#!/usr/bin/env bash
set -euE
# librechroot

# Copyright (C) 2010-2012 Nicolás Reynolds <fauno@parabola.nu>
# Copyright (C) 2011-2012 Joshua Ismael Haase Hernández (xihh) <hahj87@gmail.com>
# Copyright (C) 2012 Michał Masłowski <mtjm@mtjm.eu>
# Copyright (C) 2012-2018, 2024 Luke T. Shumaker <lukeshu@parabola.nu>
# Copyright (C) 2018 Andreas Grapentin <andreas@grapentin.org>
# Copyright (C) 2019 Bill Auger <mr.j.spam.me@gmail.com>
#
# License: GNU GPLv2+
#
# This file is part of Parabola.
#
# Parabola 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 2 of the License, or
# (at your option) any later version.
#
# Parabola is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Parabola. If not, see <http://www.gnu.org/licenses/>.

# HACKING: if a command is added or removed, it must be changed in 4 places:
#   - the usage() text
#   - the commands=() array
#   - the case statement in main() that checks the number of arguments
#   - the case statement in main() that runs them

. "$(librelib conf)"
. "$(librelib messages)"
. "$(librelib chroot/makechrootpkg)"

shopt -s nullglob
umask 0022

################################################################################
# Wrappers for files in ${pkglibexecdir}/chroot/                               #
################################################################################

readonly _arch_nspawn="$(librelib chroot/arch-nspawn)"
readonly _mkarchroot="$(librelib chroot/mkarchroot)"

arch_nspawn_flags=()
sysd_nspawn_flags=()

hack_arch_nspawn_flags() {
	local copydir="$1"

	local makepkg_conf="$copydir/etc/makepkg.conf"

	OPTIND=1
	set -- "${arch_nspawn_flags[@]}"
	while getopts 'hC:M:c:f:s' arg; do
		case "$arg" in
			M) makepkg_conf="$OPTARG" ;;
			*) : ;;
		esac
	done

	# Detect the architecture of the chroot
	local CARCH
	if [[ -f $makepkg_conf ]]; then
		eval "$(grep -a '^CARCH=' "$makepkg_conf")"
	else
		CARCH="$(uname -m)"
	fi

	local setarch interpreter
	case $CARCH in
		armv7h | armv7l)
			setarch=armv7l
			interpreter=/usr/bin/qemu-arm-static
			;;
		*)
			setarch=$CARCH
			interpreter=/usr/bin/qemu-$CARCH-static
			;;
	esac
	if ! setarch $setarch /bin/true 2>/dev/null; then
		# We're running a cross-arch chroot

		# Make sure that qemu-static is set up with binfmt_misc
		if [[ -z $(grep -l -xF \
			-e "interpreter $interpreter" \
			-r -- /proc/sys/fs/binfmt_misc 2>/dev/null |
			xargs -r grep -xF 'enabled') ]]; then
			error 'Cannot cross-compile for %s on %s' "$CARCH" "$(uname -m)"
			plain 'This requires a binfmt_misc entry for %s.' "$interpreter"
			prose 'Such a binfmt_misc entry is provided by the %s
			       package.  If you have it installed, but still see
			       this message, you may need to restart %s.' \
				qemu-user-static-binfmt binfmt
			return $EXIT_NOTINSTALLED
		fi

		# Let qemu/binfmt_misc do its thing
		arch_nspawn_flags+=(-f "$interpreter" -s)
	fi
}

# Usage: arch-nspawn $copydir $cmd...
arch-nspawn() {
	local copydir=$1
	shift
	local cmd=("$@")

	local arch_nspawn_flags=("${arch_nspawn_flags[@]}")
	hack_arch_nspawn_flags "$copydir"

	"$_arch_nspawn" \
		"${arch_nspawn_flags[@]}" \
		"$copydir" \
		"${sysd_nspawn_flags[@]}" \
		-- \
		"${cmd[@]}"
}

