export function shortUsageDate(dateString: string, monthly = false): string {

const [year, month, day] = dateString.split('-').map(Number);

if (monthly) {

return `${year}/${String(month).padStart(2, '0')}`;

}

return `${month}/${day}`;

}

export function formatUsageDate(

dateString: string,

locale: string,

dailyOptions: Intl.DateTimeFormatOptions,

monthly = false,

): string {

// Usage keys are already bucketed in the configured zone. Render the key

// itself in UTC so negative offsets cannot roll it into the previous day or

// month (#54), and use an explicit monthly flag so July 1 remains a day.

const [year, month, day] = dateString.split('-').map(Number);

const date = new Date(Date.UTC(year, month - 1, monthly ? 1 : day, 12));

const options: Intl.DateTimeFormatOptions = monthly

? { year: 'numeric', month: 'long' }

: dailyOptions;

return usageDateFormatter(locale, { ...options, timeZone: 'UTC' }).format(date);

}

// The dashboard formats one label per table row and chart point, and

// toLocaleDateString constructs a fresh Intl.DateTimeFormat on every call (the

// same cost #99 removed from dateKeys). Formatters are memoised per locale and

// options; the dashboard only ever asks for a handful of combinations.

const usageDateFormatters = new Map<string, Intl.DateTimeFormat>();

function usageDateFormatter(

locale: string,

options: Intl.DateTimeFormatOptions,

): Intl.DateTimeFormat {

const key = `${locale}|${JSON.stringify(options)}`;

const cached = usageDateFormatters.get(key);

if (cached) {

return cached;

}

// toLocaleDateString always renders a date: with no date field requested it

// defaults to numeric year, month and day. Intl.DateTimeFormat only does so

// when no time field is requested either, so apply the default explicitly.

const hasDateField = options.weekday !== undefined || options.year !== undefined ||

options.month !== undefined || options.day !== undefined ||

options.dateStyle !== undefined;

const formatter = new Intl.DateTimeFormat(

locale,

hasDateField ? options : { ...options, year: 'numeric', month: 'numeric', day: 'numeric' },

);

usageDateFormatters.set(key, formatter);

return formatter;

}