Show a tile at beginning of visible history (#5887)

src/components/views/rooms/HistoryTile.tsx

@@ -0,0 +1,47 @@
+/*
+Copyright 2021 Robin Townsend <robin@robin.town>
+
+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 React, { useContext } from "react";
+import { EventTimeline } from "matrix-js-sdk/src/models/event-timeline";
+
+import EventTileBubble from "../messages/EventTileBubble";
+import RoomContext from "../../../contexts/RoomContext";
+import { _t } from "../../../languageHandler";
+
+const HistoryTile = () => {
+    const { room } = useContext(RoomContext);
+
+    const oldState = room.getLiveTimeline().getState(EventTimeline.BACKWARDS);
+    const encryptionState = oldState.getStateEvents("m.room.encryption")[0];
+    const historyState = oldState.getStateEvents("m.room.history_visibility")[0]?.getContent().history_visibility;
+
+    let subtitle;
+    if (historyState == "invited") {
+        subtitle = _t("You don't have permission to view messages from before you were invited.");
+    } else if (historyState == "joined") {
+        subtitle = _t("You don't have permission to view messages from before you joined.");
+    } else if (encryptionState) {
+        subtitle = _t("Encrypted messages before this point are unavailable.");
+    }
+
+    return <EventTileBubble
+        className="mx_HistoryTile"
+        title={_t("You can't see earlier messages")}
+        subtitle={subtitle}
+    />;
+};
+
+export default HistoryTile;