Add duplicate sets scope to locations

app/models/location.rb

@@ -121,6 +121,19 @@ class Location < ApplicationRecord
 
   scope :visible, -> { where(discarded_at: nil) }
 
+  scope :duplicate_sets, lambda {
+    scope = visible
+    .group(*DUPLICATE_LOCATION_ATTRIBUTES)
+    .where.not(scheme_id: nil)
+    .where.not(postcode: nil)
+    .where.not(mobility_type: nil)
+    .having(
+      "COUNT(*) > 1",
+    )
+    scope.pluck("ARRAY_AGG(id)")
+  }
+
+  DUPLICATE_LOCATION_ATTRIBUTES = %w[scheme_id postcode mobility_type].freeze
   LOCAL_AUTHORITIES = LocalAuthority.all.map { |la| [la.name, la.code] }.to_h
 
   enum local_authorities: LOCAL_AUTHORITIES

spec/models/location_spec.rb

@@ -831,6 +831,71 @@ RSpec.describe Location, type: :model do
         expect(described_class.active.count).to eq(2)
       end
     end
+
+    context "when getting list of duplicate locations" do
+      let!(:scheme) { create(:scheme) }
+      let!(:location) { create(:location, postcode: "AB1 2CD", mobility_type: "M", scheme:) }
+      let!(:duplicate_location) { create(:location, postcode: "AB1 2CD", mobility_type: "M", scheme:) }
+      let(:duplicate_sets) { described_class.duplicate_sets }
+
+      it "returns a list of duplicates for the same scheme" do
+        expect(duplicate_sets.count).to eq(1)
+        expect(duplicate_sets.first).to contain_exactly(location.id, duplicate_location.id)
+      end
+
+      context "when there is a deleted duplicate location" do
+        before do
+          create(:location, postcode: "AB1 2CD", mobility_type: "M", discarded_at: Time.zone.now, scheme:)
+        end
+
+        it "does not return the deleted location as a duplicate" do
+          expect(duplicate_sets.count).to eq(1)
+          expect(duplicate_sets.first).to contain_exactly(location.id, duplicate_location.id)
+        end
+      end
+
+      context "when there is a location with a different postcode" do
+        before do
+          create(:location, postcode: "A1 1AB", mobility_type: "M", scheme:)
+        end
+
+        it "does not return a location with a different postcode as a duplicate" do
+          expect(duplicate_sets.count).to eq(1)
+          expect(duplicate_sets.first).to contain_exactly(location.id, duplicate_location.id)
+        end
+      end
+
+      context "when there is a location with a different mobility_type" do
+        before do
+          create(:location, postcode: "AB1 2CD", mobility_type: "A", scheme:)
+        end
+
+        it "does not return a location with a different mobility_type as a duplicate" do
+          expect(duplicate_sets.count).to eq(1)
+          expect(duplicate_sets.first).to contain_exactly(location.id, duplicate_location.id)
+        end
+      end
+
+      context "when there is a location with a different scheme" do
+        before do
+          create(:location, postcode: "AB1 2CD", mobility_type: "M")
+        end
+
+        it "does not return a location with a different scheme as a duplicate" do
+          expect(duplicate_sets.count).to eq(1)
+          expect(duplicate_sets.first).to contain_exactly(location.id, duplicate_location.id)
+        end
+      end
+
+      context "when there is a location with nil values for duplicate check fields" do
+        let!(:location) { build(:location, postcode: nil, mobility_type: nil, scheme:).save(validate: false) }
+        let!(:duplicate_location) { build(:location, postcode: nil, mobility_type: nil, scheme:).save(validate: false) }
+
+        it "does not return a location with nil values as a duplicate" do
+          expect(duplicate_sets).to be_empty
+        end
+      end
+    end
   end
 
   describe "status" do