#!/bin/bash
#
# Copy a good Raspbian .img or Beaglebone img.xz to an SD writer
# Alternatively, back up or copy an image
#
# Usage: ddimage [-b] [-c] [-i imgname ]  [device-tag]

mode=copy
image=""
while getopts bci:n opt
do
    case $opt in
	b) mode=backup ;;
	c) mode=copy ;;	# default mode
	i) image=$OPTARG ;;
    esac
done
shift $(($OPTIND - 1))

target=/dev/${1-sdd}
echo "Checking $target"

if ls $target >/dev/null 2>&1
then
    if [ -b $target ]
    then
       echo "$target exists as a storage device."
    else
       echo "$target is not a storage device"
       exit 1
    fi
else
    echo "$target does not exist."
    exit 1
fi

if df | grep $target >/dev/null
then
    echo "$target is mounted and cannot be used."
    exit 1
else
    echo "$target is not mounted"
fi

if [ -z "$image" ]
then
    case $mode in
	copy)
	    set -- *.img

	    if [ $# != 1 ]
	    then
		echo "Need a unique existing image file, specify with -i."
		exit 1
	    else
		image=`ls *img`
	    fi
	    ;;
	backup)
	    echo "Specify a unique image file with -i."
	    exit 1
	    ;;
    esac
fi

OPTIONS="bs=4M statusinterval=16" 
case $mode in
    copy)
	if [ -f $image ]
	then
	    echo "Copying $image..."
	    if [[ $file =~ \.gz$ ]]
	    then
		# Previously-made backup
		gunzip $file | dcfldd $OPTIONS of=$target
	    elif [[ $file =~ \.xz$ ]]
	    then
		# Beaglebone image?
		xz --decompress --stdout $file | dcfldd $OPTIONS of=$target
	    else
		# This is the arm for decompressed .img files
		dcfldd $OPTIONS sizeprobe=if if=$image of=$target
	    fi
	else
	    echo "No .img file, bailing out!"
	    exit 1
	fi
	;;
    backup)
	if [ -f ${image}.gz ]
	then
	    echo "Refusing to overwrite ${image}.gz file, bailing out!"
	    exit 1
	else
	    echo "Backing up $target to ${image}.gz..."
	    dcfldd statusinterval=16 sizeprobe=if bs=4M if=$target | gzip >${image}.gz
	fi
	;;
esac

if df | grep $target >/dev/null
then
    echo "Unmounting..."
    umount
fi

echo "Done"
exit 0