# Usage: mkarchroot $copydir $pkgs...
mkarchroot() {
	local copydir=$1
	shift
	local pkgs=("$@")

	local arch_nspawn_flags=("${arch_nspawn_flags[@]}")
	hack_arch_nspawn_flags "$copydir"

	local cmd=(
		unshare -m "$_mkarchroot"
		# mkarchroot flags: (flags are very similar to arch-nspawn)
		"${arch_nspawn_flags[@]}"
		# chroot directory:
		-- "$copydir"
		# pacman flags:
		# * hack around https://bugs.archlinux.org/task/49347
		--hookdir="$copydir/etc/pacman.d/hooks"
		# packages: (and maybe more flags... pacstrap injects
		# flags at the end, so we can't turn of flag parsing
		# with '--')
		"${pkgs[@]}"
	)
	"${cmd[@]}"
}

################################################################################
# Utility functions                                                            #
################################################################################

# Usage: make_empty_repo $copydir
make_empty_repo() {
	local copydir=$1
	mkdir -p "${copydir}/repo"
	bsdtar -czf "${copydir}/repo/repo.db.tar.gz" -T /dev/null
	ln -s "repo.db.tar.gz" "${copydir}/repo/repo.db"
}

# Usage: chroot_add_to_local_repo $copydir $pkgfiles...
chroot_add_to_local_repo() {
	local copydir=$1
	shift
	mkdir -p "$copydir/repo"
	local pkgfile
	for pkgfile in "$@"; do
		cp "$pkgfile" "$copydir/repo"
		pushd "$copydir/repo" >/dev/null
		repo-add repo.db.tar.gz "${pkgfile##*/}"
		popd >/dev/null
	done
}

# Print code to set $rootdir and $copydir; blank them on error
calculate_directories() {
	# Don't assume that CHROOTDIR or CHROOT are set,
	# but assume that COPY is set.
	local rootdir copydir

	if [[ -n ${CHROOTDIR:-} ]] && [[ -n ${CHROOT:-} ]]; then
		rootdir="${CHROOTDIR}/${CHROOT}/root"
	else
		rootdir=''
	fi

	if [[ ${COPY:0:1} == / ]]; then
		copydir=$COPY
	elif [[ -n ${CHROOTDIR:-} ]] && [[ -n ${CHROOT:-} ]]; then
		copydir="${CHROOTDIR}/${CHROOT}/${COPY}"
	else
		copydir=''
	fi

	declare -p rootdir
	declare -p copydir
}

check_mountpoint() {
	local file=$1
	local mountpoint mountopts
	mountpoint="$(df -P "$file" | sed '1d;s/.*\s//')"
	mountopts=($(LC_ALL=C mount | awk "{ if (\$3==\"$mountpoint\") { gsub(/[(,)]/, \" \", \$6); print \$6 } }"))
	! in_array nosuid "${mountopts[@]}" && ! in_array noexec "${mountopts[@]}"
}

################################################################################
# Main program                                                                 #
################################################################################

