Better emoji support in linkify/previews

ts/util/emoji.ts

@@ -0,0 +1,36 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+/* eslint-disable no-restricted-syntax */
+
+import emojiRegex from 'emoji-regex/es2015/RGI_Emoji';
+
+import { assert } from './assert';
+
+const REGEXP = emojiRegex();
+
+export function replaceEmojiWithSpaces(value: string): string {
+  return value.replace(REGEXP, ' ');
+}
+
+export type SplitElement = Readonly<{
+  type: 'emoji' | 'text';
+  value: string;
+}>;
+
+export function splitByEmoji(value: string): ReadonlyArray<SplitElement> {
+  const emojis = value.matchAll(REGEXP);
+
+  const result: Array<SplitElement> = [];
+  let lastIndex = 0;
+  for (const match of emojis) {
+    result.push({ type: 'text', value: value.slice(lastIndex, match.index) });
+    result.push({ type: 'emoji', value: match[0] });
+
+    assert(match.index !== undefined, '`matchAll` should provide indices');
+    lastIndex = match.index + match[0].length;
+  }
+
+  result.push({ type: 'text', value: value.slice(lastIndex) });
+
+  return result;
+}