#!/usr/bin/perl
# bibtex_to_paper opens the paper corresponding to a bibtex key
# and is released under the terms of the GNU GPL version 3, or any
# later version, at your option. See the file README and COPYING for
# more information.
# Copyright 2014 by Don Armstrong <don@donarmstrong.com>.


use warnings;
use strict;

use Getopt::Long;
use Pod::Usage;

use File::Find;
use Text::BibTex;

use DB_File;
use MLDBM qw(DB_FILE Storable);
use Fcntl qw/O_RDWR O_CREAT O_TRUNC/;

=head1 NAME

bibtex_to_paper - opens the paper corresponding to a bibtex key

=head1 SYNOPSIS

bibtex_to_paper [options] bibtexkey

 Options:
  --bibtex, -b bibtex file to look up key in
  --bibtex-cache, -c bibtex cache file
  --build-cache, -B build cache using bibtex files
  --pdf-dir pdf directory
  --pdfviewer, -p pdf viewer to use
  --debug, -d debugging level (Default 0)
  --help, -h display this help
  --man, -m display manual

=head1 OPTIONS

=over

=item B<--bibtex, -b>

Bibtex file to look key up in

=item B<--bibtex-cache, -c>

Bibtex cache file; rebuilt if bibtex file changes

=item B<--pdfviewer, -p>

PDF viewer to use; defaults to evince unless a .xoj exists, in which
case xournal is used.

=item B<--debug, -d>

Debug verbosity. (Default 0)

=item B<--help, -h>

Display brief usage information.

=item B<--man, -m>

Display this manual.

=back

=head1 EXAMPLES

bibtex_to_paper

=cut


use vars qw($DEBUG);

my %options = (debug           => 0,
               help            => 0,
               man             => 0,
              );

GetOptions(\%options,
           'build_cache|build-cache|B!',
           'bibtex|b=s',
           'bibtex_cache|bibtex-cache|c=s',
           'pdfviewer|p=s',
           'debug|d+','help|h|?','man|m');

pod2usage() if $options{help};
pod2usage({verbose=>2}) if $options{man};

$DEBUG = $options{debug};

my @USAGE_ERRORS;
if (not exists $options{bibtex} and
    not exists $options{bibtex_cache}) {
    push @USAGE_ERRORS,
        "You must give at least one of --bibtex".
        "or --bibtex-cache";
}

pod2usage(join("\n",@USAGE_ERRORS)) if @USAGE_ERRORS;

sub parse_bibtex_file {
    my ($file,$entries) = @_;

    my $bibfile = Text::BibTex::File->new($file)
        or die "Unable to open $bibfile for reading: $!";
    my @entry_comments;
    my $entry;
    while ($entry = Text::BibTex::Entry->new($bibfile)) {
        if ($entry->metatype() eq 'BTE_COMMENT') {
            push @entry_comments,$entry->value();
        } elsif ($entry->metatype() eq 'BTE_REGULAR') {
            my $entry_key = $entry->key();
            my $link_name;
            if (defined $entry_key) {
                # if there is a file comment, use it as the file name
                for my $comment (@entry_comments) {
                    next unless $comment =~ /^\s*file(?:name)?:?\s*(.+?)\s*$/i;
                    $link_name = $1;
                    last;
                }
                # if there is a file key, use that as the file name
                # if there is a doi, then use that
                # if there is a html, then use that
                if (not defined $link_name) {
                    my @possible_fields = $entry->get(qw(file doi html));
                    for my $possible_field (@possible_fields) {
                        if (defined $possible_field and length $possible_field) {
                            $link_name = $possible_field;
                            last;
                        }
                    }
                }
            }
            if (not exists $entries->{$entry_key} or
                defined $link_name;
               ) {
                $entries->{$entry_key} = $link_name
            }
            # reset the entry comments
            @entry_comments = ();
        } else {
            # do nothing
        }
    }
}


sub initialize_database {
    my ($cache) = @_;
    return open_cache($cache,1);
}

sub open_cache {
    my ($cache,$initialize) @_;
    my $open_flags = O_RDWR|O_CREAT;
    if ($initialize) {
        $open_flags = $open_flags | O_TRUNC;
    }

    my %entries;
    tie %entries, MLDBM => $cache
        $open_flags, 0666
        or die "Unable to create create/truncate $cache: $!";
    return \%entries;
}


__END__