usage() {
	eval "$(calculate_directories)"
	print "Usage: %s [OPTIONS] COMMAND [ARGS...]" "${0##*/}"
	print 'Interacts with an archroot (arch chroot).'
	echo
	prose 'This is configured with `chroot.conf`, either in
	       `/etc/libretools.d/`, or `$XDG_CONFIG_HOME/libretools/`.
	       The variables you may set are $CHROOTDIR, $CHROOT, and
	       $CHROOTEXTRAPKG.'
	echo
	prose 'There may be multiple chroots; they are stored in $CHROOTDIR.'
	echo
	prose 'Each chroot is named; the default is configured with $CHROOT.'
	echo
	prose 'Each named chroot has a master clean copy (named `root`), and any
	       number of other named copies; the copy used by default is the
	       current username (or $SUDO_USER, or `copy` if root).'
	echo
	prose 'The full path to the chroot copy is "$CHROOTDIR/$CHROOT/$COPY",
	       unless the copy name is manually specified as an absolute path,
	       in which case, that path is used.'
	echo
	prose 'The current settings for the above variables are:'
	printf '    CHROOTDIR : %s\n' "${CHROOTDIR:-$(_ 'ERROR: NO SETTING')}"
	printf '    CHROOT    : %s\n' "${CHROOT:-$(_ 'ERROR: NO SETTING')}"
	printf '    COPY      : %s\n' "$COPY"
	printf '    rootdir   : %s\n' "${rootdir:-$(_ 'ERROR')}"
	printf '    copydir   : %s\n' "${copydir:-$(_ 'ERROR')}"
	echo
	prose 'If the chroot or copy does not exist, it will be created
	       automatically.  A chroot by default contains the packages in the
	       group "base-devel" and any packages named in $CHROOTEXTRAPKG.
	       Unless the `-C` or `-M` flags are used, the configuration files
	       that this program installs are the stock versions supplied in the
	       packages, not the versions from your host system.  Other tools
	       (such as libremakepkg) may alter the configuration.'
	echo
	prose 'This command will make the following configuration changes in the
	       chroot:'
	bullet 'overwrite `/etc/libretools.d/chroot.conf`' # libretools/librechroot
	bullet 'overwrite `/etc/pacman.d/mirrorlist`'      # devtools/arch-nspawn
	bullet 'set `CacheDir` in `/etc/pacman.conf`'      # devtools/arch-nspawn
	prose 'If a new `pacman.conf` is inserted with the `-C` flag, the change
	       is made after the file is copied in; the `-C` flag doesn'"'"'t
	       stop the change from being effective.'
	echo
	prose 'The processor architecture of the chroot is determined
	       by the by `CARCH` variable in the `/etc/makepkg.conf`
	       file inside of the chroot.'
	echo
	prose 'The `-A CARCH` flag is *almost* simply an alias for'
	printf '    %s\n' \
		'-C "/usr/share/pacman/defaults/pacman.conf.$CARCH" \' \
		'-M "/usr/share/pacman/defaults/makepkg.conf.$CARCH"'
	prose 'However, before doing that, it actually makes a temporary copy of
	       `pacman.conf`, and modifies it to:'
	bullet 'set `Architecture` to match the `CARCH` line in `makepkg.conf`'
	bullet 'comment out any `Include = /etc/pacman.d/*.conf` lines'
	echo
	prose 'Creating a copy, deleting a copy, or syncing a copy can be fairly
	       slow; but are very fast if $CHROOTDIR is on a btrfs partition.'
	echo
	print 'Options:'
	flag \
		"-n <$(_ CHROOT)>" 'Name of the chroot to use' \
		"-l <$(_ COPY)>" 'Name of, or absolute path to, the copy to use' \
		'-N' 'Disable networking in the chroot' \
		"-C <$(_ FILE)>" 'Copy this file to `$copydir/etc/pacman.conf`' \
		"-M <$(_ FILE)>" 'Copy this file to `$copydir/etc/makepkg.conf`' \
		"-A <$(_ CARCH)>" 'Set the architecture of the copy; simply an alias for the `-C` and `-M` flags, see above.'
	flag \
		"-w <$(_ 'PATH[:INSIDE_PATH[:OPTIONS]]')>" 'Bind mount a file or directory, read/write' \
		"-r <$(_ 'PATH[:INSIDE_PATH[:OPTIONS]]')>" 'Bind mount a file or directory, read-only'
	flag \
		'-h, --help' 'Show this message'
	echo
	print 'Commands:'
	flag \
		'Create/copy/delete:' \
		'noop|make' 'Do not do anything, but still creates the chroot copy if it does not exist' \
		'sync' 'Sync the copy with the clean (`root`) copy' \
		'delete' 'Delete the chroot copy' \
		\
		'Dealing with packages:' \
		"install-file $(_ FILES...)" 'Like `pacman -U FILES...`' \
		"install-name $(_ NAMES...)" 'Like `pacman -S NAMES...`' \
		'update' 'Like `pacman -Syu`' \
		'clean-pkgs' 'Remove all packages from the chroot copy that
		                   are not in base-devel, $CHROOTEXTRAPKG, or named
		                   as a dependency in the file `/startdir/PKGBUILD`
		                   in the chroot copy; and install all packages
		                   that are.' \
		\
		'Other:' \
		"run $(_ CMD...)" 'Run CMD in the chroot copy' \
		'enter' 'Enter an interactive shell in the chroot copy' \
		'clean-repo' 'Clean /repo in the chroot copy' \
		'help' 'Show this message'
}
readonly commands=(
	noop make sync delete
	install-file install-name update clean-pkgs
	run enter clean-repo help
)

# Globals: $CHROOTDIR, $CHROOT, $COPY, $rootdir and $copydir
main() {
	COPY=$LIBREUSER
	[[ $COPY != root ]] || COPY=copy

	declare -i retconf=0
	load_conf chroot.conf CHROOTDIR CHROOT || retconf=$?

