#!/bin/bash

EXPECTED_ARGS=2
E_BADARGS=1

if [ $# -ne $EXPECTED_ARGS ]
then
  echo "usage:\n \t $0 file device"
  echo " \t $0 file size (k)"
  exit $E_BADARGS
fi

NAME=$1

if [ -e "$NAME" ]; then
    echo file $NAME already exists !
    echo please remove it before.
    exit 1
fi

shift

if [ $1 -gt 0 2>/dev/null ]; then
# number
  SIZE=$1
else
# not a number
  if [ -b $1 ]; then
      SIZE=$(fdisk -l -u $1 | awk '/^Disk/{printf "%.0f", $5/1024 }')
  else
      echo "usage:\n \t $0 file device"
      echo " \t $0 file size (k)"
      exit 1
  fi
fi

echo creating $NAME image file of "$SIZE"k

dd if=/dev/zero of=$NAME bs=1k count=$SIZE &> /dev/null &
DD=$!

while true; do
    ps --pid $DD >& /dev/null;
    if [[ $? -eq 0 ]]; then
    ls -s --block-size=1K $NAME | awk -v n=$NAME -v s=$SIZE '{printf "\r%s %10dk %3.0f %% done...", n, $1, $1 /  s *100 }'
    else
    echo -e "\r$NAME Finsihed!                               "
    break
    fi
    sleep 1
done

LOOPDEV=$(losetup -f)
echo Attaching $NAME on $LOOPDEV
losetup $LOOPDEV $NAME

echo creating partition table and partition
parted -s  $LOOPDEV mklabel msdos
parted -s  $LOOPDEV mkpart primary fat32 50k 100%

UNIT=$(fdisk -u -l /dev/sdb | awk '/Units/{ print $9 }')
SECTOR=$(fdisk -u -l $LOOPDEV | awk -v d=${LOOPDEV}p1 '$0 ~ d { print $2;}')
OFFSET=$(expr $UNIT '*' $SECTOR)

echo Offset of partition is $OFFSET !
LOOPPART=$(losetup -f)

echo Attaching partition on $LOOPPART at offset $OFFSET...
losetup -o $OFFSET $LOOPPART $NAME

echo Formating partition on $LOOPPART
mkfs.vfat -F 32 -n IMAGE_GRUB $LOOPPART

sleep 1
losetup -d $LOOPPART

parted -s $LOOPDEV  set 1 boot on
parted -s $LOOPDEV set 1 lba off

echo Mounting on /mnt and installing grub
mount -o offset=$OFFSET $LOOPDEV /mnt/
grub-install --disk-module="part_msdos biosdisk" --no-floppy --root-directory=/mnt/ $LOOPDEV

umount /mnt
sleep 1
losetup -d  $LOOPDEV