#!/bin/sh -e
# Overlay a PDF with another or a text
# Trims everything beyond the given page number
test "$1" = "-q" && quiet=$1 && shift
case "$1" in ([0-9]) page=$1; shift;; esac
test ! -r "$1" && echo "Usage: sign [page] <document.pdf> [hoffset (-160) [voffset (-310) [scale [signature-image]]]]" && exit 1

tmp_base=/tmp/sign
mkdir -p $tmp_base

texttopdf() {
  out="$tmp_base/stamp.pdf"
  echo "$1" | enscript -B -f Arial12 -o- | ps2pdf - >"$out"
  echo "$out"
}
signature=$(test -f "$5" && echo "$5" || pass info/signature$(test -n "$5" && echo "-$5") || texttopdf "$5")

# TODO make filenames unique and don't rerun unneccessarily
tmp_signed=$tmp_base/$1_${page:-last}-signature.pdf
tmp_reversed=$tmp_base/$1_reverse.pdf
sig=$tmp_base/signature_offset.pdf
result="${1%.pdf}_$(basename "${5:-signed}").pdf"

h=${2:--160}
v=${3:--310}
if test $# -lt 2; then
  case "$1" in
  (*\ TU.pdf) v=-260;;
  esac
fi
echo "Using offset ${h}x and ${v}y"
export TEXMF=""
pdfjam $quiet "$signature" --outfile "$sig" --papersize "{595pt, 842pt}" --noautoscale true \
    --offset "${h}pt ${v}pt" --scale "${4:-1}"
rm -f "$result"
pdfjam $quiet "$1" ${page:-last} "$sig" --outfile "$tmp_signed" --delta "0 -842pt" --nup "1x2" --fitpaper true
# TODO consider pdftk stamp

timg "$tmp_signed"

# https://apple.stackexchange.com/questions/198854/shell-command-to-count-pages-in-a-pdf-other-than-pdftk
if test "$page"
then test "$page" -gt 1 && pdfjam $quiet "$1" 1-$(expr $page - 1) "$tmp_signed" 1 "$1" $(expr $page + 1)-last --outfile "$result"
elif test "$(pdftk "$1" dump_data | grep Pages | cut -d' ' -f2)" -gt 1
then
    pdfjam $quiet "$1" last-1 --outfile "$tmp_reversed"
    pdfjam $quiet "$tmp_reversed" last-2 "$tmp_signed" --outfile "$result"
fi
test -f "$result" || cp -v "$tmp_signed" "$result"