#!/usr/bin/env bash

dir="$( cd "$( dirname "$0" )" && pwd )"

touch $dir/lockfile

if [ -z "$1" ] || [ -z "$2" ]; then
    echo "invalid args"
    exit
fi

lang=$1
epoch=$(date +%s%N)
basepath="/var/lib/lxc/piston/rootfs"
filepath="/tmp/$epoch/code.code"
argpath="/tmp/$epoch/args.args"
stdinpath="/tmp/$epoch/stdin.stdin"
arg=$(basename $argpath)

# write arg file
mkdir -p $basepath/tmp/$epoch
chmod 777 $basepath/tmp/$epoch
cat $2 > $basepath$filepath
cat $3 > $basepath$argpath
echo "${@:4}" > $basepath$argpath

# process incrementor
exec 200>$dir/lockfile
flock -x 200
oldinc=$(cat $dir/i | awk '{$1=$1};1')
newinc=$(expr $oldinc + 1)

if (( newinc >= 151 )); then
    newinc=1
    echo 1 > $dir/i
else
    echo $newinc > $dir/i
fi
exec 200>&-

# runner
timeout -s KILL 20 \
    lxc-attach --clear-env -n piston -- \
        /bin/bash -l -c "bash /exec/$lang $newinc $epoch"

# process janitor
lxc-attach --clear-env -n piston -- \
    /bin/bash -l -c "\
        for i in {1..100}; do pkill -u runner$newinc --signal SIGKILL; done ;\
        find /tmp -user runner$newinc -exec /bin/rm -rf {} \; ;\
        find /var/tmp -user runner$newinc -exec /bin/rm -rf {} \; ;\
        find /var/lock -user runner$newinc -exec /bin/rm -rf {} \; ;\
        find /dev/shm -user runner$newinc -exec /bin/rm -rf {} \; ;\
        find /run/lock -user runner$newinc -exec /bin/rm -rf {} \; ;\
        " > /dev/null 2>&1 &

rm -rf $basepath/tmp/$epoch