# Copyright (C) 2009-2010, 2020 Canonical Ltd.
# Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
#
# Author: Scott Moser <scott.moser@canonical.com>
# Author: Juerg Haefliger <juerg.haefliger@hp.com>
# Author: Matthew Ruffell <matthew.ruffell@canonical.com>
#
# This file is part of cloud-init. See LICENSE file for license information.
"""Grub Dpkg: Configure grub debconf installation device"""

import os
from textwrap import dedent

from cloudinit import subp, util
from cloudinit.config.schema import MetaSchema, get_meta_doc
from cloudinit.settings import PER_INSTANCE
from cloudinit.subp import ProcessExecutionError

MODULE_DESCRIPTION = """\
Configure which device is used as the target for grub installation. This module
should work correctly by default without any user configuration. It can be
enabled/disabled using the ``enabled`` config key in the ``grub_dpkg`` config
dict. The global config key ``grub-dpkg`` is an alias for ``grub_dpkg``. If no
installation device is specified this module will execute grub-probe to
determine which disk the /boot directory is associated with.

The value which is placed into the debconf database is in the format which the
grub postinstall script expects. Normally, this is a /dev/disk/by-id/ value,
but we do fallback to the plain disk name if a by-id name is not present.

If this module is executed inside a container, then the debconf database is
seeded with empty values, and install_devices_empty is set to true.
"""
distros = ["ubuntu", "debian"]
meta: MetaSchema = {
    "id": "cc_grub_dpkg",
    "name": "Grub Dpkg",
    "title": "Configure grub debconf installation device",
    "description": MODULE_DESCRIPTION,
    "distros": distros,
    "frequency": PER_INSTANCE,
    "examples": [
        dedent(
            """\
            grub_dpkg:
              enabled: true
              grub-pc/install_devices: /dev/sda
              grub-pc/install_devices_empty: false
            """
        )
    ],
}

__doc__ = get_meta_doc(meta)


def fetch_idevs(log):
    """
    Fetches the /dev/disk/by-id device grub is installed to.
    Falls back to plain disk name if no by-id entry is present.
    """
    disk = ""
    devices = []

    try:
        # get the root disk where the /boot directory resides.
        disk = subp.subp(["grub-probe", "-t", "disk", "/boot"], capture=True)[
            0
        ].strip()
    except ProcessExecutionError as e:
        # grub-common may not be installed, especially on containers
        # FileNotFoundError is a nested exception of ProcessExecutionError
        if isinstance(e.reason, FileNotFoundError):
            log.debug("'grub-probe' not found in $PATH")
        # disks from the container host are present in /proc and /sys
        # which is where grub-probe determines where /boot is.
        # it then checks for existence in /dev, which fails as host disks
        # are not exposed to the container.
        elif "failed to get canonical path" in e.stderr:
            log.debug("grub-probe 'failed to get canonical path'")
        else:
            # something bad has happened, continue to log the error
            raise
    except Exception:
        util.logexc(log, "grub-probe failed to execute for grub-dpkg")

    if not disk or not os.path.exists(disk):
        # If we failed to detect a disk, we can return early
        return ""

    try:
        # check if disk exists and use udevadm to fetch symlinks
        devices = (
            subp.subp(
                ["udevadm", "info", "--root", "--query=symlink", disk],
                capture=True,
            )[0]
            .strip()
            .split()
        )
    except Exception:
        util.logexc(
            log, "udevadm DEVLINKS symlink query failed for disk='%s'", disk
        )

    log.debug("considering these device symlinks: %s", ",".join(devices))
    # filter symlinks for /dev/disk/by-id entries
    devices = [dev for dev in devices if "disk/by-id" in dev]
    log.debug("filtered to these disk/by-id symlinks: %s", ",".join(devices))
    # select first device if there is one, else fall back to plain name
    idevs = sorted(devices)[0] if devices else disk
    log.debug("selected %s", idevs)

    return idevs


def handle(name, cfg, _cloud, log, _args):

    mycfg = cfg.get("grub_dpkg", cfg.get("grub-dpkg", {}))
    if not mycfg:
        mycfg = {}

    enabled = mycfg.get("enabled", True)
    if util.is_false(enabled):
        log.debug("%s disabled by config grub_dpkg/enabled=%s", name, enabled)
        return

    idevs = util.get_cfg_option_str(mycfg, "grub-pc/install_devices", None)
    if idevs is None:
        idevs = fetch_idevs(log)

    idevs_empty = mycfg.get("grub-pc/install_devices_empty")
    if idevs_empty is None:
        idevs_empty = not idevs
    elif not isinstance(idevs_empty, bool):
        log.warning(
            "DEPRECATED: grub_dpkg: grub-pc/install_devices_empty value of "
            f"'{idevs_empty}' is not boolean. Use of non-boolean values "
            "will be removed in a future version of cloud-init."
        )
        idevs_empty = util.translate_bool(idevs_empty)
    idevs_empty = str(idevs_empty).lower()

    # now idevs and idevs_empty are set to determined values
    # or, those set by user

    dconf_sel = (
        "grub-pc grub-pc/install_devices string %s\n"
        "grub-pc grub-pc/install_devices_empty boolean %s\n"
        % (idevs, idevs_empty)
    )

    log.debug(
        "Setting grub debconf-set-selections with '%s','%s'"
        % (idevs, idevs_empty)
    )

    try:
        subp.subp(["debconf-set-selections"], dconf_sel)
    except Exception:
        util.logexc(log, "Failed to run debconf-set-selections for grub-dpkg")


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