#!/usr/bin/env bash

#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.

# Print manual if no parameters provided or invalid amount of parameters is provided
if [[ ! -n $1 || -n $2 ]]; then
	cat <<- END
	Usage: arkanium-build [variant]
	Variants:
	  archlinux		Plain Arch Linux TTY image
	  arkanelinux		Arkane Linux GNOME image

	Variants are loaded based on their directory names, the ones listed here
	 are included by default.

	Variables:
	  ARKANIUM_NO_TAR			Do not create a compressed tarball, only create the images
	  ARKANIUM_OVERWRITE_RANDOM		Define a custom image name
	END
	exit 0
fi

## Set common variables
#
declare -r workdir='/var/tmp/rootfs'
declare -r configs_dir="./arkanium-build.d/"
declare -r variant="$1"
declare -r type="$(cat $(readlink -m $configs_dir/$variant/type))"
declare -r output_target="$(pwd)/target/"

## Common functions
#
# Cleanup and quit if error
cleanup_and_quit () {

	# If any paramters are passed we will assume it to be an error
	[[ -n $1 ]] && printf "\e[1;31m<#>\e[0m $*\e[0m\n" >&2

	umount $workdir

	btrfs property set -ts $workdir ro false
	btrfs property set -ts $workdir/etc ro false
	btrfs property set -ts $workdir/var ro false

	# Remove temporary btrfs volumes
	rm -rf $workdir/etc \
		$workdir/var \
		$workdir

	# Quit program if argument provided to function
	[[ -n $1 ]] && exit 1

	# Otherwise just quit, there is no error
	exit 0

}

# Generate a 42 character long random string, used for generating psuedo-random
# image names
gen_random_string () {

	if [[ -v ARKANIUM_OVERWRITE_RANDOM ]]; then
		random=$ARKANIUM_OVERWRITE_RANDOM
	else
		random=$(openssl rand -hex 100 | head -c 42)
	fi

	printf "${random}\n"

}

## Error checking
#
# Quit if not root
[[ ! $EUID -eq 0 ]] &&
	printf '\e[1;31m<#>\e[0m\e[1m This program has to be run as root\n\e[0m' &&
	exit 1

# Check if all dependencies are installed, quit if not
for prog in btrfs pacstrap; do
	if ! command -v $prog > /dev/null; then
		printf "\e[1;31m<#>\e[0m\e[1m Failed to locate $prog, ensure it is installed\e[0m\n"
		exit 1
	fi
done

# Check if requested variant exists
[[ ! -d arkanium-build.d/$variant ]] &&
	printf '\e[1;31m<#>\e[0m\e[1m The requested variant does not exist\e[0m\n' &&
	exit 1

## Variants
#
# Build archlinux type image
if [[ $type == 'archlinux' ]]; then

	# Ensure base.list exists, if not error and quit
	if [[ ! -e arkanium-build.d/$variant/base.list ]]; then
		printf "\e[1;31m<#>\e[0m\e[1m The required file 'base.list' is not preset in $(readlink -m $configs_dir/$variant)\e[0m\n" &&
		exit 1
	fi

	printf '\e[1;34m-->\e[0m\e[1m Started Arch linux image build\e[0m\n'

	# Create temporary Btrfs subvolume
	printf "\e[1;34m-->\e[0m\e[1m Creating temporary Btrfs subvolumes at $(readlink -m $workdir)\e[0m\n"
	btrfs subvolume create $workdir || cleanup_and_quit "Failed to create btrfs subvolume $(readlink -m $workdir)"
	btrfs subvolume create $workdir/etc || cleanup_and_quit "Failed to create btrfs subvolume $(readlink -m $workdir/etc)"
	btrfs subvolume create $workdir/var || cleanup_and_quit "Failed to create btrfs subvolume $(readlink -m $workdir/var)"

	printf "\e[1;34m-->\e[0m\e[1m Creating bind mount at $(readlink -m $workdir)\e[0m\n"
	mount --bind $workdir $workdir

	# Make /usr/local symlink in var
	mkdir -vp $workdir/{var/usrlocal,usr}
	ln -s /var/usrlocal $workdir/usr/local

	# Read base package list and install base system
	readarray base_packages < arkanium-build.d/$variant/base.list
	printf "\e[1;34m-->\e[0m\e[1m Installing base packages\e[0m\n"
	pacstrap $workdir ${base_packages[*]} || cleanup_and_quit 'Failed to install secondary package list'

	# If overlay directory exists in variant copy it's contents to the temporary subvolume
	if [[ -d arkanium-build.d/$variant/overlay ]]; then
		cp -rv arkanium-build.d/$variant/overlay/* $workdir/
	fi

	# Read package list and install secondary system components, skip if not used
	if [[ -e arkanium-build.d/$variant/package.list ]]; then
		printf '\e[1;34m-->\e[0m\e[1m Installing secondary packages...\e[0m\n'
		readarray packages < arkanium-build.d/$variant/package.list
		arch-chroot $workdir pacman -S --noconfirm ${packages[*]} || cleanup_and_quit 'Failed to install base packages'
	fi

	# Enable systemd services if requested
	if [[ -e arkanium-build.d/$variant/systemd.services ]]; then

		printf '\e[1;34m-->\e[0m\e[1m Enabling systemd services...\e[0m\n'

		readarray services < arkanium-build.d/$variant/systemd.services

		for service in ${services[*]}; do
			arch-chroot $workdir systemctl enable $service
		done

	fi

	# Clear pacman cache
	arch-chroot $workdir pacman --noconfirm -Scc

	# Remove subvolumes created by systemd
	[[ -d $workdir/var/lib/portables ]] &&
		printf "\e[1;34m-->\e[0m\e[1m Removing systemd subvolume var/lib/portables\e[0m\n"
		btrfs subvolume delete $workdir/var/lib/portables
	[[ -d $workdir/var/lib/machines ]] &&
		printf "\e[1;34m-->\e[0m\e[1m Removing systemd subvolume var/lib/machines\e[0m\n"
		btrfs subvolume delete $workdir/var/lib/machines

	# Clear pacman cache
	printf "\e[1;34m-->\e[0m\e[1m Clearing pacman cache\e[0m\n"
	rm -rf $workdir/var/cache/pacman/pkg/*
	rm -rf $workdir/var/lib/pacman/local/*

	# Make subvolume read-only
	printf "\e[1;34m-->\e[0m\e[1m Adding read-only property to subvolumes\e[0m\n"
	btrfs property set -ts $workdir ro true
	btrfs property set -ts $workdir/etc ro true
	btrfs property set -ts $workdir/var ro true

	# Generate random name for new image
	printf "\e[1;34m-->\e[0m\e[1m Generating psuedo-random image name...\e[0m\n"
	declare -r image_name=$(gen_random_string)
	printf "$image_name\n"

	# Create dir for storing the images
	mkdir -vp $(readlink -m $output_target/$image_name)

	# Write subvolume to image
	printf "\e[1;34m-->\e[0m\e[1m Creating images...\e[0m\n"
	btrfs send -f $output_target/$image_name/$image_name-rootfs.img $workdir
	btrfs send -f $output_target/$image_name/$image_name-etc.img $workdir/etc
	btrfs send -f $output_target/$image_name/$image_name-var.img $workdir/var

	if [[ ! -v ARKANIUM_NO_TAR ]]; then
		printf "\e[1;34m-->\e[0m\e[1m Compressing images...\e[0m\n"
		tar -cv -I 'zstd -12 -T0 ' -f $output_target/$image_name.tar.zst -C $output_target/$image_name .
	fi

	cleanup_and_quit

fi