#!/usr/bin/perl
use 5.012;
use warnings;

use Getopt::Long;
use Pod::Usage;
use Text::CSV;

my $out;
my $verb = 1;
my $help = 0;
GetOptions(
  'output|o=s' => \$out,
  'verbose|v+' => \$verb,
  'help|h|?' => \$help,
) or pod2usage(-exitstatus => 2);

if ($help) {
  pod2usage(-exitstatus => 0, -verbose => $verb);
}

my ($key, $doc) = @ARGV;
unless (defined $key and defined $doc) {
  pod2usage(-exitstatus => 2);
}

unless (defined $out) {
  $out = $doc =~ s/(?:\.[^.]+)?$/.csv/r;
}

$|++ if ($verb > 1);

say "Reading keywords from '$key' ..." if ($verb > 2);
my @keywords = do {
  open my $in, '<', $key or die "Error opening keyword file: $!";
  my %unique;
  while (my $_ = <$in>) {
    chomp;
    for my $keyword (split /[\s.:!?,;()]+/) {
      $unique{$keyword} = 1;
    }
  }
  keys %unique;
};

say scalar(@keywords), " keywords read" if ($verb > 1);

say "Scanning document '$doc', writing output to '$out' ..." if ($verb > 2);
my $ispdf = do {
  open my $in, '<', $doc or die "Error opening document file: $!";
  read $in, my $magic, 4;
  $magic eq '%PDF';
};

my $src;
if ($ispdf) {
  say "Document seems to be a PDF file" if ($verb > 2);
  open $src, '-|', 'pdftotext', $doc, '-' or die "Error opening document stream: $!";
}
else {
  say "Document does not seem to be a PDF file" if ($verb > 2);
  open $src, '<', $doc or die "Error opening document file: $!";
}

open my $tgt, '>', $out or die "Error opening output file: $!";
my $csv = Text::CSV->new({binary => 1, eol => $/});
$csv->print($tgt, [qw(Page Word Keyword Sentence)]);

my $page = 0;
my $word = 0;
my $sentence = '';
my @hits = ();
my $total = 0;
while (my $_ = <$src>) {
  chomp;
  while ($_ ne '') {
    if (s/^\f//) {
      $page += 1;
      $word = 0;
    }
    elsif (s/^([^\s.:!?,;()]+)//) {
      my $candidate = $1;
      for my $keyword (@keywords) {
        if ($candidate eq $keyword) {
          print "$page,$word ... " if ($verb > 2);
          push @hits, [$page, $word, $keyword];
        }
      }
      $sentence .= ' ' if ($sentence ne '');
      $sentence .= $candidate;
      $word += 1;
    }
    elsif (s/^([.:!?,;()])//) {
      $sentence .= $1;
      for my $hit (@hits) {
        push @$hit, $sentence;
        $csv->print($tgt, $hit);
      }
      $total += @hits;
      $sentence = '';
      @hits = ();
    }
    else {
      s/^\s+//;
    }
  }
}

say "Done" if ($verb > 2);
say "$total matches found" if ($verb > 1);

close $src or die "Failed to close document stream: $!";
close $tgt or die "Failed to close output stream: $!";

__END__

=head1 NAME

keywords - Find keywords in PDF or text files

=head1 SYNOPSIS

keywords [OPTION ...] KEYWORDS DOCUMENT

=head1 OPTIONS

=over 4

=item B<--output=FILE>

=item B<-o FILE>

Write output to the given file. If no such option is given, the output
filename is constructed by replacing the extension of the input document
by C<.csv>.

=item B<--verbose>

=item B<-v>

Increases the verbosity of program output. Up to two instances of this
option currently make sense.

=item B<--help>

=item B<-h>

=item B<-?>

Shows documentation about the program. Combine with B<--verbose> to
view the entire manual page.

=back

=head1 DESCRIPTION

This program reads a list of keywords from a file and scans another
file for occurrences of those keywords.

Both the keyword and document file are split into words separated by
whitespace or any of the sentence separator characters C<.:!?,;()>.

If the document file is not plain text but a PDF file, it is
automatically filtered through the program C<pdftotext> and the output
is scanned instead.

While scanning the document, each occurrence of a keyword is printed
to the output in CSV format. The fields printed are

=over 4

=item the current page number, determined by counting form feeds;

=item the number of the word counting from the start of the page;

=item the matched keyword and

=item the sentence in which the keyword occurred.

=back

=head1 LICENSE

Copyright (c) 2013 by Thomas Chust L<mailto:chust@web.de>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

=cut