forum: delete posts when topic is deleted.

Fix it so that when a forum topic is deleted, all posts in the topic are
deleted too. Also make it so that when a forum topic is undeleted, all
posts in it are undeleted too.

Before when a topic was deleted, only the topic itself was marked as
deleted, not the posts inside the topic. This meant that when a spam
topic was deleted, the OP wouldn't be marked as deleted, so any
modreports against it wouldn't be marked as handled.

Also change it so that it's not possible to undelete a post in a deleted
topic, or to delete the OP of a topic without deleting the topic itself.

Finally, add a fix script to delete all active posts in deleted topics,
and to undelete all deleted OPs in active topics.

app/controllers/forum_posts_controller.rb

@@ -55,12 +55,16 @@ class ForumPostsController < ApplicationController
   def destroy
     @forum_post = authorize ForumPost.find(params[:id])
     @forum_post.delete!
+
+    flash[:notice] = @forum_post.errors.none? ? "Post deleted" : @forum_post.errors.full_messages.join("; ")
     respond_with(@forum_post)
   end
 
   def undelete
     @forum_post = authorize ForumPost.find(params[:id])
     @forum_post.undelete!
+
+    flash[:notice] = @forum_post.errors.none? ? "Post undeleted" : @forum_post.errors.full_messages.join("; ")
     respond_with(@forum_post)
   end
 end

app/models/forum_post.rb

@@ -15,13 +15,14 @@ class ForumPost < ApplicationRecord
   has_one :bulk_update_request
 
   validates :body, presence: true, length: { maximum: 200_000 }, if: :body_changed?
+  validate :validate_deletion_of_original_post
+  validate :validate_undeletion_of_post
 
   before_create :autoreport_spam
   before_save :handle_reports_on_deletion
   after_create :update_topic_updated_at_on_create
   after_update :update_topic_updated_at_on_update_for_original_posts
   after_destroy :update_topic_updated_at_on_destroy
-  after_save :delete_topic_if_original_post
   after_update(:if => ->(rec) {rec.updater_id != rec.creator_id}) do |rec|
     ModAction.log("#{CurrentUser.user.name} updated forum ##{rec.id}", :forum_post_update)
   end
@@ -83,6 +84,18 @@ class ForumPost < ApplicationRecord
     votes.exists?(creator_id: user.id, score: score)
   end
 
+  def validate_deletion_of_original_post
+    if is_original_post? && is_deleted? && !topic.is_deleted?
+      errors.add(:base, "Can't delete original post without deleting the topic first")
+    end
+  end
+
+  def validate_undeletion_of_post
+    if topic.is_deleted? && !is_deleted?
+      errors.add(:base, "Can't undelete post without undeleting the topic first")
+    end
+  end
+
   def autoreport_spam
     if SpamDetector.new(self, user_ip: CurrentUser.ip_addr).spam?
       moderation_reports << ModerationReport.new(creator: User.system, reason: "Spam.")
@@ -153,12 +166,6 @@ class ForumPost < ApplicationRecord
     end
   end
 
-  def delete_topic_if_original_post
-    if is_deleted? && is_original_post?
-      topic.update_attribute(:is_deleted, true)
-    end
-  end
-
   def handle_reports_on_deletion
     return unless moderation_reports.pending.present? && is_deleted_change == [false, true]
 

app/models/forum_topic.rb

@@ -24,12 +24,13 @@ class ForumTopic < ApplicationRecord
   has_many :tag_implications
 
   validates :title, presence: true, length: { maximum: 200 }, if: :title_changed?
-  validates_associated :original_post
   validates :category_id, inclusion: { in: CATEGORIES.keys }
   validates :min_level, inclusion: { in: MIN_LEVELS.values }
 
   accepts_nested_attributes_for :original_post
-  after_update :update_orignal_post
+
+  after_update :update_posts_on_deletion_or_undeletion
+  after_update :update_original_post
   after_save(:if => ->(rec) {rec.is_locked? && rec.saved_change_to_is_locked?}) do |rec|
     ModAction.log("locked forum topic ##{id} (title: #{title})", :forum_topic_lock)
   end
@@ -179,7 +180,14 @@ class ForumTopic < ApplicationRecord
     (response_count / Danbooru.config.posts_per_page.to_f).ceil
   end
 
-  def update_orignal_post
+  # Delete all posts when the topic is deleted. Undelete all posts when the topic is undeleted.
+  def update_posts_on_deletion_or_undeletion
+    if saved_change_to_is_deleted?
+      forum_posts.update!(is_deleted: is_deleted) # XXX depends on current user
+    end
+  end
+
+  def update_original_post
     original_post&.update_columns(:updater_id => updater.id, :updated_at => Time.now)
   end
 

app/policies/forum_post_policy.rb

@@ -18,11 +18,11 @@ class ForumPostPolicy < ApplicationPolicy
   end
 
   def destroy?
-    unbanned? && show? && user.is_moderator?
+    unbanned? && show? && !record.is_deleted? && user.is_moderator?
   end
 
   def undelete?
-    unbanned? && show? && user.is_moderator?
+    unbanned? && show? && record.is_deleted? && !record.topic.is_deleted? && user.is_moderator?
   end
 
   def reply?

app/views/forum_posts/destroy.js.erb

@@ -1 +1 @@
-$("#forum_post_<%= @forum_post.id %>").replaceWith("<%= j render(ForumPostComponent.new(forum_post: @forum_post, current_user: CurrentUser.user)) %>");
+location.reload();

app/views/forum_posts/undelete.js.erb

@@ -1 +1 @@
-$("#forum_post_<%= @forum_post.id %>").replaceWith("<%= j render(ForumPostComponent.new(forum_post: @forum_post, current_user: CurrentUser.user)) %>");
+location.reload();