import type { Metadata } from "next";
import Link from "next/link";
import { cookies } from "next/headers";
import ReactMarkdown from "react-markdown";
import {
  Clock,
  Heart,
  MessageCircle,
  Flame,
  Layers,
  User,
  PenLine,
  ArrowRight,
  ChevronRight,
} from "lucide-react";
import {
  fetchPostDetail,
  fetchComments,
  fetchPosts,
  fetchUserProfile,
  type UserProfile,
  type PostListItem,
  type Board,
} from "@/lib/api";
import { authCookieHeader } from "@/lib/cookies";
import CommentSection from "@/components/CommentSection";
import PostActions from "@/components/PostActions";
import LikeButton from "@/components/LikeButton";
import ReadingProgress from "@/components/ReadingProgress";
import PostToc, { type TocItem } from "@/components/PostToc";
import Avatar from "@/components/Avatar";
import { IconComment, IconEye } from "@/components/Icons";

interface PageProps {
  params: Promise<{ id: string }>;
}

export async function generateMetadata({ params }: PageProps): Promise<Metadata> {
  const { id } = await params;
  try {
    const { post } = await fetchPostDetail(id);
    return {
      title: post.title,
      description: post.content.slice(0, 160),
      openGraph: {
        title: post.title,
        description: post.content.slice(0, 160),
        type: "article",
      },
    };
  } catch {
    return { title: "帖子不存在" };
  }
}

/**
 * 从 Markdown 提取二三级标题生成目录项，id 按出现顺序编号；
 * 代码围栏内的 # 不计入
 */
function extractToc(content: string): TocItem[] {
  const items: TocItem[] = [];
  let inCode = false;
  for (const raw of content.split(/\r?\n/)) {
    const line = raw.trim();
    if (line.startsWith("```")) {
      inCode = !inCode;
      continue;
    }
    if (inCode) continue;
    const m = /^(#{2,3})\s+(.+?)\s*#*\s*$/.exec(line);
    if (m) items.push({ level: m[1].length as 2 | 3, text: m[2], id: `h-${items.length}` });
  }
  return items;
}

function formatYearMonth(dateStr: string) {
  const d = new Date(dateStr);
  return `${d.getFullYear()}.${String(d.getMonth() + 1).padStart(2, "0")}`;
}

function formatYMD(dateStr: string) {
  const d = new Date(dateStr);
  return `${d.getFullYear()}.${String(d.getMonth() + 1).padStart(2, "0")}.${String(
    d.getDate()
  ).padStart(2, "0")}`;
}

function formatDateTime(dateStr: string) {
  return new Date(dateStr).toLocaleString("zh-CN", {
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
    hour: "2-digit",
    minute: "2-digit",
  });
}

/* ============================================================
   左栏模块（仅 xl 三栏时展示）
   ============================================================ */

function BoardCard({ board }: { board: Board }) {
  const colorIdx = Math.max(0, board.color_index ?? 0) % 8;
  return (
    <section className="j13-module shrink-0" aria-labelledby="board-card-title">
      <p className="j13-module-title mb-3" id="board-card-title">
        <Layers size={15} style={{ color: "var(--accent)" }} /> 所属板块
      </p>
      <Link href={`/board/${board.id}`} className="flex items-center gap-3 group">
        <span
          className={`av-${colorIdx} w-11 h-11 rounded-xl flex items-center justify-center text-lg font-extrabold shrink-0`}
        >
          {board.name.slice(0, 1)}
        </span>
        <span
          className="font-bold text-[14.5px] truncate group-hover:text-[var(--accent)] transition-colors"
          style={{ color: "var(--ink)" }}
        >
          {board.name}
        </span>
      </Link>
      {board.description && (
        <p className="mt-2.5 text-[12.5px] leading-relaxed" style={{ color: "var(--ink-3)" }}>
          {board.description}
        </p>
      )}
      <Link
        href={`/board/${board.id}`}
        className="btn btn-line btn-sm w-full justify-center mt-3.5"
      >
        进入板块 <ArrowRight size={13} />
      </Link>
    </section>
  );
}

