require 'active_record'

module Helicoid
  module Acts #:nodoc:
    module Messenger #:nodoc:

      def self.included(mod)
        mod.extend(ClassMethods)
      end

      module ClassMethods
        def acts_as_messenger(options = {})
          options[:join_table] ||= "messages_#{self.table_name}"
          options[:foreign_key] ||= self.name.to_s.foreign_key
          write_inheritable_attribute(:message_foreign_key, 'message_id')
          write_inheritable_attribute(:messaged_foreign_key, options[:foreign_key])
          write_inheritable_attribute(:message_model, 'Message'.constantize)
          write_inheritable_attribute(:messages_join_table, options[:join_table])

          class_eval do
            extend Helicoid::Acts::Messenger::SingletonMethods
            class_inheritable_reader :message_model, :messages_join_table, :message_foreign_key,  :messaged_foreign_key
            has_and_belongs_to_many :messages, :join_table => options[:join_table], :foreign_key => options[:foreign_key]
            
          end
          include Helicoid::Acts::Messenger::InstanceMethods
        end
      end

      module SingletonMethods
      end

      # Adds instance methods.
      module InstanceMethods
        def unread_messages
          unread_sql = ''
          read = self.messages
          unread_sql = ", #{messages_join_table} WHERE messages.id NOT IN (#{read.collect {|message| message.id }.join(',')})" if read.size > 0
          sql = "SELECT messages.* FROM messages" + unread_sql + ' ORDER BY created_on DESC'
          message_model.find_by_sql(sql)
        end
        
        def read_messages
          messages.find(:all, :order => 'created_on')
        end
        
        def mark_as_read(message_id)
          self.messages << message_model.find(message_id)
        end        
      end
    end
  end
end

ActiveRecord::Base.class_eval do
  include Helicoid::Acts::Messenger
end