Calculate intersection of types requested by source and layers params

helper/types.js

@@ -1,12 +1,32 @@
 var valid_types = require( '../query/types' );
 
+/**
+ * Calculate the set-style intersection of two arrays
+ */
+var intersection = function intersection(set1, set2) {
+  return set2.filter(function(value) {
+      return set1.indexOf(value) !== -1;
+  });
+};
+
 module.exports = function calculate_types(clean_types) {
   if (!clean_types) {
     return undefined;
   }
 
+
+  if (clean_types.from_layers || clean_types.from_source) {
+    var types = valid_types;
+
     if (clean_types.from_layers) {
-    return clean_types.from_layers;
+      types = intersection(types, clean_types.from_layers);
+    }
+
+    if (clean_types.from_source) {
+      types = intersection(types, clean_types.from_source);
+    }
+
+    return types;
   }
 
   if (clean_types.from_address_parser) {

test/unit/helper/types.js

@@ -55,6 +55,35 @@ module.exports.tests.layers_parameter_and_address_parser = function(test, common
   });
 };
 
+module.exports.tests.source_parameter = function(test, common) {
+  test('source parameter specified', function(t) {
+    var cleaned_types = {
+      from_source: ['openaddresses']
+    };
+
+    var actual = types(cleaned_types);
+
+    var expected = ['openaddresses'];
+    t.deepEqual(actual, expected, 'type parameter set to types specified by source');
+    t.end();
+  });
+};
+
+module.exports.tests.source_and_layers_parameters = function(test, common) {
+  test('source and layers parameter both specified', function(t) {
+    var cleaned_types = {
+      from_source: ['openaddresses'],
+      from_layers: ['osmaddress', 'openaddresses']
+    };
+
+    var actual = types(cleaned_types);
+
+    var expected = ['openaddresses'];
+    t.deepEqual(actual, expected, 'type set to intersection of source and layer types');
+    t.end();
+  });
+};
+
 module.exports.all = function (tape, common) {
 
   function test(name, testFunction) {