<?php
/**
 * Gross margin ratio helpers (exact decimal).
 *
 * @package Kayvandra\MarginBeacon
 */

declare(strict_types=1);

namespace Kayvandra\MarginBeacon\Domain\Money;

/**
 * margin = gross_profit / revenue when revenue > 0.
 */
final class MarginRatio {

	/**
	 * @param MoneyAmount|null $gross_profit Gross profit.
	 * @param MoneyAmount|null $revenue      Revenue.
	 * @param int              $scale        Decimal places for ratio string.
	 * @return string|null
	 */
	public static function decimal( $gross_profit, $revenue, $scale = 8 ) {
		if ( ! $gross_profit instanceof MoneyAmount || ! $revenue instanceof MoneyAmount ) {
			return null;
		}
		if ( ! $revenue->is_positive() ) {
			return null;
		}
		Bcmath::require_extension();
		return bcdiv(
			$gross_profit->to_decimal_string(),
			$revenue->to_decimal_string(),
			max( 0, min( 8, (int) $scale ) )
		);
	}
}