#!/bin/bash
#
#   pkgdiff - package differencing utility
#
#   Copyright (c) 2022 Pacman Development Team <pacman-dev@lists.archlinux.org>
#
#   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 2 of the License, or
#   (at your option) any later version.
#
#   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

# gettext initialization
export TEXTDOMAIN='pacman-scripts'
export TEXTDOMAINDIR='@localedir@'

declare -r myver='@PACKAGE_VERSION@'
declare -r confdir='@sysconfdir@'

LIBRARY=${LIBRARY:-'@libmakepkgdir@'}

QUIET=0
USE_COLOR='y'

source "$LIBRARY"/util/compress.sh
source "$LIBRARY"/util/message.sh
source "$LIBRARY"/util/parseopts.sh

# minimal of package before a pkgdiff is generated (bytes)
min_pkg_size=$((1024*1024))

# percent of new package above which the pkgdiff will be discarded
max_diff_size=70

# ensure we have a sane umask set
umask 0022

# print usage instructions
usage() {
	cmd=${0##*/}
	printf "%s (pacman) %s\n\n" "$cmd" "$myver"
	echo
	printf -- $(gettext "Usage: pkgdiff <old> <new>\n")
	echo
	printf -- "$(gettext "\
pkgdiff will create a file providing the differences between two packages.\n
This file can then be added to a database using repo-add.\n")"
	echo
	printf -- "$(gettext "Example:  pkgdiff pacman-6.0.0-1-x86_64.pkg.tar.gz pacman-6.0.1-1-x86_64.pkg.tar.gz")\n"
	echo
	printf -- "$(gettext "Options:\n")"
	printf -- "$(gettext "  -q, --quiet      minimize output\n")"
	printf -- "$(gettext "  --nocolor        remove color from output\n")"
	printf -- "$(gettext "  --min-pkg-size   minimum package size before pkgdiffs are generated\n")"
	printf -- "$(gettext "  --max-diff-size  percent of new package above which the pkgdiff will be discarded\n")"
}

version() {
	cmd=${0##*/}
	printf "%s (pacman) %s\n\n" "$cmd" "$myver"
	printf -- "Copyright (c) 2022 Pacman Development Team <pacman-dev@lists.archlinux.org>.\n"
	echo
	printf -- "$(gettext "\
This is free software; see the source for copying conditions.\n\
There is NO WARRANTY, to the extent permitted by law.\n")"
}

trap_exit() {
	# unhook all traps to avoid race conditions
	trap '' EXIT TERM HUP QUIT INT ERR

	echo
	error "$@"
	clean_up 1
}

clean_up() {
	local exit_code=${1:-$?}

	# unhook all traps to avoid race conditions
	trap '' EXIT TERM HUP QUIT INT ERR

	[[ -d $tmpdir ]] && rm -rf "$tmpdir"

	exit $exit_code
}

read_pkginfo() {
	unset pkgver pkgname arch
	while IFS='=' read -r field value; do
		# skip comments and invalid lines
		[[ $field = '#'* || -z $value ]] && continue

		# skip lines which aren't fields we care about
		[[ $field != @(pkgver|pkgname|arch) ]] || continue

		declare -g "${field% }=${value# }"

		[[ $pkgname && $pkgver && $arch ]] && return 0
	done < <(bsdtar -xOqf "$1" .PKGINFO 2>/dev/null)

	error "$(gettext "Invalid package file '%s'.")" "$1"
	return 1
}

create_pkgdiff() {
	local oldfile=$1
	local newfile=$2
	local \
		oldname oldver oldarch \
		newname newver newarch \
		diff_file

	read_pkginfo "$oldfile" || return 1
	oldname="$pkgname"
	oldver="$pkgver"
	oldarch="$arch"

	read_pkginfo "$newfile" || return 1
	newname="$pkgname"
	newver="$pkgver"
	newarch="$arch"

	pkgsize=$(wc -c < "$newfile")

	if ((pkgsize < min_pkg_size)); then
		msg "$(gettext "Skipping pkgdiff creation for small package: %s - size %s")" "$newname" "$pkgsize"
		return 0
	fi

	if [[ $oldname != "$newname" ]]; then
		error "$(gettext "The package names don't match : '%s' and '%s'")" "$oldname" "$newname"
		return 1
	fi

	if [[ $oldarch != "$newarch" ]]; then
		error "$(gettext "The package architectures don't match : '%s' and '%s'")" "$oldarch" "$newarch"
		return 1
	fi

	if [[ $oldver == "$newver" ]]; then
		error "$(gettext "Both packages have the same version : '%s'")" "$newver"
		return 1
	fi

