#!/usr/bin/env bash
# Copyright 2016-2018 Luke Shumaker
# This work is free. You can redistribute it and/or modify it under the
# terms of the Do What The Fuck You Want To Public License, Version 2,
# as published by Sam Hocevar. See the COPYING file for more details.

# The user should not call this script directly.

declare -r workdir=/var/lib/pristine-etc

watchdirs=(
	/etc
	/usr/share/holo/files
	/usr/lib/sysusers.d
)
readonly watchdirs

pacman-watched-name-ver-dirs() {
	local dir dirs
	dirs=()
	for dir in "${watchdirs[@]}"; do
		if [[ -d "$dir" ]]; then
			dirs+=("$dir")
		fi
	done
	LC_ALL=C pacman -Qo "${dirs[@]}" | sed -r 's| is owned by | |' |
	    awk '{i=$2" "$3; a[i]=a[i]" "$1} END{for(i in a){print i " " a[i]}}'
}

pacman-all-name-arch() {
	LC_ALL=C pacman -Qni | tr $'\n' $'\r' | sed 's/\r\r/\n/g' | sed -r 's|(.*\r)?Name\s*:\s*(\S+)(\r.*)?\rArchitecture\s*:\s*(\S+)\r.*|\2 \4|'
}

pacman-watched-name-arch-ver-dirs() {
	join <(pacman-all-name-arch|sort) <(pacman-watched-name-ver-dirs|sort)
}

commit() (
	msg="$1"

	cd "$workdir"
	if ! [[ -d etc.git ]]; then
		mkdir -p chroot/etc
		(cd chroot/etc && etckeeper init -d "$PWD")
		mv chroot/etc/.git etc.git
	fi
	rm -rf etc; ln -sfT chroot/etc etc # for compatibility with old installs
	rm -rf chroot
	mkdir chroot
	cd chroot

	err=false
	files=()
	while IFS=' ' read -r pkgname arch pkgver dirs; do
		file=("/var/cache/pacman/pkg/$pkgname-$pkgver-$arch".pkg.tar.*)
		if ! test -f "$file"; then
			printf "ERROR: no cached package for %s %s %s\n" "$pkgname" "$pkgver" "$arch"
			err=true
		fi
		files+=("$file $dirs")
	done < <(pacman-watched-name-arch-ver-dirs)
	if $err; then
		return 1
	fi
	for filespec in "${files[@]}"; do
		read file dirs_str <<<"$filespec"
		read -a dirs <<<"$dirs_str"
		printf " -> %s\n" "$file"
		bsdtar xpvf "$file" "${dirs[@]#/}"
	done

	ln -srT ../etc.git etc/.git

	# The holo libalpm hook runs before the systemd-sysusers
	# libalpm hook; but ignore that and run systemd-sysusers
	# first, because I said so.
	if type systemd-sysusers &>/dev/null; then
		systemd-sysusers --root=.
	fi
	if type holo &>/dev/null; then
		plugins=($(cat etc/holorc etc/holorc.d/* 2>/dev/null|sed -rn 's,^plugin ([a-z0-9][a-z0-9-]*)(=.*)?$,\1,p'))
		mkdir -p -- run usr/lib "${plugins[@]/#/usr/share/holo/}"
		ln -sT /usr/lib/holo usr/lib/holo
		if [ -f /etc/os-release ]; then
			ln -sT /etc/os-release usr/lib/os-release
		else
			ln -sT /usr/lib/os-release usr/lib/os-release
		fi
		HOLO_ROOT_DIR=. holo apply
	fi
	if type pwck &>/dev/null; then
		pwck --root "$PWD" --sort
	fi
	if type grpck &>/dev/null; then
		grpck --root "$PWD" --sort
	fi
	cd etc/
	etckeeper update-ignore -d "$PWD"
	if etckeeper unclean -d "$PWD"; then
		etckeeper commit -d "$PWD" "$msg"
	fi
)

pull() (
	cd /etc
	git remote add pristine "${workdir}/chroot/etc" &>/dev/null || true
	git fetch pristine
)

lock() {
	local fd=$1
	local file=$2
	eval "exec $fd>"'"$file"'
	flock "${@:3}" "$fd"
}

unlock() {
	local fd=$1
	exec {fd}>&-
}

main() {
	set -e -o pipefail
	umask 0022

	if ! lock 7 "${workdir}/chroot.lock" -n; then
		return 0
	fi
	while true; do
		lock 8 "${workdir}/spool.lock"
		if ! [[ -f "${workdir}/spool" ]]; then
			return 0
		fi
		msg="$(cat "${workdir}/spool")"
		rm -f "${workdir}/spool"
		unlock 8

		commit "$msg"
		pull
	done
}

main "$@"