Add Temporal example

examples/with-temporal/.gitignore

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+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.js
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# local env files
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+# vercel
+.vercel
+
+# compiled files
+temporal/lib

examples/with-temporal/.nvmrc

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+16

examples/with-temporal/README.md

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+# Temporal Next.js example
+
+> “Temporal does to backend and infra what React did to frontend. If you're in the React world, you've forgotten about manually adding and removing DOM elements, updating attributes and their quirks, hooking up event listeners… It's not only been a boost in developer experience, but most importantly in consistency and reliability. In the backend world, this reliability problem is absurdly amplified as monoliths break into SaaS services, functions, containers… You have to carefully manage and create queues to capture each side effect, ensure everything gets retried, state is scattered all over the place. Temporal's engine is quite complex, much like React's, but the surface exposed to the developer is a beautiful "render()" function to organize your backend workflows.”
+> —[Guillermo Rauch](https://twitter.com/rauchg/status/1316808665370820609)
+
+**Table of Contents**
+
+- [Starter project](#starter-project)
+- [Deploy your own](#deploy-your-own)
+  - [Web server](#web-server)
+  - [Worker](#worker)
+  - [Temporal Server](#temporal-server)
+- [How to use](#how-to-use)
+
+## Starter project
+
+This is a starter project for creating resilient Next.js applications with [Temporal](https://temporal.io/). Whenever our [API routes](https://nextjs.org/docs/api-routes/introduction) need to do any of the below, we can greatly increase our code's fault tolerance by using Temporal:
+
+- Perform a series of network requests (to a database, another function, an internal service, or an external API), any of which may fail (Temporal will automatically set timeouts and retry, as well as remember the state of execution in the event of power loss)
+- Do something that takes longer than 5 or 30 seconds (Vercel's serverless function execution [time limit](https://vercel.com/docs/platform/limits) for Hobby or Enterprise accounts, respectively)
+- Do something after a certain amount of time, like an hour or a month (or periodically—once an hour, or once a month)
+
+The starter project has this logic flow:
+
+- Load [`localhost:3000`](http://localhost:3000)
+- Click the “Create order” button
+- The click handler POSTs a new order object to `/api/orders`
+- The serverless function at `pages/api/orders/index.ts`:
+  - Parses the order object
+  - Tells Temporal Server to start a new Order Workflow, and passes the user ID and order info
+  - Waits for the Workflow result and returns it to the client
+- Temporal Server puts Workflow tasks on the `orders` task queue
+- The Worker executes chunks of Workflow and Activity code. The Activity code logs:
+
+```
+Reserving 2 of item B102
+Charging user 123 for 2 of item B102
+```
+
+- The Workflow completes and Temporal Server sends the result back to the serverless function, which returns it to the client, which alerts the result.
+
+Here is the Temporal code:
+
+- The Workflow: `temporal/src/workflows/order.ts`
+- The Activites: `temporal/src/activities/{payment|inventory}.ts`
+
+## Deploy your own
+
+### Web server
+
+The Next.js server can be deployed using [Vercel](https://vercel.com?utm_source=github&utm_medium=readme&utm_campaign=next-example):
+
+[![Deploy with Vercel](https://vercel.com/button)](https://vercel.com/new/git/external?repository-url=https://github.com/vercel/next.js/tree/canary/examples/with-temporal&project-name=with-temporal&repository-name=with-temporal)
+
+### Worker
+
+One or more instances of the worker (`temporal/src/worker/`) can be deployed to a PaaS (each worker is a long-running Node process, so it can't run on a FaaS/serverless platform).
+
+### Temporal Server
+
+Temporal Server is a cluster of internal services, a database of record, and a search database. It can be run locally with Docker Compose and [deployed](https://docs.temporal.io/docs/server/production-deployment) with a container orchestration service like Kubernetes or ECS.
+
+## How to use
+
+Execute [`create-next-app`](https://github.com/vercel/next.js/tree/canary/packages/create-next-app) with [npm](https://docs.npmjs.com/cli/init) or [Yarn](https://yarnpkg.com/lang/en/docs/cli/create/) to bootstrap the example:
+
+```bash
+npx create-next-app --example with-temporal next-temporal-app
+# or
+yarn create next-app --example with-temporal next-temporal-app
+```
+
+The Temporal Node SDK requires [Node `>= 14`, `node-gyp`, and Temporal Server](https://docs.temporal.io/docs/node/getting-started#step-0-prerequisites). Once you have everything installed, you can develop locally with the below commands in four different shells:
+
+In the Temporal Server docker directory:
+
+```bash
+docker-compose up
+```
+
+In the `next-temporal-app/` directory:
+
+```bash
+npm run dev
+```
+
+```bash
+npm run build-worker.watch
+```
+
+```bash
+npm run start-worker
+```

