/**
 * Normalises input to YYYY-MM-DD string
 * - Strings are passed through as is
 * - Date objects are converted to UK time
 */
export const ensureDateString = (input: Date | string): string => {
    if (typeof input === 'string') return input.trim();

    const d = new Intl.DateTimeFormat('en-GB', {
        year: 'numeric',
        month: '2-digit',
        day: '2-digit',
        timeZone: 'Europe/London'
    }).formatToParts(input);

    const part = (type: string) => d.find(p => p.type === type)?.value;

    return `${part('year')}-${part('month')}-${part('day')}`

}