handle derivation of values around buyers living in the property

- derive values where appropriate
- clear these values when the derived state no longer holds
- update the routing for pages holding questions about whether particular buyers will live in the property to reflect when they are derived
- test the deriving and associated clearing of values
- update tests on page routing and sales log factory

app/models/derived_variables/sales_log_variables.rb

@@ -30,6 +30,17 @@ module DerivedVariables::SalesLogVariables
       self.uprn = nil
       self.uprn_known = 0
     end
+
+    if buyers_will_not_live_in?
+      self.buy1livein = 2
+      if joint_purchase?
+        self.buy2livein = 2
+      end
+    end
+
+    if buyers_will_live_in? && not_joint_purchase?
+      self.buy1livein = 1
+    end
   end
 
 private

app/models/form/sales/pages/buyer1_live_in_property.rb

@@ -5,9 +5,21 @@ class Form::Sales::Pages::Buyer1LiveInProperty < ::Form::Page
     @depends_on = [
       {
         "buyer_has_seen_privacy_notice?" => true,
+        "outright_sale?" => false,
       },
       {
         "buyer_not_interviewed?" => true,
+        "outright_sale?" => false,
+      },
+      {
+        "buyer_has_seen_privacy_notice?" => true,
+        "joint_purchase?" => true,
+        "buyers_will_live_in?" => true,
+      },
+      {
+        "buyer_not_interviewed?" => true,
+        "joint_purchase?" => true,
+        "buyers_will_live_in?" => true,
       },
     ]
   end

app/models/form/sales/pages/buyer2_live_in_property.rb

@@ -4,12 +4,24 @@ class Form::Sales::Pages::Buyer2LiveInProperty < ::Form::Page
     @id = "buyer_2_live_in_property"
     @depends_on = [
       {
-        "joint_purchase?" => true,
         "buyer_has_seen_privacy_notice?" => true,
+        "outright_sale?" => false,
+        "joint_purchase?" => true,
+      },
+      {
+        "buyer_not_interviewed?" => true,
+        "outright_sale?" => false,
+        "joint_purchase?" => true,
       },
       {
+        "buyer_has_seen_privacy_notice?" => true,
         "joint_purchase?" => true,
+        "buyers_will_live_in?" => true,
+      },
+      {
         "buyer_not_interviewed?" => true,
+        "joint_purchase?" => true,
+        "buyers_will_live_in?" => true,
       },
     ]
   end

app/models/sales_log.rb

@@ -368,12 +368,48 @@ class SalesLog < Log
 
   def ownership_scheme
     case ownershipsch
-    when 1
-      "shared ownership"
-    when 2
-      "discounted ownership"
-    when 3
-      "outright sale"
+    when 1 then "shared ownership"
+    when 2 then "discounted ownership"
+    when 3 then "outright sale"
+    end
+  end
+
+private
+
+  def reset_invalidated_dependent_fields!
+    super
+
+    reset_derived_questions!
+  end
+
+  def reset_derived_questions!
+    dependencies = [
+      {
+        parent_conditions: [
+          { attribute: :buylivein, value: 2 },
+        ],
+        derived_attributes: %i[buy1livein buy2livein],
+      },
+      {
+        parent_conditions: [
+          { attribute: :buylivein, value: 1 },
+          { attribute: :jointpur, value: 1 },
+        ],
+        derived_attributes: [:buy1livein],
+      },
+    ]
+
+    dependencies.each do |dependency|
+      any_parent_attributes_changed = dependency[:parent_conditions].any? { |parent_condition| send("#{parent_condition[:attribute]}_changed?") }
+      next unless any_parent_attributes_changed
+
+      were_in_derived_state = dependency[:parent_conditions].all? { |parent_condition| send("#{parent_condition[:attribute]}_was") == parent_condition[:value] }
+      next unless were_in_derived_state
+
+      dependency[:derived_attributes].each do |derived_attribute|
+        Rails.logger.debug("Cleared derived #{derived_attribute} value")
+        send("#{derived_attribute}=", nil)
+      end
     end
   end
 end

spec/models/form/sales/pages/buyer1_live_in_property_spec.rb

@@ -28,6 +28,25 @@ RSpec.describe Form::Sales::Pages::Buyer1LiveInProperty, type: :model do
   end
 
