#!/bin/bash
#
# Set a default boot entry for GRUB, for the next boot only.
# Copyright (C) 2004,2009,2019  Free Software Foundation, Inc.
#
# GRUB is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# GRUB is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GRUB.  If not, see <http://www.gnu.org/licenses/>.

# Initialize some variables.
prefix=/usr
exec_prefix=/usr
bindir=${exec_prefix}/bin
sysconfdir="/etc"
PACKAGE_NAME=GRUB
PACKAGE_VERSION=2.02+dfsg1-20
datarootdir="/usr/share"
datadir="${datarootdir}"
if [ "x$pkgdatadir" = x ]; then
    pkgdatadir="${datadir}/grub"
fi

self=`basename $0`

grub_editenv=${bindir}/grub-editenv
rootdir=
bootdir=
grubdir=`echo "/boot/grub" | sed 's,//*,/,g'`

export TEXTDOMAIN=grub
export TEXTDOMAINDIR="${datarootdir}/locale"

. "${pkgdatadir}/grub-mkconfig_lib"

# Usage: usage
# Print the usage.
usage () {
    gettext_printf "Usage: %s [OPTION] [MENU_ENTRY]\n" "$self"
    gettext "Set the default boot menu entry for GRUB, for the next boot only."; echo
    print_option_help "-h, --help" "$(gettext "print this message and exit")"
    print_option_help "-V, --version" "$(gettext "print the version information and exit")"
    print_option_help "-s, --select" "$(gettext "interactively select entry to boot (DEFAULT)")"
    dirmsg="$(gettext_printf "expect GRUB images under the directory DIR/%s instead of the %s directory" "grub" "$grubdir")"
    print_option_help "--boot-directory=$(gettext "DIR")" "$dirmsg"
    echo

    gettext "MENU_ENTRY is a number, a menu item title or a menu item identifier. 
Please note that menu items in submenus or sub-submenus require
specifying the submenu components and then the menu item component. 
The titles should be separated using the greater-than character (>)
with no extra spaces. Depending on your shell some characters
including > may need escaping. More information about this is available
in the GRUB Manual in the section about the 'default' command. "; echo

    echo
    gettext "Report bugs to <bug-grub@gnu.org>."; echo
}

grub_parse_menu() {
    # Take a grub.cfg file from stdin.  Output a list of menu entries
    # with first word of each being that curious numerical format
    # wanted by 'grubenv set next_entry'. (e.g., "1>3>0")
    #
    # This should use the same C lexer/parser that grub actually uses.
    # Instead, here is a random snippit of awk code from @ZuZuD.
    # While woefully wrong-headed, it would work for most people.
    # (See, github.com/ZuZuD/gist:66decbe330ec560ac8e57e87150891b8)
    awk '
      BEGIN {submenu=0; menu=0};
       $1 ~ /submenu/ {submenu+=1; menu=0; sub(/\$.*$/,""); print submenu" " $0};
      /menuentry / && /Linux/ {gsub(/menuentry/,"");
     		     	      gsub(/--class.*$/,"");
    			      gsub(/\047/,"");
    			      print " "submenu">"menu " " $0;menu+=1}
      END {print "None of the above."};
    ' "$1"
}

grub_select_entry() {
    # Show grub boot menu options and ask which one to reboot into.
    # Sets choice in global variable "$entry".
    grub_config="$grubdir/grub.cfg"
    if [ ! -r "$grubdir/grub.cfg" ]; then
	gettext "Grub config file not readable: $grub_config." >&2
	echo >&2
	usage
	exit 1
    fi

    IFS=$'\n'
    mapfile -t entries < <(grub_parse_menu <"$grubdir/grub.cfg")
    unset IFS

    echo "Please pick an OS to reboot into (for this next boot only).  ^C to cancel."

    select x in "${entries[@]}"; do break; done

    if [ -z "$x" -a -n "$REPLY" ]; then
	# User typed something. Find first matching kernel or OS name.
	shopt -s nocasematch	# If user types "wIndOws" match "Windows"
	for y in "${entries[@]}"; do
	    case "$y" in
		*$REPLY*)
		    x="$y"
		    break
		    ;;
	    esac
	done
    fi

    case "$x" in
     None*|"")
	 # None of the above selected, so quit.
	 exit
	 ;;
    esac

    set - $x
    entry="$1"
    shift
    gettext_printf "Next reboot will be into \`%s'\n" "$*"
}


argument () {
  opt=$1
  shift

  if test $# -eq 0; then
      gettext_printf "%s: option requires an argument -- \`%s'\n" "$self" "$opt" 1>&2
      exit 1
  fi
  echo $1
}

# Check the arguments.
while test $# -gt 0
do
    option=$1
    shift

    case "$option" in
    -h | --help)
	usage
	exit 0 ;;
    -V | --version)
	echo "$self (${PACKAGE_NAME}) ${PACKAGE_VERSION}"
	exit 0 ;;
    -s | --select)
	sflag="true"; shift;;

# Accept for compatibility
    --root-directory)
	rootdir=`argument $option "$@"`; shift ;;
    --root-directory=*)
	rootdir=`echo "$option" | sed 's/--root-directory=//'` ;;

    --boot-directory)
    bootdir=`argument $option "$@"`; shift;;
    --boot-directory=*)
    bootdir=`echo "$option" | sed 's/--boot-directory=//'` ;;

    -*)
	gettext_printf "Unrecognized option \`%s'\n" "$option" 1>&2
	usage
	exit 1
	;;
    *)
	if test "x$entry" != x; then
	    gettext "More than one menu entry?" 1>&2
	    echo >&2
	    usage
	    exit 1
	fi
	entry="${option}" ;;
    esac
done

if [ -z "$bootdir" ]; then
    # Default bootdir if bootdir not initialized.
    bootdir=/boot

    if [ -n "$rootdir" ] ; then
        # Initialize bootdir if rootdir was initialized.
        bootdir=${rootdir}/boot
    fi
fi

grubdir=`echo "${bootdir}/grub" | sed 's,//*,/,g'`

if [ -n "$sflag" -o -z "$entry" ]; then
    grub_select_entry		# Show menu to set $entry 
fi

if test "x$entry" = x; then
    gettext "Menu entry not specified." 1>&2
    echo >&2
    usage
    exit 1
fi

# Restore saved_entry if it was set by previous version
prev_saved_entry=`$grub_editenv ${grubdir}/grubenv list | sed -n 's/^prev_saved_entry=//p'`
if [ "$prev_saved_entry" ]; then
    $grub_editenv ${grubdir}/grubenv set saved_entry="$prev_saved_entry"
    $grub_editenv ${grubdir}/grubenv unset prev_saved_entry
fi

$grub_editenv ${grubdir}/grubenv set next_entry="$entry"

# Bye.
exit 0