module Mongoid::Undo
  module Version
    extend ActiveSupport::Concern

    included do
      include Mongoid::Document
      include Mongoid::Timestamps::Created

      field :obj_id
      field :obj_class
      field :obj_attributes, type: Hash
      field :version, type: Integer
      validates_presence_of(fields.keys - ['_id', '_type', 'created_at', 'obj_attributes'])
    end

    def obj; obj_class.constantize.find(obj_id) end

    def created?; version == 1 end
    def deleted?; !obj_attributes end
    def modified?; !(created? || deleted?) end
    def latest?(obj = nil)
      unless obj; obj = self.obj end
      obj.nil? || version == obj.version
    end

    def rollback_to(obj = nil)
      if !deleted?
        if obj.nil? || obj.id != obj_id; obj = self.obj end
        if obj.nil?; obj = obj_class.constantize.new end

        obj.versions_gt(version).each {|ver| ver.destroy }
        rollback(obj)
      else
        false
      end
    end

    private

    def rollback(obj = nil)
      old_attributes = obj.attributes
      obj.attributes = obj_attributes
      obj.without_versioning :save

      old_attributes
    end
  end
end