module RSpec::Core::DSL

def self.change_global_dsl(&changes)
  (class << top_level; self; end).class_exec(&changes)
  Module.class_exec(&changes)
end

def self.example_group_aliases
  @example_group_aliases ||= []
end

def self.expose_example_group_alias(name)
  return if example_group_aliases.include?(name)
  example_group_aliases << name
  (class << RSpec; self; end).__send__(:define_method, name) do |*args, &example_group_block|
    group = RSpec::Core::ExampleGroup.__send__(name, *args, &example_group_block)
    RSpec.world.record(group)
    group
  end
  expose_example_group_alias_globally(name) if exposed_globally?
end

def self.expose_example_group_alias_globally(method_name)
  change_global_dsl do
    remove_method(method_name) if method_defined?(method_name)
    define_method(method_name) { |*a, &b| ::RSpec.__send__(method_name, *a, &b) }
  end
end

def self.expose_globally!
  return if exposed_globally?
  example_group_aliases.each do |method_name|
    expose_example_group_alias_globally(method_name)
  end
  @exposed_globally = true
end

def self.exposed_globally?
  @exposed_globally ||= false
end

def self.remove_globally!
  return unless exposed_globally?
  example_group_aliases.each do |method_name|
    change_global_dsl { undef_method method_name }
  end
  @exposed_globally = false
end