function AuthorRailCard({ profile }: { profile: UserProfile }) {
  const u = profile.user;
  return (
    <section className="j13-module shrink-0" aria-labelledby="author-card-title">
      <p className="j13-module-title mb-3" id="author-card-title">
        <User size={15} style={{ color: "var(--accent)" }} /> 作者
      </p>
      <div className="flex items-center gap-3">
        <Link href={`/u/${u.id}`} className="shrink-0" aria-label={u.nickname}>
          <Avatar name={u.nickname || u.username} size={48} />
        </Link>
        <div className="min-w-0">
          <Link
            href={`/u/${u.id}`}
            className="block font-bold text-[14.5px] truncate hover:text-[var(--accent)] transition-colors"
            style={{ color: "var(--ink)" }}
          >
            {u.nickname}
          </Link>
          {u.role === "admin" && (
            <span
              className="chip mt-1.5"
              style={{ background: "var(--accent-soft)", color: "var(--accent)" }}
            >
              管理员
            </span>
          )}
        </div>
      </div>
      <p className="meta mt-3">{formatYearMonth(u.created_at)} 加入</p>
      <div className="grid grid-cols-2 gap-2 mt-2.5">
        <div className="j13-stat">
          <span className="j13-stat-num">{profile.stats.post_count}</span>
          <span className="j13-stat-lab">发帖</span>
        </div>
        <div className="j13-stat">
          <span className="j13-stat-num">{profile.stats.comment_count}</span>
          <span className="j13-stat-lab">评论</span>
        </div>
      </div>
      <Link href={`/u/${u.id}`} className="btn btn-line btn-sm w-full justify-center mt-3.5">
        访问主页
      </Link>
    </section>
  );
}

function AuthorPosts({ posts }: { posts: PostListItem[] }) {
  if (posts.length === 0) return null;
  return (
    <section className="j13-module flex min-h-0 flex-col" aria-labelledby="author-posts-title">
      <p className="j13-module-title mb-1 shrink-0" id="author-posts-title">
        <PenLine size={15} style={{ color: "var(--accent)" }} /> TA 的其他帖子
      </p>
      <ul className="j13-rail-scroll">
        {posts.map((p) => (
          <li key={p.id}>
            <Link
              href={`/post/${p.id}`}
              title={p.title}
              className="block rounded-[10px] px-2 py-2 transition-colors hover:bg-[var(--panel-2)]"
            >
              <span
                className="block text-[13px] font-semibold leading-snug line-clamp-2"
                style={{ color: "var(--ink)" }}
              >
                {p.title}
              </span>
              <span className="meta mt-1 block text-[11px]">{formatYMD(p.created_at)}</span>
            </Link>
          </li>
        ))}
      </ul>
    </section>
  );
}

/* ============================================================
   右栏模块（lg 起展示；移动端下沉到评论之后）
   ============================================================ */

function RelatedPosts({
  posts,
  boardId,
  uid = "related",
}: {
  posts: PostListItem[];
  boardId: number;
  // 右栏与移动端内联实例同时存在，id 必须区分以免 aria-labelledby 指向隐藏副本
  uid?: string;
}) {
  if (posts.length === 0) return null;
  const titleId = `${uid}-title`;
  return (
    <section className="j13-module shrink-0" aria-labelledby={titleId}>
      <p className="j13-module-title mb-1.5" id={titleId}>
        <Flame size={15} style={{ color: "var(--clay)" }} /> 同板块热议
      </p>
      <ol>
        {posts.map((p, i) => (
          <li key={p.id}>
            <Link href={`/post/${p.id}`} className="j13-rank" title={p.title}>
              <span className="j13-rank-no">{i + 1}</span>
              <span className="min-w-0 flex-1">
                <span
                  className="block text-[13px] font-semibold leading-snug line-clamp-2"
                  style={{ color: "var(--ink)" }}
                >
                  {p.title}
                </span>
                <span className="mt-1 flex items-center gap-2.5 meta text-[11.5px]">
                  <span className="inline-flex items-center gap-1">
                    <MessageCircle size={11.5} /> {p.comment_count}
                  </span>
                  <span className="inline-flex items-center gap-1">
                    <Heart size={11.5} /> {p.like_count}
                  </span>
                </span>
              </span>
            </Link>
          </li>
        ))}
      </ol>
      <Link
        href={`/board/${boardId}`}
        className="j13-raillink justify-center mt-1.5 text-[12.5px] font-semibold"
        style={{ color: "var(--accent)" }}
      >
        查看全部 <ChevronRight size={13} />
      </Link>
    </section>
  );
}