	### TODO: check oldver < newver with vercmp ###

	declare -r startdir="$(pwd -P)"

	if [[ ${oldfile::1} != "/" ]]; then
		oldfile=${startdir}/${oldfile}
	fi

	if [[ ${newfile::1} != "/" ]]; then
		newfile=${startdir}/${newfile}
	fi

	tmpdir=$(mktemp -d "${TMPDIR:-/tmp}/pkgdiff.XXXXXXXXXX")
	pushd $tmpdir &>/dev/null


	### TODO: almost everything below here is a quick hack... ###

	bsdtar -xOf $oldfile .MTREE | zcat | awk '{for (i=1;i<=NF;i++){if ($i ~/^sha256/) {print $1 " "  $i}}}' > ${oldver}.files
	bsdtar -xOf $newfile .MTREE | zcat | awk '{for (i=1;i<=NF;i++){if ($i ~/^sha256/) {print $1 " "  $i}}}' > ${newver}.files

	files=($(diff -Naur ${oldver}.files ${newver}.files |
		grep "^+\./" |
		grep -v -e "\.BUILDINFO" -e "\.PKGINFO" |
		cut -f1 -d' ' |
		sed 's|+./||'))

	mkdir $newname
	tar -xf $newfile -C $newname

	diffdir="${oldname}-${oldver}-to-${newname}-${newver}-${newarch}.pkgdiff"
	mkdir $diffdir

	for f in ${files[@]}; do
		mkdir -p ${diffdir}/${f%/*}
		cp ${newname}/$f ${diffdir}/$f
	done

	cp ${newname}/.{BUILD,PKG}INFO ${diffdir}


	### TODO: this should use libmakepkg/compress - need PKGEXT from makepkg.conf ###
	### TODO: collect files in same order as makepkg ###

	tar -cf ${diffdir}.tar ${diffdir}
	zstd -T0 --ultra -20 ${diffdir}.tar &> /dev/null
	diff_file=${diffdir}.tar.zst


	diffsize=$(wc -c < "$diff_file")

	if ((max_diff_size * pkgsize / 100 < diffsize)); then
		msg "$(gettext "pkgdiff larger than maximum size. Removing.")"
		rm -f "$diff_file"
		return 0
	fi

	popd &>/dev/null

	mv ${tmpdir}/${diff_file} .

	msg "$(gettext "Generated pkgdiff : '%s'")" "$diff_file"
	(( QUIET )) && echo "$diff_file"

	return 0
}


# PROGRAM START

# determine whether we have gettext; make it a no-op if we do not
if ! type gettext &>/dev/null; then
	gettext() {
		echo "$@"
	}
fi

case $1 in
	-h|--help) usage; exit 0;;
	-V|--version) version; exit 0;;
esac

trap 'clean_up' EXIT
for signal in TERM HUP QUIT; do
	trap "trap_exit \"$(gettext "%s signal caught. Exiting...")\" \"$signal\"" "$signal"
done
trap 'trap_exit "$(gettext "Aborted by user! Exiting...")"' INT
trap 'trap_exit "$(gettext "An unknown error has occurred. Exiting...")"' ERR


OPT_SHORT='hqV'
OPT_LONG=('help' 'quiet' 'max-diff-size:' 'min-pkg-size:' 'nocolor' 'version')
if ! parseopts "$OPT_SHORT" "${OPT_LONG[@]}" -- "$@"; then
	exit 1
fi
set -- "${OPTRET[@]}"
unset OPT_SHORT OPT_LONG OPTRET

# parse options
while :; do
	case $1 in
		-h|--help)
			usage
			exit 0 ;;
		-V|--version)
			version
			exit 0 ;;
		-q|--quiet)
			QUIET=1;;
		--nocolor)
			USE_COLOR='n';;
		--min-pkg-size)
			### TODO ###
			shift ;;
		--max-delta-size)
			### TODO ###
			shift ;;
		--)
			shift
			break ;;
	esac
	shift
done


# check if messages are to be printed using color
if [[ -t 2 && $USE_COLOR != "n" ]]; then
	colorize
else
	unset ALL_OFF BOLD BLUE GREEN RED YELLOW
fi


if (( $# != 2 )); then
	usage
	exit 1
fi

for i in "$@"; do
	if [[ ! -f $i ]]; then
		error "$(gettext "File '%s' does not exist")" "$i"
		exit 1
	fi
done


### TODO: the creation of the pkgdiff should be done in fakeroot ###

create_pkgdiff "$@"