module Async::HTTP::Protocol::HTTP

def self.protocol_for(stream)
	# Detect HTTP/2 connection preface
	# https://www.rfc-editor.org/rfc/rfc9113.html#section-3.4
	preface = stream.peek do |read_buffer|
		if read_buffer.bytesize >= HTTP2_PREFACE_SIZE
			break read_buffer[0, HTTP2_PREFACE_SIZE]
		elsif read_buffer.bytesize > 0
			# If partial read_buffer already doesn't match, no need to wait for more bytes.
			break read_buffer unless HTTP2_PREFACE[read_buffer]
		end
	end
	
	if preface == HTTP2_PREFACE
		HTTP2
	else
		HTTP1
	end
end