#!/usr/bin/env bash

set -uo pipefail

readonly cache_dir="${XDG_CACHE_HOME:-${HOME}/.cache}/package-status"
readonly cache_file="${cache_dir}/status"
readonly attempt_file="${cache_dir}/last-attempt"
readonly pacman_log="/var/log/pacman.log"
readonly pacman_lock="/var/lib/pacman/db.lck"

mkdir -p "${cache_dir}"
chmod 700 "${cache_dir}"
touch "${attempt_file}" || exit 1

# Never inspect the package database while pacman is changing it. A later
# timer run or terminal startup will request another refresh.
if [[ -e "${pacman_lock}" ]]; then
	exit 75
fi

pacman_log_signature_before=$(stat -c '%Y:%s:%i' "${pacman_log}" 2>/dev/null || printf '0:0:0')

updates_output=''
updates_output=$(CHECKUPDATES_DB="${cache_dir}/checkupdates-db" checkupdates --nocolor 2>/dev/null)
checkupdates_status=$?

case "${checkupdates_status}" in
	0)
		updates_count=$(printf '%s\n' "${updates_output}" | awk 'NF { count++ } END { print count + 0 }')
		;;
	2)
		updates_count=0
		;;
	*)
		# A network or mirror failure must not replace a known-good cache.
		exit "${checkupdates_status}"
		;;
esac

orphans_count=$(pacman -Qdtq 2>/dev/null | awk 'NF { count++ } END { print count + 0 }')
pacman_log_signature_after=$(stat -c '%Y:%s:%i' "${pacman_log}" 2>/dev/null || printf '0:0:0')

# Discard the result if a package operation overlapped this refresh.
if [[ -e "${pacman_lock}" || "${pacman_log_signature_before}" != "${pacman_log_signature_after}" ]]; then
	exit 75
fi

umask 077
temporary_file=$(mktemp "${cache_dir}/status.XXXXXX")
trap 'rm -f "${temporary_file}"' EXIT

printf 'version=1\nupdates=%d\norphans=%d\nchecked_at=%d\npacman_log_signature=%s\n' \
	"${updates_count}" \
	"${orphans_count}" \
	"$(date +%s)" \
	"${pacman_log_signature_after}" > "${temporary_file}"

mv -f "${temporary_file}" "${cache_file}"
trap - EXIT