#!/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) 2012-2016 Luke Shumaker <lukeshu@sbcglobal.net>
#
# 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)"
load_files chroot

. libremessages

shopt -s nullglob
umask 0022

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

readonly _arch_nspawn="$(librelib chroot/arch-nspawn)"
readonly _mkarchroot="$(librelib chroot/mkarchroot)"
readonly _makechrootpkg="$(librelib chroot/makechrootpkg.sh)"

arch_nspawn_flags=()
sysd_nspawn_flags=()

hack_arch_nspawn_flags() {
	local copydir="$1"

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

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

	local CARCH
	if [[ -f "$makepkg_conf" ]]; then
		eval $(grep '^CARCH=' "$makepkg_conf")
	else
		CARCH="$(uname -m)"
	fi

	if [[ "$CARCH" == armv7h ]] && ! setarch armv7l 2>/dev/null; then
		if grep -xF 'enabled' /proc/sys/fs/binfmt_misc/arm &>/dev/null \
	        && grep -xF 'interpreter /usr/bin/qemu-arm-static' /proc/sys/fs/binfmt_misc/arm &>/dev/null; then
			arch_nspawn_flags+=(-f /usr/bin/qemu-arm-static -s)
		else
			error 'Cannot cross-compile for ARM on x86'
			plain 'This requires a binfmt_misc entry for qemu-arm-static,'
			plain 'which is provided by the %s package.' binfmt-qemu-static
			plain 'If you have this, you may need to restart %s.' systemd-binfmt.service
			return 1
		fi
	fi
}

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

	hack_arch_nspawn_flags "$copydir"

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

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

	hack_arch_nspawn_flags "$copydir"

	unshare -m "$_mkarchroot" \
	    ${arch_nspawn_flags+"${arch_nspawn_flags[@]}"} \
	    "$copydir" \
	    "${pkgs[@]}"
)

# Usage: _makechrootpkg $function $arguments...
# Don't load $_makechrootpkg directly because it doesn't work with -euE
_makechrootpkg() (
	set +euE
	. "$_makechrootpkg"
	"$@"
)

################################################################################
# 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=$1
	local mountpoint="$(df -P "$file"|sed '1d;s/.*\s//')"
	local mountopts=($(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 $CHROOTEXTRAPKG.
	       Unless the `-C` or `-M` flags are used, the configuration files
	       that this program installs are the stock versions supplied in the
	       packages, not the versions from your host system.  Other tools
	       (such as libremakepkg) may alter the configuration.'
	echo
	prose 'This command will make the following configuration changes in the
	       chroot:'
	bullet   'overwrite `/etc/libretools.d/chroot.conf`'
	bullet   'overwrite `/etc/pacman.d/mirrorlist`'
	bullet   'set `CacheDir` in `/etc/pacman.conf`'
	prose 'If a new `pacman.conf` is inserted with the `-C` flag, the change
	       is made after the file is copied in; the `-C` flag doesn'"'"'t
	       stop the change from being effective.'
	echo
	prose 'The processor architecture of the chroot is determined
	       by the by `CARCH` variable in the `/etc/makepkg.conf`
	       file inside of the chroot.'
	echo
	prose 'The `-A CARCH` flag is *almost* simply an alias for'
	printf '    %s\n' \
	       '-C "/usr/share/pacman/defaults/pacman.conf.$CARCH" \' \
	       '-M "/usr/share/pacman/defaults/makepkg.conf.$CARCH"'
	prose 'However, before doing that, it actually makes a temporary copy of
	       `pacman.conf`, and sets the `Architecture` line to match the
	       `CARCH` line in `makepkg.conf`.'
	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'
	flag "-l <$(_ COPY)>"   'Name of, or absolute path to, the copy to use'
	flag '-N'               'Disable networking in the chroot'
	flag "-C <$(_ FILE)>"   'Copy this file to `$copydir/etc/pacman.conf`'
	flag "-M <$(_ FILE)>"   'Copy this file to `$copydir/etc/makepkg.conf`'
	flag "-A <$(_ CARCH)>"  'Set the architecture of the copy; simply an
	                         alias for the `-C` and `-M` flags, see above.'
	flag "-w <$(_ 'PATH[:PATH]')>" 'Bind mount a file or directory, read/write'
	flag "-r <$(_ 'PATH[:PATH]')>" 'Bind mount a file or directory, read-only'
	echo
	print 'Commands:'
	print ' Create/copy/delete:'
	flag 'noop|make'       'Do not do anything, but still creates the chroot
	                        copy if it does not exist'
	flag 'sync'            'Sync the copy with the clean (`root`) copy'
	flag 'delete'          'Delete the chroot copy'
	print ' Dealing with packages:'
	flag "install-file $(_ FILES...)"       'Like `pacman -U FILES...`'
	flag "install-name $(_ NAMES...)"       'Like `pacman -S NAMES...`'
	flag 'update'                           'Like `pacman -Syu`'
	flag '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'
	print ' Other:'
	flag "run $(_ CMD...)" 'Run CMD in the chroot copy'
	flag 'enter'           'Enter an interactive shell in the chroot copy'
	flag 'clean-repo'      'Clean /repo in the chroot copy'
	flag '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

