/**
 * Given the current textarea value and cursor position, returns the
 * @-person-mention query being typed (the text after the last triggering @),
 * or null if no person-mention is active.
 *
 * Rules — distinct from comment-mentions in `mention.ts`:
 * - @ must be at the start of the string or preceded by whitespace
 * - The query may contain spaces (historical persons commonly have multi-word
 *   display names — "Auguste Raddatz", "Maria von Müller-Schultz")
 * - The query stops at a newline or at a second @ (the next mention starts)
 */
export function detectPersonMention(text: string, cursorPos: number): string | null {
	const before = text.slice(0, cursorPos);
	const atIndex = before.lastIndexOf('@');
	if (atIndex === -1) return null;

	if (atIndex > 0 && !/\s/.test(before[atIndex - 1])) return null;

	const query = before.slice(atIndex + 1);
	if (query.includes('\n') || query.includes('@')) return null;

	return query;
}