class Comment < ActiveRecord::Base
  acts_as_nested_set :scope => [:commentable_id, :commentable_type]

  validates :body, :presence => true
  validates :user, :presence => true

  belongs_to :commentable, :polymorphic => true
  belongs_to :user

  def self.build(commentable, user, body)
    new commentable: commentable,
        user_id:     user.id,
        body:        body
  end

  def self.find_parent(params)
    params[:commentable_type].constantize.find(params[:commentable_id])
  end
end