"""Local AF_UNIX SOCK_SEQPACKET client for B-side control delivery."""

from __future__ import annotations

import os
import socket

from omnisocket_a_side.control_codec import CONTROL_PACKET_STRUCT

from . import DEFAULT_CTRL_SOCKET_PATH


class BSideControlClient:
    def __init__(self, socket_path: str | None = None) -> None:
        self.socket_path = socket_path or os.getenv(
            "OMNIBDAEMON_CTRL_SOCKET",
            DEFAULT_CTRL_SOCKET_PATH,
        )
        self._sock: socket.socket | None = None

    def connect(self) -> None:
        if not hasattr(socket, "AF_UNIX"):
            raise OSError("AF_UNIX sockets are not available on this platform")
        if not hasattr(socket, "SOCK_SEQPACKET"):
            raise OSError("SOCK_SEQPACKET is not available on this platform")
        sock = socket.socket(socket.AF_UNIX, socket.SOCK_SEQPACKET)
        sock.connect(self.socket_path)
        self._sock = sock

    def recv_control_packet(self, timeout_ms: int = 100) -> bytes | None:
        if self._sock is None:
            raise RuntimeError("B-side control client is not connected")

        self._sock.settimeout(max(0.001, timeout_ms / 1000.0))
        try:
            payload = self._sock.recv(CONTROL_PACKET_STRUCT.size)
        except socket.timeout:
            return None
        except BlockingIOError:
            return None

        if payload == b"":
            raise ConnectionResetError("daemon control socket closed")
        if len(payload) != CONTROL_PACKET_STRUCT.size:
            return None
        return payload

    def close(self) -> None:
        if self._sock is None:
            return
        try:
            self._sock.close()
        finally:
            self._sock = None