flags: add 3 day flagging cooldown period.

app/models/post_flag.rb

@@ -7,6 +7,8 @@ class PostFlag < ActiveRecord::Base
     BANNED = "Artist requested removal"
   end
 
+  COOLDOWN_PERIOD = 3.days
+
   belongs_to :creator, :class_name => "User"
   belongs_to :post
   validates_presence_of :reason, :creator_id, :creator_ip_addr
@@ -18,6 +20,10 @@ class PostFlag < ActiveRecord::Base
   attr_accessible :post, :post_id, :reason, :is_resolved, :is_deletion
   attr_accessor :is_deletion
 
+  scope :by_users, lambda { where.not(creator: User.system) }
+  scope :by_system, lambda { where(creator: User.system) }
+  scope :in_cooldown, lambda { by_users.where("created_at >= ?", COOLDOWN_PERIOD.ago) }
+
   module SearchMethods
     def reason_matches(query)
       if query =~ /\*/
@@ -149,6 +155,11 @@ class PostFlag < ActiveRecord::Base
   def validate_post
     errors[:post] << "is locked and cannot be flagged" if post.is_status_locked?
     errors[:post] << "is deleted" if post.is_deleted?
+
+    flag = post.flags.in_cooldown.last
+    if flag.present?
+      errors[:post] << "cannot be flagged more than once every #{COOLDOWN_PERIOD.inspect} (last flagged: #{flag.created_at.to_s(:long)})"
+    end
   end
 
   def initialize_creator