<?php
declare(strict_types=1);

namespace app\mcp\service;

use app\common\service\ConfigService;
use GuzzleHttp\Client;

/**
 * 读取记录里的附件（图片、PDF）。只读取本系统存储里的文件：
 * 本地存储直接读 public 目录；云存储只允许配置的存储域名，防止被当成任意地址的下载代理。
 */
class FileFetcher
{
    /** 字段值（字符串、逗号分隔、JSON 数组、[{url:..}]）→ URL 列表 */
    public static function urls($value): array
    {
        if (is_string($value)) {
            $value = trim($value);
            if ($value !== '' && $value[0] === '[') {
                $decoded = json_decode($value, true);
                return is_array($decoded) ? self::urls($decoded) : [];
            }
            return array_values(array_filter(array_map('trim', explode(',', $value))));
        }
        if (!is_array($value)) {
            return [];
        }
        $urls = [];
        foreach ($value as $item) {
            $url = is_array($item) ? ($item['url'] ?? $item['uri'] ?? null) : $item;
            if (is_string($url) && trim($url) !== '') {
                $urls[] = trim($url);
            }
        }
        return $urls;
    }

    /** 返回 MCP 工具结果：图片为 image 内容，PDF/文本为嵌入资源 */
    public static function content(string $url, string $label): array
    {
        $bytes = self::read($url);
        $mime = (new \finfo(FILEINFO_MIME_TYPE))->buffer($bytes) ?: 'application/octet-stream';
        $size = round(strlen($bytes) / 1024) . ' KB';
        if (str_starts_with($mime, 'image/')) {
            return ['content' => [['type' => 'text', 'text' => $label . '（图片，' . $size . '）'],
                ['type' => 'image', 'data' => base64_encode($bytes), 'mimeType' => $mime]], 'isError' => false];
        }
        if ($mime === 'application/pdf' || str_starts_with($mime, 'text/')) {
            return ['content' => [['type' => 'text', 'text' => $label . '（' . $mime . '，' . $size . '）'],
                ['type' => 'resource', 'resource' => ['uri' => 'zyt-file://' . hash('sha256', $url), 'mimeType' => $mime, 'blob' => base64_encode($bytes)]]], 'isError' => false];
        }
        return ['content' => [['type' => 'text', 'text' => $label . '：该附件类型（' . $mime . '）不支持直接读取']], 'isError' => true];
    }

    private static function read(string $url): string
    {
        $max = McpConfig::maxFileBytes();
        $local = self::localPath($url);
        if ($local !== null) {
            if (filesize($local) > $max) {
                throw new McpException('附件超过 ' . round($max / 1048576, 1) . ' MB，无法读取', 'invalid');
            }
            return (string) file_get_contents($local);
        }
        $parts = parse_url($url);
        $host = strtolower((string) ($parts['host'] ?? ''));
        if (!in_array($parts['scheme'] ?? '', ['http', 'https'], true) || $host === '' || !in_array($host, self::allowedHosts(), true)) {
            throw new McpException('附件不在本系统的存储空间内，无法读取', 'denied');
        }
        $response = (new Client(['timeout' => 10, 'allow_redirects' => false, 'http_errors' => false]))->get($url, ['stream' => true]);
        if ($response->getStatusCode() !== 200) {
            throw new McpException('附件读取失败（HTTP ' . $response->getStatusCode() . '）', 'invalid');
        }
        $body = $response->getBody();
        $bytes = '';
        while (!$body->eof()) {
            $bytes .= $body->read(65536);
            if (strlen($bytes) > $max) {
                throw new McpException('附件超过 ' . round($max / 1048576, 1) . ' MB，无法读取', 'invalid');
            }
        }
        return $bytes;
    }

    /** 本地存储：相对路径或本站域名下的 uploads 路径 → public 目录里的真实文件 */
    private static function localPath(string $url): ?string
    {
        $path = $url;
        if (preg_match('#^https?://#i', $url)) {
            $host = strtolower((string) parse_url($url, PHP_URL_HOST));
            if ($host !== strtolower((string) request()->host(true))) {
                return null;
            }
            $path = (string) parse_url($url, PHP_URL_PATH);
        }
        $path = ltrim(str_replace('\\', '/', $path), '/');
        if ($path === '' || str_contains($path, '..') || !preg_match('#^(uploads|storage)/#', $path)) {
            return null;
        }
        $public = realpath(public_path());
        $full = realpath(public_path() . $path);
        return ($full && $public && str_starts_with($full, $public) && is_file($full)) ? $full : null;
    }

    private static function allowedHosts(): array
    {
        $hosts = [strtolower((string) request()->host(true))];
        $default = ConfigService::get('storage', 'default', 'local');
        if ($default !== 'local') {
            $storage = ConfigService::get('storage', $default);
            $domain = is_array($storage) ? (string) ($storage['domain'] ?? '') : '';
            $host = parse_url(str_contains($domain, '://') ? $domain : 'https://' . $domain, PHP_URL_HOST);
            if ($host) {
                $hosts[] = strtolower($host);
            }
        }
        return array_values(array_unique(array_filter($hosts)));
    }
}