package Koha::Indexer::Utils;

# Copyright (c) 2012 Equinox Software, Inc.
# This file is part of Koha.
#
# Koha 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.
#
# Koha 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 Koha; if not, see <https://www.gnu.org/licenses>.

use strict;
use warnings;
use 5.010;

use XML::LibXML;

=head1 Koha::Indexer::Utils

Koha::Indexer::Utils - utility functions for managing search indexes

=head1 DESCRIPTION

This modules contains utility functions for managing various aspects
of Koha's bibliographic and authority search indexes.

=head1 FUNCTIONS

=cut

=head2 zebra_record_abs_to_dom

$dom_config = Koha::Indexer::Utils::zebra_record_abs_to_dom($record_abs_config, $marcflavour);

Given a string containing the contents of a records.abs configuration file as
used by Zebra's GRS-1 filter, emit an equivalent DOM configuration.

=cut

our $idxNS = 'http://www.koha-community.org/schemas/index-defs';

sub zebra_record_abs_to_dom {
    my $grs1_cfg    = shift;
    my $marcflavour = shift;

    chomp $grs1_cfg;
    my @grs1_cfg_lines = split /\n/, $grs1_cfg, -1;
    my $grs1_defs      = [];

    # generate an arrayref of structures representing
    # each records.abs line
    for ( my $i = 0 ; $i <= $#grs1_cfg_lines ; $i++ ) {
        my $line = $grs1_cfg_lines[$i];
        next if _can_ignore_grs1_cfg_line($line);
        my $grs1_def = _parse_grs1_cfg_line($line);
        $grs1_def->{orig_def} = $line;
        $grs1_def->{lineno}   = $i + 1;
        push @$grs1_defs, $grs1_def;
    }

    # map the index definitions to a DOM tree representing
    # the index definitions -- if you squint hard, you
    # can see the beginnings of a more general definition language
    # for Koha index definitions
    my $dom_cfg = XML::LibXML::Document->new( '1.0', 'utf-8' );
    my $root    = $dom_cfg->createElement('index_defs');
    $root->setNamespace( $idxNS, 'kohaidx' );
    foreach my $grs1_def (@$grs1_defs) {
        _append_grs1_def_to_dom_cfg( $dom_cfg, $root, $grs1_def, $marcflavour );
    }

    # and emit the result as a string
    $dom_cfg->setDocumentElement($root);
    return $dom_cfg->toString(1);
}

#
# bunch of utility functions for zebra_record_abs_to_dom
#
sub _can_ignore_grs1_cfg_line {
    my $line = shift;
    return 1
        if $line =~ /^\s*$/
        or $line =~ /^#/
        or $line =~ /^(encoding|name|attset|esetname|marc|systag|xpath)/
        or $line =~ /^all/;    # DOM filter automatically indexes all tokens, so
                               # no need to deal with 'all any' lines in record.abs
    return 0;
}

sub _parse_grs1_cfg_line {
    my $line = shift;
    my $grs1_def;

    if ( $line =~ /^melm\s+(.*)/ || $line =~ m!^xelm /record/(.*)! ) {
        $grs1_def = _parse_xelm_melm($1);
    }
    return $grs1_def;
}

sub _parse_xelm_melm {
    my $line = shift;

    my ( $field, $index_defs ) = split /\s+/, $line, 2;

    # munge fixed field range indicators
    $index_defs =~ s/range\(data,(\d+),(\d+)\)/$1:$2/g;

    my ( $tag, $subfield ) = split /\$/, $field, 2;
    return {
        tag        => $tag,
        subfield   => $subfield,
        index_defs => [ map { _parse_grs1_index_def($_) } split /,/, $index_defs ],
    };
}

sub _parse_grs1_index_def {
    my $index_def = shift;

    my @parts      = split /:/, $index_def, -1;
    my $parsed_def = {};
    $parsed_def->{name}       = shift @parts;
    $parsed_def->{index_type} = shift @parts;
    $parsed_def->{offset}     = shift @parts;
    $parsed_def->{length}     = shift @parts;

