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.

1 files changed, 14 insertions, 7 deletions

diff --git a/synapse/rest/admin/media.py b/synapse/rest/admin/media.py
index 73470f09ae..0d072c42a7 100644
--- a/synapse/rest/admin/media.py
+++ b/synapse/rest/admin/media.py
@@ -17,9 +17,16 @@ import logging
 from http import HTTPStatus
 from typing import TYPE_CHECKING, Tuple
 
+from synapse.api.constants import Direction
 from synapse.api.errors import Codes, NotFoundError, SynapseError
 from synapse.http.server import HttpServer
-from synapse.http.servlet import RestServlet, parse_boolean, parse_integer, parse_string
+from synapse.http.servlet import (
+    RestServlet,
+    parse_boolean,
+    parse_enum,
+    parse_integer,
+    parse_string,
+)
 from synapse.http.site import SynapseRequest
 from synapse.rest.admin._base import (
     admin_patterns,
@@ -389,7 +396,7 @@ class UserMediaRestServlet(RestServlet):
         # to newest media is on top for backward compatibility.
         if b"order_by" not in request.args and b"dir" not in request.args:
             order_by = MediaSortOrder.CREATED_TS.value
-            direction = "b"
+            direction = Direction.BACKWARDS
         else:
             order_by = parse_string(
                 request,
@@ -397,8 +404,8 @@ class UserMediaRestServlet(RestServlet):
                 default=MediaSortOrder.CREATED_TS.value,
                 allowed_values=[sort_order.value for sort_order in MediaSortOrder],
             )
-            direction = parse_string(
-                request, "dir", default="f", allowed_values=("f", "b")
+            direction = parse_enum(
+                request, "dir", Direction, default=Direction.FORWARDS
             )
 
         media, total = await self.store.get_local_media_by_user_paginate(
@@ -447,7 +454,7 @@ class UserMediaRestServlet(RestServlet):
         # to newest media is on top for backward compatibility.
         if b"order_by" not in request.args and b"dir" not in request.args:
             order_by = MediaSortOrder.CREATED_TS.value
-            direction = "b"
+            direction = Direction.BACKWARDS
         else:
             order_by = parse_string(
                 request,
@@ -455,8 +462,8 @@ class UserMediaRestServlet(RestServlet):
                 default=MediaSortOrder.CREATED_TS.value,
                 allowed_values=[sort_order.value for sort_order in MediaSortOrder],
             )
-            direction = parse_string(
-                request, "dir", default="f", allowed_values=("f", "b")
+            direction = parse_enum(
+                request, "dir", Direction, default=Direction.FORWARDS
             )
 
         media, _ = await self.store.get_local_media_by_user_paginate(