import { lazy, Suspense, useCallback, useEffect, useRef, useState } from 'react'
import { useNavigate, useParams } from 'react-router'
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
import { Bold, Italic, Link2, Code, Table, Eye, EyeOff } from 'lucide-react'
import { api, ApiError } from '../lib/api'
import type { NoteItem } from '../lib/api'
import { invalidatePublic } from '../lib/invalidate'
import MarkdownViewer from '../components/MarkdownViewer'
import { slugPreview } from '../lib/utils'

// CodeMirror 体积大，单独拆 chunk，编辑器在首帧后异步加载
const Editor = lazy(() => import('../components/Editor'))

interface NoteFull extends NoteItem {
  content: string
  prev?: unknown
  next?: unknown
}

type Form = {
  title: string
  slug: string
  summary: string
  content: string
  status: 'public' | 'private'
  tags: string
  pinned: boolean
}

const emptyForm: Form = {
  title: '',
  slug: '',
  summary: '',
  content: '',
  status: 'private',
  tags: '',
  pinned: false,
}

export default function AdminEdit() {
  const { id } = useParams()
  const noteId = id ? Number(id) : null
  const isNew = noteId === null
  const navigate = useNavigate()
  const qc = useQueryClient()

  const { data: existing, isLoading } = useQuery({
    queryKey: ['admin', 'note', noteId],
    queryFn: () => api<NoteFull>(`/api/admin/notes/${noteId}`),
    enabled: !isNew,
  })

  const [form, setForm] = useState<Form>(emptyForm)
  const [savedAt, setSavedAt] = useState<number | null>(null)
  const [errorMsg, setErrorMsg] = useState<string | null>(null)
  const [slugFieldError, setSlugFieldError] = useState<string | null>(null)
  const [showPreview, setShowPreview] = useState(true)
  const [uploadMsg, setUploadMsg] = useState<string | null>(null)
  const dirtyRef = useRef(false)
  const slugTouchedRef = useRef(false)
  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null)

  useEffect(() => {
    if (existing) {
      setForm({
        title: existing.title,
        slug: existing.slug,
        summary: existing.summary,
        content: existing.content,
        status: existing.status === 'public' ? 'public' : 'private',
        tags: existing.tags.join(', '),
        pinned: existing.pinned,
      })
      slugTouchedRef.current = false
      dirtyRef.current = false
    }
  }, [existing])

  const set = <K extends keyof Form>(key: K, value: Form[K]) => {
    setForm((f) => ({ ...f, [key]: value }))
    dirtyRef.current = true
    if (key === 'slug') slugTouchedRef.current = true
    setErrorMsg(null)
  }

  const save = useMutation({
    mutationFn: async (f: Form) => {
      const payload = {
        title: f.title,
        slug: f.slug,
        summary: f.summary,
        content: f.content,
        status: f.status,
        tags: f.tags.split(/[,，]/).map((t) => t.trim()).filter(Boolean),
        pinned: f.pinned,
      }
      if (isNew) {
        // 新建：slug 由服务端从标题自动生成（首次保存即定稿，§8.2）
        return api<NoteFull>('/api/admin/notes', {
          method: 'POST',
          body: JSON.stringify({ ...payload, slug: '' }),
        })
      }
      return api<NoteFull>(`/api/admin/notes/${noteId}`, {
        method: 'PUT',
        body: JSON.stringify(payload),
      })
    },
    onSuccess: (saved) => {
      setSavedAt(Date.now())
      setSlugFieldError(null)
      setErrorMsg(null)
      dirtyRef.current = false
      // 仅失效列表与公共缓存；不失效当前编辑详情（['admin','note',id]），
      // 防 refetch 回滚保存期间继续输入的内容并抑制下一轮自动保存（评审 round2 P1-4）
      void qc.invalidateQueries({ queryKey: ['admin', 'notes'] })
      invalidatePublic(qc)
      if (isNew) {
        navigate(`/admin/notes/${saved.id}/edit`, { replace: true })
      }
    },
    onError: (e) => {
      if (e instanceof ApiError && e.code === 'slug_conflict') {
        setSlugFieldError(e.message)
      } else {
        setErrorMsg(e instanceof Error ? e.message : '保存失败')
      }
    },
  })

  const canSave = form.title.trim().length > 0
  const autosaveReady = !isNew || form.content.trim().length > 0

