segment.rb

class Segment < ActiveRecord::Base
  extend ActsAsTree::TreeView
  extend ActsAsTree::TreeWalker

  belongs_to :course
  belongs_to :section_type
  has_and_belongs_to_many :chunks, join_table: 'chunks_segments'

  acts_as_tree order: 'rank'

  def word_count
    @word_count ||= chunks.map(&:markup).join("\n").scan(/[\w-]+/).size
  end

  def required_time
    (word_count / course.reading_speed.to_f * 60.0).round
  end

end