Disallow group names longer than 32 extended graphemes

ts/components/GroupTitleInput.tsx

@@ -0,0 +1,100 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import React, { forwardRef, useRef, ClipboardEvent } from 'react';
+
+import { LocalizerType } from '../types/Util';
+import { multiRef } from '../util/multiRef';
+import * as grapheme from '../util/grapheme';
+
+const MAX_GRAPHEME_COUNT = 32;
+
+type PropsType = {
+  disabled?: boolean;
+  i18n: LocalizerType;
+  onChangeValue: (value: string) => void;
+  value: string;
+};
+
+/**
+ * Group titles must have fewer than MAX_GRAPHEME_COUNT glyphs. Ideally, we'd use the
+ * `maxLength` property on inputs, but that doesn't account for glyphs that are more than
+ * one UTF-16 code units. For example: `'💩💩'.length === 4`.
+ *
+ * This component effectively implements a "max grapheme length" on an input.
+ *
+ * At a high level, this component handles two methods of input:
+ *
+ * - `onChange`. *Before* the value is changed (in `onKeyDown`), we save the value and the
+ *   cursor position. Then, in `onChange`, we see if the new value is too long. If it is,
+ *   we revert the value and selection. Otherwise, we fire `onChangeValue`.
+ *
+ * - `onPaste`. If you're pasting something that will fit, we fall back to normal browser
+ *   behavior, which calls `onChange`. If you're pasting something that won't fit, it's a
+ *   noop.
+ */
+export const GroupTitleInput = forwardRef<HTMLInputElement, PropsType>(
+  ({ i18n, disabled = false, onChangeValue, value }, ref) => {
+    const innerRef = useRef<HTMLInputElement | null>(null);
+    const valueOnKeydownRef = useRef<string>(value);
+    const selectionStartOnKeydownRef = useRef<number>(value.length);
+
+    return (
+      <input
+        disabled={disabled}
+        className="module-GroupTitleInput"
+        onKeyDown={() => {
+          const inputEl = innerRef.current;
+          if (!inputEl) {
+            return;
+          }
+
+          valueOnKeydownRef.current = inputEl.value;
+          selectionStartOnKeydownRef.current = inputEl.selectionStart || 0;
+        }}
+        onChange={() => {
+          const inputEl = innerRef.current;
+          if (!inputEl) {
+            return;
+          }
+
+          const newValue = inputEl.value;
+          if (grapheme.count(newValue) <= MAX_GRAPHEME_COUNT) {
+            onChangeValue(newValue);
+          } else {
+            inputEl.value = valueOnKeydownRef.current;
+            inputEl.selectionStart = selectionStartOnKeydownRef.current;
+            inputEl.selectionEnd = selectionStartOnKeydownRef.current;
+          }
+        }}
+        onPaste={(event: ClipboardEvent<HTMLInputElement>) => {
+          const inputEl = innerRef.current;
+          if (!inputEl) {
+            return;
+          }
+
+          const selectionStart = inputEl.selectionStart || 0;
+          const selectionEnd =
+            inputEl.selectionEnd || inputEl.selectionStart || 0;
+          const textBeforeSelection = value.slice(0, selectionStart);
+          const textAfterSelection = value.slice(selectionEnd);
+
+          const pastedText = event.clipboardData.getData('Text');
+
+          const newGraphemeCount =
+            grapheme.count(textBeforeSelection) +
+            grapheme.count(pastedText) +
+            grapheme.count(textAfterSelection);
+
+          if (newGraphemeCount > MAX_GRAPHEME_COUNT) {
+            event.preventDefault();
+          }
+        }}
+        placeholder={i18n('setGroupMetadata__group-name-placeholder')}
+        ref={multiRef<HTMLInputElement>(ref, innerRef)}
+        type="text"
+        value={value}
+      />
+    );
+  }
+);