    # if the original index definition didn't specify an index
    # type, set it 'w' -- the DOM filter needs the index type
    # to be specified explicitly
    $parsed_def->{index_type} = 'w' unless defined $parsed_def->{index_type};
    return $parsed_def;
}

sub _append_grs1_def_to_dom_cfg {
    my $dom_cfg     = shift;
    my $root        = shift;
    my $grs1_def    = shift;
    my $marcflavour = shift;

    my $comment = $dom_cfg->createComment( 'record.abs line ' . $grs1_def->{lineno} . ': ' . $grs1_def->{orig_def} );
    $root->appendChild($comment);

    if ( defined $grs1_def->{tag} && defined $grs1_def->{subfield} ) {
        my $dom_def = $dom_cfg->createElementNS( $idxNS, 'index_subfields' );
        $dom_def->setAttribute( 'tag',       $grs1_def->{tag} );
        $dom_def->setAttribute( 'subfields', $grs1_def->{subfield} );
        _append_target_indexes( $dom_cfg, $dom_def, $grs1_def );
        $root->appendChild($dom_def);
    } elsif ( defined $grs1_def->{tag} and $grs1_def->{tag} eq 'leader' ) {

        # we're the leader
        _append_grs1_defs_for_leader( $dom_cfg, $root, $grs1_def );
    } elsif ( defined $grs1_def->{tag} and $grs1_def->{tag} < 10 ) {

        # we're a control field
        _append_grs1_defs_for_control_field( $dom_cfg, $root, $grs1_def );
    } elsif ( defined $grs1_def->{tag} ) {

        # we're indexing an entire variable data field
        my $dom_def = $dom_cfg->createElementNS( $idxNS, 'index_data_field' );
        $dom_def->setAttribute( 'tag', $grs1_def->{tag} );
        _append_target_indexes( $dom_cfg, $dom_def, $grs1_def );
        $root->appendChild($dom_def);
    }
}

sub _append_target_indexes {
    my $dom_cfg  = shift;
    my $dom_def  = shift;
    my $grs1_def = shift;

    foreach my $index_def ( @{ $grs1_def->{index_defs} } ) {
        _append_one_target_index( $dom_cfg, $dom_def, $index_def );
    }
}

sub _append_one_target_index {
    my $dom_cfg    = shift;
    my $dom_def    = shift;
    my $index_def  = shift;
    my $tgt_idx    = $dom_cfg->createElementNS( $idxNS, 'target_index' );
    my $index_name = "$index_def->{name}:$index_def->{index_type}";
    $tgt_idx->appendText($index_name);
    $dom_def->appendChild($tgt_idx);
}

sub _append_grs1_defs_for_leader {
    my $dom_cfg  = shift;
    my $root     = shift;
    my $grs1_def = shift;
    foreach my $index_def ( @{ $grs1_def->{index_defs} } ) {
        my $dom_def = $dom_cfg->createElementNS( $idxNS, 'index_leader' );
        if ( defined $index_def->{offset} && defined $index_def->{length} ) {
            $dom_def->setAttribute( 'offset', $index_def->{offset} );
            $dom_def->setAttribute( 'length', $index_def->{length} );
        }
        _append_one_target_index( $dom_cfg, $dom_def, $index_def );
        $root->appendChild($dom_def);
    }
}

sub _append_grs1_defs_for_control_field {
    my $dom_cfg  = shift;
    my $root     = shift;
    my $grs1_def = shift;
    foreach my $index_def ( @{ $grs1_def->{index_defs} } ) {
        my $dom_def = $dom_cfg->createElementNS( $idxNS, 'index_control_field' );
        $dom_def->setAttribute( 'tag', $grs1_def->{tag} );
        if ( defined $index_def->{offset} && defined $index_def->{length} ) {
            $dom_def->setAttribute( 'offset', $index_def->{offset} );
            $dom_def->setAttribute( 'length', $index_def->{length} );
        }
        _append_one_target_index( $dom_cfg, $dom_def, $index_def );
        $root->appendChild($dom_def);
    }
}

1;