/**
 * Returns the number of digits after the decimal point. Handles both the
 * normal decimal notation (`"0.25"`) and the exponential notation that JS
 * produces for very small magnitudes (`"1e-8"`).
 */
export function getDecimalPrecision(num: number): number {
	if (num === 0) {
		return 0;
	}

	// Very small numbers (|num| < 1) get serialized as "1e-8", not "0.00000001".
	if (Math.abs(num) < 1) {
		const parts = num.toExponential().split("e-");
		// biome-ignore lint/style/noNonNullAssertion: `toExponential` always yields a mantissa
		const mantissaDecimalPart = parts[0]!.split(".")[1];
		return (
			(mantissaDecimalPart ? mantissaDecimalPart.length : 0) +
			// biome-ignore lint/style/noNonNullAssertion: exponential form always has an exponent after "e-"
			Number.parseInt(parts[1]!, 10)
		);
	}

	const decimalPart = num.toString().split(".")[1];
	return decimalPart ? decimalPart.length : 0;
}

/**
 * Rounds `value` to the nearest multiple of `step`, offset by `min` — so the
 * quantization grid is always anchored on `min`, not on `0`. The result is
 * then re-quantized via `toFixed(precision)` to trim binary-float drift.
 */
export function roundValueToStep(
	value: number,
	step: number,
	min: number,
): number {
	const nearest = Math.round((value - min) / step) * step + min;
	return Number(
		nearest.toFixed(
			Math.max(getDecimalPrecision(step), getDecimalPrecision(min)),
		),
	);
}