[enh] add redis offline engine / https://redis.io/

Slightly modified merge of commit [97269be6], [01a8a5814a] and [c8d2b5eb] from
searx.

[97269be6] https://github.com/searx/searx/commit/97269be6
[01a8a581] https://github.com/searx/searx/commit/01a8a581
[c8d2b5eb] https://github.com/searx/searx/commit/c8d2b5eb

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/engines/redis_server.py

@@ -0,0 +1,75 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+# lint: pylint
+# pylint: disable=missing-function-docstring
+"""Redis engine (offline)
+
+"""
+
+import redis  # pylint: disable=import-error
+
+engine_type = 'offline'
+
+# redis connection variables
+host = '127.0.0.1'
+port = 6379
+password = ''
+db = 0
+
+# engine specific variables
+paging = False
+result_template = 'key-value.html'
+exact_match_only = True
+
+redis_client = None
+def init(_engine_settings):
+    # pylint: disable=global-statement
+    global redis_client
+    redis_client = redis.StrictRedis(
+        host = host,
+        port = port,
+        db = db,
+        password = password or None,
+        decode_responses = True,
+    )
+
+def search(query, _params):
+
+    if not exact_match_only:
+        return search_keys(query)
+
+    ret = redis_client.hgetall(query)
+    if ret:
+        ret['template'] = result_template
+        return [ret]
+
+    if ' ' in query:
+        qset, rest = query.split(' ', 1)
+        ret = []
+        for res in redis_client.hscan_iter(
+                qset, match='*{}*'.format(rest)
+        ):
+            ret.append({
+                res[0]: res[1],
+                'template': result_template,
+            })
+        return ret
+    return []
+
+def search_keys(query):
+    ret = []
+    for key in redis_client.scan_iter(
+            match='*{}*'.format(query)
+    ):
+        key_type = redis_client.type(key)
+        res = None
+
+        if key_type == 'hash':
+            res = redis_client.hgetall(key)
+        elif key_type == 'list':
+            res = dict(enumerate(redis_client.lrange(key, 0, -1)))
+
+        if res:
+            res['template'] = result_template
+            res['redis_key'] = key
+            ret.append(res)
+    return ret

searx/settings.yml

@@ -960,6 +960,15 @@ engines:
     timeout : 10.0
     disabled : True
 
+  # Required dependency: redis
+  #  - name: myredis
+  #    engine: redis_server
+  #    exact_match_only: False
+  #    host: '127.0.0.1'
+  #    port: 6379
+  #    password: ''
+  #    db: 0
+
 # tmp suspended: bad certificate
 #  - name : scanr structures
 #    shortcut: scs