/* 移动端 / 窄屏作者卡（xl 以下内联在正文与评论之间，替代左栏作者模块） */
function AuthorCardStacked({ profile }: { profile: UserProfile }) {
  return (
    <div className="panel p-5 sm:p-6">
      <p
        className="text-[11.5px] font-bold tracking-[0.08em] uppercase mb-3.5"
        style={{ color: "var(--ink-3)" }}
      >
        关于作者
      </p>
      <div className="flex items-center gap-4 flex-wrap">
        <Link href={`/u/${profile.user.id}`} className="shrink-0" aria-label={profile.user.nickname}>
          <Avatar name={profile.user.nickname || profile.user.username} size={52} />
        </Link>
        <div className="min-w-0 flex-1">
          <div className="flex items-center gap-2 flex-wrap">
            <Link
              href={`/u/${profile.user.id}`}
              className="font-bold text-[15px] hover:text-[var(--accent)] transition-colors"
              style={{ color: "var(--ink)" }}
            >
              {profile.user.nickname}
            </Link>
            {profile.user.role === "admin" && (
              <span
                className="chip"
                style={{ background: "var(--accent-soft)", color: "var(--accent)", borderColor: "transparent" }}
              >
                管理员
              </span>
            )}
          </div>
          <p className="meta mt-1">
            {formatYearMonth(profile.user.created_at)} 加入 · 发帖 {profile.stats.post_count} · 评论{" "}
            {profile.stats.comment_count}
          </p>
        </div>
        <Link href={`/u/${profile.user.id}`} className="btn btn-line btn-sm shrink-0">
          访问主页
        </Link>
      </div>
    </div>
  );
}

export default async function PostDetailPage({ params }: PageProps) {
  const { id } = await params;
  const cookie = authCookieHeader(await cookies());
  const { post } = await fetchPostDetail(id, cookie);

  // 评论 / 作者资料 / 同板块热议并行拉取；侧栏数据失败一律静默降级，不阻塞正文
  const [commentsData, profile, relatedData] = await Promise.all([
    fetchComments(id),
    fetchUserProfile(String(post.user.id), 1, cookie).catch(() => null),
    fetchPosts(1, 8, post.board_id, "hot", "", false, cookie).catch(() => null),
  ]);
  const comments = commentsData.comments;
  const related = (relatedData?.posts ?? []).filter((p) => p.id !== post.id).slice(0, 5);
  const authorPosts = (profile?.posts ?? []).filter((p) => p.id !== post.id).slice(0, 5);

  const toc = extractToc(post.content);
  const readingMinutes = Math.max(1, Math.ceil(post.content.length / 400));
  const edited =
    new Date(post.updated_at).getTime() - new Date(post.created_at).getTime() > 60_000;

  const jsonLd = {
    "@context": "https://schema.org",
    "@type": "DiscussionForumPosting",
    headline: post.title,
    articleBody: post.content,
    datePublished: post.created_at,
    dateModified: post.updated_at,
    author: { "@type": "Person", name: post.user.nickname },
    commentCount: post.comment_count,
    interactionStatistic: {
      "@type": "InteractionCounter",
      interactionType: { "@type": "ReadAction" },
      userInteractionCount: post.view_count,
    },
  };

  // 目录项与 Markdown 标题按渲染顺序一一对应（extractToc 顺序 == 文档顺序）
  let headingIndex = 0;
  const headingRenderer = (Tag: "h2" | "h3") =>
    function Heading({ children }: { children?: React.ReactNode }) {
      const item = toc[headingIndex++];
      return (
        <Tag id={item?.id} style={{ scrollMarginTop: 90 }}>
          {children}
        </Tag>
      );
    };

  const tags = post.tags
    ? [...new Set(post.tags.split(",").map((t) => t.trim()).filter(Boolean))]
    : [];

  return (
    <>
      <ReadingProgress />
      <script type="application/ld+json" dangerouslySetInnerHTML={{ __html: JSON.stringify(jsonLd) }} />

      {/* 三栏阅读布局：xl = 左导航240 + 正文 + 右辅助280；lg = 正文 + 右辅助260；以下单栏 */}
      <div className="grid grid-cols-1 items-start lg:grid-cols-[minmax(0,1fr)_260px] xl:grid-cols-[240px_minmax(0,1fr)_280px] gap-x-6 xl:gap-x-7">
        {/* 左栏：板块 / 作者 / 作者其他帖 */}
        {/* sticky 必须直接挂在 grid 子项上：aside 作为 grid item，其可粘行程
            等于行高（正文高度）；内层包裹会被 items-start 缩成内容高而失去行程 */}
        <aside
          className="hidden xl:flex w-[240px] shrink-0 sticky top-24 flex-col gap-4 max-h-[calc(100vh_-_7rem)] overflow-hidden"
          aria-label="帖子导航"
        >
          <BoardCard board={post.board} />
          {profile && <AuthorRailCard profile={profile} />}
          {profile && <AuthorPosts posts={authorPosts} />}
        </aside>

        {/* 中栏：正文主体 */}
        <div className="min-w-0">
          <article className="w-full max-w-[760px] mx-auto">
            <nav className="meta mb-5 flex items-center gap-1.5 flex-wrap text-[13px]">
              <Link href="/" className="hover:text-[var(--accent)] transition-colors">首页</Link>
              <ChevronRight size={13} />
              <Link href={`/board/${post.board.id}`} className="hover:text-[var(--accent)] transition-colors">
                {post.board.name}
              </Link>
            </nav>

