class Discussion < ActiveRecord::Base
  belongs_to :post
  has_many :posts

  def posts_arranged
#    arrange(Post.find(:all, :conditions => ["discussion_id = ?", id]))
    @posts_arranged ||= arrange(Post.find_all_by_discussion_id(id))
  end

  def depth
    _depth posts_arranged
  end

  def _depth(thread)
    return 0  unless thread.kind_of? Array
    thread.map { |e| _depth(e) + 1 }.max
  end

  private
  def arrange(posts, root=nil)
    root ||= posts.find { |post| post.parent.nil? }
    childs = posts.find_all { |p| p.parent == root.id }
    [root].concat childs.map { |p| arrange posts, p }
  end
end