#!/usr/bin/env perl

=pod

=head1 NAME

bibzbladd.pl - add Zbl numbers to papers in a given bib file

=head1 SYNOPSIS

bibzbladd  [B<-f>] [B<-o> I<output>] I<bib_file>

=head1 OPTIONS

=over 4

=item B<-f>

Force searching for Zbl numbers even if the entry already has one.

=item B<-o> I<output>

Output file.  If this option is not used, the name for the 
output file is formed by adding C<_zbl> to the input file

=back

=head1 DESCRIPTION

The script reads a BibTeX file.  It checks whether the entries have
Zbls.  If not, tries to contact internet to get the numbers.  The
result is a BibTeX file with the fields 
C<zblnumber=...> added.  

The name of the output file is either set by the B<-o> option or 
is derived by adding the suffix C<_zbl> to the output file.

=head1 AUTHOR

Boris Veytsman

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2014-2016  Boris Veytsman

This is free software.  You may redistribute copies of it under the
terms of the GNU General Public License
L<http://www.gnu.org/licenses/gpl.html>.  There is NO WARRANTY, to the
extent permitted by law.

=cut

use strict;
BEGIN {
    # find files relative to our installed location within TeX Live
    chomp(my $TLMaster = `kpsewhich -var-value=SELFAUTOPARENT`); # TL root
    if (length($TLMaster)) {
	unshift @INC, "$TLMaster/texmf-dist/scripts/bibtexperllibs";
    }
}
use IO::File;
use BibTeX::Parser;
use Getopt::Std;
use URI::Escape;
use LWP::UserAgent;

my $USAGE="USAGE: $0  [-f] [-o output] file\n";
my $VERSION = <<END;
bibzbladd v2.0
This is free software.  You may redistribute copies of it under the
terms of the GNU General Public License
http://www.gnu.org/licenses/gpl.html.  There is NO WARRANTY, to the
extent permitted by law.
$USAGE
END
my %opts;
getopts('fo:hV',\%opts) or die $USAGE;

if ($opts{h} || $opts{V}){
    print $VERSION;
    exit 0;
}

################################################################
# Defaults and parameters
################################################################

my $inputfile = shift;

my $outputfile = $inputfile;

$outputfile =~ s/\.([^\.]*)$/_zbl.$1/;

if ($opts{o}) {
    $outputfile = $opts{o};
}

my $forceSearch=$opts{f};

my $input= IO::File->new($inputfile) or 
    die "Cannot find BibTeX file $inputfile\n$USAGE\n";
my $output = IO::File->new("> $outputfile") or 
    die "Cannot write to $outputfile\n$USAGE\n";

my $parser=new BibTeX::Parser($input);



# Creating the HTTP parameters
my $mirror =
    "https://zbmath.org/citationmatching/bibtex/match";
my $userAgent = LWP::UserAgent->new;

while (my $entry = $parser->next ) {
    if (!$entry->parse_ok()) {
	print STDERR "Cannot understand entry: ";
	$entry->print(*STDERR);
	print STDERR "Skipping this entry\n";
	next;
    }
    if (!($entry->type() eq 'ARTICLE')) {
	print $output $entry->raw_bibtex(), "\n\n";
	next;
    }
    if ($entry->has('zblnumber') && !$forceSearch) {
	print $output $entry->raw_bibtex(), "\n\n";
	next;
    }
    

     # Now we have an entry with no Zbl.  Let us get to work.
     my $zbl = GetZbl($entry, $userAgent, $mirror);
     if (length($zbl)) {
 	$entry->field('zblnumber',$zbl);
     }
    print $output $entry->to_string(), "\n\n";

}

$input->close();
$output->close();
exit 0;

###############################################################
#  Getting one Zbl
###############################################################

sub GetZbl {
    my $entry=shift;
    my $userAgent=shift;
    my $mirror=shift;
    
    my @query;

    my $string=uri_escape_utf8($entry->to_string());
    


    my $response = $userAgent->get("$mirror?bibtex=$string");
    if ($response->decoded_content =~ /^\s*"zbl_id":\s*"(.*)",\s*$/m) {
	return $1;
     } else {
 	return ("");
    }

}