'use server'

export async function createPost(formData: FormData) {
  const title = formData.get('title') as string
  const content = formData.get('content') as string

  // 直接操作数据库
  await db.post.create({
    data: { title, content },
  })

  return { success: true }
}

// Next.js 15.x
import { createPost } from '@/app/actions'

export default function NewPostPage() {
  return (
    <form action={createPost}>
      <input name="title" placeholder="标题" required />
      <textarea name="content" placeholder="内容" required />
      <button type="submit">发布</button>
    </form>
  )
}

'use client'

import { createPost } from '@/app/actions'
import { useActionState } from 'react'

export function PostForm() {
  const [state, formAction, isPending] = useActionState(createPost, null)

  return (
    <form action={formAction}>
      <input name="title" placeholder="标题" disabled={isPending} />
      <textarea name="content" placeholder="内容" disabled={isPending} />
      <button type="submit" disabled={isPending}>
        {isPending ? '发布中...' : '发布'}
      </button>
      {state?.error && <p className="text-red-500">{state.error}</p>}
    </form>
  )
}

'use server'

import { z } from 'zod'
import { revalidatePath } from 'next/cache'

const PostSchema = z.object({
  title: z.string().min(1, '标题不能为空').max(100, '标题过长'),
  content: z.string().min(10, '内容至少 10 个字符'),
})

export async function createPost(prevState: any, formData: FormData) {
  // 验证数据
  const validatedFields = PostSchema.safeParse({
    title: formData.get('title'),
    content: formData.get('content'),
  })

  if (!validatedFields.success) {
    return {
      errors: validatedFields.error.flatten().fieldErrors,
      message: '验证失败',
    }
  }

  const { title, content } = validatedFields.data

  try {
    await db.post.create({ data: { title, content } })

    // 重新验证缓存
    revalidatePath('/posts')

    return { message: '发布成功' }
  } catch (error) {
    return { message: '发布失败，请重试' }
  }
}

'use client'

import { useActionState } from 'react'
import { createPost } from '@/app/actions'

const initialState = {
  message: '',
  errors: {},
}

export function PostForm() {
  const [state, formAction, isPending] = useActionState(
    createPost,
    initialState
  )

  return (
    <form action={formAction} className="space-y-4">
      <div>
        <label className="block font-medium">标题</label>
        <input
          name="title"
          className="w-full border rounded px-3 py-2"
          aria-describedby="title-error"
        />
        {state.errors?.title && (
          <p id="title-error" className="text-red-500 text-sm mt-1">
            {state.errors.title[0]}
          </p>
        )}
      </div>

      <div>
        <label className="block font-medium">内容</label>
        <textarea
          name="content"
          rows={5}
          className="w-full border rounded px-3 py-2"
          aria-describedby="content-error"
        />
        {state.errors?.content && (
          <p id="content-error" className="text-red-500 text-sm mt-1">
            {state.errors.content[0]}
          </p>
        )}
      </div>

      <button
        type="submit"
        disabled={isPending}
        className="bg-blue-600 text-white px-4 py-2 rounded disabled:opacity-50"
      >
        {isPending ? '提交中...' : '发布'}
      </button>

      {state.message && (
        <p className={state.errors ? 'text-red-500' : 'text-green-500'}>
          {state.message}
        </p>
      )}
    </form>
  )
}

'use server'

import { writeFile } from 'fs/promises'
import { join } from 'path'

export async function uploadFile(formData: FormData) {
  const file = formData.get('file') as File

  if (!file) {
    return { error: '请选择文件' }
  }

  // 验证文件类型
  const allowedTypes = ['image/jpeg', 'image/png', 'image/webp']
  if (!allowedTypes.includes(file.type)) {
    return { error: '只支持 JPG、PNG、WebP 格式' }
  }

