#!/usr/bin/env bash
# Copyright (C) 2023  Umorpha Systems
# SPDX-License-Identifier: AGPL-3.0-or-later

set -euE -o pipefail

v() {
	printf >&2 '  $ %s\n' "${*@Q}"
	"$@"
}

main() {
	local rootfs size
	case "$1" in
		*rootfs*)
			rootfs="$1"
			size=$(stat --format='%s' -- "$rootfs")
			;;
		--stdin=*)
			rootfs=/dev/stdin
			size=${1#--stdin=}
			;;
		*)
			echo >&2 "!! Filename '${1}' does not look like a rootfs filename"
			return 2
			;;
	esac

	########################################################################

	cleanup=()
	_do_cleanup() {
		if [[ $? == 0 ]]; then
			echo ":: Cleaning up..."
		else
			echo >&2 "!! ERROR! Cleaning up..."
		fi
		for (( i=${#cleanup[@]}-1; i >= 0; i-- )); do
			eval "${cleanup[$i]}"
		done
	}
	trap '_do_cleanup' EXIT

	########################################################################

	local booted other
	booted=$(awk '$2 == "/run/umorpha-root/root"{print $1}' </proc/mounts)
	booted=${booted##*_}
	if [[ $booted == a ]]; then
		other=b
	else
		other=a
	fi

	echo ":: Installing '${rootfs}' to slot '$other'"

	v rm -f -- "/boot/grub/grub_$other.cfg"

	if [[ -e /dev/mapper/vg_umorpha-lv_root_$other ]]; then
		# Ugg, lvresize exits with non-zero for no-ops, which we can't
		# even really do a pre-flight check for since it might round a
		# size up.
		v lvresize --size="${size}b" "/dev/mapper/vg_umorpha-lv_root_$other" || true
	else
		v lvcreate --zero=y --wipesignatures=y --yes --name="lv_root_$other" \
			 --size="${size}b" vg_umorpha
	fi
	if [[ "$rootfs" == /dev/stdin ]]; then
		v pv --size="${size}" >"/dev/mapper/vg_umorpha-lv_root_$other"
	else
		v pv -- "$rootfs" >"/dev/mapper/vg_umorpha-lv_root_$other"
	fi

	########################################################################

	local tmpdir
	tmpdir="$(mktemp -dt "${0##*/}.XXXXXXXXXX")"
	cleanup+="rmdir -- ${tmpdir@Q}"

	########################################################################

	echo ":: Configuring boot"

	local selector_boot selector_root selector_overlay
	selector_root="$(   blkid --output=export "/dev/mapper/vg_umorpha-lv_root_$other" | grep ^UUID=)"
	selector_boot="$(   xargs -a /proc/cmdline printf '%s\n' | sed -n 's/^boot=//p')"
	selector_overlay="$(xargs -a /proc/cmdline printf '%s\n' | sed -n 's/^overlay_root=//p')"
	v declare -p selector_boot selector_root selector_overlay

	mkdir "$tmpdir/mnt"
	cleanup+=("rmdir -- ${tmpdir@Q}/mnt")
	v mount -o ro -- "/dev/mapper/vg_umorpha-lv_root_$other" "$tmpdir/mnt"
	cleanup+=("v umount ${tmpdir@Q}/mnt")

	v mount -o bind -- /etc/mkinitcpio.d "${tmpdir}/mnt/etc/mkinitcpio.d"
	cleanup+=("v umount ${tmpdir@Q}/mnt/etc/mkinitcpio.d")

	v mount -o bind -- /boot "${tmpdir}/mnt/boot"
	cleanup+=("v umount ${tmpdir@Q}/mnt/boot")

	{
		for krnl in "$tmpdir/mnt"/usr/lib/modules/*/vmlinuz; do
			pkgbase=$(cat -- ${krnl%vmlinuz}pkgbase)
			cat <<-EOF
				menuentry 'Parabola GNU/Linux-libre, slot ${other}, ${pkgbase} kernel'
				  set search --no-floppy --fs-uuid --set=root ${selector_boot#UUID=}
				  echo 'Loading ${pkgbase} kernel...'
				  linux /vmlinuz-${pkgbase} root=$selector_root overlay_root=$selector_overlay boot=$selector_boot rw
				  echo 'Loading initial ramdisk...'
				  initrd /initramfs-${pkgbase}.img
				  echo 'Booting...'
				  boot
			EOF
		done
	} | install -Dm600 /dev/stdin "/boot/grub/grub_$other.cfg"

	v arch-chroot -- "$tmpdir/mnt" sh -c "printf '%s\n' usr/lib/modules/*/vmlinuz | /usr/share/libalpm/scripts/mkinitcpio install"
}

main "$@"