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

# Copyright (C) 2010 Nicolás Reynolds
# Copyright (C) 2011 Joshua Haase
# Copyright (C) 2012-2014 Luke Shumaker
#
# 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 3 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

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

# Because the makechrootpkg.sh library functions don't work with -euE
_makechrootpkg() (
	set +euE
	. "$_makechrootpkg"
	"$@"
)

# 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
}

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 '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 `$copydir/etc/makepkg.conf`'
	flag "-w <$(_ '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
)

# 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[@]}"
}

arch_nspawn_flags=()
sysd_nspawn_flags=()
arch-nspawn() {
	local copydir=$1; shift
	# XXX: SYSTEMD-STDOUT HACK
	if [[ -t 1 ]]; then
		cmd=("$@")
	else
		# This perl script is similar to `sed 's|\n|\r\n|g'`, (or, more
		# correctly, `sed 's|$|\r|'`) but it does't line-buffer.
		local perlcmd='
my $size;
my $buffer;
while(1) {
	$size=sysread(STDIN, $buffer, 40);
	last if ($size < 1);
	$buffer =~ s/\n/\r\n/g;
	syswrite(STDOUT, $buffer);
}'
		cmd=(bash --noprofile --norc -c "set -o pipefail; $(printf '%q ' "$@") |& perl -e $(printf '%q' "$perlcmd")")
	fi

	set +u # if an array is empty, it counts as unbound
	"$_arch_nspawn" "${arch_nspawn_flags[@]}" "$copydir" "${sysd_nspawn_flags[@]}" -- "${cmd[@]}"
	set -u
}

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

	local mode=enter
	while getopts 'n:l:NC:M: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 "$OPTARG");;
			w) sysd_nspawn_flags+=("--bind=$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/420"
		plain "https://bugs.freedesktop.org/show_bug.cgi?id=70290"
		prose "Due to a bug in systemd-nspawn, redirecting stdin is not
		       supported.  We have been able to mitigate the problems
		       with redirecting stdout, but until the bug is fixed,
		       redirecting stdin will only end in pain." >&2
		return 1
	fi

	# Keep this lock 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 ! 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"
		set +u # if an array is empty, it counts as unbound
		"$_mkarchroot" "${arch_nspawn_flags[@]}" "$rootdir" base-devel
		set -u
		make_empty_repo "$rootdir"
	fi

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

	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

	if [[ $mode != delete ]]; then
		# "touch" the chroot first
		# this will
		#  - overwrite \`/etc/pacman.d/mirrorlist'"
		#  - set \`CacheDir' in \`/etc/pacman.conf'"
		#  - apply -C or -M flags
		arch-nspawn "$copydir" true
		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" "$COPY"
			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 "$copydir" pacman -Syu --noconfirm
			;;
		clean-pkgs)
			trap "rm -f '$copydir'/bin/chcleanup '$copydir'/chrootexec" EXIT
			install -m755 "$(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 "$@"