#!/bin/bash

# Description
# A simple script useful to rotate a series of scanned pdfs files and, after
# that, concat them.
# manage_scans.bash takes as input three arguments (one of which is optional):
# - source: a path to the folder of source pdf files to manage;
# - destination: a path to the folder where you will see a new pdf file and
#   where new temp files will be put
# - output (optional): the name of the file which will be created at the end
#   of execution

if [[ -z $1 ]]; then
	echo -e "usage $0: $0 source destination [output]\n"
	cat $0 | sed -n '3,11 s/# //p'
	exit 0
elif [[ ! -d $1 || ! -r $1 ]]; then
	echo "Error: path passed as source isn't a directory or ins't readable!" 1>&2
	exit 1
elif [[ ! -d $2 || ! -r $2 ]]; then
	echo "Error: path passed as destination isn't a directory or ins't readable!" 1>&2
	exit 1
fi

if [[ -z $3 ]]; then
	output="output.pdf"
else
	output=$3
fi

if ! pdftk > /dev/null 2>&1; then
	echo -e "Error: pdftk isn't actually installed!\nPlease install it and then rerun this script." 1>&2
	exit 1
fi

src=${1%/}
dest=${2%/}

i=0
for arg in `ls -1 $src/*.pdf`; do
	file=`basename $arg`
	if [ `expr $i % 2` -eq 0 ]; then
		pdftk $arg cat 1south output $dest/$file
	else
		cp -p $arg $dest
	fi
	i=$(($i + 1))
done

# concat every temp pdf files to create a new one
pdftk $dest/*.pdf cat output $dest/$output
# delete every temp pdf files in $dest folder
ls $dest/*.pdf | grep -v $output | xargs rm