"""Simple utility to interface with BIRD using the control socket."""

from dataclasses import dataclass,field
import socket as sk
from string import digits
from select import select

class BirdError(Exception):
	def __init__(self, code, where, text):
		self.code = code
		self.start = where[0]
		self.end = where[1]
		self.text = text

@dataclass
class BirdResponse:
	text: str = ''
	codes: list[tuple[tuple[int, int], str]] = field(default_factory=list) # List of line ranges (inclusive) and the respective code.

	def raise_exceptions(self) -> None:
		# If the response contains any errors, raise them as BirdErrors
		# TODO Py3.11: use ExceptionGroups?
		# Until then, let's just report the first one?
		assert len(self.codes) >= 1, "Not a valid response."
		for where, code in self.codes:
			if code.startswith('9'):
				# Extract text
				start = where[0] - 1
				end = where[1]
				print(start,end)
				errorlines = self.text.splitlines(keepends=True)[start:end]
				exc = BirdError(code, where, ''.join(errorlines))
				raise exc

class BirdSocketConnection:
	def __init__(self, sockpath='/run/bird/bird.ctl'):
		self.socket = sk.socket(sk.AF_UNIX, sk.SOCK_STREAM)
		self.socket.setblocking(False)
		self.socket.connect(sockpath)
		# Bird announces itself by printing version. We save the response just in case.
		self.bird_prologue = self._parse_response()

	def request(self, req: str) -> BirdResponse:
		if not req.endswith('\n'):
			req = req + '\n'
		binreq = req.encode()
		self.socket.send(binreq)
		return self._parse_response()

	def _parse_response(self) -> BirdResponse:
		# We even read from the socket here in order to have the whole protocol
		# described at one place. Therefore other parts of the code do not need
		# to know anything about the protocol (maybe apart from the meaning of
		# status codes, if they are interested…)
		result = BirdResponse()
		code : str | None = None # string because of leading zeroes, and it has no numeric interpretation anyway
		start = None
		cont = True
		# The response might not yet be ready
		rrdy, wrdy, xrdy = select([self.socket], [], [], 1)
		if len(rrdy) == 0:
			print('WTF, no response in 1 second?')
		f = self.socket.makefile('r')
		for i, line in enumerate(f, start=1):
			assert cont, "WTF bad format (should not continue)."
			if line.startswith(tuple(digits)):
				if start is not None:
					end = i-1
					result.codes.append(((start, end), code))
				code = line[:4]
				start = i
				cont = line[4] == '-'
				text = line[5:]
			else:
				assert cont == True
				text = line[1:]
			result.text += text # Invariant: LF as line terminator
			if not cont:
				# Finalization. We do not have i after the end of the cycle,
				# but this is the last iteration.
				end = i
				result.codes.append(((start, end), code))
				break
		result.raise_exceptions()
		return result