module SqlAttributes

# File lib/sql_attributes.rb, line 29
  def sql_attribute(name, subquery)
    sql_attributes[name] = subquery.squish

    scope "with_#{name}".to_sym, lambda {
      select(
        arel.projections,
        "(#{subquery.squish}) as #{name}"
      )
    }

    define_method(name) do
      return read_attribute(name) if has_attribute?(name)

      raise NotLoaded, <<~MESSAGE
        Dynamic SQL attribute `#{name}` not loaded from the database.

          Use the `with_sql_attributes` scope to load the attribute.

      MESSAGE
    end
  end

# File lib/sql_attributes.rb, line 8
def sql_attributes
  @sql_attributes ||= HashWithIndifferentAccess.new
end

# File lib/sql_attributes.rb, line 12
def with_sql_attributes(*attributes)
  requested_attributes =
    if attributes.length.positive?
      Array.wrap(attributes).flatten.reject(&:nil?)
    else
      sql_attributes.keys
    end

  requested_attributes.inject(all) do |scope, name|
    unless sql_attributes.key?(name)
      raise NotDefined, "You want to load dynamic SQL attribute `#{name}` but it is not defined."
    end

    scope.public_send("with_#{name}")
  end
end