<?php
declare(strict_types=1);
namespace UploadLogger\Core\Services;

use UploadLogger\Core\Config;

final class SnifferService
{
    private Config $config;

    public function __construct(?Config $config = null)
    {
        $this->config = $config ?? new Config(['modules' => []]);
    }

    public function detectRealMime(string $tmpPath): string
    {
        $real = 'unknown';

        if (is_uploaded_file($tmpPath) && function_exists('finfo_open')) {
            $f = @finfo_open(FILEINFO_MIME_TYPE);
            if ($f) {
                $m = @finfo_file($f, $tmpPath);
                if (is_string($m) && $m !== '') {
                    $real = $m;
                }
                @finfo_close($f);
            }
        }

        return $real;
    }

    public function payloadContainsPhpMarkers(string $text, string $contentType = ''): bool
    {
        $isXmlLike = false;
        if ($contentType !== '') {
            $isXmlLike = (bool)preg_match('/xml|svg/i', $contentType);
        }

        if (preg_match('/<\?php|<\?=|<\?(?!xml)/i', $text)) {
            return true;
        }

        if (preg_match('/base64_decode\s*\(|gzinflate\s*\(|shell_exec\s*\(|passthru\s*\(|system\s*\(|proc_open\s*\(|popen\s*\(|exec\s*\(/i', $text)) {
            return true;
        }

        if (!$isXmlLike && preg_match('/\beval\s*\(/i', $text)) {
            return true;
        }

        return false;
    }

    public function sniffFileForPhpPayload(string $tmpPath): bool
    {
        $maxBytes = (int)$this->config->get('limits.sniff_max_bytes', 8192);
        $maxFilesize = (int)$this->config->get('limits.sniff_max_filesize', 2 * 1024 * 1024);

        if (!is_uploaded_file($tmpPath)) return false;

        $sz = @filesize($tmpPath);
        if ($sz === false) return false;
        if ($sz <= 0) return false;
        if ($sz > $maxFilesize) return false;

        $bytes = min($maxBytes, $sz);
        $maxlen = $bytes > 0 ? $bytes : null;
        $head = @file_get_contents($tmpPath, false, null, 0, $maxlen);
        if ($head === false) return false;

        $realMime = $this->detectRealMime($tmpPath);
        if ($this->payloadContainsPhpMarkers($head, $realMime)) {
            return true;
        }

        return false;
    }

    /**
     * @param string $head
     * @param int $maxDecoded
     * @return array{found:bool,decoded_head:?string,reason:?string}
     */
    public function detectJsonBase64Head(string $head, int $maxDecoded = 1024): array
    {
        if (preg_match('/"(?:file|data|payload|content)"\s*:\s*"(?:data:[^,]+,)?([A-Za-z0-9+\/=]{200,})"/i', $head, $m)) {
            $b64 = $m[1];
            $chunk = substr($b64, 0, 1024);
            $pad = 4 - (strlen($chunk) % 4);
            if ($pad < 4) $chunk .= str_repeat('=', $pad);
            $decoded = @base64_decode($chunk, true);
            if ($decoded === false) return ['found' => true, 'decoded_head' => null, 'reason' => 'base64_decode_failed'];
            $decoded_head = substr($decoded, 0, $maxDecoded);
            return ['found' => true, 'decoded_head' => $decoded_head, 'reason' => null];
        }

        if (preg_match('/^\s*([A-Za-z0-9+\/=]{400,})/s', $head, $m2)) {
            $b64 = $m2[1];
            $chunk = substr($b64, 0, 1024);
            $pad = 4 - (strlen($chunk) % 4);
            if ($pad < 4) $chunk .= str_repeat('=', $pad);
            $decoded = @base64_decode($chunk, true);
            if ($decoded === false) return ['found' => true, 'decoded_head' => null, 'reason' => 'base64_decode_failed'];
            return ['found' => true, 'decoded_head' => substr($decoded, 0, $maxDecoded), 'reason' => null];
        }

        return ['found' => false, 'decoded_head' => null, 'reason' => null];
    }

    public function base64IsAllowlisted(string $uri, string $ctype): bool
    {
        $uris = (array)$this->config->get('allowlists.base64_uris', []);
        $ctypes = (array)$this->config->get('allowlists.ctypes', []);

        if (!empty($uris)) {
            foreach ($uris as $p) {
                if (strlen($p) > 1 && $p[0] === '#' && substr($p, -1) === '#') {
                    if (@preg_match($p, $uri)) return true;
                } else {
                    if (strpos($uri, $p) !== false) return true;
                }
            }
        }

        if (!empty($ctypes) && $ctype !== '') {
            $base = explode(';', $ctype, 2)[0];
            foreach ($ctypes as $ct) {
                if (strtolower(trim($ct)) === strtolower(trim($base))) return true;
            }
        }

        return false;
    }

    public function isFakeImage(string $name, string $realMime): bool
    {
        if (preg_match('/\.(png|jpe?g|gif|webp|bmp|ico|svg)$/i', $name)) {
            if (!preg_match('/^image\//', $realMime)) {
                return true;
            }
        }
        return false;
    }

    public function isArchive(string $name, string $realMime): bool
    {
        if (preg_match('/\.(zip|rar|7z|tar|gz|tgz)$/i', $name)) return true;
        if (preg_match('/(zip|x-7z-compressed|x-rar|x-tar|gzip)/i', $realMime)) return true;
        return false;
    }
}