module HasMetaData
  def self.included(base)
    base.extend ClassMethods
  end
  
  module ClassMethods
    def has_meta_data(options = {}, &block)
      return if self.included_modules.include?(HasMetaData::InstanceMethods)
      include HasMetaData::InstanceMethods
      
      cattr_accessor :meta_data_class_name, :meta_data_foreign_key, :meta_data_table_name, :meta_data_columns
      
      self.meta_data_class_name = options[:class_name]  || 'Meta'
      self.meta_data_foreign_key = options[:foreign_key] || self.to_s.foreign_key
      self.meta_data_table_name = options[:table_name]  || "#{table_name_prefix}#{self.name.demodulize.underscore}_meta#{table_name_suffix}"
      
      
      # Create Relationship to Meta Data
      class_eval do
        has_one :meta, 
          :class_name => "#{self.to_s}::#{meta_data_class_name}",
          :foreign_key => meta_data_foreign_key,
          :dependent => :destroy
        
        scope :with_meta, lambda { includes(:meta).where("#{meta_data_table_name}.id IS NOT NULL") }
        scope :without_meta, lambda { includes(:meta).where("#{meta_data_table_name}.id IS NULL") }
      end
      
      # Dynamically Create Model::Meta Class
      const_set(meta_data_class_name, Class.new(ActiveRecord::Base))
      
      meta_data_class.cattr_accessor :original_class
      meta_data_class.original_class = self
      meta_data_class.table_name = meta_data_table_name
      
      # Draft Parent Association
      meta_data_class.belongs_to self.to_s.demodulize.underscore.to_sym, :class_name => "::#{self.to_s}", :foreign_key => meta_data_foreign_key
      
      # Block extension
      meta_data_class.class_eval(&block) if block_given?
      
      # Finally setup attribute delegation to the meta fields
      self.meta_data_columns = meta_data_class.content_columns.map(&:name)
      
      meta_data_columns.each do |field|
        define_method(field.to_sym) do
          meta.send(field.to_sym) if has_meta_data?
        end
        
        define_method("#{field}=".to_sym) do |value|
          self.build_meta unless has_meta_data?
          meta.send("#{field}=".to_sym, value)
        end
      end
    end
    
    def meta_data_class
      const_get(meta_data_class_name)
    end
  end
  
  module InstanceMethods
    def has_meta_data?
      !self.meta.nil?
    end
  end
end

require "has_meta_data/railtie"