Arabic.php

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<?php

namespace PhpOffice\PhpSpreadsheet\Calculation\MathTrig;

use PhpOffice\PhpSpreadsheet\Calculation\Exception;
use PhpOffice\PhpSpreadsheet\Calculation\Functions;

class Arabic
{
    private const ROMAN_LOOKUP = [
        'M' => 1000,
        'D' => 500,
        'C' => 100,
        'L' => 50,
        'X' => 10,
        'V' => 5,
        'I' => 1,
    ];

    private static function calculateArabic(array $roman, &$sum = 0, $subtract = 0)
    {
        $numeral = array_shift($roman);
        if (!isset(self::ROMAN_LOOKUP[$numeral])) {
            throw new Exception('Invalid character detected');
        }

        $arabic = self::ROMAN_LOOKUP[$numeral];
        if (count($roman) > 0 && isset(self::ROMAN_LOOKUP[$roman[0]]) && $arabic < self::ROMAN_LOOKUP[$roman[0]]) {
            $subtract += $arabic;
        } else {
            $sum += ($arabic - $subtract);
            $subtract = 0;
        }

        if (count($roman) > 0) {
            self::calculateArabic($roman, $sum, $subtract);
        }

        return $sum;
    }

    private static function mollifyScrutinizer($value): array
    {
        return is_array($value) ? $value : [];
    }

    private static function strSplit(string $roman): array
    {
        $rslt = str_split($roman);

        return self::mollifyScrutinizer($rslt);
    }

    public static function evaluate($roman)
    {
        // An empty string should return 0
        $roman = substr(trim(strtoupper((string) Functions::flattenSingleValue($roman))), 0, 255);
        if ($roman === '') {
            return 0;
        }

        // Convert the roman numeral to an arabic number
        $negativeNumber = $roman[0] === '-';
        if ($negativeNumber) {
            $roman = substr($roman, 1);
        }

        try {
            $arabic = self::calculateArabic(self::strSplit($roman));
        } catch (Exception $e) {
            return Functions::VALUE(); // Invalid character detected
        }

        if ($negativeNumber) {
            $arabic *= -1; // The number should be negative
        }

        return $arabic;
    }
}