import { useState, useEffect, useRef } from 'react'
import { useNavigate, useParams } from 'react-router-dom'
import { Layout, Modal, Input, Spin, Button, Space } from 'antd'
import { CloseOutlined, LockOutlined, FileTextOutlined, FilePdfOutlined, VerticalAlignTopOutlined, CloudDownloadOutlined } from '@ant-design/icons'
import ReactMarkdown from 'react-markdown'
import remarkGfm from 'remark-gfm'
import rehypeHighlight from 'rehype-highlight'
import rehypeSlug from 'rehype-slug'
import 'highlight.js/styles/github.css'
import GithubSlugger from 'github-slugger'
import Toast from '@/components/Toast/Toast'
import FloatingToc from '@/components/FloatingToc/FloatingToc'
import VirtualPDFViewer from '@/components/PDFViewer/VirtualPDFViewer'
import {
  getFileSharePublicInfo,
  verifyFileSharePassword,
  getFileShareContent,
  exportFileSharePDF,
} from '@/api/share'
import './PreviewPage.css'

const { Content } = Layout

function FileSharePage() {
  const { shareCode } = useParams()
  const navigate = useNavigate()
  const contentRef = useRef(null)
  const [pdfToolbarTarget, setPdfToolbarTarget] = useState(null)
  const [shareInfo, setShareInfo] = useState(null)
  const [contentInfo, setContentInfo] = useState(null)
  const [loading, setLoading] = useState(true)
  const [isMobile, setIsMobile] = useState(false)
  const [tocItems, setTocItems] = useState([])
  const [passwordModalVisible, setPasswordModalVisible] = useState(false)
  const [password, setPassword] = useState('')

  useEffect(() => {
    loadFileShare()
  }, [shareCode])

  useEffect(() => {
    const checkMobile = () => setIsMobile(window.innerWidth < 768)
    checkMobile()
    window.addEventListener('resize', checkMobile)
    return () => window.removeEventListener('resize', checkMobile)
  }, [])

  useEffect(() => {
    const markdownContent = contentInfo?.type === 'markdown' ? (contentInfo.content || '') : ''
    if (!markdownContent) {
      setTocItems([])
      return
    }

    const slugger = new GithubSlugger()
    const headings = []
    markdownContent.split('\n').forEach((line) => {
      const match = line.match(/^(#{1,6})\s+(.+)$/)
      if (!match) return
      const level = match[1].length
      const title = match[2].trim()
      const key = slugger.slug(title)
      headings.push({ key: `#${key}`, href: `#${key}`, title, level })
    })
    setTocItems(headings)
  }, [contentInfo])

  const handleClose = () => {
    if (window.history.length > 1) {
      navigate(-1)
      return
    }
    navigate('/')
  }

  const loadFileShare = async () => {
    setLoading(true)
    try {
      const infoRes = await getFileSharePublicInfo(shareCode)
      setShareInfo(infoRes.data)

      if (infoRes.data.has_password) {
        setContentInfo(null)
        setPasswordModalVisible(true)
        setLoading(false)
        return
      }

      const contentRes = await getFileShareContent(shareCode)
      setContentInfo(contentRes.data)
    } catch (error) {
      console.error('Load file share error:', error)
      Toast.error('加载失败', '分享链接不存在或已失效')
    } finally {
      setLoading(false)
    }
  }

  const handleVerifyPassword = async () => {
    if (!password.trim()) {
      Toast.warning('提示', '请输入访问密码')
      return
    }
    try {
      await verifyFileSharePassword(shareCode, password)
      const contentRes = await getFileShareContent(shareCode, password)
      setContentInfo(contentRes.data)
      setPasswordModalVisible(false)
      Toast.success('验证成功')
    } catch (error) {
      Toast.error('访问密码错误')
    }
  }

  const handleExportPDF = () => {
    if (!contentInfo || contentInfo.type === 'pdf') return
    window.open(exportFileSharePDF(shareCode), '_blank')
  }

  const scrollContentToTop = () => {
    if (contentRef.current) {
      contentRef.current.scrollTo({ top: 0, behavior: 'smooth' })
    }
  }

  const isExternalHref = (href) => {
    return Boolean(href && (/^[a-z][a-z\d+.-]*:/i.test(href) || href.startsWith('//')))
  }

