#!/bin/sh

set -xeu

chroot_dir="/mnt"

arch="$(uname -m)"
mirror="https://dl-cdn.alpinelinux.org/alpine"
alpine_version="v3.20"
apk_version="2.14.4-r1"
apk_link="${mirror}/${alpine_version}/main/${arch}/apk-tools-static-${apk_version}.apk"

fatal() {
	echo "$1" >&2
}

die() {
	fatal "$2"
	exit "$1"
}

usage() {
	cat >&2 <<EOF
Usage: $0 <action> [-r <chroot_dir>] [-h]

Action:
	rootfs			deploy alpine rootfs in <chroot_dir>
	setup			setup rootfs inside chroot environment
	full			deploy rootfs and run setup inside chroot

Options:
	-r <chroot_dir>		specify chroot directory
				[default: $chroot_dir]
	-h			show this help message
EOF
	exit "$1"
}

ensure_root() {
	if [ "$(id -u)" = 0 ]; then
		return 0
	fi

	die 1 "The script must be run as root"
}

parse_action() {
	case "$1" in
		rootfs|setup|full) action="$1" ;;
		*)
			fatal "unknown op: $1"
			usage 1
			;;
	esac
}

parse_args() {
	[ "$#" -lt 1 ] && usage 1
	parse_action "$1" && shift

	while getopts "r:h" opt; do
		case "$opt" in
		r) chroot_dir="$(realpath "$OPTARG")" ;;
		h) usage 0 ;;
		?) usage 1 ;;
		esac
	done
}

# download static apk and print the executable filename
download_apk() {
	local tmpdir
	tmpdir="$(mktemp -d)"

	curl -L "$apk_link" | tar -C "$tmpdir" -xzf -

	echo "$tmpdir/sbin/apk.static"
}

install_rootfs() {
	apk_bin="$(download_apk)"

	mkdir -p "$chroot_dir/etc/apk"

	"$apk_bin" -X "$mirror/$alpine_version/main" -U --allow-untrusted \
		-p "$chroot_dir" --initdb add alpine-base e2fsprogs

	cat > "$chroot_dir/etc/resolv.conf" <<EOF
nameserver 1.1.1.1
nameserver 1.0.0.1
nameserver 8.8.8.8
EOF

	cat > "$chroot_dir/etc/apk/repositories" <<EOF
$mirror/$alpine_version/main
$mirror/$alpine_version/community
EOF
}

umount_vfs_cleanup() {
	for fs in proc sys dev; do
		umount "$chroot_dir/$fs"
	done
}

bind_mount_vfs() {
	for fs in proc sys dev; do
		mount -o bind "/$fs" "$chroot_dir/$fs"
	done
}

install_inside_chroot() {
	deploy_name="$(realpath "$0")"
	inside_deploy_path="$chroot_dir/deploy.sh"

	cp "$deploy_name" "$inside_deploy_path"
	chmod +x "$inside_deploy_path"

	bind_mount_vfs
	trap umount_vfs_cleanup EXIT

	chroot "$chroot_dir" /deploy.sh setup

	trap - EXIT
	umount_vfs_cleanup
}

extra_setup_vim() {
	apk add vim
	ln -s "$(which vim)" /usr/local/bin/vi
}

extra_setup_fish() {
	apk add fish
	# chsh -s "$(which fish)"
}

setup_extra() {
	extra_setup_vim
	extra_setup_fish
}

install_kernel() {
	apk add linux-virt linux-firmware-none
}

install_packages() {
	apk add chrony acpi busybox-mdev-openrc
	apk add grub grub-bios

	apk add openssh blkid

	install_kernel
}

part_uuid() {
	blkid -o export -s UUID "$1" | sed -n -e 2p
}

mountpoint_dev() {
	mount | grep "on $1 " | awk '{ print $1 }'
}

mountpoint_fstype() {
	mount | grep "on $1 " | awk '{ print $5 }'
}

mountpoint_options() {
	mount | grep "on $1 " | awk '{ print $6 }' | tr -d '()'
}

# $1: mountpoint
# $2: check on boot
gen_fstab_entry() {
	_mnt="$1"
	_dev="$(mountpoint_dev "$_mnt")"
	_fs="$(mountpoint_fstype "$_mnt")"
	_options="$(mountpoint_options "$_mnt")"
	_uuid="$(part_uuid "$_dev")"

	case "$2" in
		y|Y|1) _check=1 ;;
		*) _check=0 ;;
	esac

	echo "$_uuid	$_mnt	$_fs	$_options	0	$_check"
}

gen_fstab() {
	gen_fstab_entry / y
	echo "tmpfs	/tmp	tmpfs	nosuid,nodev	0	0"
}

populate_fstab() {
	gen_fstab | tee /etc/fstab
}

enable_services() {
	rc-update add devfs sysinit
	rc-update add dmesg sysinit
	rc-update add mdev sysinit

	rc-update add hwclock boot
	rc-update add modules boot
	rc-update add sysctl boot
	rc-update add hostname boot
	rc-update add bootmisc boot
	rc-update add syslog boot
	rc-update add localmount boot
	rc-update add networking boot

	rc-update add mount-ro shutdown
	rc-update add killprocs shutdown
	rc-update add savecache shutdown

	rc-update add acpid default
	rc-update add crond default
	rc-update add chronyd default
	rc-update add sshd default
}

setup_rootfs() {
	install_packages
	enable_services

	echo "Set root password:"
	passwd

	setup_extra
}

full_install() {
	install_rootfs
	install_inside_chroot
}

parse_args "$@"

ensure_root

case "$action" in
	rootfs) install_rootfs ;;
	setup) setup_rootfs ;;
	full) full_install ;;
	*) usage 1;;
esac