<?php
// +----------------------------------------------------------------------
// | YwxApp [ WE CAN DO IT JUST THINK ]
// +----------------------------------------------------------------------
// | Copyright (c) 2026-2036 http://ywxapp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Author: ywxapp<admin@ywxapp.cn>
// +----------------------------------------------------------------------
declare (strict_types = 1);

namespace addon\wxchat\service;

/**
 * 内容安全服务：敏感词过滤 + 风险评分
 * 敏感词存放于 wxapp_wxchat_banwords，缺失时使用内置兜底词库
 */
class SafetyService
{
    private static $instance = null;

    /** @var array|null [['word'=>, 'level'=>, 'replace'=>], ...] */
    private $words = null;

    
    public static function instance(): self
    {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * 加载敏感词（带缓存 + 兜底）
     */
    private function loadWords(): array
    {
        if ($this->words !== null) {
            return $this->words;
        }
        $this->words = [];
        try {
            $rows = \think\facade\Db::name('wxchat_banwords')
                ->where('status', 1)
                ->order('level', 'desc')
                ->select();
            foreach ($rows as $r) {
                $this->words[] = [
                    'word'    => $r['word'],
                    'level'   => (int)$r['level'],
                    'replace' => $r['replace_char'] ?: '**',
                ];
            }
        } catch (\Throwable $e) {
            // 表可能未创建，忽略，使用兜底词库
        }
        // 兜底词库
        foreach (['fuck', 'shit', '赌博', '色情', '诈骗', '代开发票'] as $w) {
            $this->words[] = ['word' => $w, 'level' => 1, 'replace' => '**'];
        }
        return $this->words;
    }

    /**
     * 过滤敏感词（level=1 替换为 **；level=2 命中则整段清空并返回命中标记）
     * @return string 过滤后的文本
     */
    public function filter(string $text): string
    {
        if ($text === '') {
            return $text;
        }
        foreach ($this->loadWords() as $w) {
            if ($w['level'] >= 2) {
                if (mb_stripos($text, $w['word']) !== false) {
                    // 高危词：整段清空（拦截）
                    return '';
                }
            } else {
                $text = $this->mbStrReplace($w['word'], $w['replace'], $text);
            }
        }
        return $text;
    }

    /**
     * 内容安全检测：返回是否命中高危词
     */
    public function check(string $text): array
    {
        $hit = [];
        foreach ($this->loadWords() as $w) {
            if (mb_stripos($text, $w['word']) !== false) {
                $hit[] = $w['word'];
                if ($w['level'] >= 2) {
                    return ['blocked' => true, 'hit' => $hit];
                }
            }
        }
        return ['blocked' => false, 'hit' => $hit];
    }

    /**
     * 多字节安全的字符串替换
     */
    private function mbStrReplace($search, $replace, $subject): string
    {
        if ($search === '') {
            return $subject;
        }
        $parts = mb_split(preg_quote($search), $subject);
        if ($parts === false) {
            return str_ireplace($search, $replace, $subject);
        }
        return implode($replace, $parts);
    }
}