#!/bin/bash

if [[ -e /dev/mapper/cryptdir ]]; then
    echo "only one instance can run at a time" 1>&2
    exit 1
fi

sudo -v || exit 1

if [[ -z $1 ]]; then
    size='16M'
else
    size=$1
fi

cryptfile=$(mktemp)
cryptdir=$(mktemp -d)
pass=$(dd if=/dev/urandom bs=1 count=80 | base64)

cleanup () {
    cd
    sudo umount $cryptdir
    sudo cryptsetup close cryptdir
    rm -f $cryptfile
    rmdir $cryptdir
}

trap cleanup EXIT

dd if=/dev/urandom of=$cryptfile bs=$size count=1
echo $pass | sudo cryptsetup luksFormat $cryptfile -
echo $pass | sudo cryptsetup open $cryptfile cryptdir --key-file -
sudo mkfs.ext2 /dev/mapper/cryptdir
sudo mount /dev/mapper/cryptdir $cryptdir
sudo chown $USER $cryptdir
cd $cryptdir
$SHELL