<?php

declare(strict_types=1);

namespace App\Model\Faktura;

use Mpdf\QrCode\Output\Png;
use Mpdf\QrCode\QrCode;

/**
 * Český QR platební kód (SPD / SPAYD).
 */
final class SpaydQr
{
	/**
	 * Binární PNG QR kódu pro mPDF imageVars, nebo null pokud nelze sestavit.
	 */
	public static function png(
		string $ucetNeboIban,
		float $castka,
		string $vs = '',
		?\DateTimeInterface $splatnost = null,
		string $zprava = '',
		int $size = 240,
	): ?string {
		$spd = self::spd($ucetNeboIban, $castka, $vs, $splatnost, $zprava);
		if ($spd === null) {
			return null;
		}

		return (new Png())->output(new QrCode($spd), $size, [255, 255, 255], [0, 0, 0]);
	}

	public static function spd(
		string $ucetNeboIban,
		float $castka,
		string $vs = '',
		?\DateTimeInterface $splatnost = null,
		string $zprava = '',
	): ?string {
		$iban = self::toIban($ucetNeboIban);
		if ($iban === null) {
			return null;
		}

		$parts = [
			'SPD',
			'1.0',
			'ACC:' . $iban,
		];

		if ($castka > 0) {
			$parts[] = 'AM:' . number_format($castka, 2, '.', '');
		}
		$parts[] = 'CC:CZK';

		if ($splatnost !== null) {
			$parts[] = 'DT:' . $splatnost->format('Ymd');
		}

		$msg = self::spdText($zprava, 60);
		if ($msg !== '') {
			$parts[] = 'MSG:' . $msg;
		}

		$vsDigits = self::variableSymbol($vs);
		if ($vsDigits !== '') {
			$parts[] = 'X-VS:' . $vsDigits;
		}

		return implode('*', $parts) . '*';
	}

	/**
	 * IBAN z IBAN řetězce nebo českého formátu „účet/kód banky“.
	 */
	public static function toIban(string $value): ?string
	{
		$value = strtoupper(preg_replace('/\s+/', '', trim($value)) ?? '');
		if ($value === '') {
			return null;
		}

		if (preg_match('/^CZ\d{22}$/', $value)) {
			return self::isValidIban($value) ? $value : null;
		}

		if (!preg_match('/^(?:(\d{1,6})-)?(\d{2,10})\/(\d{4})$/', $value, $m)) {
			return null;
		}

		$prefix = str_pad($m[1] !== '' ? $m[1] : '0', 6, '0', STR_PAD_LEFT);
		$number = str_pad($m[2], 10, '0', STR_PAD_LEFT);
		$bank = $m[3];
		$bban = $bank . $prefix . $number;

		// CZ = 12 35 → kontrolní číslo z BBAN + "123500"
		$checkBase = $bban . '123500';
		$mod = self::mod97($checkBase);
		if ($mod === null) {
			return null;
		}
		$check = 98 - $mod;

		return 'CZ' . sprintf('%02d', $check) . $bban;
	}

	private static function variableSymbol(string $value): string
	{
		$digits = preg_replace('/\D+/', '', $value) ?? '';
		if ($digits === '') {
			return '';
		}
		if (strlen($digits) > 10) {
			$digits = substr($digits, -10);
		}

		return ltrim($digits, '0') !== '' ? $digits : '';
	}

	private static function spdText(string $value, int $maxLen): string
	{
		$value = self::bezDiakritiky(trim($value));
		$value = preg_replace('/[^A-Za-z0-9 \/?:().,+\-]/', '', $value) ?? '';
		$value = trim(preg_replace('/\s+/', ' ', $value) ?? '');

		return mb_substr($value, 0, $maxLen);
	}

	private static function bezDiakritiky(string $value): string
	{
		$ascii = @iconv('UTF-8', 'ASCII//TRANSLIT//IGNORE', $value);
		if ($ascii === false) {
			return $value;
		}

		return $ascii;
	}

	private static function isValidIban(string $iban): bool
	{
		$rearranged = substr($iban, 4) . substr($iban, 0, 4);
		$numeric = '';
		$length = strlen($rearranged);
		for ($i = 0; $i < $length; $i++) {
			$ch = $rearranged[$i];
			if ($ch >= 'A' && $ch <= 'Z') {
				$numeric .= (string) (ord($ch) - 55);
			} elseif ($ch >= '0' && $ch <= '9') {
				$numeric .= $ch;
			} else {
				return false;
			}
		}

		$mod = self::mod97($numeric);

		return $mod === 1;
	}

	private static function mod97(string $number): ?int
	{
		if ($number === '' || !ctype_digit($number)) {
			return null;
		}

		$remainder = 0;
		$length = strlen($number);
		for ($i = 0; $i < $length; $i++) {
			$remainder = ($remainder * 10 + (int) $number[$i]) % 97;
		}

		return $remainder;
	}
}