#!/usr/bin/env bash

if [ -z "$1" ] || [ -z "$2" ] || [[ $2 != "encode" && $2 != "decode" && $2 != "encode_enc" ]]
	then echo "launch the script with the desired filename and operation"
	echo "./AmazonPrimeWhatever.sh FILENAME OPERATION(encode or decode)"
	exit
fi

# check for prerequisites:
if ! [ -x "$(command -v convert)" ]; then
  echo 'Error: convert (part of the imagemagick suite) is not installed.' >&2
  exit 1
fi

if [ $2 = "encode_enc" ] || [ $(echo $1 | cut -d "_" -f1) = "FakeKittenENC" ]; then
	if ! [ -x "$(command -v gpg)" ]; then
	  echo 'Error: gpg is not installed, it is needed for encryption/decryption' >&2
	  exit 1
	fi
fi

if [ $2 = "encode" ] || [ $2 = "encode_enc" ]; then
        imagejpg="random.jpg"
        image="random.DNG"
        #generate random image:
        mx=320;my=256;head -c "$((3*mx*my))" /dev/urandom | convert -depth 8 -size "${mx}x${my}" RGB:- $imagejpg
        mv $imagejpg $image
        imagesize=$(du -b $image | cut -f1)
	if [ $2 = "encode" ]; then
	        origsha=$(sha1sum $1 | cut -d " " -f1)
	        destimage="FakeKitten_"$imagesize"_"$1"_"$origsha"_"$image
	        mv $image $destimage
	        dd if=$1 bs=1M >> "$destimage"
	        echo "encode completed in $destimage"
	fi
	if [ $2 = "encode_enc" ]; then
		#
		gpg --symmetric --cipher-algo AES256 $1
		#
	        origsha=$(sha1sum $1.gpg | cut -d " " -f1)
	        destimage="FakeKittenENC_"$imagesize"_"$1.gpg"_"$origsha"_"$image
	        mv $image $destimage
	        dd if=$1.gpg bs=1M >> "$destimage"
	        echo "encode completed in $destimage"
	fi
fi


if [ $2 = "decode" ]; then
	imageconst=$(echo $1 | cut -d "_" -f1)
	imagebs=$(echo $1 | cut -d "_" -f2)
	origname=$(echo $1 | cut -d "_" -f3)
	origsha=$(echo $1 | cut -d "_" -f4)
	origimage=$(echo $1 | cut -d "_" -f5)

	dd if=$1 bs=1M skip=$imagebs iflag=skip_bytes > "$origname"

	if [ $imageconst = "FakeKittenENC" ]; then
		#decrypt the file
		orignamenogpg=$(echo "$origname" | sed 's/.gpg//')
		gpg --output $orignamenogpg --decrypt $origname
	fi

	echo "decode completed in $origname, checking file integrity"
	echo $origsha"  "$origname > $origname".sha1"
	shaoutput=$(sha1sum -c $origname".sha1")
	echo $shaoutput
	if [[ $shaoutput != *"OK"* ]]; then
		echo ""
		echo "!!! FAILED SHA VERIFICATION!!! EXITING"
		echo "!!! DELETING ALL CREATED FILES !!!"
		rm $origname
		rm $origname".sha1"
		exit
	fi
        if [ $imageconst = "FakeKittenENC" ]; then
		#remove the file that contains .gpg at the end
                rm $origname
        fi
	rm $origname".sha1"
fi


echo ""
echo "end of my job"