"""The interactive shell netmiko opens, made fit to be read before the first command."""

from __future__ import annotations

import logging
from typing import Any

logger = logging.getLogger(__name__)

#: The end of a command's output when nothing better is known: a line that looks
#: like a shell prompt.
PROMPT_RE = r"[#$\>]\s*$"

#: Sent before anything else in the interactive session (NetOrk/netork#1039):
#: the shell writes no history file and records nothing more. The leading space
#: keeps this line itself out of a history under ``HISTCONTROL=ignorespace``;
#: a shell without ``set -o history`` (dash) only complains, to /dev/null.
HISTORY_OFF = " unset HISTFILE; set +o history 2>/dev/null; true"

#: Sent right after ``HISTORY_OFF`` (#41): systemd 258's
#: ``/etc/profile.d/80-systemd-osc-context.sh`` wraps every command in OSC 3008
#: sequences from ``PS0`` and ``PROMPT_COMMAND``, each with a fresh UUID. It appends
#: to ``PROMPT_COMMAND`` as an array, so only ``unset`` removes its hook.
PROMPT_HOOKS_OFF = " unset PS0 PROMPT_COMMAND; true"

#: Keeps the PTY from wrapping long output lines (e.g. docker JSON).
NO_LINE_WRAP = "stty cols 10000 2>/dev/null || true"


def prepare_shell(device: Any, hostname: str) -> None:
    """Make netmiko's fresh shell *device* fit to read, one step at a time.

    A step the shell refuses is logged and skipped: none of them is worth
    failing the connection for.
    """
    # No history before anything else is typed (NetOrk/netork#1039).
    try:
        device.send_command(HISTORY_OFF, expect_string=PROMPT_RE)
    except Exception:
        logger.debug("Could not switch the shell history off on %s", hostname, exc_info=True)

    # No systemd OSC 3008 context around every command (#41). netmiko learned
    # the prompt with those sequences in front, and a prompt carrying a fresh
    # UUID never matches again, so it reads the prompt anew once they are gone.
    try:
        device.send_command(PROMPT_HOOKS_OFF, expect_string=PROMPT_RE)
        device.set_base_prompt()
    except Exception:
        logger.debug("Could not switch the prompt hooks off on %s", hostname, exc_info=True)

    try:
        device.send_command(NO_LINE_WRAP, expect_string=PROMPT_RE)
    except Exception:
        logger.debug("%s: ignored", hostname, exc_info=True)