Add helper to parse an enum from query args & use it. (#14956)

The `parse_enum` helper pulls an enum value from the query string
(by delegating down to the parse_string helper with values generated
from the enum).

This is used to pull out "f" and "b" in most places and then we thread
the resulting Direction enum throughout more code.

6 files changed, 27 insertions, 22 deletions

diff --git a/synapse/storage/databases/main/__init__.py b/synapse/storage/databases/main/__init__.py
index 0e47592be3..837dc7646e 100644
--- a/synapse/storage/databases/main/__init__.py
+++ b/synapse/storage/databases/main/__init__.py
@@ -17,6 +17,7 @@
 import logging
 from typing import TYPE_CHECKING, List, Optional, Tuple, cast
 
+from synapse.api.constants import Direction
 from synapse.config.homeserver import HomeServerConfig
 from synapse.storage.database import (
     DatabasePool,
@@ -167,7 +168,7 @@ class DataStore(
         guests: bool = True,
         deactivated: bool = False,
         order_by: str = UserSortOrder.NAME.value,
-        direction: str = "f",
+        direction: Direction = Direction.FORWARDS,
         approved: bool = True,
     ) -> Tuple[List[JsonDict], int]:
         """Function to retrieve a paginated list of users from
@@ -197,7 +198,7 @@ class DataStore(
             # Set ordering
             order_by_column = UserSortOrder(order_by).value
 
-            if direction == "b":
+            if direction == Direction.BACKWARDS:
                 order = "DESC"
             else:
                 order = "ASC"
diff --git a/synapse/storage/databases/main/events_worker.py b/synapse/storage/databases/main/events_worker.py
index f42af34a2f..d7d08369ca 100644
--- a/synapse/storage/databases/main/events_worker.py
+++ b/synapse/storage/databases/main/events_worker.py
@@ -38,7 +38,7 @@ from typing_extensions import Literal
 
 from twisted.internet import defer
 
-from synapse.api.constants import EventTypes
+from synapse.api.constants import Direction, EventTypes
 from synapse.api.errors import NotFoundError, SynapseError
 from synapse.api.room_versions import (
     KNOWN_ROOM_VERSIONS,
@@ -2240,7 +2240,7 @@ class EventsWorkerStore(SQLBaseStore):
         )
 
     async def get_event_id_for_timestamp(
-        self, room_id: str, timestamp: int, direction: str
+        self, room_id: str, timestamp: int, direction: Direction
     ) -> Optional[str]:
         """Find the closest event to the given timestamp in the given direction.
 
@@ -2248,14 +2248,14 @@ class EventsWorkerStore(SQLBaseStore):
             room_id: Room to fetch the event from
             timestamp: The point in time (inclusive) we should navigate from in
                 the given direction to find the closest event.
-            direction: ["f"|"b"] to indicate whether we should navigate forward
+            direction: indicates whether we should navigate forward
                 or backward from the given timestamp to find the closest event.
 
         Returns:
             The closest event_id otherwise None if we can't find any event in
             the given direction.
         """
-        if direction == "b":
+        if direction == Direction.BACKWARDS:
             # Find closest event *before* a given timestamp. We use descending
             # (which gives values largest to smallest) because we want the
             # largest possible timestamp *before* the given timestamp.
@@ -2307,9 +2307,6 @@ class EventsWorkerStore(SQLBaseStore):
 
             return None
 
-        if direction not in ("f", "b"):
-            raise ValueError("Unknown direction: %s" % (direction,))
-
         return await self.db_pool.runInteraction(
             "get_event_id_for_timestamp_txn",
             get_event_id_for_timestamp_txn,
diff --git a/synapse/storage/databases/main/media_repository.py b/synapse/storage/databases/main/media_repository.py
index 9b172a64d8..b202c5eb87 100644
--- a/synapse/storage/databases/main/media_repository.py
+++ b/synapse/storage/databases/main/media_repository.py
@@ -26,6 +26,7 @@ from typing import (
     cast,
 )
 
+from synapse.api.constants import Direction
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import (
     DatabasePool,
@@ -176,7 +177,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
         limit: int,
         user_id: str,
         order_by: str = MediaSortOrder.CREATED_TS.value,
-        direction: str = "f",
+        direction: Direction = Direction.FORWARDS,
     ) -> Tuple[List[Dict[str, Any]], int]:
         """Get a paginated list of metadata for a local piece of media
         which an user_id has uploaded
@@ -199,7 +200,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
             # Set ordering
             order_by_column = MediaSortOrder(order_by).value
 
