Accept parsed query as argument.

Author: RubenVerborgh

lib/sparql/SparqlIterator.js

@@ -1,5 +1,5 @@
 /*! @license ©2014 Ruben Verborgh - Multimedia Lab / iMinds / Ghent University */
-/* An SparqlIterator returns the results of a SPARQL query. */
+/* A SparqlIterator returns the results of a SPARQL query. */
 
 var SparqlParser = require('sparqljs').Parser,
     AsyncIterator = require('asynciterator'),
@@ -21,23 +21,28 @@ var queryConstructors = {
 };
 
 // Creates an iterator from a SPARQL query
-function SparqlIterator(source, queryText, options) {
-  // Shift arguments if `source` was omitted
-  if (typeof source === 'string')
-    options = queryText, queryText = source, source = null;
+function SparqlIterator(source, query, options) {
+  // Set argument defaults
+  if (typeof source.read !== 'function')
+    options = query, query = source, source = null;
+  options = options || {};
+  source = source || AsyncIterator.single({});
 
   // Transform the query into a cascade of iterators
   try {
+    // Parse the query if needed
+    if (typeof query === 'string')
+      query = new SparqlParser(options.prefixes).parse(query);
+
     // Create an iterator that projects the bindings according to the query type
-    var query = new SparqlParser(options.prefixes).parse(queryText),
-        queryIterator, QueryConstructor = queryConstructors[query.queryType];
+    var queryIterator, QueryConstructor = queryConstructors[query.queryType];
     if (!QueryConstructor)
       throw new Error('No iterator available for query type: ' + query.queryType);
     queryIterator = new QueryConstructor(null, query, options);
-
     // Create an iterator for bindings of the query's graph pattern
-    var graphIterator = new SparqlGroupsIterator(source || AsyncIterator.single({}),
+    var graphIterator = new SparqlGroupsIterator(source,
                               queryIterator.patterns || query.where, options);
+
     // Create iterators for each order
     for (var i = query.order && (query.order.length - 1); i >= 0; i--) {
       var order = new SparqlExpressionEvaluator(query.order[i].expression),
@@ -66,9 +71,9 @@ function SparqlIterator(source, queryText, options) {
   }
   catch (error) {
     if (/Parse error/.test(error.message))
-      error = new InvalidQueryError(queryText, error);
+      error = new InvalidQueryError(query, error);
     else
-      error = new UnsupportedQueryError(queryText, error);
+      error = new UnsupportedQueryError(query, error);
     throw error;
   }
 }