	local args mode=unspecified opt
	if ! args="$(getopt -n "${0##*/}" -o '+hn:l:NC:M:A:w:r:' -l 'help' -- "$@")"; then
		mode=errusage
	else
		eval "set -- $args"
		local flag
		declare -Ai used_flags
		while true; do
			flag=$1
			shift
			case "$flag" in
				-h | --help) [[ $mode == errusage ]] || mode=usage ;;
				-n)
					CHROOT=$1
					shift
					;;
				-l)
					COPY=$1
					shift
					;;
				-N) sysd_nspawn_flags+=(--private-network) ;;
				-C | -M)
					arch_nspawn_flags+=("$flag" "$1")
					shift
					;;
				-A)
					if ! [[ -f "/usr/share/pacman/defaults/pacman.conf.$1" && -f "/usr/share/pacman/defaults/makepkg.conf.$1" ]]; then
						gnuerror 'Unsupported architecture: %s' "$1"
						gnuerror 'See the files in %q for valid architectures.' /usr/share/pacman/defaults/
						mode=errusage
					else
						trap 'rm -f -- "$tmppacmanconf"' EXIT
						tmppacmanconf="$(mktemp --tmpdir librechroot-pacman.conf.XXXXXXXXXX)"
						sed -E \
							-e "s|^#?\\s*Architecture.+|Architecture = $1|g" \
							-e "s|^.*Include\s*=\s*/etc/pacman.d/.*\.conf|#&|" \
							<"/usr/share/pacman/defaults/pacman.conf.$1" \
							>"$tmppacmanconf"
						cat >>"$tmppacmanconf" <<-'eot'

							# Enable the volatile i686 [build-support] repo only as needed.
							#[build-support]
							#Server = http://mirror.archlinux32.org/$arch/$repo/

							# Enable the volatile arm [aur] repo only as needed.
							#[aur]
							#Server = https://mirror.archlinuxarm.org/$arch/$repo/
						eot
						arch_nspawn_flags+=(
							-C "$tmppacmanconf"
							-M "/usr/share/pacman/defaults/makepkg.conf.$1"
						)
					fi
					shift
					;;
				-w)
					sysd_nspawn_flags+=("--bind=$1")
					shift
					;;
				-r)
					sysd_nspawn_flags+=("--bind-ro=$1")
					shift
					;;
				--) break ;;
				*) panic 'unhandled flag: %q' "$flag" ;;
			esac
			used_flags[${1#-}]+=1
		done
		for opt in n l C M A; do
			if ((${used_flags[$opt]:-0} > 1)); then
				gnuerror "Option -%s may only be given once" "$opt"
				mode=errusage
			fi
		done
		if ((${used_flags[A]:-0} && (${used_flags[C]:-0} || ${used_flags[M]:-0}))); then
			gnuerror "Option -A may not be used together with -C or -M"
			mode=errusage
		fi
		if [[ $mode == unspecified ]]; then
			if [[ $# -lt 1 ]]; then
				gnuerror "Must specify a command"
				mode=errusage
			elif ! in_array "$1" "${commands[@]}"; then
				gnuerror "Unrecognized command: %s" "$1"
				mode=errusage
			elif [[ $1 == help ]]; then
				mode=usage
				shift
			else
				mode=$1
				shift
			fi
		fi
		case "$mode" in
			usage | errusage) : ;;
			noop | make | sync | delete | update | enter | clean-pkgs | clean-repo)
				if [[ $# -gt 0 ]]; then
					gnuerror 'Command `%s` does not take any arguments: %s' "$mode" "$*"
					mode=errusage
				fi
				;;
			install-file)
				if [[ $# -lt 1 ]]; then
					gnuerror 'Command `%s` requires at least one file' "$mode"
					mode=errusage
				else
					local missing=()
					local file
					for file in "$@"; do
						if ! [[ -f $file ]]; then
							missing+=("$file")
						fi
					done
					if [[ ${#missing[@]} -gt 0 ]]; then
						gnuerror "%s: file(s) not found: %s" "$mode" "${missing[*]}"
						mode=errusage
					fi
				fi
				;;
			install-name)
				if [[ $# -lt 1 ]]; then
					gnuerror 'Command `%s` requires at least one package name' "$mode"
					mode=errusage
				fi
				;;
			run)
				if [[ $# -lt 1 ]]; then
					gnuerror 'Command `%s` requires at least one argument' "$mode"
					mode=errusage
				fi
				;;
			*) panic 'invalid mode: %q' "$mode" ;;
		esac
	fi
	case "$mode" in
		errusage)
			print "Try '%s --help' for more information." "${0##*/}" >&2
			return $EXIT_INVALIDARGUMENT
			;;
		usage)
			usage
			return $EXIT_SUCCESS
			;;
	esac

