MSC3531 - Implementing message hiding pending moderation (#7518)

Signed-off-by: David Teller <davidt@element.io>

src/components/views/messages/HiddenBody.tsx

@@ -0,0 +1,55 @@
+/*
+Copyright 2022 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 React from "react";
+import { MatrixEvent } from "matrix-js-sdk/src/models/event";
+
+import { _t } from "../../../languageHandler";
+import { IBodyProps } from "./IBodyProps";
+
+interface IProps {
+    mxEvent: MatrixEvent;
+}
+
+/**
+ * A message hidden from the user pending moderation.
+ *
+ * Note: This component must not be used when the user is the author of the message
+ * or has a sufficient powerlevel to see the message.
+ */
+const HiddenBody = React.forwardRef<any, IProps | IBodyProps>(({ mxEvent }, ref) => {
+    let text;
+    const visibility = mxEvent.messageVisibility();
+    switch (visibility.visible) {
+        case true:
+            throw new Error("HiddenBody should only be applied to hidden messages");
+        case false:
+            if (visibility.reason) {
+                text = _t("Message pending moderation: %(reason)s", { reason: visibility.reason });
+            } else {
+                text = _t("Message pending moderation");
+            }
+            break;
+    }
+
+    return (
+        <span className="mx_HiddenBody" ref={ref}>
+            { text }
+        </span>
+    );
+});
+
+export default HiddenBody;