  // 验证文件大小（5MB）
  if (file.size > 5 * 1024 * 1024) {
    return { error: '文件大小不能超过 5MB' }
  }

  const bytes = await file.arrayBuffer()
  const buffer = Buffer.from(bytes)

  // 生成唯一文件名
  const uniqueName = `${Date.now()}-${file.name}`
  const path = join(process.cwd(), 'public', 'uploads', uniqueName)

  await writeFile(path, buffer)

  return { url: `/uploads/${uniqueName}` }
}

'use client'

import { useState } from 'react'
import { uploadFile } from '@/app/actions'

export function FileUpload() {
  const [uploading, setUploading] = useState(false)
  const [result, setResult] = useState<{ url?: string; error?: string } | null>(
    null
  )

  async function handleSubmit(formData: FormData) {
    setUploading(true)
    const res = await uploadFile(formData)
    setResult(res)
    setUploading(false)
  }

  return (
    <form action={handleSubmit}>
      <input type="file" name="file" accept="image/*" />
      <button type="submit" disabled={uploading}>
        {uploading ? '上传中...' : '上传'}
      </button>

      {result?.error && <p className="text-red-500">{result.error}</p>}
      {result?.url && (
        <img src={result.url} alt="Uploaded" className="mt-4 max-w-xs" />
      )}
    </form>
  )
}

'use client'

import { useOptimistic, useTransition } from 'react'
import { toggleLike } from '@/app/actions'

interface Props {
  postId: string
  initialLiked: boolean
  initialCount: number
}

export function LikeButton({ postId, initialLiked, initialCount }: Props) {
  const [isPending, startTransition] = useTransition()
  const [optimisticState, addOptimistic] = useOptimistic(
    { liked: initialLiked, count: initialCount },
    (state, newLiked: boolean) => ({
      liked: newLiked,
      count: state.count + (newLiked ? 1 : -1),
    })
  )

  function handleClick() {
    startTransition(async () => {
      // 立即更新 UI
      addOptimistic(!optimisticState.liked)
      // 执行服务端操作
      await toggleLike(postId)
    })
  }

  return (
    <button
      onClick={handleClick}
      disabled={isPending}
      className="flex items-center gap-2"
    >
      <span>{optimisticState.liked ? '❤️' : '🤍'}</span>
      <span>{optimisticState.count}</span>
    </button>
  )
}

'use server'

import { revalidatePath } from 'next/cache'

export async function toggleLike(postId: string) {
  const userId = await getCurrentUserId()

  const existing = await db.like.findUnique({
    where: { postId_userId: { postId, userId } },
  })

  if (existing) {
    await db.like.delete({
      where: { postId_userId: { postId, userId } },
    })
  } else {
    await db.like.create({
      data: { postId, userId },
    })
  }

  revalidatePath('/posts')
}

'use client'

import { useOptimistic } from 'react'
import { addTodo, deleteTodo } from '@/app/actions'

interface Todo {
  id: string
  text: string
  pending?: boolean
}

export function TodoList({ initialTodos }: { initialTodos: Todo[] }) {
  const [optimisticTodos, addOptimisticTodo] = useOptimistic(
    initialTodos,
    (state, action: { type: 'add' | 'delete'; todo?: Todo; id?: string }) => {
      if (action.type === 'add' && action.todo) {
        return [...state, { ...action.todo, pending: true }]
      }
      if (action.type === 'delete' && action.id) {
        return state.filter((t) => t.id !== action.id)
      }
      return state
    }
  )

  async function handleAdd(formData: FormData) {
    const text = formData.get('text') as string
    const tempId = `temp-${Date.now()}`

    addOptimisticTodo({ type: 'add', todo: { id: tempId, text } })
    await addTodo(formData)
  }

  async function handleDelete(id: string) {
    addOptimisticTodo({ type: 'delete', id })
    await deleteTodo(id)
  }

  return (
    <div>
      <form action={handleAdd} className="flex gap-2 mb-4">
        <input
          name="text"
          placeholder="新任务"
          className="border rounded px-2"
        />
        <button type="submit" className="bg-blue-600 text-white px-4 rounded">
          添加
        </button>
      </form>

