#!/usr/bin/perl

use strict;
use warnings;

use RDF::Query;

### helper functions
sub hash_to_string {
  my %results_row = @_;
  my $str = join('|', %results_row);
  %results_row = ();
  return $str;
}

sub string_to_hash {
  my $str = shift;
  my @vals = split(/\|/, $str);
  my %results_row;
  for (my $i = 0; $i < $#vals; $i += 2) {
    $results_row{$vals[$i]} = $vals[$i + 1];
  }
  return %results_row;
}

sub execute_query {
	#my $select_clause = shift;
	my $where_clause = shift;
	#my $order_by_clause = shift;
	my $filename = shift;

	print "running query...\n";
	my $start_time = time();
	my $sparql	= <<"END";
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX relation: <http://discoursedb.org/wiki/Special:URIResolver/Relation-3A>

SELECT *
FROM <http://discoursedb.org/RDF/discoursedb.xml>
WHERE {
END
	$sparql .= $where_clause;
	$sparql .= "}";

	my $query = RDF::Query->new( $sparql, undef, undef, 'sparql' );
	my $stream = $query->execute();

	open (RESULTS_FILE, ">query-results/$filename");
	while (my $data = $stream->()) {
		my @values	= map { $query->bridge->as_string( $_ ) } @$data;
		my @keys	= $stream->binding_names;
	
		my %values;
		@values{ @keys }	= @values;
		print RESULTS_FILE &hash_to_string(%values) . "\n";
		%values = ();
	}
	$query = 0;
	close (RESULTS_FILE);
	my $end_time = time();
	print "took " . ($end_time - $start_time) . " seconds.\n";
	#foreach my $row (@rows) {
	#	print RESULTS_FILE "$row\n";
	#}
}

### MAIN

my $where_clause;

### Create results files with data on topics, authors, etc.

$where_clause = <<"END";
	?item relation:Addresses_topic ?topic
END
&execute_query($where_clause, "topic");

$where_clause = <<"END";
	?item relation:Is_for ?position
END
&execute_query($where_clause, "is_for");

$where_clause = <<"END";
	?item relation:Is_against ?position
END
&execute_query($where_clause, "is_against");

$where_clause = <<"END";
	?item relation:Is_mixed_on ?position
END
&execute_query($where_clause, "is_mixed");

$where_clause = <<"END";
	?item relation:Was_written_by ?author
END
&execute_query($where_clause, "author");