  // 自动保存：防抖 2s（§8.2）
  useEffect(() => {
    if (!canSave || !autosaveReady || !dirtyRef.current) return
    if (timerRef.current) clearTimeout(timerRef.current)
    timerRef.current = setTimeout(() => {
      if (dirtyRef.current) save.mutate(form)
    }, 2000)
    return () => {
      if (timerRef.current) clearTimeout(timerRef.current)
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [form, canSave, autosaveReady])

  const wrapSelection = useCallback(
    (before: string, after = before, placeholder = '文本') => {
      const el = document.querySelector<HTMLElement>('.cm-content')
      // 简化实现：在内容末尾/光标处理由 CodeMirror 自行接管，这里直接改源码
      void el
      set('content', form.content + `${before}${placeholder}${after}`)
    },
    [form.content],
  )

  if (!isNew && isLoading) {
    return <p className="py-12 text-center text-zinc-400">加载中…</p>
  }

  return (
    <div className="flex h-[calc(100vh-8rem)] flex-col">
      <div className="mb-3 flex items-center gap-3">
        <input
          value={form.title}
          onChange={(e) => set('title', e.target.value)}
          placeholder="标题（必填）"
          className="min-w-0 flex-1 rounded-lg border border-transparent bg-transparent px-2 py-1.5 text-xl font-semibold outline-none hover:border-zinc-200 focus:border-blue-500 dark:hover:border-zinc-800"
        />
        <button
          type="button"
          onClick={() => setShowPreview((v) => !v)}
          className="inline-flex items-center gap-1 rounded-lg border border-zinc-300 px-2.5 py-1.5 text-xs text-zinc-600 dark:border-zinc-700 dark:text-zinc-400"
          title="切换预览"
        >
          {showPreview ? <EyeOff size={13} /> : <Eye size={13} />}
          {showPreview ? '隐藏预览' : '显示预览'}
        </button>
        <button
          type="button"
          onClick={() => save.mutate(form)}
          disabled={!canSave || save.isPending}
          className="rounded-lg bg-zinc-900 px-4 py-1.5 text-sm font-medium text-white disabled:opacity-50 dark:bg-zinc-100 dark:text-zinc-900"
        >
          {save.isPending ? '保存中…' : '保存'}
        </button>
      </div>

      <div className="mb-2 flex flex-wrap items-center gap-2 text-xs text-zinc-400">
        <button type="button" onClick={() => wrapSelection('**')} className="rounded p-1 hover:bg-zinc-100 dark:hover:bg-zinc-800"><Bold size={14} /></button>
        <button type="button" onClick={() => wrapSelection('*')} className="rounded p-1 hover:bg-zinc-100 dark:hover:bg-zinc-800"><Italic size={14} /></button>
        <button type="button" onClick={() => set('content', form.content + '[标题](https://)')} className="rounded p-1 hover:bg-zinc-100 dark:hover:bg-zinc-800"><Link2 size={14} /></button>
        <button type="button" onClick={() => set('content', form.content + '\n```\n代码\n```\n')} className="rounded p-1 hover:bg-zinc-100 dark:hover:bg-zinc-800"><Code size={14} /></button>
        <button type="button" onClick={() => set('content', form.content + '\n| 列1 | 列2 |\n| --- | --- |\n| a | b |\n')} className="rounded p-1 hover:bg-zinc-100 dark:hover:bg-zinc-800"><Table size={14} /></button>
        <span className="mx-1 text-zinc-300 dark:text-zinc-700">|</span>
        <span>粘贴 / 拖拽图片即可上传</span>
        <span className="ml-auto">
          {save.isPending
            ? '保存中…'
            : savedAt
              ? `已保存 ${new Date(savedAt).toLocaleTimeString('zh-CN')}`
              : isNew
                ? '未保存'
                : '无改动'}
        </span>
      </div>

