#!/bin/sh -euf

# Copyright 2013-2014 Intel Corporation
# Author: Artem Bityutskiy
# License: GPLv2

PROG="setup-extlinux-conf"
VER="1.0"

srcdir="$(readlink -ev -- ${0%/*})"
if [ -f "$srcdir/setup-ivi-sh-functions" ]; then
	. "$srcdir/setup-ivi-sh-functions"
else
	.  /usr/share/setup-ivi/setup-ivi-sh-functions
fi

# This is a small trick which I use to make sure my scripts are portable -
# check if 'dash' is present, and if yes - use it.
if can_switch_to_dash; then
	exec dash -euf -- "$srcdir/$PROG" "$@"
	exit $?
fi

# Common preparations for all subcommands.
prepare()
{
	verbose "Boot directory is $bootdir"
	[ -d "$bootdir" ] || \
		fatal "boot directory path \"$bootdir\" does not exist"

	# The extlinux configuration directory
	conf_dir="$bootdir/extlinux"
	# The extlinux configuration file
	conf_file="$conf_dir/extlinux.conf"
}

# Create the default extlinux configuration file.
create_default_conf_file()
{
	verbose "creating the default configuration file \"$conf_file\""

	mkdir -p $verbose -- "$conf_dir" >&2
	cat > "$conf_file" <<-EOF
	# Generated by $PROG
	ui vesamenu.c32
	prompt 0
	timeout 1
	default $1
	EOF
}

# Check wheter the extlinux configuration file exist and if not:
#   o create the default one if --force option was specified
#   o fail if no --force option was specified
check_and_create_default_conf_file()
{
	if [ -s "$conf_file" ]; then
		return 0
	fi

	if [ -n "$force" ]; then
		create_default_conf_file "$1"
	else
		fatal "cannot find the extlinux configuration file" \
		      "(\"$conf_file\") (use -f to force creating the" \
		      "default one)"
	fi
}

# Get a regular expression for matching extlinux configuration file option "$1"
get_regexp()
{
	local opt="$(esc_regexp "$1")"

	opt="$(case_insensitive_regexp "$opt")"
	printf "%s" "\(^[[:blank:]]*$opt[[:blank:]]\+\)\([^[:blank:]]\+\)\([[:blank:]]*$\)"
}

# Return a regular expression for matching label with name "$1".
label_regexp()
{
	local opt="$(case_insensitive_regexp "label")"
	local label="$(esc_regexp "$1")"

	printf "%s" "\(^[[:blank:]]*$opt[[:blank:]]\+\)\($label\)\([[:blank:]]*$\)"
}

remove_label()
{
	local label="$1"
	local l_regexp="$(label_regexp "$label")"
	local anyl_regexp="$(get_regexp "label")"

	LC_ALL=C sed -i -n -e "/$l_regexp/ { # mathes our label line
	                :l n;                # get the next line
			/$l_regexp/bl        # same label again, keep skipping
			/$anyl_regexp/!bl    # a different label, stop skipping
	            }
	            /$l_regexp/!p            # print all other lines
		    " -- "$conf_file"

	remove_trailing_empty_lines "$conf_file"
}

#
# -----------------------------------------------------------------------------
# The "add" subcommand
# -----------------------------------------------------------------------------
#

show_add_usage()
{
	cat <<-EOF
Usage: $PROG add [options] <label> <title> <kernel> <options>

Add a new extlinux boot menu entry. The mandatory arguments are:

    <label>   - a unique name of the boot menu entry to add, the entry will be
                further refurred by the label
    <title>   - the boot menu entry title
    <kernel>  - name of the kernel binary corresponding to the entry
    <options> - kernel boot options

Options:
  -f, --force  if <label> already exists - re-create it, if
               <bootdir>/extlinux/extlinux.conf does not exist - create it, if
	       <bootdir>/<kernel> does not exist - do not fail
  -h, --help   show this text and exit
EOF
}

show_add_usage_fail()
{
	IFS= printf "%s\n\n" "$PROG: error: $*" >&2
	show_add_usage >&2
	exit 1
}

add_subcommand()
{
	if [ "$#" -eq 0  ]; then
		show_add_usage
		exit 0
	fi

	local tmp
	tmp=`getopt -n $PROG -o f,h --long force,help -- "$@"` ||
		show_add_usage_fail "cannot parse command-line options"
	eval set -- "$tmp"

	local force=
	while true; do
		case "$1" in
		-f|--force)
			force="-f"
			;;
		-h|--help)
			show_add_usage
			exit 0
			;;
		--) shift; break
			;;
		*) show_add_usage_fail "unrecognized option \"$1\""
			;;
		esac
		shift
	done

