<?php

namespace App\Services\Chain;

use Elliptic\EC;
use kornrunner\Keccak;
use RuntimeException;

final class EthSigner
{
    /**
     * Sign a legacy EIP-155 transaction.
     *
     * @param  array{nonce: string, gasPrice: string, gas: string, to: string, value: string, data: string}  $tx
     * @return string 0x-prefixed raw tx hex
     */
    public static function signLegacy(string $privateKeyHex, array $tx, int $chainId): string
    {
        $privateKeyHex = strtolower($privateKeyHex);
        if (str_starts_with($privateKeyHex, '0x')) {
            $privateKeyHex = substr($privateKeyHex, 2);
        }
        $to = strtolower($tx['to']);
        if (str_starts_with($to, '0x')) {
            $to = substr($to, 2);
        }
        $data = strtolower($tx['data'] ?? '');
        if (str_starts_with($data, '0x')) {
            $data = substr($data, 2);
        }

        $fields = [
            EthRlp::intToBin($tx['nonce']),
            EthRlp::intToBin($tx['gasPrice']),
            EthRlp::intToBin($tx['gas']),
            hex2bin($to) ?: '',
            EthRlp::intToBin($tx['value']),
            $data === '' ? '' : (hex2bin($data) ?: ''),
            EthRlp::intToBin((string) $chainId),
            '',
            '',
        ];

        $unsigned = EthRlp::encodeList($fields);
        $hash = Keccak::hash($unsigned, 256);

        $ec = new EC('secp256k1');
        $key = $ec->keyFromPrivate($privateKeyHex);
        $sig = $key->sign($hash, ['canonical' => true]);

        // Encode r/s as canonical big-endian integers (minimal bytes, no leading
        // zero bytes). Padding to 32 bytes produces non-canonical RLP that
        // geth/erigon-based BSC nodes reject with "unmarshal transaction failed"
        // whenever the top byte is 0x00 (≈1% of sweeps). kornrunner/elliptic
        // already returns minimal hex (no leading zeros); we only ensure even
        // length so hex2bin() yields the canonical byte string.
        $r = $sig->r->toString(16);
        $s = $sig->s->toString(16);
        if (strlen($r) % 2 !== 0) {
            $r = '0'.$r;
        }
        if (strlen($s) % 2 !== 0) {
            $s = '0'.$s;
        }
        $recovery = (int) ($sig->recoveryParam ?? 0);
        $v = (string) ($recovery + 35 + $chainId * 2);

        $signed = EthRlp::encodeList([
            EthRlp::intToBin($tx['nonce']),
            EthRlp::intToBin($tx['gasPrice']),
            EthRlp::intToBin($tx['gas']),
            hex2bin($to) ?: '',
            EthRlp::intToBin($tx['value']),
            $data === '' ? '' : (hex2bin($data) ?: ''),
            EthRlp::intToBin($v),
            hex2bin($r) ?: '',
            hex2bin($s) ?: '',
        ]);

        return '0x'.bin2hex($signed);
    }

    public static function publicAddress(string $privateKeyHex): string
    {
        $privateKeyHex = strtolower($privateKeyHex);
        if (str_starts_with($privateKeyHex, '0x')) {
            $privateKeyHex = substr($privateKeyHex, 2);
        }
        $ec = new EC('secp256k1');
        $pub = $ec->keyFromPrivate($privateKeyHex)->getPublic(false, 'hex');

        return EthAddress::fromUncompressedPublicKey($pub);
    }
}