Next.js 14でトップ画面を作成し、ログイン・アカウント登録画面への遷移を実装する方法

$ npx create-next-app@14.0.4 tutorial-nextjs-14-auth

Need to install the following packages:
create-next-app@14.0.4
Ok to proceed? (y) y
✔ Would you like to use TypeScript? … No / Yes
✔ Would you like to use ESLint? … No / Yes
✔ Would you like to use Tailwind CSS? … No / Yes
✔ Would you like to use `src/` directory? … No / Yes
✔ Would you like to use App Router? (recommended) … No / Yes
✔ Would you like to customize the default import alias (@/*)? … No / Yes
Creating a new Next.js app in /Users/test/Documents/workspace/tutorial-nextjs-14-auth.

Using npm.

Initializing project with template: app-tw

Installing dependencies:
- react
- react-dom
- next

Installing devDependencies:
- typescript
- @types/node
- @types/react
- @types/react-dom
- autoprefixer
- postcss
- tailwindcss
- eslint
- eslint-config-next

$ npm run dev

npx shadcn@latest init

✔ Preflight checks.
✔ Verifying framework. Found Next.js.
✔ Validating Tailwind CSS.
✔ Validating import alias.
✔ Which style would you like to use? › New York
✔ Which color would you like to use as the base color? › Slate
✔ Would you like to use CSS variables for theming? … no / yes
✔ Writing components.json.
✔ Checking registry.
✔ Updating tailwind.config.ts
✔ Updating app/globals.css
✔ Installing dependencies.
✔ Created 1 file:
  - lib/utils.ts

Success! Project initialization completed.
You may now add components.

{
  "$schema": "https://ui.shadcn.com/schema.json",
  "style": "new-york",
  "rsc": true,
  "tsx": true,
  "tailwind": {
    "config": "tailwind.config.ts",
    "css": "app/globals.css",
    "baseColor": "slate",
    "cssVariables": true,
    "prefix": ""
  },
  "aliases": {
    "components": "@/components",
    "utils": "@/lib/utils",
    "ui": "@/components/ui",
    "lib": "@/lib",
    "hooks": "@/hooks"
  }
}

import { clsx, type ClassValue } from "clsx"
import { twMerge } from "tailwind-merge"

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs))
}

$ npx shadcn@latest add button

import * as React from "react"
import { Slot } from "@radix-ui/react-slot"
import { cva, type VariantProps } from "class-variance-authority"

import { cn } from "@/lib/utils"

const buttonVariants = cva(
  "inline-flex items-center justify-center whitespace-nowrap rounded-md text-sm font-medium transition-colors focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:pointer-events-none disabled:opacity-50",
  {
    variants: {
      variant: {
        default:
          "bg-primary text-primary-foreground shadow hover:bg-primary/90",
        destructive:
          "bg-destructive text-destructive-foreground shadow-sm hover:bg-destructive/90",
        outline:
          "border border-input bg-background shadow-sm hover:bg-accent hover:text-accent-foreground",
        secondary:
          "bg-secondary text-secondary-foreground shadow-sm hover:bg-secondary/80",
        ghost: "hover:bg-accent hover:text-accent-foreground",
        link: "text-primary underline-offset-4 hover:underline",
      },
      size: {
        default: "h-9 px-4 py-2",
        sm: "h-8 rounded-md px-3 text-xs",
        lg: "h-10 rounded-md px-8",
        icon: "h-9 w-9",
      },
    },
    defaultVariants: {
      variant: "default",
      size: "default",
    },
  }
)

export interface ButtonProps
  extends React.ButtonHTMLAttributes<HTMLButtonElement>,
    VariantProps<typeof buttonVariants> {
  asChild?: boolean
}

const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
  ({ className, variant, size, asChild = false, ...props }, ref) => {
    const Comp = asChild ? Slot : "button"
    return (
      <Comp
        className={cn(buttonVariants({ variant, size, className }))}
        ref={ref}
        {...props}
      />
    )
  }
)
Button.displayName = "Button"

export { Button, buttonVariants }

import { Button } from "@/components/ui/button"

export default function Home() {
  return (
    <main>
      <Button variant='destructive' size='lg'>テスト用のボタン</Button>
    </main>
  )
}

@tailwind base;
@tailwind components;
@tailwind utilities;

+ html,
+ body,
+ :root {
+   height: 100%;
+ }

以下、略

'use client'

import { useRouter } from 'next/navigation'
import { Button } from '../ui/button'

export const LoginButton = () => {
  const router = useRouter()
  const onClick = () => {
    router.push('/auth/login')
  }
  return (
    <Button onClick={onClick} className="w-full cursor-pointer">
      ログインする
    </Button>
  )
}

'use client'

import { useRouter } from 'next/navigation'
import { Button } from '../ui/button'

export const RegisterButton = () => {
  const router = useRouter()
  const onClick = () => {
    router.push('/auth/register')
  }
  return (
    <Button
      onClick={onClick}
      variant="secondary"
      className="w-full cursor-pointer"
    >
      アカウントを登録する
    </Button>
  )
}

import { LoginButton } from '@/components/auth/login-button'
import { RegisterButton } from '@/components/auth/register-button'

export default function Home() {
  return (
    <main className="flex h-full flex-col items-center justify-center bg-sky-100">
      <div className="space-y-6 text-center">
        <h1 className={'text-6xl font-semibold drop-shadow-md'}>
          トップ画面
        </h1>
        <p className="text-lg">Next.jsによる認証チュートリアル</p>
        <div>
          <LoginButton />
        </div>
        <div>
          <RegisterButton />
        </div>
      </div>
    </main>
  )
}

const LoginPage = () => {
  return <div>ログイン画面</div>
}

export default LoginPage

const RegisterPage = () => {
  return <div>アカウント登録画面</div>
}

export default RegisterPage