	if [ "$#" -lt 4 ]; then
		show_add_usage_fail "too little arguments"
	fi
	if [ "$#" -gt 4 ]; then
		show_add_usage_fail "too many arguments: \"$1\""
	fi

	prepare

	local label="$1"; shift
	local title="$1"; shift
	local kernel="$1"; shift
	local options="$1"; shift
	local kernel_path="$bootdir/$kernel"

	verbose "label is \"$label\""
	verbose "title is \"$title\""
	verbose "kernel is \"$kernel\""
	verbose "options are \"$options\""

	if ! [ -f "$kernel_path" ] && [ -z "$force" ]; then
		fatal "cannot find kernel \"$kernel_path\"" \
		      "(use -f to ignore this error)"
	fi

	# Make sure the extlinux configuration file exists
	check_and_create_default_conf_file "$label"

	if LC_ALL=C grep -q -e "$(label_regexp "$label")" -- "$conf_file" && \
	   [ -z "$force" ]; then
		fatal "extlinux boot menu label \"$label\" already exists" \
		      "(use -f to force re-creating it)"
	fi

	# Find out the kernel version from its name
	local kernel_version="$(printf "%s" "$kernel" | LC_ALL=C \
		   sed -e 's/[^[:digit:]]\+-\([[:digit:]]\+.*\)/\1/')"
	[ -n "$kernel_version" ] || \
		fatal "cannot fetch kernel version from \"$kernel\""

	# Remove the label if it exists, since we are going to add a new one
	remove_label "$label"

	local block="label $label
	menu label $title ($kernel_version)
	linux /$kernel
	append $options"

	printf "\n%s\n" "$block" >> "$conf_file"

	if [ -n "$verbose" ]; then
		verbose "Added the following to \"$conf_file\":"
		printf "%s\n" "$block" >&2
	fi
}

#
# -----------------------------------------------------------------------------
# The "remove" subcommand
# -----------------------------------------------------------------------------
#

show_remove_usage()
{
	cat <<-EOF
Usage: $PROG remove [options] <label>

Delete extlinux boot entry which has label <label>.

Options:
  -f, --force  do not fail if the entry doesn't exist
  -h, --help   show this text and exit
EOF
}

show_remove_usage_fail()
{
	IFS= printf "%s\n\n" "$PROG: error: $*" >&2
	show_remove_usage >&2
	exit 1
}

remove_subcommand()
{
	if [ "$#" -eq 0  ]; then
		show_remove_usage
		exit 0
	fi

	local tmp
	tmp=`getopt -n $PROG -o f,h --long force,help -- "$@"` ||
		show_remove_usage_fail "cannot parse command-line options"
	eval set -- "$tmp"

	local force=
	while true; do
		case "$1" in
		-f|--force)
			force="-f"
			;;
		-h|--help)
			show_remove_usage
			exit 0
			;;
		--) shift; break
			;;
		*) show_remove_usage_fail "unrecognized option \"$1\""
			;;
		esac
		shift
	done

	if [ "$#" -lt 1 ]; then
		show_remove_usage_fail "too little arguments"
	fi
	if [ "$#" -gt 1 ]; then
		show_remove_usage_fail "too many arguments: \"$1\""
	fi

	prepare

	local label="$1"

	if ! LC_ALL=C grep -q -e "$(label_regexp "$label")" -- "$conf_file" && \
	   [ -z "$force" ]; then
		fatal "cannot find label \"$label\" in \"$conf_file\"" \
		      "(use -f to ignore this error)"
	fi

	remove_label "$label"
	verbose "removed $label"
}

#
# -----------------------------------------------------------------------------
# The "default" subcommand
# -----------------------------------------------------------------------------
#

# Get the kernel binary name by its extlinux.conf label name
get_kernel_by_label()
{
	local label="$1"
	local l_regexp="$(label_regexp "$label")"  # Regexp for our label
	local anyl_regexp="$(get_regexp "label")"  # Regexp for any label
	local linux_regexp="$(get_regexp "linux")"
	local kernel_regexp="$(get_regexp "kernel")"
	local result

	[ -z "$label" ] && return 0

	result="$(LC_ALL=C sed -n -e "/$l_regexp/ {
		:l n;
		/$linux_regexp/ { s/$linux_regexp/\2/p }
		/$kernel_regexp/ { s/$kernel_regexp/\2/p }
		/$anyl_regexp/!bl # Loop till the next label
	}" -- "$conf_file")"

	printf "%s" "${result##*/}"
}

show_default_usage()
{
	cat <<-EOF
Usage: $PROG default [options] <label>

Set the default boot kernel to be the kernel which is marked with label <label>
the extlinux configuration file. If <label> is omited, this command prints the
currently default entry name.

