n8n/packages/@n8n/utils/src/string/truncate.ts

export const truncate = (text: string, length = 30): string =>
	text.length > length ? text.slice(0, length) + '...' : text;

/**
 * Replace part of given text with ellipsis following the rules below:
 *
 * - Remove chars just before the last word, as long as the last word is under 15 chars
 * - Otherwise preserve the last 5 chars of the name and remove chars before that
 */
export function truncateBeforeLast(text: string, maxLength: number): string {
	const chars: string[] = [];

	const segmenter = new Intl.Segmenter(undefined, { granularity: 'grapheme' });

	for (const { segment } of segmenter.segment(text)) {
		chars.push(segment);
	}

	if (chars.length <= maxLength) {
		return text;
	}

	const lastWhitespaceIndex = chars.findLastIndex((ch) => ch.match(/^\s+$/));
	const lastWordIndex = lastWhitespaceIndex + 1;
	const lastWord = chars.slice(lastWordIndex);
	const ellipsis = '…';
	const ellipsisLength = ellipsis.length;

	if (lastWord.length < 15) {
		const charsToRemove = chars.length - maxLength + ellipsisLength;
		const indexBeforeLastWord = lastWordIndex;
		const keepLength = indexBeforeLastWord - charsToRemove;

		if (keepLength > 0) {
			return (
				chars.slice(0, keepLength).join('') + ellipsis + chars.slice(indexBeforeLastWord).join('')
			);
		}
	}

	return (
		chars.slice(0, maxLength - 5 - ellipsisLength).join('') + ellipsis + chars.slice(-5).join('')
	);
}