<?php

class BaseUAEN
{
    private const CHARACTERS = 'ABCEHKMOPTXY'; // Characters valid in both English and Ukrainian
    private const MIN_LENGTH = 4;
    private const MAX_LENGTH = 8;

    public function intToCode(int $number, int $length): string
    {
        if ($length < self::MIN_LENGTH || $length > self::MAX_LENGTH) {
            throw new InvalidArgumentException("Length must be between " . self::MIN_LENGTH . " and " . self::MAX_LENGTH);
        }

        $base = strlen(self::CHARACTERS);
        $code = '';

        do {
            $remainder = $number % $base;
            $code = self::CHARACTERS[$remainder] . $code;
            $number = intdiv($number, $base);
        } while ($number > 0);

        return str_pad($code, $length, self::CHARACTERS[0], STR_PAD_LEFT);
    }

    public function codeToInt(string $code): int
    {
        $base = strlen(self::CHARACTERS);
        $length = strlen($code);
        $number = 0;

        for ($i = 0; $i < $length; $i++) {
            $char = $code[$i];
            $charIndex = strpos(self::CHARACTERS, $char);
            if ($charIndex === false) {
                throw new InvalidArgumentException("Invalid character in code");
            }
            $number = $number * $base + $charIndex;
        }

        return $number;
    }

    public function generateRandomInt(int $length): int
    {
        if ($length < self::MIN_LENGTH || $length > self::MAX_LENGTH) {
            throw new InvalidArgumentException("Length must be between " . self::MIN_LENGTH . " and " . self::MAX_LENGTH);
        }

        $base = strlen(self::CHARACTERS);
        $maxNumber = bcpow($base, $length) - 1;

        return random_int(0, $maxNumber);
    }
}