post replacement: delete old files after image is replaced.

app/helpers/delayed_jobs_helper.rb

@@ -61,6 +61,9 @@ module DelayedJobsHelper
     when "Pool#update_category_pseudo_tags_for_posts"
       "<strong>update pool category pseudo tags for posts</strong>"
 
+    when "Post.delete_files"
+      "<strong>delete old files</strong>"
+
     else
       h(job.name)
     end
@@ -122,6 +125,9 @@ module DelayedJobsHelper
     when "Pool#update_category_pseudo_tags_for_posts"
       %{<a href="/pools/#{job.payload_object.id}">#{h(job.payload_object.name)}</a>}
 
+    when "Post.delete_files"
+      %{<a href="/posts/#{job.payload_object.args.first}">post ##{job.payload_object.args.first}</a>}
+
     else
       h(job.handler)
     end

app/models/post.rb

@@ -7,6 +7,8 @@ class Post < ActiveRecord::Base
   class RevertError < Exception ; end
   class SearchError < Exception ; end
 
+  DELETION_GRACE_PERIOD = 3.days
+
   before_validation :initialize_uploader, :on => :create
   before_validation :merge_old_changes
   before_validation :normalize_tags
@@ -29,7 +31,6 @@ class Post < ActiveRecord::Base
   after_save :expire_essential_tag_string_cache
   after_destroy :remove_iqdb_async
   after_destroy :delete_files
-  after_destroy :delete_remote_files
   after_commit :update_iqdb_async, :on => :create
   after_commit :notify_pubsub
 
@@ -60,24 +61,31 @@ class Post < ActiveRecord::Base
   attr_accessor :old_tag_string, :old_parent_id, :old_source, :old_rating, :has_constraints, :disable_versioning, :view_count
 
   module FileMethods
+    extend ActiveSupport::Concern
+
+    module ClassMethods
+      def delete_files(post_id, file_path, large_file_path, preview_file_path)
+        # the large file and the preview don't necessarily exist. if so errors will be ignored.
+        FileUtils.rm_f(file_path)
+        FileUtils.rm_f(large_file_path)
+        FileUtils.rm_f(preview_file_path)
+
+        RemoteFileManager.new(file_path).delete
+        RemoteFileManager.new(large_file_path).delete
+        RemoteFileManager.new(preview_file_path).delete
+      end
+    end
+
+    def delete_files
+      Post.delete_files(id, file_path, large_file_path, preview_file_path)
+    end
+
     def distribute_files
       RemoteFileManager.new(file_path).distribute
       RemoteFileManager.new(preview_file_path).distribute if has_preview?
       RemoteFileManager.new(large_file_path).distribute if has_large?
     end
 
-    def delete_remote_files
-      RemoteFileManager.new(file_path).delete
-      RemoteFileManager.new(preview_file_path).delete if has_preview?
-      RemoteFileManager.new(large_file_path).delete if has_large?
-    end
-
-    def delete_files
-      FileUtils.rm_f(file_path)
-      FileUtils.rm_f(large_file_path)
-      FileUtils.rm_f(preview_file_path)
-    end
-
     def file_path_prefix
       Rails.env == "test" ? "test." : ""
     end
@@ -1400,6 +1408,11 @@ class Post < ActiveRecord::Base
         upload.process_upload
         upload.update(status: "completed", post_id: id)
 
+        # queue the deletion *before* updating the post so that we use the old
+        # md5/file_ext to delete the old files. if saving the post fails,
+        # this is rolled back so the job won't run.
+        Post.delay(queue: "default", run_at: Time.now + DELETION_GRACE_PERIOD).delete_files(id, file_path, large_file_path, preview_file_path)
+
         self.md5 = upload.md5
         self.file_ext = upload.file_ext
         self.image_width = upload.image_width