import { useMemo, useState } from 'react';
import { BookOpen, RefreshCw, Loader2 } from 'lucide-react';
import { useQuery } from '@tanstack/react-query';
import { Marked } from 'marked';
import { gfmHeadingId } from 'marked-gfm-heading-id';
import { api } from '@/lib/api';

type DocKind = 'guide' | 'api';

const meta: Record<DocKind, { title: string; subtitle: string }> = {
  guide: { title: '使用指南', subtitle: '每个功能一句话讲清：是什么 → 怎么用 → 实用技巧' },
  api: { title: '接口文档', subtitle: '与当前后端代码对齐；调用需登录 Token，敏感字段只写不回显' },
};

// 从 Markdown 提取 ## 级标题做目录（marked-gfm-heading-id 生成锚点 id）
function extractToc(md: string): { text: string; id: string; level: number }[] {
  const out: { text: string; id: string; level: number }[] = [];
  for (const line of md.split('\n')) {
    const m = /^(#{2,3})\s+(.+)$/.exec(line.trim());
    if (!m) continue;
    const text = m[2].trim();
    out.push({ text, id: headingId(text), level: m[1].length });
  }
  return out;
}

// 与 marked-gfm-heading-id 的默认 slug 规则保持一致（小写、去标点、空格转 -）
function headingId(text: string): string {
  return text.toLowerCase().replace(/[^\p{L}\p{N}\s-]/gu, '').trim().replace(/\s+/g, '-');
}

export default function Docs() {
  const [kind, setKind] = useState<DocKind>('guide');

  const { data, isLoading, refetch, isRefetching } = useQuery({
    queryKey: ['docs'],
    queryFn: () => api<any>('/api/docs'),
  });

  const raw = (kind === 'guide' ? data?.guide : data?.api) || '';

  const html = useMemo(() => {
    const marked = new Marked(gfmHeadingId());
    return marked.parse(raw, { async: false }) as string;
  }, [raw]);

  const toc = useMemo(() => extractToc(raw), [raw]);

  return (
    <div className="h-full flex flex-col" style={{ background: 'var(--canvas-bg)' }}>
      {/* Header */}
      <div className="px-5 py-3 border-b flex items-center justify-between flex-shrink-0" style={{ background: 'var(--panel-bg)', borderColor: 'var(--border-color)' }}>
        <div className="flex items-center gap-3">
          <BookOpen className="w-4.5 h-4.5" style={{ color: 'var(--accent-blue)' }} />
          <h1 className="text-[15px] font-semibold" style={{ color: 'var(--text-primary)' }}>文档</h1>
          {/* 指南/接口 切换 */}
          <div className="flex items-center rounded-md border overflow-hidden ml-2" style={{ borderColor: 'var(--border-color-light)' }}>
            {(['guide', 'api'] as DocKind[]).map((k) => (
              <button key={k} onClick={() => setKind(k)} className="px-3 py-[3px] text-[11px] font-medium"
                style={{ background: kind === k ? 'var(--accent-blue)' : 'transparent', color: kind === k ? '#fff' : 'var(--text-secondary)' }}>
                {meta[k].title}
              </button>
            ))}
          </div>
        </div>
        <button onClick={() => refetch()} className="flex items-center gap-1 px-3 py-[5px] text-[12px] font-medium rounded-md border" style={{ borderColor: 'var(--border-color-light)', color: 'var(--text-secondary)' }}>
          <RefreshCw className={`w-3.5 h-3.5 ${isRefetching ? 'animate-spin' : ''}`} />刷新
        </button>
      </div>

      <div className="flex-1 flex overflow-hidden">
        {/* 左侧目录 */}
        <div className="w-56 border-r overflow-y-auto custom-scrollbar flex-shrink-0 py-3" style={{ background: 'var(--panel-bg)', borderColor: 'var(--border-color)' }}>
          <div className="px-4 pb-2 text-[11px] font-semibold" style={{ color: 'var(--text-tertiary)' }}>目录</div>
          {isLoading ? (
            <div className="px-4 py-4 text-[12px]" style={{ color: 'var(--text-tertiary)' }}>加载中…</div>
          ) : (
            toc.map((t) => (
              <a key={t.id + t.text} href={`#${t.id}`}
                className={`block truncate hover:bg-black/[0.03] ${t.level === 3 ? 'pl-7' : 'pl-4'} pr-3 py-[5px] text-[12px]`}
                style={{ color: t.level === 3 ? 'var(--text-tertiary)' : 'var(--text-secondary)' }}>
                {t.text}
              </a>
            ))
          )}
        </div>

        {/* 右侧内容 */}
        <div className="flex-1 overflow-y-auto custom-scrollbar">
          {isLoading ? (
            <div className="flex items-center justify-center gap-2 py-20 text-[13px]" style={{ color: 'var(--text-tertiary)' }}>
              <Loader2 className="w-4 h-4 animate-spin" />加载文档中…
            </div>
          ) : (
            <div className="max-w-3xl mx-auto px-8 py-6">
              <div className="mb-4 pb-4 border-b" style={{ borderColor: 'var(--border-color)' }}>
                <h2 className="text-[17px] font-bold" style={{ color: 'var(--text-primary)' }}>{meta[kind].title}</h2>
                <p className="text-[12px] mt-1" style={{ color: 'var(--text-tertiary)' }}>{meta[kind].subtitle}</p>
              </div>
              <div className="md-body" dangerouslySetInnerHTML={{ __html: html }} />
            </div>
          )}
        </div>
      </div>
    </div>
  );
}