Move free functions into PushRuleEvaluatorForEvent. (#12677)

* Move `_condition_checker` into `PushRuleEvaluatorForEvent`.
* Move the condition cache into `PushRuleEvaluatorForEvent`.
* Improve docstrings.
* Inline a method which is only called once.

synapse/push/push_rule_evaluator.py

@@ -129,9 +129,55 @@ class PushRuleEvaluatorForEvent:
         # Maps strings of e.g. 'content.body' -> event["content"]["body"]
         self._value_cache = _flatten_dict(event)
 
+        # Maps cache keys to final values.
+        self._condition_cache: Dict[str, bool] = {}
+
+    def check_conditions(
+        self, conditions: List[dict], uid: str, display_name: Optional[str]
+    ) -> bool:
+        """
+        Returns true if a user's conditions/user ID/display name match the event.
+
+        Args:
+            conditions: The user's conditions to match.
+            uid: The user's MXID.
+            display_name: The display name.
+
+        Returns:
+             True if all conditions match the event, False otherwise.
+        """
+        for cond in conditions:
+            _cache_key = cond.get("_cache_key", None)
+            if _cache_key:
+                res = self._condition_cache.get(_cache_key, None)
+                if res is False:
+                    return False
+                elif res is True:
+                    continue
+
+            res = self.matches(cond, uid, display_name)
+            if _cache_key:
+                self._condition_cache[_cache_key] = bool(res)
+
+            if not res:
+                return False
+
+        return True
+
     def matches(
         self, condition: Dict[str, Any], user_id: str, display_name: Optional[str]
     ) -> bool:
+        """
+        Returns true if a user's condition/user ID/display name match the event.
+
+        Args:
+            condition: The user's condition to match.
+            uid: The user's MXID.
+            display_name: The display name, or None if there is not one.
+
+        Returns:
+             True if the condition matches the event, False otherwise.
+        """
         if condition["kind"] == "event_match":
             return self._event_match(condition, user_id)
         elif condition["kind"] == "contains_display_name":
@@ -146,6 +192,16 @@ class PushRuleEvaluatorForEvent:
             return True
 
     def _event_match(self, condition: dict, user_id: str) -> bool:
+        """
+        Check an "event_match" push rule condition.
+
+        Args:
+            condition: The "event_match" push rule condition to match.
+            user_id: The user's MXID.
+
+        Returns:
+             True if the condition matches the event, False otherwise.
+        """
         pattern = condition.get("pattern", None)
 
         if not pattern:
@@ -167,13 +223,22 @@ class PushRuleEvaluatorForEvent:
 
             return _glob_matches(pattern, body, word_boundary=True)
         else:
-            haystack = self._get_value(condition["key"])
+            haystack = self._value_cache.get(condition["key"], None)
             if haystack is None:
                 return False
 
             return _glob_matches(pattern, haystack)
 
     def _contains_display_name(self, display_name: Optional[str]) -> bool:
+        """
+        Check an "event_match" push rule condition.
+
+        Args:
+            display_name: The display name, or None if there is not one.
+
+        Returns:
+             True if the display name is found in the event body, False otherwise.
+        """
         if not display_name:
             return False
 
@@ -191,9 +256,6 @@ class PushRuleEvaluatorForEvent:
 
         return bool(r.search(body))
 
-    def _get_value(self, dotted_key: str) -> Optional[str]:
-        return self._value_cache.get(dotted_key, None)
-
 
 # Caches (string, is_glob, word_boundary) -> regex for push. See _glob_matches
 regex_cache: LruCache[Tuple[str, bool, bool], Pattern] = LruCache(