#!/bin/sh
[ -z "$1" ] && echo "Give either a pdf file or a DOI as an argument." && exit

if [ -f "$1" ]; then
	# Try to get DOI from pdfinfo or pdftotext output.
	doi=$(pdfinfo "$1" | grep -io "doi:.*") ||
	doi=$(pdftotext "$1" 2>/dev/null - | sed -n '/[dD][oO][iI]:/{s/.*[dD][oO][iI]:\s*\(\S\+[[:alnum:]]\).*/\1/p;q}') ||
	exit 1
else
	doi="$1"
fi

# Check crossref.org for the bib citation.
curl -s "https://api.crossref.org/works/$doi/transform/application/x-bibtex" -w "\\n"