/**
 * Number formatting helpers used by `<NumberField.Root>` and `<NumberField.Input>`.
 *
 * Mirrors `packages/react/src/utils/formatNumber.ts`. A module-scope cache
 * keyed by `(locale, options)` keeps repeated formats cheap — constructing
 * `Intl.NumberFormat` dominates the cost.
 */

const FORMATTER_CACHE = new Map<string, Intl.NumberFormat>();

export function getFormatter(
	locale?: Intl.LocalesArgument,
	options?: Intl.NumberFormatOptions,
): Intl.NumberFormat {
	const key = JSON.stringify({ locale, options });
	const cached = FORMATTER_CACHE.get(key);
	if (cached) return cached;
	const formatter = new Intl.NumberFormat(locale, options);
	FORMATTER_CACHE.set(key, formatter);
	return formatter;
}

/**
 * Formats `value` with `Intl.NumberFormat(locale, format)`. Returns the
 * empty string when `value` is `null` or non-finite so the visible `<input>`
 * can clear cleanly.
 */
export function formatNumber(
	value: number | null,
	locale?: Intl.LocalesArgument,
	format?: Intl.NumberFormatOptions,
): string {
	if (value == null || Number.isNaN(value)) return "";
	return getFormatter(locale, format).format(value);
}

/**
 * Like {@link formatNumber} but forces maximum precision (20 fraction
 * digits) when the caller didn't pin an explicit precision. Used for
 * controlled-input display where the consumer's `value` prop must round-trip
 * through the formatter without losing digits.
 */
export function formatNumberMaxPrecision(
	value: number | null,
	locale?: Intl.LocalesArgument,
	format?: Intl.NumberFormatOptions,
): string {
	if (value == null || Number.isNaN(value)) return "";
	const nextFormat: Intl.NumberFormatOptions = {
		...format,
		maximumFractionDigits: 20,
	};
	return getFormatter(locale, nextFormat).format(value);
}