Chore: Sync fuzzer: Allow generating large amounts of test data for Joplin Server (#13636)

Co-authored-by: Laurent Cozic <laurent22@users.noreply.github.com>

packages/tools/fuzzer/utils/randomString.ts

@@ -0,0 +1,29 @@
+type OnRandomInt = (low: number, high: number)=> number;
+
+const randomString = (nextRandomInteger: OnRandomInt) => (length: number) => {
+	const charCodes = [];
+	for (let i = 0; i < length; i++) {
+		charCodes.push(nextRandomInteger(0, 0xFFFF));
+	}
+
+	let text = String.fromCharCode(...charCodes);
+	// Normalize to avoid differences when reading/writing content from Joplin clients.
+	// TODO: Can the note comparison logic be adjusted to remove some of this?
+	text = text.normalize();
+	text = text.replace(/[\r\b\f\v\0\u007F]/g, '!');
+	text = text.replace(/\p{C}/ug, '-'); // Other control characters
+
+	// Remove invalid UTF-8
+	text = new TextDecoder().decode(new TextEncoder().encode(text));
+
+	// Attempt to work around issues related to unexpected differences in items when reading from
+	// the Joplin client: Remove certain invalid unicode:
+	if ('toWellFormed' in String.prototype && typeof String.prototype.toWellFormed === 'function') {
+		// toWellFormed requires Node >= v20
+		text = String.prototype.toWellFormed.call(text);
+	}
+
+	return text;
+};
+
+export default randomString;