_from_termination.rb

@@ -2,9 +2,10 @@
 
 module CreditNotes
   class CreateFromTermination < BaseService
-    def initialize(subscription:, reason: 'order_change')
+    def initialize(subscription:, reason: 'order_change', upgrade: false)
       @subscription = subscription
       @reason = reason
+      @upgrade = upgrade
 
       super
     end
@@ -37,7 +38,7 @@ def call
 
     private
 
-    attr_accessor :subscription, :reason
+    attr_accessor :subscription, :reason, :upgrade
 
     delegate :plan, :terminated_at, :customer, to: :subscription
 
@@ -70,6 +71,7 @@ def terminated_at_in_timezone
 
     def remaining_duration
       billed_from = terminated_at_in_timezone.end_of_day.utc.to_date
+      billed_from -= 1.day if upgrade
 
       if plan.has_trial? && subscription.trial_end_date >= billed_from
         billed_from = if subscription.trial_end_date > to_date
@@ -79,7 +81,9 @@ def remaining_duration
         end
       end
 
-      (to_date - billed_from).to_i
+      duration = (to_date - billed_from).to_i
+
+      duration.negative? ? 0 : duration
     end
 
     def creditable_amount_cents(item_amount)

app/services/fees/create_true_up_service.rb

@@ -39,11 +39,7 @@ def prorated_min_amount_cents
       # NOTE: number of days between beginning of the period and the termination date
       from_datetime = boundaries.charges_from_datetime.to_time
       to_datetime = boundaries.charges_to_datetime.to_time
-      number_of_day_to_bill = Utils::DatetimeService.date_diff_with_timezone(
-        from_datetime,
-        to_datetime,
-        subscription.customer.applicable_timezone,
-      )
+      number_of_day_to_bill = subscription.date_diff_with_timezone(from_datetime, to_datetime)
 
       date_service.charge_single_day_price(charge:) * number_of_day_to_bill
     end

app/services/fees/subscription_service.rb

@@ -181,11 +181,7 @@ def terminated_amount
       end
 
       # NOTE: number of days between beginning of the period and the termination date
-      number_of_day_to_bill = Utils::DatetimeService.date_diff_with_timezone(
-        from_datetime,
-        to_datetime,
-        customer.applicable_timezone,
-      )
+      number_of_day_to_bill = subscription.date_diff_with_timezone(from_datetime, to_datetime)
 
       # Remove later customer timezone fix while passing optional_from_date
       # single_day_price method should return correct amount even without the timezone fix since

app/services/subscriptions/create_service.rb

@@ -148,7 +148,7 @@ def upgrade_subscription
 
       # NOTE: When upgrading, the new subscription becomes active immediatly
       #       The previous one must be terminated
-      Subscriptions::TerminateService.call(subscription: current_subscription)
+      Subscriptions::TerminateService.call(subscription: current_subscription, upgrade: true)
 
       new_subscription.mark_as_active!
       perform_later(job_class: SendWebhookJob, arguments: ['subscription.started', new_subscription])

app/services/subscriptions/terminate_service.rb

@@ -2,9 +2,10 @@
 
 module Subscriptions
   class TerminateService < BaseService
-    def initialize(subscription:, async: true)
+    def initialize(subscription:, async: true, upgrade: false)
       @subscription = subscription
       @async = async
+      @upgrade = upgrade
 
       super
     end
@@ -25,6 +26,7 @@ def call
           credit_note_result = CreditNotes::CreateFromTermination.new(
             subscription:,
             reason: 'order_cancellation',
+            upgrade:,
           ).call
           credit_note_result.raise_if_error!
         end
@@ -76,7 +78,7 @@ def terminate_and_start_next(timestamp:)
 
     private
 
-    attr_reader :subscription, :async
+    attr_reader :subscription, :async, :upgrade
 
     def bill_subscription
       if async

spec/models/subscription_spec.rb

@@ -396,4 +396,50 @@
       end
     end
   end
+
+  describe '.date_diff_with_timezone' do
+    let(:from_datetime) { Time.zone.parse('2023-08-31T23:10:00') }
+    let(:to_datetime) { Time.zone.parse('2023-09-30T22:59:59') }
+    let(:customer) { create(:customer, timezone:) }
+    let(:terminated_at) { nil }
+    let(:timezone) { 'Europe/Paris' }
+
+    let(:subscription) do
+      create(
+        :subscription,
+        plan:,
+        customer:,
+        terminated_at:,
+      )
+    end
+
+    let(:result) do
+      subscription.date_diff_with_timezone(from_datetime, to_datetime)
+    end
+
+    it 'returns the number of days between the two datetime' do
+      expect(result).to eq(30)
+    end
+
+    context 'with terminated and upgraded subscription' do
+      let(:terminated_at) { Time.zone.parse('2023-09-30T22:59:59') }
+      let(:new_subscription) do
+        create(
+          :subscription,
+          plan:,
+          customer:,
+          previous_subscription_id: subscription.id,
+        )
+      end
+
+      before do
+        subscription.terminated!
+        new_subscription
+      end
+
+      it 'takes the daylight saving time into account' do
+        expect(result).to eq(29)
+      end
+    end
+  end
 end

spec/scenarios/charge_models/prorated_graduated_spec.rb

@@ -566,7 +566,7 @@
 
           subscription = customer.subscriptions.first
 
-          travel_to(DateTime.new(2023, 10, 18)) do
+          travel_to(DateTime.new(2023, 10, 18, 5, 20)) do
             create(
               :graduated_charge,
               billable_metric:,
@@ -608,7 +608,7 @@
 
             invoice = subscription.invoices.order(created_at: :desc).first
             expect(invoice.fees.charge_kind.count).to eq(1)
-            # 30226 (17 / 31 * 75 units) + 2.58 = 2 / 31 * 20 units (prorated event in termination period)
+            # 30226 (17 / 31 * 75 units) + 2.58 (2 / 31 * 20 units - prorated event in termination period)
             expect(invoice.total_amount_cents).to eq(27_323)
           end