WordPressの投稿編集画面に内部リンク候補を自動表示する方法

// リンク候補（投稿編集画面に表示）
add_action('edit_form_after_title', function($post){
    if($post->post_type !== 'post') return;

    echo '<div id="related-link-candidates" style="margin:10px 0;">';
    echo '<button type="button" id="show-candidates" class="button">リンク候補を表示</button>';
    echo '<div id="candidate-list" style="margin-top:10px;"></div>';
    echo '</div>';

    $data = [
        'post_id' => $post->ID,
        'title'   => trim($post->post_title),
        'tags'    => wp_get_post_tags($post->ID, ['fields'=>'ids']),
        'cats'    => wp_get_post_categories($post->ID),
        'ajax_url'=> admin_url('admin-ajax.php')
    ];
    echo '<script>var relatedData='.json_encode($data).';</script>';
});

// Ajax処理：候補取得（上位5件固定）
add_action('wp_ajax_get_related_candidates', function(){
    $post_id = intval($_POST['post_id']);
    $title   = trim($_POST['title']);
    $tags    = $_POST['tags'] ?? [];
    $cats    = $_POST['cats'] ?? [];

    $posts = get_posts([
        'post_type'=>'post',
        'post_status'=>['publish','draft','future'],
        'post__not_in'=>[$post_id],
        'posts_per_page'=>-1,
    ]);

    $candidates = [];
    foreach($posts as $p){
        $score = 0;
        if($title && stripos($p->post_title, $title)!==false) $score+=3;
        if($tags) $score+=count(array_intersect($tags, wp_get_post_tags($p->ID,['fields'=>'ids'])))*2;
        if($cats) $score+=count(array_intersect($cats, wp_get_post_categories($p->ID)));
        if($score>0) $candidates[$p->ID]=$score;
    }

    if($candidates){
        arsort($candidates);
        $candidates=array_slice($candidates,0,5,true);

        foreach(array_keys($candidates) as $pid){
            $p = get_post($pid);
            $status = $p->post_status;
            $title_text = esc_html($p->post_title);

            // 公開済みならフロント、下書き/予約なら編集画面
            if($status === 'publish'){
                $front = get_permalink($p->ID);
            } else {
                $front = get_edit_post_link($p->ID,'');
            }

            // ステータス表示
            $label = '';
            if($status === 'draft') $label = '（下書き）';
            if($status === 'future') $label = '（予約投稿）';

            echo '<div style="margin-bottom:6px;">';
            echo '・<a href="'.esc_url($front).'" target="_blank">'.$title_text.'</a> '.$label.' - <a href="'.esc_url(get_edit_post_link($p->ID,'')).'" target="_blank">編集画面</a>';
            echo '</div>';
        }
    } else {
        echo '<p>リンク候補の記事はありません。</p>';
    }

    wp_die();
});

// 管理画面用最小JS
add_action('admin_footer', function(){
?>
<script>
jQuery(function($){
    $('#show-candidates').on('click', function(){
        $.post(relatedData.ajax_url,{
            action:'get_related_candidates',
            post_id:relatedData.post_id,
            title:relatedData.title,
            tags:relatedData.tags,
            cats:relatedData.cats
        }, function(response){
            $('#candidate-list').html(response);
        });
    });
});
</script>
<?php
});