Fix for csv preview with legacy_url_path

Reference issue:https://govuk.sentry.io/issues/4265154142/?alert_rule_id=3654813&alert_type=issue&notification_uuid=8ab09d48-0416-4305-9e3c-0de49561a46a&project=202225&referrer=slack

Currently content item when it returns attachments, it returns modern url
hence when it tries to find  for legacy url, it fails and @attachment_metadata is empty
this cause @attachment_metadata.first to be nil and hence the error.

With the fix we try to not rely on legacy_url_path, instead we look for the filename.

app/controllers/csv_preview_controller.rb

@@ -16,10 +16,10 @@ def show
 
     parent_document_path = URI(@asset["parent_document_url"]).request_uri
     @content_item = GdsApi.content_store.content_item(parent_document_path).to_hash
-
     @attachment_metadata = @content_item.dig("details", "attachments").select do |attachment|
-      attachment["url"] =~ /#{Regexp.escape(asset_path)}$/
+      attachment["filename"] == filename
     end
+
     original_error = nil
     row_sep = :auto
     download_file = params[:legacy] ? whitehall_media_download : media_download
@@ -58,6 +58,10 @@ def asset_path
     request.path.sub("/preview", "").sub(/^\//, "")
   end
 
+  def asset_filename
+    asset_path.split("/").last
+  end
+
   def whitehall_media_download
     GdsApi.asset_manager.whitehall_media(asset_path).body
   end

test/integration/csv_preview_test.rb

@@ -243,6 +243,7 @@ def setup_asset_manager(legacy_url_path, parent_document_url, asset_manager_id =
   end
 
   def setup_content_item_legacy(legacy_url_path, parent_document_base_path)
+    filename = legacy_url_path.split("/").last
     content_item = {
       base_path: parent_document_base_path,
       document_type: "guidance",
@@ -251,11 +252,13 @@ def setup_content_item_legacy(legacy_url_path, parent_document_base_path)
         attachments: [
           {
             title: "Attachment 1",
-            url: "https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/5678/filename.csv",
+            filename: "file.csv",
+            url: "https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/5678/file.csv",
             file_size: "1024",
           },
           {
             title: "Attachment 2",
+            filename:,
             url: "https://www.gov.uk/#{legacy_url_path}",
             file_size: "2048",
           },
@@ -280,6 +283,7 @@ def setup_content_item_legacy(legacy_url_path, parent_document_base_path)
   end
 
   def setup_content_item_non_legacy(non_legacy_url_path, parent_document_base_path)
+    filename = non_legacy_url_path.split("/").last
     content_item = {
       base_path: parent_document_base_path,
       document_type: "guidance",
@@ -288,11 +292,13 @@ def setup_content_item_non_legacy(non_legacy_url_path, parent_document_base_path
         attachments: [
           {
             title: "Attachment 1",
-            url: "https://www.gov.uk/media/5678/filename.csv",
+            filename: "file.csv",
+            url: "https://www.gov.uk/media/5678/file.csv",
             file_size: "1024",
           },
           {
             title: "Attachment 2",
+            filename:,
             url: "https://www.gov.uk/#{non_legacy_url_path}",
             file_size: "2048",
           },