class EcoRake
  module Default
    module Const
      class << self
        def included(base)
          super
          base.extend EcoRake::Base::SymbolResolver
          base.extend ClassMethods
        end
      end

      module ClassMethods
        # Creates (overridable) method(s) that link to an expected constant with same name (in capitals).
        # @note this creates one method on the class and one on instances thereof.
        # @param required [Boolean] whether an exception should be raised if the constant does not exist
        #   when the created method is called.
        # @param override [Boolean] whether an exception should NOT be raised if the method exists.
        # @param default [Variant] whether if this defaults to some value (won't raise NameError).
        def attr_const(*attrs, required: false, override: false, default: :not_used)
          attrs.each do |attr|
            attr = attr.to_s.freeze

            unless override
              msg  = "#{__method__} does not allow method override. Offending attr: #{attr}"
              raise ArgumentError, "#{msg} (class method)"    if methods.include?(attr)
              raise ArgumentError, "#{msg} (instance method)" if instance_methods.include?(attr)
            end

            define_singleton_method attr do
              value = resolve_const(attr)
              value = default if value.nil? && default != :not_used

              msg   = "Missing const '#{attr.to_s.upcase}' in #{self}"
              raise NameError, msg if value.nil? && required

              yield(value) if block_given?
              value
            end

            define_method attr do |&block|
              self.class.send(attr, &block)
            end
          end
        end
      end
    end
  end
end