[enh] add quick answer functionality with an example answerer

searx/answerers/__init__.py

@@ -0,0 +1,46 @@
+from os import listdir
+from os.path import realpath, dirname, join, isdir
+from searx.utils import load_module
+from collections import defaultdict
+
+
+answerers_dir = dirname(realpath(__file__))
+
+
+def load_answerers():
+    answerers = []
+    for filename in listdir(answerers_dir):
+        if not isdir(join(answerers_dir, filename)):
+            continue
+        module = load_module('answerer.py', join(answerers_dir, filename))
+        if not hasattr(module, 'keywords') or not isinstance(module.keywords, tuple) or not len(module.keywords):
+            exit(2)
+        answerers.append(module)
+    return answerers
+
+
+def get_answerers_by_keywords(answerers):
+    by_keyword = defaultdict(list)
+    for answerer in answerers:
+        for keyword in answerer.keywords:
+            for keyword in answerer.keywords:
+                by_keyword[keyword].append(answerer.answer)
+    return by_keyword
+
+
+def ask(query):
+    results = []
+    query_parts = filter(None, query.query.split())
+
+    if query_parts[0] not in answerers_by_keywords:
+        return results
+
+    for answerer in answerers_by_keywords[query_parts[0]]:
+        result = answerer(query)
+        if result:
+            results.append(result)
+    return results
+
+
+answerers = load_answerers()
+answerers_by_keywords = get_answerers_by_keywords(answerers)