Allow moderators to start anonymising as specified

app/models/parliament.rb

@@ -27,6 +27,10 @@ def current
       where(archived_at: nil).order(created_at: :asc)
     end
 
+    def previous(opening_at)
+      where(opening_at: ...opening_at).order(opening_at: :desc).first
+    end
+
     def government
       instance.government
     end
@@ -198,8 +202,10 @@ def defaults
   validate on: :anonymize_petitions do
     errors.add(:opening_at, :blank) unless opening_at?
 
-    if opening_at?
-      errors.add(:opening_at, :too_soon) unless opening_at < 6.months.ago
+    if previous_dissolution_at.present?
+      errors.add(:opening_at, :too_soon) unless previous_dissolution_at < 6.months.ago
+    else
+      errors.add(:opening_at, :previous_blank)
     end
   end
 
@@ -229,6 +235,18 @@ def period?
     period.present?
   end
 
+  def previous
+    return @previous if defined?(@previous)
+
+    if previous_parliament = self.class.previous(opening_at)
+      @previous = self.class.previous(opening_at)
+    end
+  end
+
+  def previous_dissolution_at
+    previous.present? && previous.dissolution_at
+  end
+
   def dissolving?(now = Time.current)
     dissolution_at? && dissolution_at > now
   end
@@ -272,7 +290,7 @@ def start_archiving!(now = Time.current)
     end
   end
 
-  def start_anonymizing!(now = Time.current)
+  def start_anonymizing!
     if can_anonymize_petitions?
       Archived::AnonymizePetitionsJob.set(wait_until: midnight).perform_later(midnight.iso8601)
     end

config/locales/activerecord.en-GB.yml

@@ -104,7 +104,8 @@ en-GB:
               blank: Please enter a notification cut-off
             opening_at:
               blank: Please enter the date and time when parliament will reopen
-              too_soon: Please wait until six months after reopening before anonymizing petitions
+              previous_blank: There are no previous parliaments to anonymize
+              too_soon: Please wait until six months after dissolution before anonymizing petitions
             registration_closed_at:
               blank: Please enter the date and time at which voter registration closes
             show_dissolution_notification:

features/admin/anonymize_petitions.feature

@@ -9,7 +9,7 @@ Feature: An admin anonymizes petitions
   @javascript
   Scenario: Admin anonymizes petitions 6 months after parliament closes
     Given 2 archived petitions exist
-    And 6 months has passed since parliament opened
+    And 6 months has passed since the previous parliament dissolved
     When I go to the admin parliament page
     And I press "Anonymize petitions"
     And I accept the alert

features/step_definitions/common_steps.rb

@@ -44,6 +44,16 @@
   Parliament.update!(opening_at: number.months.ago)
 end
 
+Given('{int} months has passed since the previous parliament dissolved') do |number|
+  Parliament.instance.previous.update!(
+    dissolution_at: number.months.ago,
+    dissolution_heading: "Parliament is dissolving",
+    dissolution_message: "This means all petitions will close in 2 weeks",
+    dissolved_heading: "Parliament has been dissolved",
+    dissolved_message: "All petitions have been closed"
+  )
+end
+
 Given(/^the request is not local$/) do
   page.driver.options[:headers] = { "REMOTE_ADDR" => "192.168.1.128" }
 end

spec/controllers/admin/parliaments_controller_spec.rb

@@ -374,9 +374,17 @@
 
       context "when clicking the 'Anonymize petitions' button" do
         let(:anonymized_at) { nil }
+        let(:dissolution_at) { 7.months.ago }
+
+        let(:archived_parliament) do
+          FactoryBot.create(:parliament, :dissolved, :archived,
+            opening_at: 4.years.ago,
+            dissolution_at: dissolution_at
+          )
+        end
 
         before do
-          FactoryBot.create(:archived_petition, anonymized_at: anonymized_at)
+          FactoryBot.create(:archived_petition, parliament: archived_parliament, anonymized_at: anonymized_at)
 
           patch :update, params: { parliament: params, button: "anonymize_petitions" }
         end
@@ -401,9 +409,11 @@
           end
         end
 
-        context "and the params are valid, but the site has been reopened for less than six months" do
+        context "and the params are valid, but it is less than 6 months since dissolution" do
+          let(:dissolution_at) { 5.months.ago }
+
           let :params do
-            { government: "Conservative", opening_at: 5.months.ago.iso8601 }
+            { government: "Conservative", opening_at: 2.months.ago.iso8601 }
           end
 
           it_behaves_like "an invalid request"