Add FileUtils

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/utils/FileUtils.ts

@@ -0,0 +1,53 @@
+/*
+Copyright 2021 Šimon Brandner <simon.bra.ag@gmail.com>
+
+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 filesize from 'filesize';
+import { IMediaEventContent } from '../customisations/models/IMediaEventContent';
+import { _t } from '../languageHandler';
+
+/**
+ * Extracts a human readable label for the file attachment to use as
+ * link text.
+ *
+ * @param {IMediaEventContent} content The "content" key of the matrix event.
+ * @param {string} fallbackText The fallback text
+ * @param {boolean} withSize Whether to include size information. Default true.
+ * @return {string} the human readable link text for the attachment.
+ */
+export function presentableTextForFile(
+    content: IMediaEventContent,
+    fallbackText = _t("Attachment"),
+    withSize = true,
+): string {
+    let text = fallbackText;
+    if (content.body && content.body.length > 0) {
+        // The content body should be the name of the file including a
+        // file extension.
+        text = content.body;
+    }
+
+    if (content.info && content.info.size && withSize) {
+        // If we know the size of the file then add it as human readable
+        // string to the end of the link text so that the user knows how
+        // big a file they are downloading.
+        // The content.info also contains a MIME-type but we don't display
+        // it since it is "ugly", users generally aren't aware what it
+        // means and the type of the attachment can usually be inferrered
+        // from the file extension.
+        text += ' (' + filesize(content.info.size) + ')';
+    }
+    return text;
+}