      <div className="flex min-h-0 flex-1 gap-3">
        <div className="flex min-w-0 flex-1 flex-col gap-3">
          <div className="min-h-0 flex-1">
            <Suspense fallback={<div className="flex h-full items-center justify-center text-sm text-zinc-500">编辑器加载中…</div>}>
              <Editor
                value={form.content}
                onChange={(v) => set('content', v)}
                onUploadStart={(name) => setUploadMsg(`上传中：${name}…`)}
                onUploadEnd={(err) => setUploadMsg(err ?? null)}
              />
            </Suspense>
          </div>
          {uploadMsg && <p className="text-xs text-zinc-400">{uploadMsg}</p>}
          {showPreview && (
            <div className="hidden min-h-0 flex-1 overflow-auto rounded-lg border border-zinc-200 p-4 lg:block dark:border-zinc-800">
              <MarkdownViewer source={form.content} />
            </div>
          )}
        </div>

        <aside className="w-64 shrink-0 space-y-4 overflow-auto rounded-lg border border-zinc-200 p-4 dark:border-zinc-800">
          <div>
            <label className="text-xs font-medium text-zinc-500">slug</label>
            <input
              value={form.slug}
              onChange={(e) => set('slug', e.target.value)}
              placeholder={form.title ? slugPreview(form.title, new Date()) : '保存后自动生成'}
              className={`mt-1 w-full rounded-md border px-2 py-1.5 font-mono text-xs outline-none ${
                slugFieldError
                  ? 'border-red-500 bg-red-50 dark:bg-red-950'
                  : 'border-zinc-300 dark:border-zinc-700'
              }`}
            />
            {slugFieldError && <p className="mt-1 text-xs text-red-600">{slugFieldError}</p>}
            <p className="mt-1 text-[10px] leading-relaxed text-zinc-400">
              留空保持不变；首次保存自动生成后定稿
            </p>
          </div>
          <div>
            <label className="text-xs font-medium text-zinc-500">标签（逗号分隔）</label>
            <input
              value={form.tags}
              onChange={(e) => set('tags', e.target.value)}
              placeholder="随笔, go"
              className="mt-1 w-full rounded-md border border-zinc-300 px-2 py-1.5 text-xs outline-none focus:border-blue-500 dark:border-zinc-700"
            />
          </div>
          <div>
            <label className="text-xs font-medium text-zinc-500">摘要（留空自动截取正文）</label>
            <textarea
              value={form.summary}
              onChange={(e) => set('summary', e.target.value)}
              rows={3}
              className="mt-1 w-full resize-none rounded-md border border-zinc-300 px-2 py-1.5 text-xs outline-none focus:border-blue-500 dark:border-zinc-700"
            />
          </div>
          <div className="flex items-center justify-between">
            <span className="text-xs font-medium text-zinc-500">公开</span>
            <button
              type="button"
              role="switch"
              aria-checked={form.status === 'public'}
              onClick={() => set('status', form.status === 'public' ? 'private' : 'public')}
              className={`relative h-5 w-9 rounded-full transition ${
                form.status === 'public' ? 'bg-green-500' : 'bg-zinc-300 dark:bg-zinc-700'
              }`}
            >
              <span
                className={`absolute top-0.5 h-4 w-4 rounded-full bg-white transition-all ${
                  form.status === 'public' ? 'left-[1.15rem]' : 'left-0.5'
                }`}
              />
            </button>
          </div>
          <div className="flex items-center justify-between">
            <span className="text-xs font-medium text-zinc-500">置顶</span>
            <button
              type="button"
              role="switch"
              aria-checked={form.pinned}
              onClick={() => set('pinned', !form.pinned)}
              className={`relative h-5 w-9 rounded-full transition ${
                form.pinned ? 'bg-amber-500' : 'bg-zinc-300 dark:bg-zinc-700'
              }`}
            >
              <span
                className={`absolute top-0.5 h-4 w-4 rounded-full bg-white transition-all ${
                  form.pinned ? 'left-[1.15rem]' : 'left-0.5'
                }`}
              />
            </button>
          </div>
          {errorMsg && <p className="text-xs text-red-600">{errorMsg}</p>}
        </aside>
      </div>
    </div>
  )
}