feat(answers): add findAnswers

src/algoliasearch.helper.js

@@ -8,6 +8,8 @@ var requestBuilder = require('./requestBuilder');
 var events = require('events');
 var inherits = require('./functions/inherits');
 var objectHasKeys = require('./functions/objectHasKeys');
+var omit = require('./functions/omit');
+var merge = require('./functions/merge');
 
 var version = require('./version');
 
@@ -248,6 +250,50 @@ AlgoliaSearchHelper.prototype.searchOnce = function(options, cb) {
   });
 };
 
+/**
+ * Start the search for answers with the parameters set in the state.
+ * This method returns a promise.
+ * @return {AlgoliaSearchHelper}
+ * @return {promise.<FacetSearchResult>} the answer results
+ */
+AlgoliaSearchHelper.prototype.searchForAnswers = function(attributesForPrediction, queryLanguages, nbHits) {
+  var state = this.state;
+  var derivedHelper = this.derivedHelpers[0];
+  if (!derivedHelper) {
+    return Promise.resolve([]);
+  }
+  var derivedState = derivedHelper.getModifiedState(state);
+  var data = merge(
+    {
+      attributesForPrediction: attributesForPrediction,
+      nbHits: nbHits
+    },
+    {
+      params: omit(requestBuilder._getHitsSearchParams(derivedState), [
+        'attributesToSnippet',
+        'hitsPerPage',
+        'restrictSearchableAttributes',
+        'snippetEllipsisText' // FIXME remove this line once the engine is fixed.
+      ])
+    }
+  );
+
+  if (
+    typeof this.client.initIndex !== 'function'
+  ) {
+    throw new Error(
+      'search for answers was called, but this client does not have a function client.initIndex'
+    );
+  }
+  var index = this.client.initIndex(derivedState.index);
+  if (typeof index.findAnswers !== 'function') {
+    throw new Error(
+      'search for answers was called, but this client does not have a function client.initIndex(index).findAnswers'
+    );
+  }
+  return index.findAnswers(derivedState.query, queryLanguages, data);
+};
+
 /**
  * Structure of each result when using
  * [`searchForFacetValues()`](reference.html#AlgoliaSearchHelper#searchForFacetValues)