#!/bin/bash
#           _  __       _                                         _     
# _ __   __| |/ _|     (_) __ _ _ __ ___  _ __ ___   ___ _ __ ___| |__  
#| '_ \ / _` | |_ _____| |/ _` | '_ ` _ \| '_ ` _ \ / _ \ '__/ __| '_ \ 
#| |_) | (_| |  _|_____| | (_| | | | | | | | | | | |  __/ | _\__ \ | | |
#| .__/ \__,_|_|      _/ |\__,_|_| |_| |_|_| |_| |_|\___|_|(_)___/_| |_|
#|_|                 |__/                                               
#

# Ensure necessary binaries
for cmd in pdfjam pdfcrop pdfinfo pdfcropmargins; do
  if ! command -v "$cmd" &>/dev/null; then
    echo "Please install $cmd to use this script."
    exit 1
  fi
done

# Args
if [ "$#" -lt 3 ] || [ "$#" -gt 4 ]; then
  echo "Usage: $0 input.pdf rows columns [margin]"
  exit 1
fi

input_pdf="$1"
rows="$2"
columns="$3"
margin="${4:-0}" # Set margin if provided, else default to 0

intermediate_pdf=$(mktemp --suffix=.pdf)
cropped_output_pdf=$(mktemp --suffix=.pdf)

# Cleanup temporary files on exit
trap 'rm -f "$intermediate_pdf" "$cropped_output_pdf"' EXIT

# Generate the grid PDF
pdfjam \
	--nup "$columns"x"$rows" \
	--a4paper \
	--outfile "$intermediate_pdf" \
	$(for i in $(seq 1 $((rows * columns))); do echo "$input_pdf"; done)
if [ $? -ne 0 ]; then
  echo "Error: pdfjam failed to generate the grid PDF."
  exit 1
fi

# Apply margin if provided
if [[ "$margin" != 0 ]]; then
  pdfcropmargins \
	  -o "$cropped_output_pdf" \
	  -s \
	  -p 100 \
	  -a4 \
	  -$margin -$margin -$margin -$margin \
	  "$intermediate_pdf"
  if [ $? -ne 0 ]; then
    echo "Error: pdfcropmargins failed to apply the margins."
    exit 1
  fi
else
  mv "$intermediate_pdf" "$cropped_output_pdf"
fi

final_pdf="jammed.pdf"
mv "$cropped_output_pdf" "$final_pdf"

echo "Final centered PDF created as $final_pdf"