post events: show post-related mod actions on post event page.

Show the following actions on the post events page:

* Post bans and unbans
* Post deletions and undeletions
* Thumbnail regenerations and IQDB regenerations
* Favorites moves
* Rating locks and unlocks
* Note locks and unlocks

Fixes #3825: Events/Moderation page for each post should show eventual ban actions

app/models/post_event.rb

@@ -6,16 +6,40 @@ class PostEvent < ApplicationRecord
   belongs_to :post
 
   def self.model_types
-    %w[Post PostAppeal PostApproval PostDisapproval PostFlag PostReplacement]
+    %w[Post PostAppeal PostApproval PostDisapproval PostFlag PostReplacement ModAction]
+  end
+
+  def self.categories
+    # model_types.excluding("ModAction") + ModAction.categories.keys.grep(/\Apost_(?!permanent_delete|vote)/).map(&:camelize)
+    %w[Upload Flag Appeal Approval Disapproval Delete Undelete Ban Unban Replacement Regenerate RegenerateIqdb MoveFavorites NoteLockCreate NoteLockDelete RatingLockCreate RatingLockDelete]
   end
 
   def self.visible(user)
     all
   end
 
+  def self.category_matches(category)
+    category = category.squish.titleize.delete(" ")
+
+    case category
+    when "Upload"
+      where(model_type: "Post")
+    when "Flag", "Appeal", "Approval", "Disapproval", "Replacement"
+      where(model_type: "Post" + category)
+    when *categories
+      where(model: ModAction.where(category: "post_" + category.underscore))
+    else
+      none
+    end
+  end
+
   def self.search(params, current_user)
     q = search_attributes(params, [:model, :post, :creator, :event_at], current_user: current_user)
 
+    if params[:category]
+      q = q.category_matches(params[:category])
+    end
+
     case params[:order]
     when "event_at_asc"
       q = q.order(event_at: :asc, model_id: :asc)
@@ -34,6 +58,20 @@ class PostEvent < ApplicationRecord
     [:post, :model] # XXX creator isn't included because it leaks flagger/disapprover names
   end
 
+  def category
+    if model_type == "Post"
+      "Upload"
+    elsif model_type == "ModAction"
+      model.category.camelize.delete_prefix("Post")
+    else
+      model_type.delete_prefix("Post")
+    end
+  end
+
+  def pretty_category
+    category.titleize.delete_prefix("Post ")
+  end
+
   def readonly?
     true
   end