#!/bin/bash

if [ "$#" -ne 1 ]
then
  echo "Output folder not specified"
  exit 1
fi

a=0
b=0
c=0

for FILE in ./*.pdf; do
    ((a+=$(stat -c%s "${FILE}")))
done


for FILE in ./*.pdf; do
 gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/prepress -dNOPAUSE -dBATCH  -dQUIET -sOutputFile=temp.pdf "${FILE}"

 oldsize=$(stat -c%s "${FILE}")
 newsize=$(stat -c%s temp.pdf)

 if (("$newsize" < "$oldsize"))
 then
    ((c++))
    cp -f temp.pdf $1/"${FILE}"
 else
    cp -f "${FILE}" $1/"${FILE}"
    rm -f temp.pdf
 fi
done

for FILE in $1/*.pdf; do
    ((b+=$(stat -c%s "${FILE}")))
done


d=$(bc -l <<< "scale=2; (($a-$b))/1024")
e=$(bc -l <<< "scale=2; 100*$b/$a")

echo "Shrinked $c PDFs, saving $d kiB at $e% compression ratio."