	[[ $retconf == 0 ]] || exit $retconf
	eval "$(calculate_directories)"

	readonly LIBREUSER LIBREHOME
	readonly CHROOTDIR CHROOT COPY
	readonly rootdir copydir
	readonly mode

	########################################################################

	if ((EUID)); then
		error "This program must be run as root."
		return $EXIT_NOPERMISSION
	fi

	umask 0022

	# Keep this lock for as long as we are running
	# Note that '9' is the same FD number as in mkarchroot et al.
	lock 9 "$copydir.lock" \
		"Waiting for existing lock on chroot copy to be released: [%s]" "$COPY"

	if [[ $mode != delete ]]; then
		if ! check_mountpoint "$copydir.lock"; then
			error "Chroot copy is mounted with nosuid or noexec options: [%s]" "$COPY"
			return $EXIT_FAILURE
		fi

		if [[ ! -d $rootdir ]]; then
			msg "Creating 'root' copy for chroot [%s]" "$CHROOT"
			mkarchroot "$rootdir" base-devel </dev/null
			make_empty_repo "$rootdir"
		fi

		if [[ ! -d $copydir ]] || [[ $mode == sync ]]; then
			msg "Syncing copy [%s] with root copy" "$COPY"
			sync_chroot "$CHROOTDIR/$CHROOT/root" "$copydir" "$COPY"
		fi

		# Note: the in-chroot pkgconfdir is non-configurable, this is
		# intentionally hard-coded.
		mkdir -p "$copydir/etc/libretools.d"
		{
			if [[ ${#CHROOTEXTRAPKG[*]} -eq 0 ]]; then
				echo 'CHROOTEXTRAPKG=()'
			else
				printf 'CHROOTEXTRAPKG=('
				printf '%q ' "${CHROOTEXTRAPKG[@]}"
				printf ')\n'
			fi
		} >"$copydir"/etc/libretools.d/chroot.conf

		# "touch" the chroot first
		# this will
		#  - overwrite '/etc/pacman.d/mirrorlist'"
		#  - set 'CacheDir' in \`/etc/pacman.conf'"
		#  - apply -C or -M flags
		arch-nspawn "$copydir" true </dev/null
		if [[ -n ${tmppacmanconf:-} ]]; then
			rm -f -- "$tmppacmanconf"
		fi
		trap EXIT            # clear the trap to remove the tmp pacman.conf from -A
		arch_nspawn_flags=() # XXX dirty hack, don't apply -C or -M again
	fi

	########################################################################

	case "$mode" in
		# Create/copy/delete
		noop | make | sync) : ;;
		delete)
			if [[ -d $copydir ]]; then
				delete_chroot "$copydir"
			fi
			;;

		# Dealing with packages
		install-file)
			install_packages "$copydir" "$@" </dev/null
			chroot_add_to_local_repo "$copydir" "$@"
			;;
		install-name)
			arch-nspawn "$copydir" pacman -Sy --noconfirm -- "$@" </dev/null
			;;
		update)
			arch-nspawn "$copydir" pacman -Syu --noconfirm </dev/null
			;;
		clean-pkgs)
			trap "rm -f -- ${copydir@Q}/{chcleanup,chrootexec}" EXIT
			install -m755 "$(librelib chroot/chcleanup)" "$copydir/chcleanup"
			printf '%s\n' \
				'#!/bin/bash' \
				'mkdir -p /startdir' \
				'cd /startdir' \
				'/chcleanup' \
				>"$copydir/chrootexec"
			chmod 755 "$copydir/chrootexec"
			arch-nspawn "$copydir" /chrootexec </dev/null
			;;

		# Other
		run)
			arch-nspawn "$copydir" "$@"
			;;
		enter)
			arch-nspawn "$copydir" bash
			;;
		clean-repo)
			rm -rf "${copydir}"/repo/*
			make_empty_repo "$copydir"
			;;
		*) panic 'invalid mode: %q' "$mode" ;;
	esac
}

main "$@"
