import type { Metadata } from 'next';
import { notFound } from 'next/navigation';
import { articleUrl, getPublishedArticle } from '@/lib/articles';

const siteUrl = (process.env.NEXT_PUBLIC_SITE_URL || process.env.PUBLIC_SITE_URL || 'https://www.aiameiba.com').replace(/\/$/, '');

const formatDate = (value: string) => {
  const date = new Date(value);
  return Number.isNaN(date.getTime()) ? value : date.toLocaleDateString('zh-CN');
};

const paragraphs = (body: string) => body.split(/\n\s*\n/).map(item => item.trim()).filter(Boolean);

export async function generateMetadata({ params }: { params: { identifier: string } }): Promise<Metadata> {
  const article = await getPublishedArticle(params.identifier);
  if (!article) return { title: '文章不存在' };
  const localUrl = `${siteUrl}${articleUrl(article)}`;
  const canonical = article.canonical_url || localUrl;
  return {
    title: article.title,
    description: article.summary,
    alternates: { canonical },
    openGraph: {
      type: 'article',
      title: article.title,
      description: article.summary,
      url: canonical,
      images: article.cover_image_url ? [{ url: article.cover_image_url }] : undefined,
      publishedTime: article.published_at,
      modifiedTime: article.updated_at,
      authors: [article.author_name],
    },
  };
}

export default async function KnowledgeArticlePage({ params }: { params: { identifier: string } }) {
  const article = await getPublishedArticle(params.identifier);
  if (!article) notFound();
  const localUrl = `${siteUrl}${articleUrl(article)}`;
  const canonical = article.canonical_url || localUrl;
  const jsonLd = {
    '@context': 'https://schema.org',
    '@type': 'Article',
    headline: article.title,
    description: article.summary,
    url: canonical,
    mainEntityOfPage: localUrl,
    author: { '@type': 'Organization', name: article.author_name },
    publisher: { '@type': 'Organization', name: '阿美巴AI', url: siteUrl },
    datePublished: article.published_at,
    dateModified: article.updated_at,
    image: article.cover_image_url || undefined,
    articleSection: article.category,
  };

  return (
    <div className="container-narrow">
      <nav className="breadcrumb" aria-label="面包屑导航">
        <ol><li><a href="/">首页</a></li><li><a href="/knowledge">知识中心</a></li><li><span aria-current="page">{article.title}</span></li></ol>
      </nav>
      <article className="knowledge-article">
        <script type="application/ld+json" dangerouslySetInnerHTML={{ __html: JSON.stringify(jsonLd) }} />
        <header className="knowledge-article-header">
          <p className="article-meta"><span>{article.category}</span><span>{article.author_name}</span><time dateTime={article.published_at}>发布于 {formatDate(article.published_at)}</time><time dateTime={article.updated_at}>更新于 {formatDate(article.updated_at)}</time></p>
          <h1>{article.title}</h1>
          {article.summary && <p className="knowledge-article-summary">{article.summary}</p>}
        </header>
        <div className="knowledge-article-body">
          {paragraphs(article.body_plain).map((paragraph, index) => <p key={index}>{paragraph}</p>)}
        </div>
        <footer className="knowledge-article-footer"><a href="/knowledge">← 返回知识中心</a></footer>
      </article>
    </div>
  );
}