#!/bin/sh -efu

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

# This script assumes there is a working gummiboot configuration exists. This
# scripts then scanse the boot partition, finds out which kernels are
# available, and updates the gummiboot kernel entries: adds missing kernel
# entries and delets non-existing kernel entries. The default entry is always
# set to the latest kernel.
#
# We make several assumptions in this script.
# 1. The kernel binary names are 'vmlinuz-<version>'
# 2. Kernel entry file names are 'vmlinuz-<version>.conf'
# 3. There is always the "default" keyword in loader.conf, and we use the
#    corresponding kernel entry for adding new kernels.
# 4. The 'default' entry in loader.conf does not does not use the wildcard ("*")
# 5. Kernels binaries are placed in the ESP root
#
# May be there are few more implicit assumption. This all can be improved and
# made to be more flexible if needed.

PROG="setup-gummiboot-conf"

# This is a helper function which printfs an error message and exits
fatal()
{
	printf "%s\n" "$PROG: error: $1\n" 1>&2
	exit 1
}

# Right now we assume that ESP is always in "/boot", but later we can add a
# command line option for this.
esp="/home/dedekind/tmp/boot"
conf_file="$esp/loader/loader.conf"
entries_dir="$esp/loader/entries"

# Make sure the gummiboot configuration file exists
[ -f "$conf_file" ] || \
	fatal "cannot find the gummiboot configuration file (\"$conf_file\")"

# Get the list of installed kernels
kernels="$(ls -1 "$esp" | grep '^vmlinuz-' | sort -r)"
[ -n "$kernels" ] || \
	fatal "no vmlinuz-* files found in \"$esp\""

# Get the list of gummiboot kernel entries
entries="$(ls -1 "$entries_dir" | sed -e 's/\.conf$//g' | sort -r)"
[ -n "$entries" ] || \
	fatal "no gummiboot entries found in \"$entries_dir\""

# Get the default entry name
default_entry="$(cat "$conf_file" | sed -n -e 's/[ \t]*default[ \t]\+\(.\+\)[ \t]*/\1/p')"
[ -n "$default_entry" ] || \
	fatal "cannot find the default entry in \"$conf_file\""
[ "$(printf "%s\n" "$default_entry" | wc -l)" -eq "1" ] || \
	fatal "more than one default entry in \"$conf_file\""

if ! [ -f "$entries_dir/$default_entry" ]; then
	# The default entry does not exist anymore. Pick the entry
	# corresponding to the newest kernel then.
	default_entry="$(printf "%s" "$entries" | head -n1)"
fi

# Use the default entry to prepare the pattern for other entries
pattern="$(cat "$entries_dir/$default_entry")"
# Drop few keywords which we won't need
pattern="$(printf "%s" "$pattern" | sed -e '/[ \t]*linux[ \t]\+/d')"
pattern="$(printf "%s" "$pattern" | sed -e '/[ \t]*efi[ \t]\+/d')"
pattern="$(printf "%s" "$pattern" | sed -e '/[ \t]*version[ \t]\+/d')"

# Create an entry for every new kernel
printf "%s\n" "$kernels" | while IFS= read -r kernel; do

	if [ -f "$entries_dir/$kernel.conf" ]; then
		continue
	fi

	kernel_version="$(printf "%s" $kernel | sed -e 's/vmlinuz-\(.*\)/\1/')"

	printf "%s" "$pattern" > "$entries_dir/$kernel.conf"
	printf "\n%s" "version $kernel_version" >> "$entries_dir/$kernel.conf"
	printf "\n%s" "efi /$kernel" >> "$entries_dir/$kernel.conf"
done

# Update the default entry
newest_kernel="$(printf "%s" "$kernels" | head -n1)"
sed -i -e "s/[ \t]*default[ \t]\+.*/default $newest_kernel.conf/" "$conf_file"

# Remove gummiboot entries for non-existing kernels
printf "%s\n" "$entries" | while IFS= read -r entry; do
	kernel="$entry"
	[ -f "$esp/$kernel" ] || rm "$entries_dir/$entry.conf"
done