#!/usr/bin/env bash
# 2018 Luke Shumaker
declare -r NAME=mkosi
declare -r VERSION=20180805

# 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
#   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
}

in_array() {
	local needle=$1
	local straw
	for straw in "${@:2}"; do
		if [[ $needle = "$straw" ]]; then
			return 0
		fi
	done
	return 1
}

loaded_modules=()
require_module() {
	local module
	module="$(realpath -- "$1")"
	if in_array "$module" "${loaded_modules[@]}"; then
		_loaded_modules+=("$module")
		source "$1"
	fi
}

mkosi:directories() {
	local arg_mountpoint=$1
	local spec outside inside
	for spec in "${arg_directories[@}"; do
		outside="${spec%:*}"
		inside="${spec#"${outside}:"}"
		cp -rT "$outside" "${arg_mountpoint}/${inside}"
	done
}

main() {
	set -euE

	local arg_mode=outside
	local arg_mountpoint=
	local arg_size=1G

	local arg_directories=()
	local arg_modules=()
	local arg_packages=()

	local args
	if ! args="$(getopt -n "${0##*/}" -o "s:d:m:p:hV" -l "inside:,size:,directory:,module:,package:,help,version" -- "$@")"; then
		arg_mode=error
	else
		eval "args=($args)"
		set -- "${args[@]}"
		while true; do
			case "$1" in
				--inside) shift; arg_mode=inside; arg_mountpoint=$1; shift;;
				-s|--size) shift; arg_size=$1; shift;;

				-d|--directory) shift arg_directories+=("$1"); shift;;
				-m|--module) shift; arg_modules+=("$1"); shift;;
				-p|--package) shift arg_packages+=("$1"); shift;;

				-V|--version) shift; arg_mode=version;;
				-h|--help) shift; arg_mode=usage;;
				--) shift; break;;
				*) error 1 'Internal error.  The programmer writing this tool screwed up.';;
			esac
		done
		case "$arg_mode" in
			outside|inside)
				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=$1
				fi
				;;
		esac
	fi
	case "$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 '  -d OUTSIDE:INSIDE, --directory=OUTSIDE:INSIDE  include the given directory'
			print '  -m MOD.sh, --module=MOD.sh                     include the given module'
			print '  -p PACKAGE, --package=package                  include the given package (or group)'
			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"

			### Load modules ###
			packages=("${arg_packages[@]}")
			post_install=(50:mkosi:directories)
			for module in "${arg_modules[@]}"; do
				source "$module"
			done

			#### Base install ###
			# The --hookdir bit is to hack around https://bugs.archlinux.org/task/49347
			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"

			### post_install ###
			while IFS=: read -r n fn; do
				fn "$arg_mountpoint"
			done < <(printf '%s\n' "${post_install[@]}" | sort)

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

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

main "$@"