#!/usr/bin/env bash

# Pretty name for firmware interface
biosname="Firmware Configuration" 

# Check if systemd-boot is available
bootctl is-installed &> /dev/null && sdboot=1

# Check if rebooting to the firmware interface is supported
[[ "$(bootctl reboot-to-firmware)" == "supported" ]] && fwboot=1


selectentry() {
	# Usage: selectentry <title> <prompt>
	local sel PS3 COLUMNS
	PS3="$2 "
	COLUMNS=1

	# Print title to stderr
	printf "\n%s\n\n" "$1" >&2

	# Populate entry list array
	# If we're in EFI mode
	if [[ -v efimode ]]; then
		# This one is fun
		# mapfile splits stdin on \n to an array
		# The sed regex looks for an asterisk in the 8th position (0 indexed),
		#  which marks an efi boot entry as "active", so those are the only ones
		#  we care to add to the list.
		# It *seems* like one could put mapfile at the end of the pipeline, but
		#  each command gets run in a subshell, so the array is lost. (ref: SC2031)
		mapfile -t entrylist < <(efibootmgr | sed -n '/.\{8\}\*/p')

		# Add firmware interface entry if supported
		[[ -v fwboot ]] && entrylist+=("$biosname")

	# If we're in systemd-boot mode
	elif [[ ! -v efimode ]]; then
		# Put all systemd-boot loder entry confs into an array
		mapfile -t entrylist < <(systemctl --boot-loader-entry=help)

		# Only add the firmware interface to the list if booting to it is supported
		[[ -v fwboot ]] && entrylist+=("$biosname")
	fi

	# Get user selection
	select sel in "${entrylist[@]}"; do
		break
	done

	# If in efi mode and the user did not select the firmware config menu item, 
	#  then drop everything except for the BOOTNUM (character 4-8)
	[[ -v efimode && "$sel" != "$biosname" ]] && sel="${sel:4:4}"

	# Print result to stdout
	printf "%s" "$sel"
}


# Parse command line options
while getopts ":en" opt; do
	case $opt in 
		e)
			efimode=1
			;;
		n)
			noreboot=1
			;;
		\?)
			echo "E: Invalid option: -$OPTARG" >&2
			exit 1
			;;
	esac
done


# If -e wasn't set, and systemd-boot isn't installed, fail over to efimode anyways
if [[ ! -v efimode && ! -v sdboot ]]; then
	echo "W: systemd-boot not installed. Choosing EFI boot entries instead..."
	efimode=1
fi


# If we're in EFI mode
if [[ -v efimode ]]; then
	title="Pick EFI boot entry"

# If we're in systemd-boot mode
elif [[ ! -v efimode ]]; then
	title="Pick systemd-boot entry config"

else
	echo "E: idk how you got here..."
	exit 1
fi


# Specialize prompt for reboot mode
if [[ -v noreboot ]]; then
	prompt="Entry for next boot:"
elif [[ ! -v noreboot ]]; then
	prompt="Entry to boot IMMEDIATELY:"
else
	echo "E: idk how you got here either..."
	exit 1
fi


# Prompt for the user's choice
choice="$(selectentry "$title" "$prompt")"


# A special case to boot into firmware interface
if [[ "$choice" == "$biosname" ]]; then
	sudo bootctl reboot-to-firmware true

# For all other entry selections
elif [[ "$choice" != "$biosname" ]]; then

	# If we're in EFI mode
	if [[ -v efimode ]]; then

		# Set bootnext in nvram
		sudo efibootmgr -q --bootnext "$choice"

	# If we're in systemd-boot mode
	elif [[ ! -v efimode ]]; then

		# Set default boot entry only for next boot
		sudo bootctl set-oneshot "$choice"

		# Add an option to speed past the boot menu, since we've already 
		#  chosen the desired entry.
		rebootopts+=("--boot-loader-menu=1")

	else
		echo "E: you DEFINITELY don't belong here..."
		exit 1
	fi
else
	echo "E: must you insist on breaking my things?"
	exit 1
fi


# Reboot if necessary
[[ ! -v noreboot ]] && sudo systemctl reboot "${rebootopts[@]}"