#!/bin/bash
#/##################################################################\
#| Script to merge multiple pdf's in one file adding white pages    |
#| if the the number of each one is odd.                            |
#| Guzmán Castanedo (guzman@castanedo.es)                           |
#| February 2017                                                    |
#| Licence: GPL 3.0 -> https://www.gnu.org/licenses/gpl-3.0.en.html |
#\##################################################################/

function usage {
	printf "USAGE:\t"$(basename "$0")" [PDFin.pdf] <PDFout.pdf>\n"
	printf "INFO:\n"
	printf "\tMerge PDFin.pdf in one PDFout.pdf adding white pages if PDFin.pdf\n"
	printf "\thas an odd number of pages.\n"
	printf "OPTIONS:\n"
	printf "\t-h, --help help\n"
	printf "\t-v, --verbose verbose mode\n"
	printf "\t-y, --yes enable overwrite mode\n"
}

#Check if pdfunite, pdfinfo and convert are installed
echo
if [ ! -x /usr/bin/pdfinfo ]; then
	printf "ERROR: pdfinfo is not installed\n"
	exit 1
fi
if [ ! -x /usr/bin/pdfunite ]; then
	printf "ERROR: pdfunite is not installed\n"
	exit 1
fi
if [ ! -x /usr/bin/convert ]; then
	printf "ERROR: convert is not installed\n"
	exit 1
fi

#Parse args
verbose=false
overwrite=false
#With getopts
TEMP="$(getopt -q -o hvy --long help,verbose,yes -n "$(basename "$0")" -- "$@")"
eval set -- "$TEMP"
unset TEMP
while true; do
	case "$1" in
		-h|--help)
			#Help
			usage
			exit
			;;
		-v|--verbose)
			#Verbose
			verbose=true
			shift
			;;
		-y|--yes)
			#Overwrite
			overwrite=true
			shift
			;;
		--)
			#Last one
			shift
			break
			;;
		*)
			#Unspected
			usage
			echo "ERROR: Invalid option $1"
			exit 1
			;;
	esac
done
#Create white pdf (random name)
whitepdf=$(cat /dev/urandom | tr -dc 'a-z0-9' | fold -w 32 | head -n 1)
whitepdf="$whitepdf.pdf"
while [ -e $whitepdf ]; do
	#Extremly rare, but possible->Choose another one
	whitepdf=$(cat /dev/urandom | tr -dc 'a-z0-9' | fold -w 32 | head -n 1)
	whitepdf="$whitepdf.pdf"
done
#Make whitepdf with convert
convert xc:none -page A4 $whitepdf
if [ $verbose = true ];then
	printf "White PDF:\t%s\n" $whitepdf
fi

#Parse arguments
unite="pdfunite"
cont=0
for i in $@; do
	cont=$((cont+1))
	unite+=" $i"
	if [ $cont -lt $# ]; then
		temp=$(pdfinfo $i 2>/dev/null)
		if [ ! $? -eq 0 ]; then
			printf "ERROR: %s aren't a valid PDF file.\n" $i
			usage
			exit 1
		fi
		pages=$(pdfinfo $i|grep Pages:|awk '{print $2}')
		if [ $verbose = true ]; then
			printf "PDFin:\t%s (%s Pages)\n" $i $pages
		fi
		if [ ! $((pages%2)) -eq 0 ]; then
			#Odd number
			unite+=" $whitepdf"
		fi
	else
		#Last one
		if [ $overwrite = false ]; then
			if [ -e $i ]; then
				printf "Warning: Output file $i exists. Overwrite? [y/n]: "
				read confirm
				case ${confirm:0:1} in
					y|Y)
						;;
					*)
						rm $whitepdf
						exit 1
						;;
				esac
			fi
		fi
		#Execute pdfunite
		$($unite)
		if [ ! $? -eq 0 ];then
			printf "Warning: something was wrong\n"
		else
			printf "Creation Successful\n"
			if [ $verbose = true ]; then
				pages=$(pdfinfo $i|grep Pages:|awk '{print $2}')
				printf "PDFOut:\t$s (%s Pages)\n" $i $pages
			fi
		fi
	fi
done

#Remove whitepdf
if [ $verbose = true ]; then
	printf "Deletting temporal files\n"
fi
rm $whitepdf