package Search::Xapian::QueryParser;

use 5.006;
use strict;
use warnings;
use Carp;

require Exporter;
require DynaLoader;

our @ISA = qw(Exporter DynaLoader);
# Items to export into caller's namespace by default. Note: do not export
# names by default without a very good reason. Use EXPORT_OK instead.
# Do not simply export all your public functions/methods/constants.

# If you do not need this, moving things directly into @EXPORT or @EXPORT_OK
# will save memory.
our @EXPORT_OK = ( );

our @EXPORT = qw( );

# Preloaded methods go here.

use overload '='  => sub { $_[0]->clone() },
             'fallback' => 1;

sub clone() {
  my $self = shift;
  my $class = ref( $self );
  my $copy = new2( $self );
  bless $copy, $class;
  return $copy;
}

sub new() {
  my $class = shift;
  my $qp = new0();
  
  bless $qp, $class;
  $qp->set_database(@_) if scalar(@_) == 1;

  return $qp;
}

1;

__END__

=head1 NAME

Search::Xapian::QueryParser - Parse a query string into a Search::Xapian::Query object

=head1 DESCRIPTION

This module turns a human readable string into something Xapian can
understand.  The syntax supported is designed to be similar to other web
based search engines, so that users familiar with them don't have to learn
a whole new syntax.

=head1 SYNOPSIS

  use Search::Xapian qw/:standard/;

  my $qp = new Search::Xapian::QueryParser( [$database] );
  $qp->set_stemmer(new Search::Xapian::Stem("english"));
  $qp->set_default_op(OP_AND);

  $database->enquire($qp->parse_query('a word OR two NEAR "a phrase" NOT (too difficult) +eh'));
 
=head1 METHODS

=over 4

=item new <database>

QueryParser constructor.

=item set_stemmer <stemmer>

Set the Search::Xapian::Stem object to be used for stemming query terms.

=item set_stemming_strategy <strategy>

Set the stemming strategy.  Valid values are STEM_ALL, STEM_SOME, STEM_NONE.

=item set_stopper <stopper>

Set the Search::Xapian::Stopper object to be used for identifying stopwords.

=item set_default_op <operator>

Set default operator for joining elements. Useful values are
OP_AND and OP_OR.  See L<Search::Xapian> for descriptions of these constants.

=item get_default_op

Returns the default operator for joining elements.

=item set_database <database>

Pass a L<Search::Xapian::Database> object which is used to check whether
terms exist in some situations.

=item parse_query <query_string> [<flags>]

parses the query string according to the rules defined in the query parser
documentation below. Allows you to specify certain flags to modify the
searching behaviour:

  FLAG_BOOLEAN=1, FLAG_PHRASE=2, FLAG_LOVEHATE=4,
  FLAG_BOOLEAN_ANY_CASE=8, FLAG_WILDCARD = 16

default flags are FLAG_PHRASE, FLAG_BOOLEAN and FLAG_LOVEHATE

=item add_prefix <field> <prefix>

Add a probabilistic term prefix.  E.g. $qp->add_prefix("author", "A");

Allows the user to search for author:orwell which will search for the term
"Aorwel" (assuming English stemming is in use). Multiple fields can be mapped
to the same prefix (so you can e.g. make title: and subject: aliases for each
other).

Parameters:
field 	The user visible field name
prefix 	The term prefix to map this to

=item add_boolean_prefix <field> prefix

Add a boolean term prefix allowing the user to restrict a search with a 
boolean filter specified in the free text query.  E.g. 
$p->add_boolean_prefix("site", "H");

Allows the user to restrict a search with site:xapian.org which will be 
converted to Hxapian.org combined with any probabilistic query with OP_FILTER.

Multiple fields can be mapped to the same prefix (so you can e.g. make site: 
and domain: aliases for each other).

Parameters:
field 	The user visible field name
prefix 	The term prefix to map this to

=item stoplist_begin

=item stoplist_end

=item unstem_begin

=item unstem_end

=item get_description

Returns a string describing this object.  (for introspection)

=back

=head1 REFERENCE

  http://www.xapian.org/docs/queryparser.html
  http://www.xapian.org/docs/sourcedoc/html/classXapian_1_1QueryParser.html

=cut