byte-me/src/lib/format.ts

/**
 * Formats a number of bytes into a human-readable string using binary units (KiB, MiB, GiB, TiB).
 *
 * - For values less than 1024, returns the value in bytes (e.g., "512 B").
 * - For larger values, converts to the appropriate unit and formats:
 *   - If the integer part is 1000 or more, shows no decimal (e.g., "1024 KiB").
 *   - If the decimal part is at least 0.1, shows one decimal place (e.g., 1228.8 KiB formats as "1.2 MiB").
 *   - Otherwise, shows no decimal (e.g., 1075.2 MiB == 1.05 GiB, formats as "1 GiB").
 *
 * @param v - The number of bytes to format.
 * @returns The formatted string with the appropriate unit.
 */
export function formatBytes(v: number): string {
	if (v < 1024) return `${v} B`;

	const units = ["KiB", "MiB", "GiB", "TiB"];
	let unitIndex = -1;
	let value = v;

	while (value >= 1024 && unitIndex < units.length - 1) {
		value /= 1024;
		unitIndex++;
	}

	const intValue = Math.floor(value);
	const decimal = value - intValue;

	if (intValue >= 1000) {
		// More than 3 digits, no decimal
		return `${intValue} ${units[unitIndex]}`;
	} else if (decimal >= 0.1) {
		// Show 1 decimal if decimal >= 0.1
		return `${value.toFixed(1)} ${units[unitIndex]}`;
	} else {
		// No decimal
		return `${intValue} ${units[unitIndex]}`;
	}
}