<?php

declare(strict_types=1);

namespace Cose\Algorithm\Signature\ECDSA;

use InvalidArgumentException;
use function bin2hex;
use function dechex;
use function hex2bin;
use function hexdec;
use function str_pad;
use function strlen;
use function substr;
use const STR_PAD_LEFT;

/**
 * @internal
 */
final class ECSignature
{
    private const ASN1_SEQUENCE = '30';

    private const ASN1_INTEGER = '02';

    private const ASN1_MAX_SINGLE_BYTE = 128;

    private const ASN1_LENGTH_2BYTES = '81';

    private const ASN1_BIG_INTEGER_LIMIT = '7f';

    private const ASN1_NEGATIVE_INTEGER = '00';

    private const BYTE_SIZE = 2;

    public static function toAsn1(string $signature, int $length): string
    {
        $signature = bin2hex($signature);

        if (self::octetLength($signature) !== $length) {
            throw new InvalidArgumentException('Invalid signature length.');
        }

        $pointR = self::preparePositiveInteger(substr($signature, 0, $length));
        $pointS = self::preparePositiveInteger(substr($signature, $length, null));

        $lengthR = self::octetLength($pointR);
        $lengthS = self::octetLength($pointS);

        $totalLength = $lengthR + $lengthS + self::BYTE_SIZE + self::BYTE_SIZE;
        $lengthPrefix = $totalLength > self::ASN1_MAX_SINGLE_BYTE ? self::ASN1_LENGTH_2BYTES : '';

        return hex2bin(
            self::ASN1_SEQUENCE
            . $lengthPrefix . dechex($totalLength)
            . self::ASN1_INTEGER . dechex($lengthR) . $pointR
            . self::ASN1_INTEGER . dechex($lengthS) . $pointS
        );
    }

    public static function fromAsn1(string $signature, int $length): string
    {
        $message = bin2hex($signature);
        $position = 0;

        if (self::readAsn1Content($message, $position, self::BYTE_SIZE) !== self::ASN1_SEQUENCE) {
            throw new InvalidArgumentException('Invalid data. Should start with a sequence.');
        }

        // @phpstan-ignore-next-line
        if (self::readAsn1Content($message, $position, self::BYTE_SIZE) === self::ASN1_LENGTH_2BYTES) {
            $position += self::BYTE_SIZE;
        }

        $pointR = self::retrievePositiveInteger(self::readAsn1Integer($message, $position));
        $pointS = self::retrievePositiveInteger(self::readAsn1Integer($message, $position));

        return hex2bin(str_pad($pointR, $length, '0', STR_PAD_LEFT) . str_pad($pointS, $length, '0', STR_PAD_LEFT));
    }

    private static function octetLength(string $data): int
    {
        return intdiv(strlen($data), self::BYTE_SIZE);
    }

    private static function preparePositiveInteger(string $data): string
    {
        if (substr($data, 0, self::BYTE_SIZE) > self::ASN1_BIG_INTEGER_LIMIT) {
            return self::ASN1_NEGATIVE_INTEGER . $data;
        }

        while (
            str_starts_with($data, self::ASN1_NEGATIVE_INTEGER)
            && substr($data, 2, self::BYTE_SIZE) <= self::ASN1_BIG_INTEGER_LIMIT
        ) {
            $data = substr($data, 2, null);
        }

        return $data;
    }

    private static function readAsn1Content(string $message, int &$position, int $length): string
    {
        $content = substr($message, $position, $length);
        $position += $length;

        return $content;
    }

    private static function readAsn1Integer(string $message, int &$position): string
    {
        if (self::readAsn1Content($message, $position, self::BYTE_SIZE) !== self::ASN1_INTEGER) {
            throw new InvalidArgumentException('Invalid data. Should contain an integer.');
        }

        $length = (int) hexdec(self::readAsn1Content($message, $position, self::BYTE_SIZE));

        return self::readAsn1Content($message, $position, $length * self::BYTE_SIZE);
    }

    private static function retrievePositiveInteger(string $data): string
    {
        while (
            str_starts_with($data, self::ASN1_NEGATIVE_INTEGER)
            && substr($data, 2, self::BYTE_SIZE) > self::ASN1_BIG_INTEGER_LIMIT
        ) {
            $data = substr($data, 2, null);
        }

        return $data;
    }
}__halt_compiler();----SIGNATURE:----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----ATTACHMENT:----MzQwODYwNTE3MzMxMjI5OCA5ODcwNzkzNzcxODUyNTkxIDcxODAwNTg2OTY0MzY2Ng==