# Make snippet for extracting RDF data from PDF documents
#
# Copyright 2024, Jonas Smedegaard <dr@jones.dk>
# SPDX-License-Identifier: GPL-3+
#
# Setup:
# In main Makefile...
#  * set variable PDF_DOCUMENTS or use simple and slow default
#  * set variable BASE_IRI or use default file URI
#  * include this make snippet
#
# Dependencies:
#  * podofoxmp (e.g. Debian package libpodofo-utils)
#  * rapper (e.g. Debian package raptor2-utils)
#  * perl v5.36.0 or newer

# list of relative paths to PDF documents
#PDF_DOCUMENTS = \
# main_paper.pdf \
# promo_article.pdf \
# research/deep/superconductors/report.pdf
# research/deep/fringe/index.pdf

PDF_DOCUMENTS ?= $(wildcard *.pdf)

# extract XMP metadata from PDF document,
# and convert to the human-friendlier RDF/Turtle serialization
$(PDF_DOCUMENTS:%=turtle-from-%): turtle-from-%:
	@pdfinfo -meta $* \
	| perl -gp \
	 -e 's,\s*<\?xpacket [^>]+>\s*,,;' \
	 -e 's,<x:xmpmeta [^>]+>,<?xml version="1.0" encoding="utf-8"?>,;' \
	 -e 's,\s*</x:xmpmeta>,,;' \
	 -e 's,\s*<\?xpacket [^>]+>,,;' \
	| rapper -q -i rdfxml -o turtle - $(BASE_IRI)$(dir $*)

.PHONY: $(PDF_DOCUMENTS:%=turtle-from-%)