Pillify event permalinks (#10392)

src/hooks/usePermalinkTargetRoom.ts

@@ -0,0 +1,103 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { Room } from "matrix-js-sdk/src/matrix";
+import { useEffect, useState } from "react";
+
+import { PillType } from "../components/views/elements/Pill";
+import { MatrixClientPeg } from "../MatrixClientPeg";
+import { PermalinkParts } from "../utils/permalinks/PermalinkConstructor";
+
+/**
+ * Tries to determine the initial room.
+ * Initial here means it should be possible to load the room without sending API requests.
+ * For an @room or a user mention it is the permalinkRoom.
+ * If the parse result contains a room Id or alias try to find it with {@link findRoom}.
+ * Otherwise returns null.
+ *
+ * @param type - Pill type
+ * @param permalinkRoom - Room in which the permalink is displayed.
+ * @param parseResult - Permalink parser result
+ * @returns Initial room or null if it cannot be determined.
+ */
+const determineInitialRoom = (
+    type: PillType | null,
+    parseResult: PermalinkParts | null,
+    permalinkRoom: Room | undefined,
+): Room | null => {
+    if (type === PillType.AtRoomMention && permalinkRoom) return permalinkRoom;
+
+    if (type === PillType.UserMention && permalinkRoom) {
+        return permalinkRoom;
+    }
+
+    if (parseResult?.roomIdOrAlias) {
+        const room = findRoom(parseResult.roomIdOrAlias);
+        if (room) return room;
+    }
+
+    return null;
+};
+
+/**
+ * Tries to find a room by room Id or searching all rooms for an alias.
+ *
+ * @param roomIdOrAlias - Id or alias of the room to find.
+ * @returns Room if found, else null.
+ */
+const findRoom = (roomIdOrAlias: string): Room | null => {
+    const client = MatrixClientPeg.get();
+
+    return roomIdOrAlias[0] === "#"
+        ? client.getRooms().find((r) => {
+              return r.getCanonicalAlias() === roomIdOrAlias || r.getAltAliases().includes(roomIdOrAlias);
+          }) ?? null
+        : client.getRoom(roomIdOrAlias);
+};
+
+/**
+ * Hook to get the permalink target room:
+ *
+ * @param type - Permalink type
+ * @param parseResult - Permalink parse result
+ * @param permalinkRoom - Room in which the permalink is rendered
+ * @returns Returns the target room:
+ *          - The permalinkRoom for an @room or user mention
+ *          - The room of the parse result for a room mention
+ *          - The room of the event for an event permalink
+ *          - Null in other cases or if the room cannot be found
+ */
+export const usePermalinkTargetRoom = (
+    type: PillType | null,
+    parseResult: PermalinkParts | null,
+    permalinkRoom: Room | null,
+): Room | null => {
+    // The listed permalink types require a room.
+    // If it cannot be initially determined, it will be looked up later by a memo hook.
+    const shouldLookUpRoom =
+        type && [PillType.RoomMention, PillType.EventInSameRoom, PillType.EventInOtherRoom, "space"].includes(type);
+    const initialRoom = determineInitialRoom(type, parseResult, permalinkRoom);
+    const [targetRoom, setTargetRoom] = useState<Room | null>(initialRoom);
+
+    useEffect(() => {
+        if (shouldLookUpRoom && !targetRoom && parseResult?.roomIdOrAlias) {
+            const newRoom = findRoom(parseResult.roomIdOrAlias);
+            setTargetRoom(newRoom);
+        }
+    }, [parseResult?.roomIdOrAlias, shouldLookUpRoom, targetRoom]);
+
+    return targetRoom;
+};