class IO::Endpoint::Wrapper

def accept(server, timeout: nil, linger: nil, **options, &block)
	# Ensure we use a `loop do ... end` so that state is not leaked between iterations:
	loop do
		socket, address = server.accept
		
		if linger
			socket.setsockopt(SOL_SOCKET, SO_LINGER, 1)
		end
		
		if timeout
			set_timeout(socket, timeout)
		end
		
		async do
			# Some sockets, notably SSL sockets, need application level negotiation before they are ready:
			if socket.respond_to?(:start)
				begin
					socket.start
				rescue
					socket.close
					raise
				end
			end
			
			# It seems like OpenSSL doesn't return the address of the peer when using `accept`, so we need to get it from the socket:
			address ||= socket.remote_address
			
			yield socket, address
		end
	end
end

def async
	raise NotImplementedError
end

def bind(local_address, protocol: 0, reuse_address: true, reuse_port: nil, linger: nil, bound_timeout: nil, backlog: Socket::SOMAXCONN, **options, &block)
	socket = nil
	
	begin
		socket = ServerSocket.new(local_address.afamily, local_address.socktype, protocol)
		
		if reuse_address
			socket.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
		end
		
		if reuse_port
			socket.setsockopt(SOL_SOCKET, SO_REUSEPORT, 1)
		end
		
		if linger
			socket.setsockopt(SOL_SOCKET, SO_LINGER, 1)
		end
		
		# Set the timeout:
		if bound_timeout
			set_timeout(socket, bound_timeout)
		end
		
		socket.bind(local_address.to_sockaddr)
		
		if backlog
			begin
				# Generally speaking, bind/listen is a common pattern, but it's not applicable to all socket types. We ignore the error if it's not supported as the alternative is exposing this upstream, which seems less desirable than handling it here. In other words, `bind` in this context means "prepare it to accept connections", whatever that means for the given socket type.
				socket.listen(backlog)
			rescue Errno::EOPNOTSUPP
				# Ignore.
			end
		end
	rescue
		socket&.close
		raise
	end
	
	return socket unless block_given?
	
	async do
		begin
			yield socket
		ensure
			socket.close
		end
	end
end

def connect(remote_address, local_address: nil, linger: nil, timeout: nil, buffered: false, **options)
	socket = nil
	
	begin
		socket = ::Socket.new(remote_address.afamily, remote_address.socktype, remote_address.protocol)
		
		if linger
			socket.setsockopt(SOL_SOCKET, SO_LINGER, 1)
		end
		
		if buffered == false
			set_buffered(socket, buffered)
		end
		
		if timeout
			set_timeout(socket, timeout)
		end
		
		if local_address
			if defined?(IP_BIND_ADDRESS_NO_PORT)
				# Inform the kernel (Linux 4.2+) to not reserve an ephemeral port when using bind(2) with a port number of 0. The port will later be automatically chosen at connect(2) time, in a way that allows sharing a source port as long as the 4-tuple is unique.
				socket.setsockopt(SOL_IP, IP_BIND_ADDRESS_NO_PORT, 1)
			end
			
			socket.bind(local_address.to_sockaddr)
		end
	rescue
		socket&.close
		raise
	end
	
	begin
		socket.connect(remote_address.to_sockaddr)
	rescue Exception
		socket.close
		raise
	end
	
	return socket unless block_given?
	
	begin
		yield socket
	ensure
		socket.close
	end
end

def set_buffered(socket, buffered)
	case buffered
	when true
		socket.setsockopt(IPPROTO_TCP, TCP_NODELAY, 0)
	when false
		socket.setsockopt(IPPROTO_TCP, TCP_NODELAY, 1)
	end
rescue Errno::EINVAL
	# On Darwin, sometimes occurs when the connection is not yet fully formed. Empirically, TCP_NODELAY is enabled despite this result.
rescue Errno::EOPNOTSUPP
	# Some platforms may simply not support the operation.
rescue Errno::ENOPROTOOPT
	# It may not be supported by the protocol (e.g. UDP). ¯\_(ツ)_/¯
end

def set_timeout(io, timeout)
	if io.respond_to?(:timeout=)
		io.timeout = timeout
	end
end