module IO::Event::Selector

def self.default(env = ENV)
	if name = env['IO_EVENT_SELECTOR']&.to_sym
		return const_get(name)
	end
	
	if self.const_defined?(:URing)
		URing
	elsif self.const_defined?(:EPoll)
		EPoll
	elsif self.const_defined?(:KQueue)
		KQueue
	else
		Select
	end
end

def self.new(loop, env = ENV)
	selector = default(env).new(loop)
	
	if debug = env['IO_EVENT_DEBUG_SELECTOR']
		selector = Debug::Selector.wrap(selector, env)
	end
	
	return selector
end

def self.nonblock(io, &block)
	io.nonblock(&block)
rescue Errno::EBADF
	# Windows.
	yield
end