            <div className="panel p-6 sm:p-8">
              <header className="mb-7">
                <div className="flex items-center gap-2 mb-4 flex-wrap">
                  {post.pinned > 0 && <span className="badge-pin">置顶</span>}
                  {post.recommended && <span className="badge-rec">推荐</span>}
                  <Link href={`/board/${post.board.id}`} className="chip">
                    {post.board.name}
                  </Link>
                </div>
                <h1 className="text-[26px] sm:text-[34px] font-extrabold leading-tight tracking-tight mb-6" style={{ color: "var(--ink)" }}>
                  {post.title}
                </h1>

                {/* 作者行：头像 + 昵称居左，点赞/更多操作居右 */}
                <div
                  className="flex items-center justify-between gap-4 flex-wrap pb-4"
                  style={{ borderBottom: "1px solid var(--line)" }}
                >
                  <div className="flex items-center gap-3 min-w-0">
                    <Link href={`/u/${post.user.id}`} className="shrink-0" aria-label={post.user.nickname}>
                      <Avatar name={post.user.nickname || post.user.username} size={40} />
                    </Link>
                    <Link
                      href={`/u/${post.user.id}`}
                      className="min-w-0 truncate text-[15px] font-bold hover:text-[var(--accent)] transition-colors"
                      style={{ color: "var(--ink)" }}
                    >
                      {post.user.nickname}
                    </Link>
                  </div>
                  {/* 管理操作已收进单个下拉按钮；普通读者此处不渲染内容 */}
                  <PostActions postId={id} authorId={post.user.id} pinned={post.pinned} recommended={post.recommended} />
                </div>

                {/* 元信息条：阅读数据居左、发布/更新时间居右（窄屏自动折行）；
                    原右栏“帖子数据”卡已移除，点赞数由点赞按钮承载，此处不重复 */}
                <div className="mt-3.5 flex flex-wrap items-center gap-x-4 gap-y-2">
                  <div className="flex items-center gap-4 meta">
                    <span className="inline-flex items-center gap-1.5" aria-label={`浏览 ${post.view_count} 次`}>
                      <IconEye size={14} /> {post.view_count} 浏览
                    </span>
                    <span className="inline-flex items-center gap-1.5" aria-label={`评论 ${post.comment_count} 条`}>
                      <IconComment size={14} /> {post.comment_count} 评论
                    </span>
                    <span className="inline-flex items-center gap-1.5" aria-label={`阅读约需 ${readingMinutes} 分钟`}>
                      <Clock size={14} /> 约 {readingMinutes} 分钟读完
                    </span>
                  </div>
                  <p className="meta w-full text-[12px] sm:w-auto sm:ml-auto">
                    发布于 {formatDateTime(post.created_at)}
                    {edited && <> · 更新于 {formatDateTime(post.updated_at)}</>}
                  </p>
                </div>
              </header>

              {tags.length > 0 && (
                <div className="flex flex-wrap gap-2 mb-7">
                  {tags.map((t, i) => (
                    <span key={`${t}-${i}`} className="chip">
                      # {t}
                    </span>
                  ))}
                </div>
              )}

              <div className="prose-content">
                <ReactMarkdown components={{ h2: headingRenderer("h2"), h3: headingRenderer("h3") }}>
                  {post.content}
                </ReactMarkdown>
              </div>

              {/* 文末点赞：分隔线后居中，唯一的点赞入口（作者行不再放置） */}
              <div
                className="mt-9 pt-7 flex justify-center"
                style={{ borderTop: "1px solid var(--line)" }}
              >
                <LikeButton
                  postId={id}
                  liked={post.liked}
                  likeCount={post.like_count}
                  variant="article"
                />
              </div>
            </div>

            {/* 窄屏作者卡（xl 起由左栏承载，避免重复展示） */}
            {profile && (
              <div className="xl:hidden mt-6">
                <AuthorCardStacked profile={profile} />
              </div>
            )}

            <CommentSection postId={id} comments={comments} />

            {/* 窄屏相关讨论（lg 起由右栏承载） */}
            <div className="lg:hidden mt-6">
              <RelatedPosts posts={related} boardId={post.board_id} uid="related-inline" />
            </div>
          </article>
        </div>

        {/* 右栏：目录 / 同板块热议（阅读数据已并入标题下元信息条） */}
        <aside
          className="hidden lg:flex w-[260px] xl:w-[280px] shrink-0 sticky top-24 flex-col gap-4 max-h-[calc(100vh_-_7rem)] overflow-hidden"
          aria-label="阅读辅助"
        >
          {toc.length > 0 && <PostToc items={toc} />}
          <RelatedPosts posts={related} boardId={post.board_id} />
        </aside>
      </div>
    </>
  );
}