#!/usr/bin/perl

=head1 NAME

subject-remove - remove subject headings

=head1 SYNOPSIS

    subject-remove --in=in.dat --out=out.dat --source=bidex

=head1 DESCRIPTION

subject-remove allows you to remove subject headings from a batch of 
MARC records which are from a particular source. The example from 
the synopsis shows you how to use it to remove any subject headings
that are from the 'bidex' source.

Records that lack the appropriate subject headings will be written
out unchanged to the output file.

=cut

use strict;
use warnings;
use MARC::Batch;
use Getopt::Long;
use Pod::Usage;
use IO::File;

my ($in,$out,$source) = ('','','');
GetOptions(
    'in:s'      => \$in,
    'out:s'     => \$out,
    'source:s'  => \$source,
);

## verify options
pod2usage( verbose => 2 ) if ! -f $in or ! $source or ! $out;

## open output file
my $outHandle = IO::File->new( ">$out" );
pod2usage( verbose => 2 ) if ! $outHandle;

## open input records
my $batch = MARC::Batch->new( 'USMARC', $in );
my $recordCount = 0;
my $fieldCount = 0;

## process each record and write possibly modified records to output file
while ( my $r = $batch->next() ) {
    foreach my $f ( $r->field( '6..' ) ) { 
        my $subfield2 = $f->subfield(2) || '';
        if ( $f->indicator(2) eq '7' and $subfield2 eq $source ) {
            $r->delete_field($f);
            $fieldCount++;
        }
    }
    $recordCount++;
    $outHandle->print( $r->as_usmarc() );
}

print "\nremoved $fieldCount subject headings in $recordCount records.\n\n";