feat(credit-note): Add estimate route before creation

lib/lago/api/resources/credit_note.rb

@@ -57,6 +57,25 @@ def void(credit_note_id)
 
           JSON.parse(response.to_json, object_class: OpenStruct).credit_note
         end
+
+        def estimate(params)
+          uri = URI("#{client.base_api_url}#{api_resource}/estimate")
+
+          payload = whitelist_estimate_params(params)
+          response = connection.post(payload, uri)['estimated_credit_note']
+
+          JSON.parse(response.to_json, object_class: OpenStruct)
+        end
+
+        def whitelist_estimate_params(params)
+          result_hash = { invoice_id: params[:invoice_id] }.compact
+
+          whitelist_items(params[:items] || []).tap do |items|
+            result_hash[:items] = items unless items.empty?
+          end
+
+          { root_name => result_hash }
+        end
       end
     end
   end

spec/factories/credit_note.rb

@@ -15,4 +15,9 @@
   factory :update_credit_note, class: OpenStruct do
     refund_status { 'pending' }
   end
+
+  factory :estimate_credit_note, class: OpenStruct do
+    invoice_id { '1a901a90-1a90-1a90-1a90-1a901a901a90' }
+    items { build_list(:create_credit_note_item, 2).map(&:to_h) }
+  end
 end

spec/fixtures/api/credit_note.json

@@ -16,7 +16,7 @@
     "taxes_amount_cents": 40,
     "taxes_rate": "20.0",
     "sub_total_excluding_taxes_amount_cents": 200,
-    "coupons_adjustement_amount_cents": 0,
+    "coupons_adjustment_amount_cents": 0,
     "created_at": "2022-10-04 16:21:00",
     "updated_at": "2022-10-04 16:21:00",
     "items": [

spec/fixtures/api/credit_note_estimated.json

@@ -0,0 +1,19 @@
+{
+  "estimated_credit_note": {
+    "lago_invoice_id": "1a901a90-1a90-1a90-1a90-1a901a901a90",
+    "invoice_number": "LAG15",
+    "currency": "EUR",
+    "max_creditable_amount_cents": 100,
+    "max_refundable_amount_cents": 100,
+    "taxes_amount_cents": 40,
+    "taxes_rate": "20.0",
+    "sub_total_excluding_taxes_amount_cents": 200,
+    "coupons_adjustment_amount_cents": 0,
+    "items": [
+      {
+        "lago_fee_id": "1a901a90-1a90-1a90-1a90-1a901a901a90",
+        "amount_cents": 100
+      }
+    ]
+  }
+}

spec/lago/api/resources/credit_note_spec.rb

@@ -167,4 +167,21 @@
       expect(response.lago_id).to eq(credit_note_id)
     end
   end
+
+  describe '#estimate' do
+    let(:estimate_response) { load_fixture(:credit_note_estimated) }
+    let(:params) { create(:estimate_credit_note) }
+
+    before do
+      stub_request(:post, "https://api.getlago.com/api/v1/credit_notes/estimate")
+        .with(body: { credit_note: params.to_h })
+        .to_return(body: estimate_response, status: 200)
+    end
+
+    it 'returns an estimated credit_note' do
+      response = resource.estimate(params)
+
+      expect(response.sub_total_excluding_taxes_amount_cents).to eq(200)
+    end
+  end
 end