# AWEXOME LABS
# DoesKeyValue
#
# Indexes -- ActiveRecord::Base methods for settings and retrieval of values based
#   on key indexes

module DoesKeyValue
  module Indexes
    
    def declare_index(key_value_column, key_name, opts={})
      raise DoesKeyValue::NoColumnNameSpecified unless key_value_column
      raise DoesKeyValue::NoKeyNameSpecified unless key_name
      raise DoesKeyValue::KeyAndIndexOptionsMustBeHash unless opts.is_a?(Hash)
      
      search_key = "#{key_value_column}.#{key_name}"
      # TODO: raise DoesKeyValue::NoKeyForThatIndex if !self.respond_to?(key_name) || !self.respond_to?("#{key_name}=")
      
      class_name = self.name.underscore
      class_table_name = self.table_name
      index_table_name = "key_value_index"
      
      # INDEX TABLE: key_value_index
      #  id:int
      #  key_name:string
      #  value:string
      #  obj_type:string
      #  obj_id:int
      
      # Define finders that leverage the custom index table:
      instance_eval <<-EOS
        def find_all_by_#{key_value_column}_#{key_name}(value)
          find(
            :all, 
            :select=>"*",
            :from=>"#{index_table_name}",
            :conditions=>["`#{index_table_name}`.obj_type = ? AND `#{index_table_name}`.key_name = ? AND `#{index_table_name}`.value = ?", self.to_s, "#{search_key}", value], 
            :joins => "LEFT JOIN `#{class_table_name}` ON `#{class_table_name}`.id = `#{index_table_name}`.obj_id"          
          )
        end
        
        def find_all_by_#{key_name}(value)
          find_all_by_#{key_value_column}_#{key_name}(value)
        end
        
        def find_all_with_#{key_value_column}(opts={})
          conds = Array.new
          opts.each do |k, v|
            conds.add_condition(["`#{index_table_name}`.obj_type = ? AND `#{index_table_name}`.key_name = ? AND `#{index_table_name}`.value = ?", self.to_s, "#{search_key}", v])
          end
          find(
            :all,
            :select=>"*",
            :from=>"#{index_table_name}",
            :conditions=>conds,
            :joins=>"LEFT JOIN `#{class_table_name}` ON `#{class_table_name}`.id = `#{index_table_name}`.obj_id"
          )
        end
      EOS
      
      # Provide a callback after save which updates the index
      define_method("update_index_#{key_value_column}_#{key_name}_after_save") do
        class_name = self.class.name.underscore
        class_table_name = self.class.table_name
        index_table_name = "key_value_index"

        # TODO: Restrict value to 255 characters, the table-enforced limit
        
        # TODO: Serialize value in such a nils to be properly represented
        #  Sample JSON Serialization: tab.to_json
        #  Sample JSON Reconstruction: Tab.new( JSON.parse(tab.to_json)["tab"] )
        
        new_value = self.send(key_name)
        up_count = ActiveRecord::Base.connection.update("
          UPDATE `#{index_table_name}` SET `value` = \"#{new_value}\", `updated_at` = NOW()
          WHERE `obj_type`=\"#{self.class}\" AND `obj_id`=#{self.id} AND `key_name`=\"#{search_key}\"
        ")
        if !new_value.nil? && up_count == 0
          idx_id = ActiveRecord::Base.connection.insert(
            "INSERT INTO `#{index_table_name}` (`obj_type`,`obj_id`,`key_name`,`value`,`created_at`,`updated_at`) VALUES (\"#{self.class}\", #{self.id}, \"#{search_key}\", \"#{new_value}\", NOW(), NOW())
          ")
          return idx_id
        end
        
      end
      after_save "update_index_#{key_value_column}_#{key_name}_after_save"
      
      # Provide a callback after destroy to likewise update the index
      define_method("update_index_#{key_value_column}_#{key_name}_after_destroy") do
        class_name = self.class.name.underscore
        class_table_name = self.class.table_name
        index_table_name = "key_value_index"
        num_del = ActiveRecord::Base.connection.delete("DELETE FROM `#{index_table_name}` WHERE `obj_type` = \"#{self.class}\" AND `obj_id` = #{self.id}")
      end
      after_destroy "update_index_#{key_value_column}_#{key_name}_after_destroy"
      
      
      # Add the index to the key and column manager:
      DoesKeyValue::KeyManager.instance.declare_index(self, key_value_column, key_name, opts)
      
    end
        
    
  end # Indexes
end # DoesKeyValue