#!/bin/sh

if grep -q '^disable_trigger=1' /etc/update-raspberrypi-bootloader.conf 2>/dev/null; then
	exit 0
fi

# see https://www.raspberrypi.com/documentation/computers/config_txt.html#kernel
# use the last found kernel for for example vmlinuz-rpi16k gets preference over
# vmlinuz-rpi
for i in /boot/vmlinuz* /boot/vmlinuz-lts /boot/vmlinuz-rpi /boot/vmlinuz-rpi*; do
	if [ -e "$i" ]; then
		kernel="${i#/boot/}"
		initramfs="initramfs${kernel#vmlinuz}"
	fi
done

if [ -z "$kernel" ]; then
	echo "$0: WARNING: no kernel found" >&2
	exit
fi

case "$(uname -m)" in
	aarch64) arm_64bit=1;;
	*) arm_64bit=0;;
esac

# busybox sed has no q command support so use grep to test pattern first
if grep -q '^kernel=' /boot/config.txt 2>/dev/null && \
	grep -q '^initramfs' /boot/config.txt && \
	grep -q '^arm_64bit=' /boot/config.txt; then
		cp -fa /boot/config.txt /boot/config.txt.new
		sed -i -e "s/^kernel=.*/kernel=$kernel/" \
			-e "s/^initramfs.*/initramfs $initramfs/" \
			-e "s/^arm_64bit=.*/arm_64bit=$arm_64bit/" /boot/config.txt.new
else
	cat > /boot/config.txt.new <<-EOF
	# do not modify this file as it will be overwritten on upgrade.
	# create and/or modify usercfg.txt instead.
	# https://www.raspberrypi.com/documentation/computers/config_txt.html
	#

	kernel=$kernel
	initramfs $initramfs
	arm_64bit=$arm_64bit
	include usercfg.txt
	EOF
fi

if diff -bBN /boot/config.txt.new /boot/config.txt >/dev/null; then
	rm -f /boot/config.txt.new
else
	mv -f /boot/config.txt /boot/config.txt.old 2>/dev/null
	mv -f /boot/config.txt.new /boot/config.txt
	echo "$0: INFO: replaced config.txt and saved config.txt.old, with following changes:"
	diff -bBN /boot/config.txt.old /boot/config.txt 2>/dev/null
fi

echo "Configured kernel $kernel / $initramfs"