module GeocodableModel
  def self.included(base)
    base.extend(ClassMethods)
  end
  
  module ClassMethods
    def geocodable_model(&block)
      return if included_modules.include?(GeocodableModel::InstanceMethods)
      
      class_inheritable_accessor :_geocode_address_block
      self._geocode_address_block = block
      
      has_one :geocode, :as => :geocodable, :dependent => :destroy
      
      after_save :update_geocode
      
      include InstanceMethods
    end
  end
  
  module InstanceMethods
    def update_geocode
      addresses = _geocode_address_block.call(self)
      addresses = [*addresses] unless addresses.is_a?(Array)
      addresses.reject!(&:blank?)
      
      case
        when geocode && addresses.empty?
          geocode.destroy
          self.geocode = nil
          
        when geocode && !addresses.empty?
          geocode.update_attributes(:addresses => addresses)
          
        when !geocode && !addresses.empty?
          create_geocode(:addresses => addresses)
      end
    end
    
    def latitude
      geocode.latitude if geocode
    end
    
    def longitude
      geocode.longitude if geocode
    end
    
    def to_location
      geocode.to_location if geocode
    end
  end
end

class ActiveRecord::Base
  include GeocodableModel
end