From 5be13fb066cd311c8e2cddfd6fd66c1cb1607f5f Mon Sep 17 00:00:00 2001
From: Steve Howell <showell@zulipchat.com>
Date: Mon, 30 Oct 2017 16:31:47 -0700
Subject: [PATCH] Add cachify decorator.

---
 zerver/decorator.py             | 16 +++++++-
 zerver/tests/test_decorators.py | 66 ++++++++++++++++++++++++++++++++-
 2 files changed, 80 insertions(+), 2 deletions(-)

diff --git a/zerver/decorator.py b/zerver/decorator.py
index eb090315a1..f11ebdfcfd 100644
--- a/zerver/decorator.py
+++ b/zerver/decorator.py
@@ -30,7 +30,7 @@ import logging
 from io import BytesIO
 from six.moves import zip, urllib
 
-from typing import Union, Any, Callable, Sequence, Dict, Optional, TypeVar, Text, cast
+from typing import Union, Any, Callable, Sequence, Dict, Optional, TypeVar, Text, Tuple, cast
 from zerver.lib.str_utils import force_bytes
 from zerver.lib.logging_util import create_logger
 
@@ -74,6 +74,20 @@ def asynchronous(method):
         wrapper.csrf_exempt = True  # type: ignore # https://github.com/JukkaL/mypy/issues/1170
     return wrapper
 
+def cachify(method):
+    # type: (Callable) -> Callable
+    dct = {}  # type: Dict[Tuple, Any]
+
+    def cache_wrapper(*args):
+        # type: (*Any) -> Any
+        tup = tuple(args)
+        if tup in dct:
+            return dct[tup]
+        result = method(*args)
+        dct[tup] = result
+        return result
+    return cache_wrapper
+
 def update_user_activity(request, user_profile, query):
     # type: (HttpRequest, UserProfile, Optional[str]) -> None
     # update_active_status also pushes to rabbitmq, and it seems
diff --git a/zerver/tests/test_decorators.py b/zerver/tests/test_decorators.py
index e490f15bf0..060ce94e38 100644
--- a/zerver/tests/test_decorators.py
+++ b/zerver/tests/test_decorators.py
@@ -29,7 +29,7 @@ from zerver.lib.request import \
     RequestVariableConversionError
 from zerver.decorator import (
     api_key_only_webhook_view,
-    authenticate_notify,
+    authenticate_notify, cachify,
     get_client_name, internal_notify_view, is_local_addr,
     rate_limit, validate_api_key, logged_in_and_active,
     return_success_on_head_request
@@ -1255,6 +1255,70 @@ class RestAPITest(ZulipTestCase):
         self.assertEqual(result.status_code, 302)
         self.assertTrue(result["Location"].endswith("/login/?next=/json/users"))
 
+class CacheTestCase(ZulipTestCase):
+    def test_cachify_basics(self):
+        # type: () -> None
+
+        @cachify
+        def add(w, x, y, z):
+            # type: (Any, Any, Any, Any) -> Any
+            return w + x + y + z
+
+        for i in range(2):
+            self.assertEqual(add(1, 2, 4, 8), 15)
+            self.assertEqual(add('a', 'b', 'c', 'd'), 'abcd')
+
+    def test_cachify_is_per_call(self):
+        # type: () -> None
+
+        def test_greetings(greeting):
+            # type: (Text) -> Tuple[List[Text], List[Text]]
+
+            result_log = []  # type: List[Text]
+            work_log = []  # type: List[Text]
+
+            @cachify
+            def greet(first_name, last_name):
+                # type: (Text, Text) -> Text
+                msg = '%s %s %s' % (greeting, first_name, last_name)
+                work_log.append(msg)
+                return msg
+
+            result_log.append(greet('alice', 'smith'))
+            result_log.append(greet('bob', 'barker'))
+            result_log.append(greet('alice', 'smith'))
+            result_log.append(greet('cal', 'johnson'))
+
+            return (work_log, result_log)
+
+        work_log, result_log = test_greetings('hello')
+        self.assertEqual(work_log, [
+            'hello alice smith',
+            'hello bob barker',
+            'hello cal johnson',
+        ])
+
+        self.assertEqual(result_log, [
+            'hello alice smith',
+            'hello bob barker',
+            'hello alice smith',
+            'hello cal johnson',
+        ])
+
+        work_log, result_log = test_greetings('goodbye')
+        self.assertEqual(work_log, [
+            'goodbye alice smith',
+            'goodbye bob barker',
+            'goodbye cal johnson',
+        ])
+
+        self.assertEqual(result_log, [
+            'goodbye alice smith',
+            'goodbye bob barker',
+            'goodbye alice smith',
+            'goodbye cal johnson',
+        ])
+
 class TestUserAgentParsing(ZulipTestCase):
     def test_user_agent_parsing(self):
         # type: () -> None