feat(precise_amount): Add migration, model methods and serializer (#2516

)

## Context

For some customers some amounts are not enough precise as Lago convert
fees to `amount_cent`.

## Description

Add migration for columns for precise amount cents, add model methods
and serializer attributes.

app/models/fee.rb

@@ -31,6 +31,9 @@ class Fee < ApplicationRecord
   monetize :amount_cents
   monetize :taxes_amount_cents, with_model_currency: :currency
   monetize :total_amount_cents
+  monetize :precise_amount_cents, with_model_currency: :currency
+  monetize :taxes_precise_amount_cents, with_model_currency: :currency
+  monetize :precise_total_amount_cents
   monetize :unit_amount_cents, disable_validation: true, allow_nil: true, with_model_currency: :currency
 
   # TODO: Deprecate add_on type in the near future
@@ -132,11 +135,20 @@ def sub_total_excluding_taxes_amount_cents
     amount_cents - precise_coupons_amount_cents
   end
 
+  def sub_total_excluding_taxes_precise_amount_cents
+    precise_amount_cents - precise_coupons_amount_cents
+  end
+
   def total_amount_cents
     amount_cents + taxes_amount_cents
   end
   alias_method :total_amount_currency, :currency
 
+  def precise_total_amount_cents
+    precise_amount_cents + taxes_precise_amount_cents
+  end
+  alias_method :precise_total_amount_currency, :currency
+
   def creditable_amount_cents
     amount_cents - credit_note_items.sum(:amount_cents)
   end
@@ -175,12 +187,14 @@ def has_charge_filters?
 #  invoiceable_type                    :string
 #  pay_in_advance                      :boolean          default(FALSE), not null
 #  payment_status                      :integer          default("pending"), not null
+#  precise_amount_cents                :decimal(40, 15)  default(0.0), not null
 #  precise_coupons_amount_cents        :decimal(30, 5)   default(0.0), not null
 #  precise_unit_amount                 :decimal(30, 15)  default(0.0), not null
 #  properties                          :jsonb            not null
 #  refunded_at                         :datetime
 #  succeeded_at                        :datetime
 #  taxes_amount_cents                  :bigint           not null
+#  taxes_precise_amount_cents          :decimal(40, 15)  default(0.0), not null
 #  taxes_rate                          :float            default(0.0), not null
 #  total_aggregated_units              :decimal(, )
 #  unit_amount_cents                   :bigint           default(0), not null

app/models/fee/applied_tax.rb

@@ -15,17 +15,18 @@ class AppliedTax < ApplicationRecord
 #
 # Table name: fees_taxes
 #
-#  id              :uuid             not null, primary key
-#  amount_cents    :bigint           default(0), not null
-#  amount_currency :string           not null
-#  tax_code        :string           not null
-#  tax_description :string
-#  tax_name        :string           not null
-#  tax_rate        :float            default(0.0), not null
-#  created_at      :datetime         not null
-#  updated_at      :datetime         not null
-#  fee_id          :uuid             not null
-#  tax_id          :uuid
+#  id                   :uuid             not null, primary key
+#  amount_cents         :bigint           default(0), not null
+#  amount_currency      :string           not null
+#  precise_amount_cents :decimal(40, 15)  default(0.0), not null
+#  tax_code             :string           not null
+#  tax_description      :string
+#  tax_name             :string           not null
+#  tax_rate             :float            default(0.0), not null
+#  created_at           :datetime         not null
+#  updated_at           :datetime         not null
+#  fee_id               :uuid             not null
+#  tax_id               :uuid
 #
 # Indexes
 #

app/serializers/v1/fee_serializer.rb

@@ -3,6 +3,8 @@
 module V1
   class FeeSerializer < ModelSerializer
     def serialize
+      # subunit_to_unit = model.amount.currency.subunit_to_unit
+
       payload = {
         lago_id: model.id,
         lago_charge_filter_id: model.charge_filter_id,
@@ -29,7 +31,10 @@ def serialize
         invoiceable:,
         amount_cents: model.amount_cents,
         amount_currency: model.amount_currency,
+        # precise_amount: model.precise_amount_cents.fdiv(subunit_to_unit),
+        # precise_total_amount: model.precise_total_amount_cents.fdiv(subunit_to_unit),
         taxes_amount_cents: model.taxes_amount_cents,
+        # taxes_precise_amount: model.taxes_precise_amount_cents.fdiv(subunit_to_unit),
         taxes_rate: model.taxes_rate,
         total_amount_cents: model.total_amount_cents,
         total_amount_currency: model.amount_currency,

db/migrate/20240829093425_add_precise_amount_cents_columns.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class AddPreciseAmountCentsColumns < ActiveRecord::Migration[7.1]
+  def change
+    safety_assured do
+      change_table :fees, bulk: true do |t|
+        t.decimal :precise_amount_cents, precision: 40, scale: 15, default: '0.0', null: false
+        t.decimal :taxes_precise_amount_cents, precision: 40, scale: 15, default: '0.0', null: false
+      end
+
+      change_table :fees_taxes, bulk: true do |t|
+        t.decimal :precise_amount_cents, precision: 40, scale: 15, default: '0.0', null: false
+      end
+    end
+  end
+end

spec/factories/fees.rb

@@ -9,8 +9,10 @@
     subscription
 
     amount_cents { 200 }
+    precise_amount_cents { 200.0000000001 }
     amount_currency { 'EUR' }
     taxes_amount_cents { 2 }
+    taxes_precise_amount_cents { 2.0000000001 }
 
     invoiceable_type { 'Subscription' }
     invoiceable_id { subscription.id }

spec/models/fee_spec.rb

@@ -326,6 +326,26 @@
     it { expect(fee.total_amount_currency).to eq('EUR') }
   end
 
+  describe '#precise_total_amount_cents' do
+    subject(:method_call) { fee.precise_total_amount_cents }
+
+    let(:fee) { create(:fee, precise_amount_cents: 200.0000000123, taxes_precise_amount_cents: 20.00000000012) }
+
+    it 'returns sum of precise amount cents and taxes precise amount cents' do
+      expect(subject).to eq(220.00000001242)
+    end
+  end
+
+  describe '#sub_total_excluding_taxes_precise_amount_cents' do
+    subject(:method_call) { fee.sub_total_excluding_taxes_precise_amount_cents }
+
+    let(:fee) { create(:fee, precise_amount_cents: 200.00456000123, precise_coupons_amount_cents: 150.00123) }
+
+    it 'returns sub total minus coupons amount cents' do
+      expect(subject).to eq(50.00333000123)
+    end
+  end
+
   describe '#invoice_sorting_clause' do
     let(:charge) { create(:standard_charge, properties:) }
     let(:fee) { fee_model.new(charge:, fee_type: 'charge', grouped_by:) }

spec/serializers/v1/fee_serializer_spec.rb

@@ -36,6 +36,9 @@
         'taxes_rate' => fee.taxes_rate,
         'total_amount_cents' => fee.total_amount_cents,
         'total_amount_currency' => fee.amount_currency,
+        # 'precise_amount' => fee.precise_amount_cents.fdiv(100),
+        # 'taxes_precise_amount' => fee.taxes_precise_amount_cents.fdiv(100),
+        # 'precise_total_amount' => fee.precise_total_amount_cents.fdiv(100),
         'units' => fee.units.to_s,
         'precise_unit_amount' => fee.precise_unit_amount.to_s,
         'precise_coupons_amount_cents' => fee.precise_coupons_amount_cents.to_s,