<?php 
/**
  * A script to process an Exhibit JSON template 
  * file into one or more SPARQL queries, and return the results as
  * an Exhibit JSON file.
  *  The template file should be a normal Exhibit database, except objects under the "types" and "properties" objects    
  *  should have a property called "uri", containing the URI of the Class or Property, 
  *  items should have some properties with empty values, 
  *  and an item's "label" should be the name of another property.
  * Author: Keith Alexander 
 */

/*Instantiate ARC API */
require_once("arc/ARC_api.php");
$api_args = array(
  "inc_path"=>"./arc/",
  "config_path"=>"./arc_config.php"
);
$api = new ARC_api($api_args);
$api->db_connect();

//read the JSON template file
require('json.php');
$json = new Services_JSON();
$data = $json->decode(file_get_contents('template.json'));
//get all the items - we will create a query for each item we find
$template_items = $data->items;
//empty the items array from our original JSON file - we will fill it with results
$data->items = array();
//iterate over the template items, creating a query
foreach($template_items as $item)
{
	//the subject of the graph - can be preset by the user, or left blank
	//so we either turn it into  <http://example.com/users-id#> or ?id
	$subject = (isset($item->id) && !empty($item->id))? '<'.$item->id.'>' : '?id';
	// get the human readable type label
	$type_name = $item->type;
	// get the type's IRI
	$type = '<'.$data->types->$type_name->uri.'>';
	//get the label's property name
	$label_prop_name = $item->label;
	//get the label's property's IRI
	$label_prop = '<'.$data->properties->$label_prop_name->uri.'>';
	
	//for storing WHERE conditions
	$triples = array();
	//vars in the select statement
	$vars = array();
	//jsonc is a parameter that the ARC store accepts to strip out 
	// unwanted meta properties from the JSON results object
	$jsonc = array('id');
	
	//iterate over the template item's properties
	foreach($item as $k => $v)
	{
		//determine node type of object
		if(empty($v))
		{
			$object = '?'.$k;
		}
		elseif( (substr($v,0,1)=='<') && (substr($v,-1,1)=='>') )
		{
			$object = $k;
		}
		else 
		{
			$object ='"'.$v. '"';
		}
		$vars[]='?'.$k;
		$jsonc[]= $k;
		if(!in_array($k, array('type','id','label')) )
		{
			$property = $data->properties->$k->uri;
		 	$triples[] = <<<_SPQL_
		$subject <{$property}> $object  . 
_SPQL_;
		}
	}
	$sparql = "SELECT ?id ".implode(" ", $vars)." \r\n WHERE { \r\n\t GRAPH ?id {
		 $subject <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> $type . \r\n 
$subject <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?type . \r\n 
 $subject $label_prop ?label . \r\n 
 ?id $label_prop ?label . \r\n 

".implode("\r\n", $triples)."  \r\n\t }  \r\n   } LIMIT 100";

	$args=array(
	  "result_type"=>'json', // (rows|json|xml|single|rows_n_count|row_count|sql)
	  "query"=>$sparql,
	 "result_type_args"=>array("jsonc"=> implode(",",$jsonc),)
);
	$qr=$api->query($args);
	$result = $json->decode($qr['result']);
	
	foreach($result->results->bindings as $row)
	{
		//make the rdf:type human readable
		$row->type = $type_name;
		$data->items[] = $row;
	}
}
//output
header("Content-type: text");
echo stripslashes($json->encode($data));
?>