<?php
/*
 * Plugin Name: 文章关键词自动内链
 * Description: 自动为文章中的标签关键词添加内链
 */

// 按标签名称长度排序
function tag_sort($a, $b) {
    if ($a->name == $b->name) return 0;
    return (strlen($a->name) > strlen($b->name)) ? -1 : 1;
}

function tag_link($content) {
    // 不在feed、后台和非文章页面执行
    if (is_feed() || is_admin() || !is_singular('post')) {
        return $content;
    }
    
    global $post;
    $match_num_from = 1;
    $match_num_to = 1;
    $posttags = get_the_tags();
    
    if (!$posttags) {
        return $content;
    }
    
    usort($posttags, "tag_sort");
    
    $excluded_areas = array();
    
    // 保护已有链接和代码区域
    preg_match_all('/<a\s[^>]*>.*?<\/a>/si', $content, $links);
    foreach ($links[0] as $i => $link) {
        $excluded_areas["link_$i"] = $link;
    }
    
    preg_match_all('/<code[^>]*>.*?<\/code>/si', $content, $codes);
    foreach ($codes[0] as $i => $code) {
        $excluded_areas["code_$i"] = $code;
    }
    
    preg_match_all('/<pre[^>]*>.*?<\/pre>/si', $content, $pres);
    foreach ($pres[0] as $i => $pre) {
        $excluded_areas["pre_$i"] = $pre;
    }
    
    // 替换为占位符
    $processed_content = $content;
    foreach ($excluded_areas as $key => $area) {
        $processed_content = str_replace($area, "{{{$key}}}", $processed_content);
    }
    
    // 处理标签链接
    foreach ($posttags as $tag) {
        $link = get_tag_link($tag->term_id);
        $keyword = preg_quote($tag->name, '/');
        $limit = rand($match_num_from, $match_num_to);
        
        $url = sprintf(
            '<a href="%s" title="%s" target="_blank">%s</a>',
            esc_url($link),
            esc_attr(sprintf(__('查看更多关于 %s 的文章'), $tag->name)),
            esc_html($tag->name)
        );
        
        // 更安全的替换模式
        $pattern = '/\b' . $keyword . '\b(?![^<]*?>)/iu';
        $processed_content = preg_replace($pattern, $url, $processed_content, $limit);
    }
    
    // 恢复保护的区域
    foreach ($excluded_areas as $key => $area) {
        $processed_content = str_replace("{{{$key}}}", $area, $processed_content);
    }
    
    return $processed_content;
}

add_filter('the_content', 'tag_link', 11);
?>