class Page < ActiveRecord::Base
  belongs_to :book

  has_many :entry_versions, :order => "created_at", :dependent => true
  has_one  :current_version, :class_name => "EntryVersion", :order => "created_at DESC"
  
  def before_create
    revision_number = 1
  end
  
  def find_or_build_version(number = nil)
    number ? entry_versions[number.to_i - 1] : entry_versions.build(:body => body)
  end
  
  def body
    current_version ? current_version.body : nil
  end
  
  def to_param
    title
  end
  
  def continuous_edit?(author, time = Time.now)
    current_version and 
    current_version.author == author and 
    time <= current_version.updated_at + 30.minutes
  end
  
  def create_version(author, base_revision_number, options)
    if self.revision_number > base_revision_number
      last_author = current_version.author.name
      raise "While you were working on this page, #{last_author} has created a new version of it."
    end
    if continuous_edit?(author)
      version = self.current_version
      version.body = options[:body]
    else
      version = self.entry_versions.build(options)
      version.author = author
    end
    increment!(:revision_number)
    version.save
  end
  
end