      <ul className="space-y-2">
        {optimisticTodos.map((todo) => (
          <li
            key={todo.id}
            className={`flex justify-between items-center p-2 border rounded ${
              todo.pending ? 'opacity-50' : ''
            }`}
          >
            <span>{todo.text}</span>
            <button
              onClick={() => handleDelete(todo.id)}
              className="text-red-500"
            >
              删除
            </button>
          </li>
        ))}
      </ul>
    </div>
  )
}

'use server'

import { redirect } from 'next/navigation'
import { revalidatePath } from 'next/cache'

export async function createPost(formData: FormData) {
  const post = await db.post.create({
    data: {
      title: formData.get('title') as string,
      content: formData.get('content') as string,
    },
  })

  // 重新验证列表页缓存
  revalidatePath('/posts')

  // 重定向到新文章
  redirect(`/posts/${post.id}`)
}

export async function deletePost(id: string) {
  await db.post.delete({ where: { id } })

  revalidatePath('/posts')
  redirect('/posts')
}

'use server'

import { revalidateTag } from 'next/cache'

export async function updateProduct(id: string, formData: FormData) {
  await db.product.update({
    where: { id },
    data: {
      name: formData.get('name') as string,
      price: Number(formData.get('price')),
    },
  })

  // 重新验证特定产品的缓存
  revalidateTag(`product-${id}`)

  // 重新验证产品列表
  revalidateTag('products')
}

'use server'

export async function createUser(formData: FormData) {
  const email = formData.get('email') as string

  // 检查邮箱是否已存在
  const existing = await db.user.findUnique({ where: { email } })
  if (existing) {
    return { error: '该邮箱已被注册' }
  }

  try {
    const user = await db.user.create({
      data: {
        email,
        name: formData.get('name') as string,
      },
    })

    return { success: true, user }
  } catch (error) {
    return { error: '创建用户失败，请重试' }
  }
}

'use server'

export async function dangerousAction() {
  // 抛出的错误会被最近的 error.tsx 捕获
  throw new Error('操作失败')
}

'use client'

export default function Error({
  error,
  reset,
}: {
  error: Error & { digest?: string }
  reset: () => void
}) {
  return (
    <div className="p-4 bg-red-50 rounded">
      <h2 className="text-red-600 font-bold">出错了</h2>
      <p>{error.message}</p>
      <button onClick={reset} className="mt-2 text-blue-600">
        重试
      </button>
    </div>
  )
}

'use server'

import { z } from 'zod'

const CommentSchema = z.object({
  content: z
    .string()
    .min(1, '评论不能为空')
    .max(1000, '评论过长')
    .transform((s) => s.trim()),
  postId: z.string().uuid('无效的文章 ID'),
})

export async function addComment(formData: FormData) {
  const result = CommentSchema.safeParse({
    content: formData.get('content'),
    postId: formData.get('postId'),
  })

  if (!result.success) {
    return { error: result.error.flatten().fieldErrors }
  }

  // 使用验证后的数据
  await db.comment.create({ data: result.data })
}

'use server'

import { auth } from '@/lib/auth'
import { redirect } from 'next/navigation'

export async function updateProfile(formData: FormData) {
  const session = await auth()

  // 未登录重定向
  if (!session?.user) {
    redirect('/login')
  }

  // 只能修改自己的资料
  const userId = formData.get('userId') as string
  if (userId !== session.user.id) {
    return { error: '无权修改' }
  }

  await db.user.update({
    where: { id: userId },
    data: { name: formData.get('name') as string },
  })

  return { success: true }
}

'use server'

import { headers } from 'next/headers'

export async function sensitiveAction(formData: FormData) {
  const headersList = await headers()
  const csrfToken = headersList.get('x-csrf-token')

