WIP: Erase comments that have been hidden for a while

TODO: Add a nightly cron task that calls `Comment.erase_old_hidden`

app/models/comment.rb

@@ -37,6 +37,12 @@ class Comment < ApplicationRecord
                  instance_accessor: false,
                  default: DEFAULT_CREATION_RATE_LIMITS
 
+  cattr_accessor :old_age_in_days,
+                 instance_reader: false,
+                 instance_writer: false,
+                 instance_accessor: false,
+                 default: 30
+
   strip_attributes allow_empty: true
 
   belongs_to :user,
@@ -52,14 +58,16 @@ class Comment < ApplicationRecord
 
   # validates_presence_of :user # breaks during construction of new ones :(
   validate :check_body_has_content,
-           :check_body_uses_mixed_capitals
+           :check_body_uses_mixed_capitals, unless: :hidden?
 
   scope :visible, -> {
     joins(:info_request).
       merge(InfoRequest.is_searchable.except(:select)).
         where(visible: true)
   }
 
+  scope :hidden -> { where(visible: false) }
+
   scope :embargoed, -> {
     joins(info_request: :embargo).
       where('embargoes.id IS NOT NULL').
@@ -79,6 +87,15 @@ class Comment < ApplicationRecord
 
   default_url_options[:host] = AlaveteliConfiguration.domain
 
+  def self.erase_old_hidden(editor: User.internal_admin_user)
+    old_hidden = hidden.where('updated_at > ?', old_age_in_days.days.ago)
+    reason = "Hidden for longer than #{old_age_in_days} days"
+
+    old_hidden.find_each do |comment|
+      comment.erase(editor: editor, reason: reason)
+    end
+  end
+
   # When posting a new comment, use this to check user hasn't double
   # submitted.
   def self.find_existing(info_request_id, body)
@@ -194,6 +211,22 @@ def hide(editor:)
     end
   end
 
+  # TODO: Maybe add an erase_comment event
+  def erase(editor:, reason:)
+    return false unless hidden?
+
+    ActiveRecord::Base.transaction do
+      event_params = {
+        comment_id: id,
+        editor: editor.url_name,
+        reason: "Erased: #{reason}"
+      }
+
+      update!(body: '')
+      info_request.log_event('edit_comment', event_params)
+    end
+  end
+
   def cached_urls
     [
       request_path(info_request),