Render published date using change_history

* first_published_at does not have reliable data, at time of writing
dates could be after public_updated_at
* the standard approach using details[“first_public_at”] is not
available
* Instead use first date in change history

When https://trello.com/c/xCJ3RN6W/ has been fixed, and when the dates
are reliable this can be switched back.

Add some tests to updatable to be explicit about expected behaviour
around presence of first_public_at

app/presenters/specialist_document_presenter.rb

@@ -14,4 +14,17 @@ def title_and_context
       t.delete(:context)
     end
   end
+
+private
+
+  # first_published_at does not have reliable data
+  # at time of writing dates could be after public_updated_at
+  # details.first_public_at is not provided
+  # https://trello.com/c/xCJ3RN6W/
+  #
+  # Instead use first date in change history
+  def first_public_at
+    changes = reverse_chronological_change_history
+    changes.any? ? changes.last[:timestamp] : nil
+  end
 end

test/integration/specialist_document_test.rb

@@ -17,6 +17,30 @@ class SpecialistDocumentTest < ActionDispatch::IntegrationTest
     assert_has_component_document_footer_pair("from", [aaib])
   end
 
+  test "renders published and updated in metadata and document footer" do
+    setup_and_visit_content_item('countryside-stewardship-grants')
+
+    assert_has_component_metadata_pair("first_published", "2 April 2015")
+    assert_has_component_metadata_pair("last_updated", "29 March 2016")
+
+    assert_has_component_document_footer_pair("published", "2 April 2015")
+    assert_has_component_document_footer_pair("updated", "29 March 2016")
+  end
+
+  test "renders change history in reverse chronological order" do
+    setup_and_visit_content_item('countryside-stewardship-grants')
+
+    within shared_component_selector("document_footer") do
+      # Flatten top level / "other" args, for consistent hash access
+      component_args = JSON.parse(page.text)
+      history = component_args.fetch("history")
+
+      assert_equal history.first["note"], @content_item["details"]["change_history"].last["note"]
+      assert_equal history.last["note"], @content_item["details"]["change_history"].first["note"]
+      assert_equal history.size, @content_item["details"]["change_history"].size
+    end
+  end
+
   test "renders a contents list" do
     setup_and_visit_content_item('aaib-reports')
 

test/presenters/specialist_document_presenter_test.rb

@@ -26,6 +26,28 @@ class PresentedSpecialistDocument < SpecialistDocumentTestCase
       assert presented_item('aaib-reports').is_a?(ContentsList)
     end
 
+    test 'presents the published date using the oldest date in the change history' do
+      example = schema_item('aaib-reports')
+      example["first_published_at"] = "2001-01-01"
+      example["details"]["change_history"] = [
+        {
+          "note" => "Newer",
+          "public_timestamp" => "2003-03-03"
+        },
+        {
+          "note" => "Oldest",
+          "public_timestamp" => "2002-02-02"
+        },
+        {
+          "note" => "More recent",
+          "public_timestamp" => "2013-03-03"
+        },
+      ]
+
+      presented = present_example(example)
+      assert DateTime.parse(presented.published) == DateTime.parse("2002-02-02")
+    end
+
     test 'has title without context' do
       assert presented_item('aaib-reports').is_a?(TitleAndContext)
       title_component_params = {

test/presenters/updatable_test.rb

@@ -20,6 +20,54 @@ def content_item
     assert_empty @updatable.history
   end
 
+  test '#history returns updates when first_public_at does not match public_updated_at' do
+    class << @updatable
+      def content_item
+        {
+          'public_updated_at' => '2002-02-02',
+          'details' => {
+            'first_public_at' => '2001-01-01',
+            'change_history' => [
+              {
+                'note' => 'note',
+                'public_timestamp' => '2002-02-02'
+              }
+            ]
+          }
+        }
+      end
+
+      def display_date(date)
+        date
+      end
+    end
+
+    assert @updatable.history.any?
+    assert_equal @updatable.updated, '2002-02-02'
+  end
+
+  test '#history returns no updates when first_public_at matches public_updated_at' do
+    class << @updatable
+      def content_item
+        {
+          'public_updated_at' => '2002-02-02',
+          'details' => {
+            'first_public_at' => '2002-02-02',
+            'change_history' => [
+              {
+                'note' => 'note',
+                'public_timestamp' => '2002-02-02'
+              }
+            ]
+          }
+        }
+      end
+    end
+
+    assert @updatable.history.empty?
+    refute @updatable.updated
+  end
+
   test '#history returns an array of hashes when there is change history' do
     class << @updatable
       def any_updates?