  const isInternalFileHref = (href) => {
    if (!href) return false
    if (href.startsWith('#')) return false
    if (isExternalHref(href)) return false
    const pathOnly = href.split(/[?#]/)[0]
    return pathOnly.endsWith('.md') || pathOnly.toLowerCase().endsWith('.pdf')
  }

  const handleMarkdownLink = (e, href) => {
    if (!isInternalFileHref(href)) return
    e.preventDefault()
    Toast.error('无法打开内部文件链接', '单文件分享模式不支持跳转到其他内部文件')
  }

  const markdownComponents = {
    a: ({ node, href, children, ...props }) => {
      const isExternal = isExternalHref(href)
      return (
        <a
          href={href}
          onClick={(e) => handleMarkdownLink(e, href)}
          target={isExternal ? '_blank' : undefined}
          rel={isExternal ? 'noopener noreferrer' : undefined}
          {...props}
        >
          {children}
        </a>
      )
    },
  }

  const isHeaderPdf = contentInfo?.type === 'pdf'
  const HeaderIcon = isHeaderPdf ? FilePdfOutlined : FileTextOutlined
  const headerLabel = contentInfo?.filename || '文件分享'

  return (
    <div className="preview-page file-share-page">
      <div className="file-share-shell">
        <Layout className="file-share-content-layout">
          <Content className="file-share-content" ref={contentRef}>
            <div className="preview-content-header file-share-content-header">
              <button
                type="button"
                className="project-back-button"
                onClick={handleClose}
                aria-label="关闭文档分享"
              >
                <CloseOutlined />
              </button>
              <h3 className="preview-header-title">
                <HeaderIcon className="preview-header-icon" style={isHeaderPdf ? { color: '#f5222d' } : undefined} />
                <span className="preview-header-text">{headerLabel}</span>
              </h3>
              {contentInfo?.type === 'markdown' && (
                <Space className="preview-header-actions">
                  <Button
                    icon={<VerticalAlignTopOutlined />}
                    onClick={scrollContentToTop}
                    size="small"
                  >
                    回到顶部
                  </Button>
                  <Button
                    icon={<CloudDownloadOutlined />}
                    onClick={handleExportPDF}
                    size="small"
                  >
                    下载PDF
                  </Button>
                </Space>
              )}
              {contentInfo?.type === 'pdf' && <div className="preview-header-actions pdf-header-toolbar" ref={setPdfToolbarTarget} />}
            </div>
            {loading ? (
              <div className="preview-loading">
                <Spin size="large">
                  <div style={{ marginTop: 16 }}>加载中...</div>
                </Spin>
              </div>
            ) : (
              <div className={`preview-content-wrapper ${contentInfo?.type === 'pdf' ? 'pdf-mode' : ''}`}>
                {contentInfo?.type === 'pdf' ? (
                  <VirtualPDFViewer
                    url={contentInfo.document_url}
                    filename={contentInfo.filename}
                    toolbarTarget={pdfToolbarTarget}
                  />
                ) : (
                  <div className="markdown-body">
                    <ReactMarkdown
                      remarkPlugins={[remarkGfm]}
                      rehypePlugins={[rehypeSlug, rehypeHighlight]}
                      components={markdownComponents}
                    >
                      {contentInfo?.content || ''}
                    </ReactMarkdown>
                  </div>
                )}
              </div>
            )}

          </Content>

          {!isMobile && contentInfo?.type === 'markdown' && (
            <FloatingToc
              items={tocItems}
              getContainer={() => contentRef.current}
            />
          )}
        </Layout>
      </div>

      <Modal
        title={<div style={{ display: 'flex', alignItems: 'center', gap: 8 }}><LockOutlined /><span>访问验证</span></div>}
        open={passwordModalVisible}
        onOk={handleVerifyPassword}
        onCancel={() => setPasswordModalVisible(false)}
        okText="验证"
        cancelText="取消"
        maskClosable={false}
      >
        <div style={{ marginTop: 16 }}>
          <p>该文件分享需要访问密码，请输入密码后继续浏览。</p>
          <Input.Password
            placeholder="请输入访问密码"
            value={password}
            onChange={(e) => setPassword(e.target.value)}
            onPressEnter={handleVerifyPassword}
            prefix={<LockOutlined />}
          />
        </div>
      </Modal>
    </div>
  )
}

export default FileSharePage