From 052a2a51d2b5d912f32c1d62c016109c673aa40b Mon Sep 17 00:00:00 2001
From: Thomas Leese <thomas.leese@digital.cabinet-office.gov.uk>
Date: Fri, 11 May 2018 08:46:47 +0100
Subject: [PATCH 1/3] Add canonical URL to content items

This generates a canonical URL for content items based on its
web_url combined with a part slug if necessary.
---
 app/presenters/content_item_presenter.rb       |  8 ++++++++
 test/presenters/content_item_presenter_test.rb | 12 ++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/app/presenters/content_item_presenter.rb b/app/presenters/content_item_presenter.rb
index dac8a18cf..216c62b3a 100644
--- a/app/presenters/content_item_presenter.rb
+++ b/app/presenters/content_item_presenter.rb
@@ -53,6 +53,14 @@ def web_url
     Plek.current.website_root + content_item["base_path"]
   end
 
+  def canonical_url
+    if requesting_a_part?
+      web_url + "/" + part_slug
+    else
+      web_url
+    end
+  end
+
 private
 
   def display_date(timestamp, format = "%-d %B %Y")
diff --git a/test/presenters/content_item_presenter_test.rb b/test/presenters/content_item_presenter_test.rb
index 68835adfb..b5ed60b20 100644
--- a/test/presenters/content_item_presenter_test.rb
+++ b/test/presenters/content_item_presenter_test.rb
@@ -21,6 +21,18 @@ class ContentItemPresenterTest < ActiveSupport::TestCase
     assert_equal "Type", ContentItemPresenter.new("document_type" => "Type").document_type
   end
 
+  test "#canonical_url without a part" do
+    assert_equal "https://www.test.gov.uk/test", ContentItemPresenter.new("base_path" => "/test").canonical_url
+  end
+
+  test "#canonical_url with a part" do
+    example_with_parts = govuk_content_schema_example('travel_advice', 'full-country')
+    request_path = example_with_parts['base_path'] + '/safety-and-security'
+    presented_example = TravelAdvicePresenter.new(example_with_parts, request_path)
+
+    assert_equal "https://www.test.gov.uk/foreign-travel-advice/albania/safety-and-security", presented_example.canonical_url
+  end
+
   test "available_translations sorts languages by locale with English first" do
     translated = govuk_content_schema_example('case_study', 'translated')
     locales = ContentItemPresenter.new(translated).available_translations

From 95d5569f2217a6ba0056b0fba444c52227ecaa74 Mon Sep 17 00:00:00 2001
From: Thomas Leese <thomas.leese@digital.cabinet-office.gov.uk>
Date: Fri, 11 May 2018 08:48:35 +0100
Subject: [PATCH 2/3] Present canonical URL in a link tag

---
 app/views/layouts/application.html.erb | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index 1fe8056fe..8ff190fc6 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -25,6 +25,8 @@
     <meta name="description" content="<%= strip_tags(@content_item.description) %>" />
   <% end %>
 
+  <link rel="canonical" href="<%= @content_item.canonical_url %>" />
+
   <meta property="og:site_name" content="GOV.UK" />
   <meta property="og:type" content="article" />
   <meta property="og:url" content="<%= @content_item.web_url %>" />

From 8f2992d5fe3daddef75d7febe446382539c1b35b Mon Sep 17 00:00:00 2001
From: Thomas Leese <thomas.leese@digital.cabinet-office.gov.uk>
Date: Fri, 11 May 2018 08:48:45 +0100
Subject: [PATCH 3/3] Use canonical URL in opengraph tags instead of web URL

This ensures that a content item with parts will have the correct
URL.
---
 app/views/layouts/application.html.erb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index 8ff190fc6..9ae1711ac 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -29,7 +29,7 @@
 
   <meta property="og:site_name" content="GOV.UK" />
   <meta property="og:type" content="article" />
-  <meta property="og:url" content="<%= @content_item.web_url %>" />
+  <meta property="og:url" content="<%= @content_item.canonical_url %>" />
   <meta property="og:title" content="<%= @content_item.page_title %>" />
   <meta property="og:description" content="<%= strip_tags(@content_item.description) %>" />