WIP: Erase comments that have been hidden for a while

app/helpers/admin/link_helper.rb

@@ -80,8 +80,10 @@ def comment_both_links(comment)
     title = 'View comment on public website'
     icon = prominence_icon(comment)
 
+    body = comment.body.present? ? comment.body : tag.tt('[ERASED]')
+
     link_to(icon, comment_path(comment), title: title) + ' ' +
-      link_to(truncate(comment.body, length: 60), edit_admin_comment_path(comment),
+      link_to(truncate(body, length: 60), edit_admin_comment_path(comment),
               title: admin_title)
   end
 

app/models/comment.rb

@@ -21,6 +21,8 @@
 # Email: [email protected]; WWW: http://www.mysociety.org/
 
 class Comment < ApplicationRecord
+  include Comment::Erasable
+
   include Rails.application.routes.url_helpers
   include LinkToHelper
 
@@ -52,14 +54,16 @@ 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').

app/models/comment/erasable.rb

@@ -0,0 +1,31 @@
+module Comment::Erasable
+  extend ActiveSupport::Concern
+
+  included do
+    cattr_accessor :old_age_in_days,
+                   instance_reader: false,
+                   instance_writer: false,
+                   instance_accessor: false,
+                   default: 30
+  end
+
+  class_methods do
+    def 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
+  end
+
+  def erase(**kwargs)
+    return false unless hidden?
+    Comment::Erasure.new(self, **kwargs).erase
+  end
+
+  def erased?
+    info_request_events.erase_comment_events.any?
+  end
+end

app/models/comment/erasure.rb

@@ -0,0 +1,43 @@
+class Comment::Erasure
+  def initialize(comment, editor: User.internal_admin_user, reason:)
+    @comment = comment
+    @editor = editor
+    @reason = reason
+  end
+
+  def erase
+    ActiveRecord::Base.transaction do
+      erase_comment
+      erase_comment_events
+    end
+  end
+
+  protected
+
+  attr_reader :comment, :editor, :reason
+
+  private
+
+  def erase_comment
+    event_params = {
+      comment_id: comment.id,
+      editor: editor.url_name,
+      reason: "Erased: #{reason}"
+    }
+
+    comment.update!(body: '')
+    comment.info_request.log_event('erase_comment', event_params)
+  end
+
+  def erase_comment_events
+    comment.info_request_events.edit_comment_events.find_each do |event|
+      params = event.params.dup
+
+      params.each do |key, _|
+        params[key] = "[ERASED]" if key =~ /body/
+      end
+
+      event.update(params: params)
+    end
+  end
+end

app/models/info_request_event.rb

@@ -35,6 +35,7 @@ class InfoRequestEvent < ApplicationRecord
     'edit_comment', # comment edited (in admin interface)
     'hide_comment', # comment hidden by admin
     'report_comment', # comment reported for admin attention by user
+    'erase_comment', # comment is erased
     'report_request', # a request reported for admin attention by user
     'destroy_incoming', # deleted an incoming message (in admin interface)
     'destroy_outgoing', # deleted an outgoing message (in admin interface)

app/views/admin_comment/edit.html.erb

@@ -23,12 +23,17 @@
 </div>
 
 <%= form_tag admin_comment_path(@comment), :method => 'put' do %>
+  <% if @comment.erased? %>
+    <p class="text-warning">
+      <%= icon('ban-circle') %> <strong>Editing is restricted for erased comments</strong>
+    </p>
+  <% end %>
 
   <p><label for="comment_body">Body of annotation</label><br/>
-    <%= text_area 'comment', 'body', :rows => 10, :cols => 60  %></p>
+    <%= text_area 'comment', 'body', :rows => 10, :cols => 60, disabled: @comment.erased?  %></p>
 
   <p><label for="comment_visible">Visible</label>
-    <%= select('comment', "visible", [["Yes – show comment",true],["No – hide comment",false]]) %>
+    <%= select('comment', "visible", [["Yes – show comment",true],["No – hide comment",false]], disabled: @comment.erased?) %>
   </p>
 
   <p><label for="comment_attention_requested">Admin attention requested</label>
@@ -44,8 +49,9 @@
 
 <hr>
 <h2>Events</h2>
+
 <div class="accordion" id="events">
-  <% @comment.info_request_events.each do |info_request_event| %>
+  <% @comment.info_request_events.order(created_at: :asc).each do |info_request_event| %>
     <div class="accordion-group">
       <div class="accordion-heading">
         <span class="item-title">