disable checkboxes for rent periods if they are in use so that users are not able to make existing logs invalid

hint text added to the question to explain this
I have also added all rent periods to a hidden field to remove the need to fetch them again form the db in the update method

app/controllers/organisations_controller.rb

@@ -79,7 +79,7 @@ class OrganisationsController < ApplicationController
   end
 
   def create
-    selected_rent_periods = rent_period_params
+    selected_rent_periods = rent_period_params[:rent_periods].compact_blank
     @organisation = Organisation.new(org_params)
     if @organisation.save
       OrganisationRentPeriod.transaction do
@@ -96,6 +96,7 @@ class OrganisationsController < ApplicationController
   def edit
     if current_user.data_coordinator? || current_user.support?
       current_allowed_rent_periods = @organisation.organisation_rent_periods.pluck(:rent_period).map(&:to_s)
+      @used_rent_periods = @organisation.lettings_logs.pluck(:period).uniq.compact.map(&:to_s)
       @rent_periods = helpers.rent_periods_with_checked_attr(checked_periods: current_allowed_rent_periods)
       render "edit", layout: "application"
     else
@@ -116,7 +117,7 @@ class OrganisationsController < ApplicationController
   end
 
   def update
-    selected_rent_periods = rent_period_params
+    selected_rent_periods = rent_period_params[:rent_periods].compact_blank
     if (current_user.data_coordinator? && org_params[:active].nil?) || current_user.support?
       if @organisation.update(org_params)
         case org_params[:active]
@@ -135,11 +136,9 @@ class OrganisationsController < ApplicationController
         else
           flash[:notice] = I18n.t("organisation.updated")
         end
-        existing_rent_periods = @organisation.organisation_rent_periods.pluck(:rent_period)
+        rent_periods_to_delete = rent_period_params[:all_rent_periods] - selected_rent_periods
-        rent_periods_to_create = selected_rent_periods.map(&:to_i) - existing_rent_periods
-        rent_periods_to_delete = existing_rent_periods - selected_rent_periods.map(&:to_i)
         OrganisationRentPeriod.transaction do
-          rent_periods_to_create.each { |period| OrganisationRentPeriod.create!(organisation: @organisation, rent_period: period) }
+          selected_rent_periods.each { |period| OrganisationRentPeriod.create(organisation: @organisation, rent_period: period) }
           OrganisationRentPeriod.where(organisation: @organisation, rent_period: rent_periods_to_delete).destroy_all
         end
         redirect_to details_organisation_path(@organisation)
@@ -294,7 +293,7 @@ private
   end
 
   def rent_period_params
-    params.require(:organisation).permit(rent_periods: [])[:rent_periods].compact_blank
+    params.require(:organisation).permit(rent_periods: [], all_rent_periods: [])
   end
 
   def codes_only_export?

app/views/organisations/edit.html.erb

@@ -34,15 +34,21 @@
         width: 20 %>
 
       <%= f.govuk_check_boxes_fieldset :rent_periods,
-        legend: { text: "What are the rent periods for the organisation?" } do %>
+        legend: { text: "What are the rent periods for the organisation?" },
+        hint: { text: "It is not possible to deselect rent periods that are used in logs" } do %>
         <% @rent_periods.map do |key, period| %>
           <%= f.govuk_check_box :rent_periods,
             key,
             label: { text: period["value"] },
-            checked: period[:checked] %>
+            checked: period[:checked],
+            disabled: @used_rent_periods.include?(key) %>
         <% end %>
       <% end %>
 
+      <% @rent_periods.keys.each do |period_key| %>
+        <%= f.hidden_field :all_rent_periods, value: period_key, multiple: true %>
+      <% end %>
+
       <%= f.govuk_submit "Save changes" %>
     </div>
   </div>

spec/requests/OrganisationsController/organisations_controller_rent_periods_spec.rb

@@ -91,6 +91,7 @@ RSpec.describe OrganisationsController, type: :request do
         "organisation": {
           name: organisation.name,
           rent_periods: [initially_unchecked_rent_period_id],
+          all_rent_periods: [initially_unchecked_rent_period_id, initially_checked_rent_period_id],
         },
       }
     end

spec/requests/organisations_controller_spec.rb

@@ -8,7 +8,7 @@ RSpec.describe OrganisationsController, type: :request do
   let(:user) { create(:user, :data_coordinator) }
   let(:new_value) { "Test Name 35" }
   let(:active) { nil }
-  let(:params) { { id: organisation.id, organisation: { name: new_value, active:, rent_periods: [] } } }
+  let(:params) { { id: organisation.id, organisation: { name: new_value, active:, rent_periods: [], all_rent_periods: [] } } }
 
   before do
     Timecop.freeze(Time.zone.local(2024, 3, 1))
@@ -1426,7 +1426,7 @@ RSpec.describe OrganisationsController, type: :request do
       end
 
       describe "#update" do
-        let(:params) { { id: organisation.id, organisation: { active:, rent_periods: [] } } }
+        let(:params) { { id: organisation.id, organisation: { active:, rent_periods: [], all_rent_periods: [] } } }
 
         context "with active parameter false" do
           let(:active) { false }