	local mode=enter
	while getopts 'n:l:NC:M:A:w:r:' opt; do
		case $opt in
			n) CHROOT=$OPTARG;;
			l) COPY=$OPTARG;;
			N) sysd_nspawn_flags+=(--private-network);;
			C|M) arch_nspawn_flags+=(-$opt "$OPTARG");;
			A)
				trap 'rm -f -- "$tmppacmanconf"' EXIT
				tmppacmanconf="$(mktemp --tmpdir librechroot-pacman.conf.XXXXXXXXXX)"
				< "/usr/share/pacman/defaults/pacman.conf.$OPTARG" sed -r "s|^#?\\s*Architecture.+|Architecture = ${OPTARG}|g" > "$tmppacmanconf"
				arch_nspawn_flags+=(
					-C "$tmppacmanconf"
					-M "/usr/share/pacman/defaults/makepkg.conf.$OPTARG"
				);;
			w) sysd_nspawn_flags+=("--bind=$OPTARG");;
			r) sysd_nspawn_flags+=("--bind-ro=$OPTARG");;
			*) usage >&2; return 1;;
		esac
	done
	shift $(($OPTIND - 1))
	if [[ $# -lt 1 ]]; then
		error "Must specify a command"
		usage >&2
		return 1
	fi
	mode=$1
	if ! in_array "$mode" "${commands[@]}"; then
		error "Unrecognized command: %s" "$mode"
		usage >&2
		return 1
	fi
	shift
	case "$mode" in
		noop|make|sync|delete|update|enter|clean-pkgs|clean-repo)
			if [[ $# -gt 0 ]]; then
				error 'Command `%s` does not take any arguments: %s' "$mode" "$*"
				usage >&2
				return 1
			fi
			:;;
		install-file)
			if [[ $# -lt 1 ]]; then
				error 'Command `%s` requires at least one file' "$mode"
				usage >&2
				return 1
			else
				local missing=()
				local file
				for file in "$@"; do
					if ! [[ -f $file ]]; then
						missing+=("$file")
					fi
				done
				if [[ ${#missing[@]} -gt 0 ]]; then
					error "%s: file(s) not found: %s" "$mode" "${missing[*]}"
					return 1
				fi
			fi
			:;;
		install-name)
			if [[ $# -lt 1 ]]; then
				error 'Command `%s` requires at least one package name' "$mode"
				usage >&2
				return 1
			fi
			:;;
		run)
			if [[ $# -lt 1 ]]; then
				error 'Command `%s` requires at least one argument' "$mode"
				usage >&2
				return 1
			fi
			:;;
	esac


	if [[ $mode == help ]]; then
		usage
		return 0
	fi

	check_vars chroot CHROOTDIR CHROOT
	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 1
	fi

	umask 0022

	# XXX: SYSTEMD-STDIN HACK
	if ! [[ -t 0 ]]; then
		error "Input is not a TTY"
		plain "https://labs.parabola.nu/issues/431"
		plain "https://bugs.freedesktop.org/show_bug.cgi?id=70290"
		prose "Due to a bug in systemd-nspawn, redirecting stdin is not
		       supported." >&2
		return 1
	fi

	# 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 1
		fi

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

		if [[ ! -d $copydir ]] || [[ $mode == sync ]]; then
			msg "Syncing copy [%s] with root copy" "$COPY"
			_makechrootpkg sync_chroot "$CHROOTDIR/$CHROOT" "$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
		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
		# Creat/copy/delete
		noop|make|sync) :;;
		delete)
			if [[ -d $copydir ]]; then
				_makechrootpkg delete_chroot "$copydir"
			fi
			;;

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

		# Other
		run)
			arch-nspawn "$copydir" "$@"
			;;
		enter)
			arch-nspawn "$copydir" bash
			;;
		clean-repo)
			rm -rf "${copydir}"/repo/*
			make_empty_repo "$copydir"
			;;
	esac
}

main "$@"