Use new-style csv preview links for attachments

app/presenters/content_item/attachments.rb

@@ -1,19 +1,37 @@
 module ContentItem
   module Attachments
     def attachments
-      return [] unless content_item["details"]["attachments"]
+      content_item_attachments = content_item.dig("details", "attachments")
+      return [] unless content_item_attachments
 
-      docs = content_item["details"]["attachments"].select { |a| !a.key?("locale") || a["locale"] == locale }
+      docs = content_item_attachments.select { |a| !a.key?("locale") || a["locale"] == locale }
       docs.each do |doc|
         doc["type"] = "html" unless doc["content_type"]
         doc["type"] = "external" if doc["attachment_type"] == "external"
-        doc["preview_url"] = "#{doc['url']}/preview" if doc["preview_url"]
+        doc["preview_url"] = preview_url(doc) if doc["preview_url"]
         doc["alternative_format_contact_email"] = nil if doc["accessible"] == true
       end
     end
 
     def attachments_from(attachment_id_list)
       attachments.select { |doc| (attachment_id_list || []).include? doc["id"] }
     end
+
+  private
+
+    def preview_url(doc)
+      case doc.symbolize_keys
+      in { preview_url: String, attachment_data_id:, filename: }
+        # We have attachment_data_id and filename, so we can redirect to a new style CSV preview
+        # Note: using a path rather than a full URL so the user doesn't flip from a draft frontend
+        #       to a live frontend if previewing a live asset of a draft document
+        "/csv-preview/#{attachment_data_id}/#{filename}"
+      in { preview_url: String, url: }
+        # TODO: remove this branch once we're confident attachment_data_id is present everywhere
+        Rails.logger.warn("Attachment at #{url} using old style preview, because no attachment_data_id present")
+        # NOTE: we're using "#{url}/preview" here because the preview_url fields have the wrong ids in them
+        "#{url}/preview"
+      end
+    end
   end
 end

test/presenters/content_item/attachments_test.rb

@@ -0,0 +1,58 @@
+require "test_helper"
+
+class AttachmentsTest < ActiveSupport::TestCase
+  setup do
+    @subject = (Class.new do
+      attr_accessor :content_item
+
+      include ContentItem::Attachments
+    end).new
+  end
+
+  test "#attachments returns an empty array when there are no attachments" do
+    attachments = []
+    @subject.content_item = { "details" => { "attachments" => attachments } }
+    assert_equal [], @subject.attachments
+  end
+
+  test "#attachments returns attachments with type html by default" do
+    attachments = [
+      { "any-key" => "any-value" },
+    ]
+    @subject.content_item = { "details" => { "attachments" => attachments } }
+    assert_equal [{ "any-key" => "any-value", "type" => "html" }], @subject.attachments
+  end
+
+  test "#attachments returns attachments with preview_urls based on url" do
+    attachments = [
+      { "preview_url" => "some-preview-url", "url" => "some-url" },
+    ]
+    @subject.content_item = { "details" => { "attachments" => attachments } }
+    assert_equal [{ "preview_url" => "some-url/preview", "url" => "some-url", "type" => "html" }], @subject.attachments
+  end
+
+  test "#attachments returns attachments with preview_urls based on attachment_data_id and filename" do
+    attachments = [{
+      "preview_url" => "some-preview-url",
+      "url" => "some-url",
+      "attachment_data_id" => "some-attachment-data-id",
+      "filename" => "some-filename",
+    }]
+    @subject.content_item = { "details" => { "attachments" => attachments } }
+    assert_equal [{
+      "preview_url" => "/csv-preview/some-attachment-data-id/some-filename",
+      "url" => "some-url",
+      "attachment_data_id" => "some-attachment-data-id",
+      "filename" => "some-filename",
+      "type" => "html",
+    }], @subject.attachments
+  end
+
+  test "#attachments raises an error if preview_url is present, but both url and attachment_data_id / filename are absent" do
+    attachments = [{
+      "preview_url" => "some-preview-url",
+    }]
+    @subject.content_item = { "details" => { "attachments" => attachments } }
+    assert_raises(NoMatchingPatternError) { @subject.attachments }
+  end
+end

test/presenters/publication_presenter_test.rb

@@ -50,6 +50,27 @@ def schema_name
     assert presented_item("statistics_publication").national_statistics?
   end
 
+  test "#attachments_for_components presents featured attachments" do
+    content_item = schema_item
+    content_item["details"]["featured_attachments"] = %w[some-id]
+    content_item["details"]["attachments"] = [{
+      "id" => "some-id",
+      "content_type" => "text/csv",
+      "preview_url" => "some-preview-url",
+      "url" => "some-url",
+    }]
+    presented = present_example(content_item)
+    expected = [{
+      "id" => "some-id",
+      "content_type" => "text/csv",
+      # NOTE: preview_url is the url with /preview appended, not the preview_url from above,
+      #       because we're working around a bug with preview_url
+      "preview_url" => "some-url/preview",
+      "url" => "some-url",
+    }]
+    assert_equal expected, presented.attachments_for_components
+  end
+
   test "presents withdrawn notices" do
     example = schema_item("withdrawn_publication")
     presented = presented_item("withdrawn_publication")