#!/bin/sh
#

#set -e

check_stamp()
{
    stamp="$1"
    interval="$2"

    if [ $interval -eq 0 ]; then
        return 1
    fi

    if [ ! -f $stamp ]; then
        return 0
    fi

    # compare midnight today to midnight the day the stamp was updated
    stamp=$(date --date=$(date -r $stamp --iso-8601) +%s)
    now=$(date --date=$(date --iso-8601) +%s)
    delta=$(($now-$stamp))

    if [ $delta -ge $interval ]; then
        return 0
    fi

    return 1
}

update_stamp()
{
    stamp="$1"

    touch $stamp
}



# we check here if autoclean was enough sizewise
check_size_constraints()
{
    # min-age in days
    MaxAge=0
    MaxSize=0
    CacheDir="var/cache/apt"
    CacheArchive="archives/"
    eval $(apt-config shell MaxAge APT::Archives::MaxAge)
    eval $(apt-config shell MaxSize APT::Archives::MaxSize)
    eval $(apt-config shell CacheDir Dir::Cache)
    eval $(apt-config shell CacheArchive Dir::Cache::archives)

    # sanity check
    if [ -z "$CacheDir" -o -z "$CacheArchive" ]; then
	echo "empty Dir::Cache or Dir::Cache::archives, exiting"
	exit
    fi
    Cache="/"$CacheDir$CacheArchive

    # check age
    if [ ! $MaxAge -eq 0 ]; then
	find $Cache -name "*.deb"  -mtime +$MaxAge -print0 | xargs -r -0 rm -f
    fi
    
    # check size
    if [ ! $MaxSize -eq 0 ]; then
	# reverse-sort by mtime
	for file in $(ls -rt $Cache/*.deb); do 
	    du=$(du -s $Cache)
	    size=${du%%/*}
	    # check if the cache is small enough
	    if [ $size -lt $MaxSize ]; then
		break
	    fi
	    # delete oldest file
	    rm -f $file
	done
    fi
}

check_size_constraints

UpdateInterval=0
DownloadUpgradeableInterval=0
eval $(apt-config shell UpdateInterval APT::Periodic::Update-Package-Lists DownloadUpgradeableInterval APT::Periodic::Download-Upgradeable-Packages)
AutocleanInterval=$DownloadUpgradeableInterval
eval $(apt-config shell AutocleanInterval APT::Periodic::Autoclean)

# laptop check, on_ac_power returns:
#       0 (true)    System is on mains power
#       1 (false)   System is not on mains power
#       255 (false) Power status could not be determined
# Desktop systems always return 255 it seems
if which on_ac_power >/dev/null; then
    on_ac_power
    if [ $? -eq 1 ]; then
	exit 0
    fi
fi

UPDATE_STAMP=/var/lib/apt/periodic/update-stamp
if check_stamp $UPDATE_STAMP $UpdateInterval; then
    if apt-get -qq update 2>/dev/null; then
	if which dbus-send >/dev/null; then
	    dbus-send --system / app.apt.dbus.updated boolean:true
	fi
        update_stamp $UPDATE_STAMP
    fi
fi

DOWNLOAD_UPGRADEABLE_STAMP=/var/lib/apt/periodic/download-upgradeable-stamp
if check_stamp $DOWNLOAD_UPGRADEABLE_STAMP $DownloadUpgradeableInterval; then
    apt-get -qq -d dist-upgrade 2>/dev/null
    update_stamp $DOWNLOAD_UPGRADEABLE_STAMP
fi

AUTOCLEAN_STAMP=/var/lib/apt/periodic/autoclean-stamp
if check_stamp $AUTOCLEAN_STAMP $AutocleanInterval; then
    apt-get -qq autoclean
    check_size_contrains
    update_stamp $AUTOCLEAN_STAMP
fi