#!/usr/bin/perl

# wpdf -- view, watch and remake pdf based on Makefile

use strict;
use warnings;

my %deps;

# collect dependencies for given pdf files
for (@ARGV) {
	if (/\.pdf$/) {
		(my $name = $_) =~ s/\.pdf$//;
		open my $f, '<', 'Makefile'
			or die "could not open Makefile: $!\n";
		while (<$f>) {
			if (/^\Q$name.pdf\E:\s*(.*)/) {
				$deps{$_} = $name for split /\s/, $1;
				last;
			}
		}
		close $f;
		exec('xpdf', '-remote', "wpdf-$name", "$name.pdf") if fork == 0;
	} else {
		warn "skipping $_: not a pdf\n";
	}
}

# make pdf on demand
open my $p, '-|', 'watch', keys %deps
	or die "could not start watch: $!\n";
while (<$p>) {
	chomp;
	system('make', "$deps{$_}.pdf") == 0
		&& system('xpdf', '-remote', "wpdf-$deps{$_}", '-reload');
}
close $p;