   it "has correct depends_on" do
-    expect(page.depends_on).to eq([{ "buyer_has_seen_privacy_notice?" => true }, { "buyer_not_interviewed?" => true }])
+    expect(page.depends_on).to eq([
+      {
+        "buyer_has_seen_privacy_notice?" => true,
+        "outright_sale?" => false,
+      },
+      {
+        "buyer_not_interviewed?" => true,
+        "outright_sale?" => false,
+      },
+      {
+        "buyer_has_seen_privacy_notice?" => true,
+        "joint_purchase?" => true,
+        "buyers_will_live_in?" => true,
+      },
+      {
+        "buyer_not_interviewed?" => true,
+        "joint_purchase?" => true,
+        "buyers_will_live_in?" => true,
+      },
+    ])
   end
 end

spec/models/form/sales/pages/buyer2_live_in_property_spec.rb

@@ -30,12 +30,24 @@ RSpec.describe Form::Sales::Pages::Buyer2LiveInProperty, type: :model do
   it "has correct depends_on" do
     expect(page.depends_on).to eq([
       {
-        "joint_purchase?" => true,
         "buyer_has_seen_privacy_notice?" => true,
+        "outright_sale?" => false,
+        "joint_purchase?" => true,
+      },
+      {
+        "buyer_not_interviewed?" => true,
+        "outright_sale?" => false,
+        "joint_purchase?" => true,
       },
       {
+        "buyer_has_seen_privacy_notice?" => true,
         "joint_purchase?" => true,
+        "buyers_will_live_in?" => true,
+      },
+      {
         "buyer_not_interviewed?" => true,
+        "joint_purchase?" => true,
+        "buyers_will_live_in?" => true,
       },
     ])
   end

spec/models/sales_log_spec.rb

@@ -220,6 +220,61 @@ RSpec.describe SalesLog, type: :model do
       record_from_db = ActiveRecord::Base.connection.execute("select mortgage from sales_logs where id=#{sales_log.id}").to_a[0]
       expect(record_from_db["mortgage"]).to eq(0.0)
     end
+
+    context "when outright sale and buyers will live in the property" do
+      let(:sales_log) { create(:sales_log, :outright_sale_setup_complete, buylivein: 1, jointpur:) }
+
+      context "and the sale is not a joint purchase" do
+        let(:jointpur) { 2 }
+
+        it "derives that buyer 1 will live in the property" do
+          expect(sales_log.buy1livein).to be 1
+        end
+
+        it "does not derive a value for whether buyer 2 will live in the property" do
+          expect(sales_log.buy2livein).to be nil
+        end
+
+        it "clears that buyer 1 will live in the property if joint purchase is updated" do
+          sales_log.update!(jointpur: 1)
+          expect(sales_log.buy1livein).to be nil
+        end
+      end
+
+      context "and the sale is a joint purchase" do
+        let(:jointpur) { 1 }
+
+        it "does not derive values for whether buyer 1 or buyer 2 will live in the property" do
+          expect(sales_log.buy1livein).to be nil
+          expect(sales_log.buy2livein).to be nil
+        end
+      end
+    end
+
+    context "when outright sale and buyers will not live in the property" do
+      let(:sales_log) { create(:sales_log, :outright_sale_setup_complete, buylivein: 2, jointpur:) }
+
+      context "and the sale is not a joint purchase" do
+        let(:jointpur) { 2 }
+
+        it "derives that buyer 1 will not live in the property" do
+          expect(sales_log.buy1livein).to be 2
+        end
+
+        it "does not derive a value for whether buyer 2 will live in the property" do
+          expect(sales_log.buy2livein).to be nil
+        end
+      end
+
+      context "and the sale is a joint purchase" do
+        let(:jointpur) { 1 }
+
+        it "derives that neither buyer 1 nor buyer 2 will live in the property" do
+          expect(sales_log.buy1livein).to be 2
+          expect(sales_log.buy2livein).to be 2
+        end
+      end
+    end
   end
 
   context "when saving addresses" do

spec/models/validations/sales/household_validations_spec.rb

@@ -203,7 +203,7 @@ RSpec.describe Validations::Sales::HouseholdValidations do
   end
 
   describe "validating fields about buyers living in the property" do
-    let(:sales_log) { FactoryBot.create(:sales_log, :outright_sale, noint: 1, companybuy: 2, buylivein:, jointpur:, jointmore:, buy1livein:) }
+    let(:sales_log) { FactoryBot.create(:sales_log, :outright_sale_setup_complete, noint: 1, companybuy: 2, buylivein:, jointpur:, jointmore:, buy1livein:) }
 
     context "when buyers will live in the property and the sale is a joint purchase" do
       let(:buylivein) { 1 }