require 'pervasives'

module Attributes
  VERSION = '3.5.0'
  def self.version() VERSION end

  def attributes *a, &b
    unless a.empty?
      hashes, names = a.partition{|x| Hash === x}

      names_and_defaults = {}
      hashes.each{|h| names_and_defaults.update h}
      names.flatten.compact.each{|name| names_and_defaults.update name => nil}

      names_and_defaults.each do |name, default|
        init = b || lambda { default }
        ivar, getter, setter, query, banger =
          "@#{ name }", "#{ name }", "#{ name }=", "#{ name }?", "#{ name }!"

        define_method(setter) do |value|
          __pervasive__('instance_variable_set', ivar, value)
        end

        define_method(getter) do |*value|
          unless value.empty?
            __pervasive__('send', setter, value.shift)
          else
            defined = __pervasive__('instance_eval', "defined? #{ ivar }")
            __pervasive__('send', setter, __pervasive__('instance_eval', &init)) unless defined
            __pervasive__('instance_variable_get', ivar)
          end
        end

        define_method(banger) do
          __pervasive__('send', setter, __pervasive__('instance_eval', &init))
          __pervasive__('instance_variable_get', ivar)
        end

        alias_method query, getter

        (attributes << name.to_s).uniq!
        attributes
      end
    else
      begin
        __attribute_list__
      rescue NameError
        singleton_class =
          class << self
            self
          end
        klass = self
        singleton_class.module_eval do
          attribute_list = []
          define_method('attribute_list'){ klass == self ? attribute_list : raise(NameError) }
          alias_method '__attribute_list__', 'attribute_list'
        end
        __attribute_list__
      end
    end
  end

  %w( __attributes__ __attribute__ attribute ).each{|dst| alias_method dst, 'attributes'}
end

class Object
  def attributes *a, &b
    sc = 
      class << self
        self
      end
    sc.attributes *a, &b
  end
  %w( __attributes__ __attribute__ attribute ).each{|dst| alias_method dst, 'attributes'}
end

class Module
  include Attributes
end