gistfile1.rb

class Message
  include DataMapper::Resource

  property :id, Serial
  property :subject, String
  property :body, Text
  property :unread, Boolean, :default => true, :required => true
  property :created_at, DateTime
  property :updated_at, DateTime

  ## обновляет updated_at у родительского сообщения, нужно для сортировки
  belongs_to :parent, "Message", :required => false #  :touch => true
  belongs_to :sender, "User"
  belongs_to :recipient, "User"
  has n, :messages, :child_key => [:parent_id] # :dependent => :delete_all

  def self.ordered_by_creation; all(:order => [:created_at.desc]) end
  def self.threads; all(:parent => nil) end
  def self.unread; all(:unread => true) end
  def self.with_user user
    # all(:conditions => ["recipient_id = ? or sender_id = ?", user.id, user.id])
    all(:recipient => user) + all(:sender => user)
  end
  def self.written_by user; all(:sender => user) end
  def self.received_by user; all(:recipient => user) end
  def self.unread_by user; unread.received_by(user) end
  def self.ordered_by_activity; all(:order => [:updated_at.desc]) end

  ## что-то одно должно присутствовать
  #validates_presence_of :body, :if => proc {|msg| msg.subject.blank? }

  def thread_starter?; !parent end
  def reply?; !thread_starter? end

  def thread; parent || self end
  #def thread_id; parent_id || id end

  ## TODO try to get this via association
  def thread_messages
    Message.all(:conditions => ["id = ? or parent_id = ?", thread.id, thread.id]).ordered_by_creation
  end

  def thread_messages_count
    thread.messages.count + 1
  end

  def new_reply(author)
    msg = thread.messages.new :sender => author
    # можно писать в свой же тред
    msg.recipient = (thread.sender == author) ? thread.recipient : thread.sender
    msg
  end

  delegate :subject, :to => :thread, :prefix => :thread

  def unread_by?(reader)
    unread? && reader != sender
  end

  def unread_count_for(reader)
    thread_messages.unread_by(reader).count
  end

  def thread_unread_by?(reader)
    unread_count_for(reader) != 0
  end

  def first_unread_or_last_read_for(reader)
    thread_messages.unread_by(reader).first || thread_messages.last
  end

  def read!(reader)
    thread_messages.unread_by(reader).update! :unread => false
  end

end