gibtar/server.py

import asyncio
import asyncio.streams
import logging
from typing import Iterable

from proto import control_pb2

LOGGER = logging.getLogger("server")

MAGIC = "e8437140-4347-48cc-a31d-dcdc944ffc15"
SUPPORTED_FORMATS = [
	"protobuf",
	"json",
]

class Connection:
	def __init__(self, reader, writer, namespace: str, app_name: str, app_version: str, chosen_format: str, client_key: str):
		self.reader = reader
		self.writer = writer
		self.namepsace = namespace
		self.app_name = app_name
		self.app_version = app_version
		self.chosen_format = chosen_format
		self.client_key = client_key

def main():
	logging.basicConfig(level=logging.DEBUG)
	try:
		asyncio.run(run())
	except KeyboardInterrupt:
		LOGGER.info("Exiting")

async def on_connect(reader, writer):
	LOGGER.info("connected")
	try:
		connection = await handshake(reader, writer)
		while True:
			data = await reader.read(4096)
			LOGGER.debug("Got data: '%s'", data)
			command = control_pb2.Command.FromString(data)
			LOGGER.info("Command: %s", command)
			await asyncio.sleep(1)
	except ClientError:
		LOGGER.info("Client error")

class ClientError(Exception):
	pass

async def handshake(reader, writer) -> Connection:
	data = await reader.read(36 + 1)
	magic = data.decode("UTF-8")
	LOGGER.debug("Received magic '%s'", magic)
	if magic != MAGIC + " ":
		await _write_error(writer, 1, "Magic not recognized")
	LOGGER.debug("Magic looks good.")
	data = await reader.read(1024)
	client_hand = data.decode("UTF-8")
	client_formats, namespace, app_name, app_version, client_key = client_hand.split(" ")
	chosen_format = _select_format(client_formats.split(","), SUPPORTED_FORMATS)
	if not chosen_format:
		await _write_error(writer, 2, "server does not support any of " + client_formats)
	target_url = "127.0.0.1:9988"
	server_pub_key = "fakeserverkey"
	server_hand = " ".join([
		chosen_format,
		target_url,
		server_pub_key,
	])
	writer.write(server_hand.encode("UTF-8"))
	LOGGER.info("Sending %s", server_hand)
	return Connection(
		reader, writer, namespace, app_name, app_version, chosen_format, client_key)
		
async def run():
	server = await asyncio.start_server(on_connect, host="localhost", port=9988)
	async with server:
		try:
			await server.serve_forever()
		except KeyboardInterrupt:
			LOGGER.info("Exiting at user request.")

def _select_format(client_formats: Iterable[str], supported_formats: Iterable[str]) -> str:
	"Pick a format to use with the client."
	for f in supported_formats:
		if f in client_formats:
			return f
	
async def _write_error(writer, code: int, message: str) -> None:
	await writer.write(f"ERR{code}: {message}".encode("UTF-8"))
	writer.close()
	LOGGER.info("Client error: %d %s", code, message)
	raise ClientError("Failed")


if __name__ == "__main__":
	main()