#!/usr/bin/env bash
# 2018 Luke Shumaker
declare -r NAME=mkosi
declare -r VERSION=20180725

# Why is this different than mkosi[1]?
#
# - mkosi claims to be "legacy-free"--but they call everything that's
#   not systemd "legacy"; that clearly won't do for creating OpenRC or
#   GNU Shepherd images.
#
# - mkosi claims to be "legacy-free", only supporting GPT
#   disk-labels--but btrfs can be booted directly, without a separate
#   disk-label, or a separate ESP partition.  To a btrfs disk, GPT/ESP
#   is legacy.
#
# - Using a raw btrfs disk means that it can easily be mounted without
#   first disecting the disk-label.
#
# [1]: https://github.com/systemd/mkosi


print() {
	# shellcheck disable=SC2059
	printf "$(gettext -- "$1")\\n" "${@:2}"
}

error() {
	local msg
	msg="$(print "${@:2}")"
	printf '%s: %s\n' "${0##*/}" "$msg" >&2
	if (( $1 != 0 )); then
		exit "$1"
	fi
}

main() {
	set -euE

	local arg_mode=outside
	local arg_mountpoint=
	local arg_size=1G
	local arg_file
	local args
	if ! args="$(getopt -n "${0##*/}" -o "Vhs" -l "inside:,version,help,size" -- "$@")"; then
		arg_mode=error
	else
		eval "args=($args)"
		set -- "${args[@]}"
		while true; do
			case "$1" in
				--inside) shift; arg_mode=inside; arg_mountpoint=$1; shift;;
				-V|--version) shift; arg_mode=version;;
				-h|--help) shift; arg_mode=usage;;
				-s|--size) shift; arg_size=$1;;
				--) shift; break;;
			esac
		done
		if (( $# != 1 )); then
			if (( $# == 0 )); then
				error 0 "Expected 1 positional argument, got none"
			else
				error 0 "Expected 1 positional argument, got %d: %s" "$#" "${@@Q}"
			fi
			arg_mode=error
		else
			arg_file=$1
		fi
	fi
	case "$arg_mode" in
		error) print "Try '%q --help' for more information" "${0##*/}" >&2; return 2;;
		version)
			print "%s (notsystemd) %s" "$NAME" "$VERSION"
			return 0
			;;
		usage)
			print 'Usage: %s [OPTIONS]' "${0##*/} FILENAME.IMG"
			print 'Make Operating System Image'
			echo
			print 'Create a mountable, bootable OS image.'
			echo
			print 'OPTIONS:'
			# --inside is internal-only; undocumented
			print '  -s SIZE, --size=SIZE  set the size of the image (default: 1G)'
			echo
			print '  -h, --help     display this help'
			print '  -V, --version  output version information'
			return 0
			;;

		# main code starts here
		outside)
			if [[ -e "$arg_file" ]]; then
				error 1 'Image file already exists, refusing to overwrite: %s' "$arg_file"
			fi
			truncate --size="$arg_size" -- "$arg_file"
			mkfs.btrfs -- "$arg_file"
			arg_mountpoint=$(mktemp -dt -- "${0##*/}.XXXXXXXXXX")
			# shellcheck disable=SC2064
			trap "rmdir -- ${arg_mountpoint@Q}" EXIT
			sudo -- unshare --mount -- "${BASH_SOURCE[0]}" --inside="$arg_mountpoint" "${args[@]}"
			;;
		inside) # just keep reading...
			if (( UID != 0 )); then
				error 4 "Must be invoked as root."
			fi
			mount --make-rslave /
			mount "$arg_file" "$arg_mountpoint"

			# Base install
			#
			# The --hookdir won't work with pacstrap>18, because git after v18 tightens
			# up option parsing.  Fortunately, it's only there to work around the fact
			# that pacstrap=18 hasn't yet migrated from --root to --sysroot.
			packages=(
				# Base bootable system
				base grub btrfs-progs
				# Integration tests
				dhclient net-tools strace
			)
			pacstrap -c -M -C /usr/share/pacman/defaults/pacman.conf.x86_64 -- "$arg_mountpoint" \
				 --hookdir="$arg_mountpoint/etc/pacman.d/hooks" "${packages[@]}"
			genfstab -t uuid "$arg_mountpoint" > "${arg_mountpoint}/etc/fstab"

			# Bootloader
			cat <<-'EOT' >> "$arg_mountpoint/etc/default/grub"
			GRUB_TIMEOUT=0
			GRUB_DEFAULT=1
			GRUB_CMDLINE_LINUX_DEFAULT="console=ttyS0 console=tty0"
			GRUB_TERMINAL_OUTPUT="serial console"
			EOT
			arch-chroot -- "$arg_mountpoint" sh -c \
				'grub-install "$(awk '\''$2 == "/" { print $1 }'\'' </proc/mounts)"'
			arch-chroot -- "$arg_mountpoint" grub-mkconfig -o /boot/grub/grub.cfg

			# Networking
			cat <<-'EOT' > "${arg_mountpoint}/etc/udev/rules.d/81-dhcpcd.rules"
			ACTION=="add", SUBSYSTEM=="net", ENV{SYSTEMD_WANTS}="dhcpcd@$name.service"
			EOT
			mkdir "${arg_mountpoint}/etc/systemd/system/dhcpcd@.service.d"
			cat <<-'EOT' > "${arg_mountpoint}/etc/systemd/system/dhcpcd@.service.d/wait-online.conf"
			[Unit]
			Before=network-online.target
			EOT
			mkdir "${arg_mountpoint}/etc/systemd/system/network-online.target.d"
			cat <<-'EOT' > "${arg_mountpoint}/etc/systemd/system/network-online.target.d/udev-settle.conf"
			[Unit]
			Wants=systemd-udev-settle.service
			After=systemd-udev-settle.service
			EOT

			# Autologin
			mkdir "${arg_mountpoint}/etc/systemd/system/serial-getty@ttyS0.service.d"
			cat <<-EOT >"${arg_mountpoint}/etc/systemd/system/serial-getty@ttyS0.service.d/autologin.conf"
			[Service]
			ExecStart=
			$(sed -n '/^ExecStart=/s/ / --autologin root /p' < "${arg_mountpoint}/usr/lib/systemd/system/serial-getty@.service")
			EOT

			# End
			;;

		*) error 1 'Internal error.  The programmer writing this tool screwed up.'; exit 1;;
	esac
}

main "$@"