-            if direction == "b":
+            if direction == Direction.BACKWARDS:
                 order = "DESC"
             else:
                 order = "ASC"
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index fbbc018887..4ddb27f686 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -35,6 +35,7 @@ from typing import (
 import attr
 
 from synapse.api.constants import (
+    Direction,
     EventContentFields,
     EventTypes,
     JoinRules,
@@ -2204,7 +2205,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
         self,
         start: int,
         limit: int,
-        direction: str = "b",
+        direction: Direction = Direction.BACKWARDS,
         user_id: Optional[str] = None,
         room_id: Optional[str] = None,
     ) -> Tuple[List[Dict[str, Any]], int]:
@@ -2213,8 +2214,8 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
         Args:
             start: event offset to begin the query from
             limit: number of rows to retrieve
-            direction: Whether to fetch the most recent first (`"b"`) or the
-                oldest first (`"f"`)
+            direction: Whether to fetch the most recent first (backwards) or the
+                oldest first (forwards)
             user_id: search for user_id. Ignored if user_id is None
             room_id: search for room_id. Ignored if room_id is None
         Returns:
@@ -2236,7 +2237,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
                 filters.append("er.room_id LIKE ?")
                 args.extend(["%" + room_id + "%"])
 
-            if direction == "b":
+            if direction == Direction.BACKWARDS:
                 order = "DESC"
             else:
                 order = "ASC"
diff --git a/synapse/storage/databases/main/stats.py b/synapse/storage/databases/main/stats.py
index 0c1cbd540d..d7b7d0c3c9 100644
--- a/synapse/storage/databases/main/stats.py
+++ b/synapse/storage/databases/main/stats.py
@@ -22,7 +22,7 @@ from typing_extensions import Counter
 
 from twisted.internet.defer import DeferredLock
 
-from synapse.api.constants import EventContentFields, EventTypes, Membership
+from synapse.api.constants import Direction, EventContentFields, EventTypes, Membership
 from synapse.api.errors import StoreError
 from synapse.storage.database import (
     DatabasePool,
@@ -663,7 +663,7 @@ class StatsStore(StateDeltasStore):
         from_ts: Optional[int] = None,
         until_ts: Optional[int] = None,
         order_by: Optional[str] = UserSortOrder.USER_ID.value,
-        direction: Optional[str] = "f",
+        direction: Direction = Direction.FORWARDS,
         search_term: Optional[str] = None,
     ) -> Tuple[List[JsonDict], int]:
         """Function to retrieve a paginated list of users and their uploaded local media
@@ -714,7 +714,7 @@ class StatsStore(StateDeltasStore):
                     500, "Incorrect value for order_by provided: %s" % order_by
                 )
 
-            if direction == "b":
+            if direction == Direction.BACKWARDS:
                 order = "DESC"
             else:
                 order = "ASC"
diff --git a/synapse/storage/databases/main/transactions.py b/synapse/storage/databases/main/transactions.py
index f8c6877ee8..6b33d809b6 100644
--- a/synapse/storage/databases/main/transactions.py
+++ b/synapse/storage/databases/main/transactions.py
@@ -19,6 +19,7 @@ from typing import TYPE_CHECKING, Iterable, List, Optional, Tuple, cast
 import attr
 from canonicaljson import encode_canonical_json
 
+from synapse.api.constants import Direction
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.storage._base import db_to_json
 from synapse.storage.database import (
@@ -496,7 +497,7 @@ class TransactionWorkerStore(CacheInvalidationWorkerStore):
         limit: int,
         destination: Optional[str] = None,
         order_by: str = DestinationSortOrder.DESTINATION.value,
-        direction: str = "f",
+        direction: Direction = Direction.FORWARDS,
     ) -> Tuple[List[JsonDict], int]:
         """Function to retrieve a paginated list of destinations.
         This will return a json list of destinations and the
@@ -518,7 +519,7 @@ class TransactionWorkerStore(CacheInvalidationWorkerStore):
         ) -> Tuple[List[JsonDict], int]:
             order_by_column = DestinationSortOrder(order_by).value
 
-            if direction == "b":
+            if direction == Direction.BACKWARDS:
                 order = "DESC"
             else:
                 order = "ASC"
@@ -550,7 +551,11 @@ class TransactionWorkerStore(CacheInvalidationWorkerStore):
         )
 
     async def get_destination_rooms_paginate(
-        self, destination: str, start: int, limit: int, direction: str = "f"
+        self,
+        destination: str,
+        start: int,
+        limit: int,
+        direction: Direction = Direction.FORWARDS,
     ) -> Tuple[List[JsonDict], int]:
         """Function to retrieve a paginated list of destination's rooms.
         This will return a json list of rooms and the
@@ -569,7 +574,7 @@ class TransactionWorkerStore(CacheInvalidationWorkerStore):
             txn: LoggingTransaction,
         ) -> Tuple[List[JsonDict], int]:
 
-            if direction == "b":
+            if direction == Direction.BACKWARDS:
                 order = "DESC"
             else:
                 order = "ASC"