Options:
  -f, --force  <bootdir>/extlinux/extlinux.conf does not exist - create it, if
               <label> does not exist - do not fail
  -h, --help   show this text and exit
EOF
}

show_default_usage_fail()
{
	IFS= printf "%s\n\n" "$PROG: error: $*" >&2
	show_default_usage >&2
	exit 1
}

default_subcommand()
{
	local tmp
	tmp=`getopt -n $PROG -o f,h --long force,help -- "$@"` ||
		show_default_usage_fail "cannot parse command-line options"
	eval set -- "$tmp"

	local force=
	while true; do
		case "$1" in
		-f|--force)
			force="-f"
			;;
		-h|--help)
			show_default_usage
			exit 0
			;;
		--) shift; break
			;;
		*) show_default_usage_fail "unrecognized option \"$1\""
			;;
		esac
		shift
	done

	if [ "$#" -gt 1 ]; then
		show_default_usage_fail "too many arguments: \"$1\""
	fi

	prepare

	local label="${1:-}";

	# Make sure the extlinux configuration file exists
	check_and_create_default_conf_file "$label"

	# Find the current default label
	local regexp="$(get_regexp "default")"
	local default_label="$(LC_ALL=C sed -n -e "s/$regexp/\2/p" -- \
				"$conf_file")"

	if [ -z "$label" ]; then
		printf "%s\n" "label: $default_label"
		printf "%s\n" "kernel: $(get_kernel_by_label "$default_label")"
		return 0
	fi

	local l_regexp="$(label_regexp "$label")"
	local labels="$(LC_ALL=C grep -e "$l_regexp" -- "$conf_file" | wc -l)"

	if [ "$labels" -eq "0" ] && [ -z "$force" ]; then
		fatal "cannot find label \"$label\" in \"$conf_file\"" \
		      "(use -f to ignore this error)"
	fi

	if [ "$labels" -gt "1" ]; then
		fatal "more than one labels \"$label\" in \"$conf_file\""
	fi

	if [ -z "$default_label" ]; then
		verbose "no default label found, adding \"$label\""

		local def="$(esc_sed_replacement "default $label")"
		local anyl_regexp="$(get_regexp "label")"

		LC_ALL=C sed -i -e "
			$                 { s/.*/&\n$def/; q }
			/^[[:blank:]]*$/  { s/.*/$def\n&/; q }
			/$(anyl_regexp)/  { s/.*/$def\n&/; q }
			" -- "$conf_file"
		return 0
	fi

	# Escape special sed characters in "$entry" and replace the old default
	# entry with the new one
	local esc_label="$(esc_sed_replacement "$label")"
	LC_ALL=C sed -i -e "s/$regexp/\1$esc_label\3/" -- "$conf_file"
	verbose "set the default boot kernel to \"$label"\"
}

#
# -----------------------------------------------------------------------------
#

show_usage()
{
	cat <<-EOF
Usage: $PROG [options] <subcommand> [options] <arguments>

This program changes the extlinux bootloader configuration. Supported
subcommands are:
   add     - add an extlinux boot menu entry for a kernel
   remove  - remove an extlinux boot menu entry
   default - get or set the default extlinux boot menu entry

Run "$PROG <subcommand>" to see subcommand-specific help.

Options:
  -b, --bootdir  path to the boot directory (default is "/boot")
  --version      show the program version and exit
  -v, --verbose  be verbose
  -h, --help     show this text and exit
EOF
}

show_usage_fail()
{
	IFS= printf "%s\n\n" "$PROG: error: $*" >&2
	show_usage >&2
	exit 1
}

bootdir="/boot"
verbose=
while [ -n "${1:-""}" ] && [ -z "${1##-*}" ]; do
	case "$1" in
	-b|--bootdir)
		shift
		# If there is no argument or it starts with "-", complain
		if [ -z "${1:-""}" ] || [ -z "${1##-*}" ]; then
			fatal "--bootdir requires an argument"
		fi
		bootdir="$1"
		;;
	--version)
		printf "%s\n" "$VER"
		exit 0
		;;
	-v|--verbose)
		verbose="-v"
		;;
	-h|--help)
		show_usage
		exit 0
		;;
	--) shift; break
		;;
	*) show_usage_fail "unrecognized option \"$1\""
		;;
	esac
	shift
done

# Parse subcommands

if [ "$#" -eq 0 ]; then
	show_usage
	exit 0
fi


subcommand="$1"; shift

case "$subcommand" in
add)
	add_subcommand "$@"
	break
	;;
remove)
	remove_subcommand "$@"
	break
	;;
default)
	default_subcommand "$@"
	break
	;;
*) show_usage_fail "unrecognized subcommand \"$subcommand\""
	;;
esac