Extract isContentActionable to a separate helper

This moves the check about whether an event is actionable (for the purpose of
replies, edits, reactions, etc.) to shared utils module.

src/utils/EventUtils.js

@@ -0,0 +1,45 @@
+/*
+Copyright 2019 New Vector Ltd
+
+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 { EventStatus } from 'matrix-js-sdk';
+
+/**
+ * Returns whether an event should allow actions like reply, reactions, edit, etc.
+ * which effectively checks whether it's a regular message that has been sent and that we
+ * can display.
+ *
+ * @param {MatrixEvent} mxEvent The event to check
+ * @returns {boolean} true if actionable
+ */
+export function isContentActionable(mxEvent) {
+    const { status: eventStatus } = mxEvent;
+
+    // status is SENT before remote-echo, null after
+    const isSent = !eventStatus || eventStatus === EventStatus.SENT;
+
+    if (isSent && mxEvent.getType() === 'm.room.message') {
+        const content = mxEvent.getContent();
+        if (
+            content.msgtype &&
+            content.msgtype !== 'm.bad.encrypted' &&
+            content.hasOwnProperty('body')
+        ) {
+            return true;
+        }
+    }
+
+    return false;
+}