#!/bin/bash

set -eu -o pipefail

dev="$1"
dir="$2"
img="$3"

echo
echo "unmount $dev"
sudo umount  "$dev" || true

echo
echo "unpack $img to $dev"
pv "$img" | unxz | sudo dd of="$dev"

started="$(date +%s)"

echo
echo "mount $dev on $dir"
sudo mount "$dev" "$dir"

echo
echo "delete all files under $dir"
find "$dir" -mindepth 2 ! -delete

echo
echo "unmount $dev"
sudo umount "$dev"

ended="$(date +%s)"
duration=$(("$ended" - "$started"))

echo
echo "seconds to delete: $duration"

echo
echo "done"