package RDF::Trine::Store::LDF;

use strict;
use warnings;
no warnings 'redefine';
use feature qw(state);
use utf8;
use base qw(RDF::Trine::Store);

use RDF::Trine::Store;
use RDF::Trine::Iterator;
use RDF::LDF;
use RDF::Trine::Error qw(:try);

sub new {
    my ($class,%opts) = @_;
    my $ref = \%opts;
    $ref->{ldf} =  RDF::LDF->new( url => $ref->{url});

    return undef unless $ref->{ldf}->is_fragment_server;
    
    bless $ref , $class;
}

sub _new_with_string {
    my ($class, $cfg) = @_;
    $class->new(url => $cfg);
}
sub _new_with_config {
    my ($class,$cfg) = @_;
    $class->new(url => $cfg->{url});
}

sub get_statements {
    my ($self,$subject,$predicate,$object,$context) = @_;

    my $sub = $self->{ldf}->get_statements($subject,$predicate,$object);
    RDF::Trine::Iterator::Graph->new($sub);
}

sub get_pattern {
    my ($self,$bgp,$context) = @_;

    $self->{ldf}->get_pattern($bgp,$context);
}

sub get_contexts {
    undef;
}

sub add_statement {
    throw RDF::Trine::Error::UnimplementedError -text => "LDF add_statement support not implemented";
}

sub remove_statement {
    throw RDF::Trine::Error::UnimplementedError -text => "LDF remove_statement support not implemented";
}

sub remove_statements {
    throw RDF::Trine::Error::UnimplementedError -text => "LDF remove_statements support not implemented";
}

sub count_statements {
    my ($self,$subject,$predicate,$object,$context) = @_;

    my $it = $self->{ldf}->get_statements($subject,$predicate,$object);

    my ($triples,$info) = $it->();

    $info->{hydra_totalItems};
}

sub size {
    shift->count_statements;
}

sub supports {
    undef;
}

1;

=head1 NAME

RDF::Trine::Store::LDF - RDF Store proxy for a Linked Data Fragment endpoint 

=head1 SYNOPSIS

    use RDF::Trine::Store::LDF;
    use RDF::Trine::Store;

    my $store = RDF::Trine::Store->new_with_config({
            storetype => 'LDF',
            url => $url
    });

    my $it = $store->get_statements();

    while (my $st = $it->next) {
        # $st is a RDF::Trine::Statement
        print "$st\n";
    }

    # Or query the store with SPAQRL

    use RDF::Query;
    my $model =  RDF::Trine::Model->new($store);

    my $rdf_query = RDF::Query->new(<<EOF);
    .
    .
    SPARQL
    .
    .
    EOF

    my $iter = $rdf_query->execute($model);

    while (my $s = $iter->next) {
        # $s is a RDF::Trine::VariableBinding
        print $s->value . "\n";
    }

=head1 DESCRIPTION

RDF::Trine::Store::LDF provides a RDF::Trine::Store API to interact with a remote 
Linked Data Fragment endpoint. For details see: <http://linkeddatafragments.org/>.

=head1 METHODS

Beyond the methods documented below, this class inherits methods from the L<RDF::Trine::Store> class.

=over 

=item new({ url => url })

Returns a new RDF::Trine::Store object that will act as a proxy for the Linked Data Fragment
endpoint accessible via the supplied $url.

Expertimental: more than one url as an ARRAY reference can be provided for an federated 
query over many LDF endpoints.

=item new_with_config( $hashref )

Returns a new RDF::Trine::Store object configured by a hashref with the url as required key.

=item get_statements( $subject, $predicate, $object )

Returns a stream object of all statements matching the specified subject, predicate and objects. 
Any of the arguments may be undef to match any value.

=item get_pattern( $bgp )

Returns an iterator object of all bindings matching the specified graph pattern.

=item get_contexts

Not supported.

=item add_statement ( $statement [, $context] )

Not supported.

=item remove_statement ( $statement [, $context])

Not supported.

=item remove_statements ( $subject, $predicate, $object [, $context])

Not supported.

=item count_statements ( $subject, $predicate, $object )

Returns a count of all the statements matching the specified subject, predicate and object. 
Any of the arguments may be undef to match any value.

=item size

Returns the number of statements in the store.

=item supports ( [ $feature ] )

Not supported.

=back

=head1 AUTHOR

Patrick Hochstenbach, C<< patrick.hochstenbach at ugent.be >>

=head1 CONTRIBUTORS

Gregory Todd Williams, C<< greg@evilfunhouse.com >>

=head1 LICENSE

This program is free software; you can redistribute it and/or modify it under the terms of either: 
the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See L<http://dev.perl.org/licenses/> for more information.

=encoding utf8

=cut