  // 验证 CSRF Token
  if (!validateCsrfToken(csrfToken)) {
    return { error: '无效的请求' }
  }

  // 执行操作
}

'use server'

import { z } from 'zod'
import { revalidatePath } from 'next/cache'
import { redirect } from 'next/navigation'
import { auth } from '@/lib/auth'
import { db } from '@/lib/db'

const PostSchema = z.object({
  title: z.string().min(1).max(200),
  content: z.string().min(1),
  published: z.boolean().default(false),
})

// 创建
export async function createPost(prevState: any, formData: FormData) {
  const session = await auth()
  if (!session?.user) {
    return { error: '请先登录' }
  }

  const validated = PostSchema.safeParse({
    title: formData.get('title'),
    content: formData.get('content'),
    published: formData.get('published') === 'true',
  })

  if (!validated.success) {
    return { errors: validated.error.flatten().fieldErrors }
  }

  const post = await db.post.create({
    data: {
      ...validated.data,
      authorId: session.user.id,
    },
  })

  revalidatePath('/posts')
  redirect(`/posts/${post.id}`)
}

// 更新
export async function updatePost(
  id: string,
  prevState: any,
  formData: FormData
) {
  const session = await auth()
  if (!session?.user) {
    return { error: '请先登录' }
  }

  const post = await db.post.findUnique({ where: { id } })
  if (!post || post.authorId !== session.user.id) {
    return { error: '无权修改' }
  }

  const validated = PostSchema.safeParse({
    title: formData.get('title'),
    content: formData.get('content'),
    published: formData.get('published') === 'true',
  })

  if (!validated.success) {
    return { errors: validated.error.flatten().fieldErrors }
  }

  await db.post.update({
    where: { id },
    data: validated.data,
  })

  revalidatePath('/posts')
  revalidatePath(`/posts/${id}`)

  return { success: true }
}

// 删除
export async function deletePost(id: string) {
  const session = await auth()
  if (!session?.user) {
    return { error: '请先登录' }
  }

  const post = await db.post.findUnique({ where: { id } })
  if (!post || post.authorId !== session.user.id) {
    return { error: '无权删除' }
  }

  await db.post.delete({ where: { id } })

  revalidatePath('/posts')
  redirect('/posts')
}

'use client'

import { useActionState } from 'react'
import { createPost, updatePost } from '@/app/actions/posts'

interface Post {
  id: string
  title: string
  content: string
  published: boolean
}

interface Props {
  post?: Post
}

export function PostEditor({ post }: Props) {
  const action = post ? updatePost.bind(null, post.id) : createPost

  const [state, formAction, isPending] = useActionState(action, null)

  return (
    <form action={formAction} className="space-y-4 max-w-2xl">
      <div>
        <label className="block font-medium mb-1">标题</label>
        <input
          name="title"
          defaultValue={post?.title}
          className="w-full border rounded px-3 py-2"
        />
        {state?.errors?.title && (
          <p className="text-red-500 text-sm">{state.errors.title[0]}</p>
        )}
      </div>

      <div>
        <label className="block font-medium mb-1">内容</label>
        <textarea
          name="content"
          defaultValue={post?.content}
          rows={10}
          className="w-full border rounded px-3 py-2"
        />
        {state?.errors?.content && (
          <p className="text-red-500 text-sm">{state.errors.content[0]}</p>
        )}
      </div>

      <label className="flex items-center gap-2">
        <input
          type="checkbox"
          name="published"
          value="true"
          defaultChecked={post?.published}
        />
        <span>立即发布</span>
      </label>

      {state?.error && <p className="text-red-500">{state.error}</p>}

      <button
        type="submit"
        disabled={isPending}
        className="bg-blue-600 text-white px-6 py-2 rounded disabled:opacity-50"
      >
        {isPending ? '保存中...' : post ? '更新' : '创建'}
      </button>
    </form>
  )
}