examples/with-temporal/components/Layout.tsx

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+import React, { ReactNode } from 'react'
+import Link from 'next/link'
+import Head from 'next/head'
+
+type Props = {
+  children?: ReactNode
+  title?: string
+}
+
+const Layout = ({ children, title = 'This is the default title' }: Props) => (
+  <div>
+    <Head>
+      <title>{title}</title>
+      <meta charSet="utf-8" />
+      <meta name="viewport" content="initial-scale=1.0, width=device-width" />
+    </Head>
+    <header>
+      <nav>
+        <Link href="/">
+          <a>Home</a>
+        </Link>{' '}
+        |{' '}
+        <Link href="/about">
+          <a>About</a>
+        </Link>{' '}
+      </nav>
+    </header>
+    {children}
+    <footer>
+      <hr />
+      <span>I'm here to stay (Footer)</span>
+    </footer>
+  </div>
+)
+
+export default Layout

examples/with-temporal/components/List.tsx

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+import * as React from 'react'
+import ListItem from './ListItem'
+import { User } from '../interfaces'
+
+type Props = {
+  items: User[]
+}
+
+const List = ({ items }: Props) => (
+  <ul>
+    {items.map((item) => (
+      <li key={item.id}>
+        <ListItem data={item} />
+      </li>
+    ))}
+  </ul>
+)
+
+export default List

examples/with-temporal/components/ListDetail.tsx

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+import * as React from 'react'
+
+import { User } from '../interfaces'
+
+type ListDetailProps = {
+  item: User
+}
+
+const ListDetail = ({ item: user }: ListDetailProps) => (
+  <div>
+    <h1>Detail for {user.name}</h1>
+    <p>ID: {user.id}</p>
+  </div>
+)
+
+export default ListDetail

examples/with-temporal/components/ListItem.tsx

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+import React from 'react'
+import Link from 'next/link'
+
+import { User } from '../interfaces'
+
+type Props = {
+  data: User
+}
+
+const ListItem = ({ data }: Props) => (
+  <Link href="/users/[id]" as={`/users/${data.id}`}>
+    <a>
+      {data.id}: {data.name}
+    </a>
+  </Link>
+)
+
+export default ListItem

examples/with-temporal/interfaces/index.ts

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+// You can include shared interfaces/types in a separate file
+// and then use them in any component by importing them. For
+// example, to import the interface below do:
+//
+// import { User } from 'path/to/interfaces';
+
+export type User = {
+  id: number
+  name: string
+}

examples/with-temporal/next-env.d.ts

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+/// <reference types="next" />
+/// <reference types="next/types/global" />
+/// <reference types="next/image-types/global" />
+
+// NOTE: This file should not be edited
+// see https://nextjs.org/docs/basic-features/typescript for more information.

examples/with-temporal/package.json

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+{
+  "private": true,
+  "scripts": {
+    "dev": "next",
+    "build": "next build",
+    "start": "next start",
+    "type-check": "tsc",
+    "build-worker": "tsc --build temporal/src/worker/tsconfig.json",
+    "build-worker.watch": "tsc --build --watch temporal/src/worker/tsconfig.json",
+    "start-worker": "nodemon -w temporal/lib/ -x 'node temporal/lib/worker || (sleep 5; touch temporal/lib/worker/index.js)'"
+  },
+  "dependencies": {
+    "@babel/core": "^7.15.0",
+    "next": "latest",
+    "react": "^17.0.2",
+    "react-dom": "^17.0.2",
+    "temporalio": "^0.3.0"
+  },
+  "devDependencies": {
+    "@tsconfig/node14": "^1.0.0",
+    "@types/node": "^12.12.21",
+    "@types/react": "^17.0.2",
+    "@types/react-dom": "^17.0.1",
+    "nodemon": "^2.0.12",
+    "typescript": "^4.3.5"
+  }
+}

examples/with-temporal/pages/about.tsx

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+import type { NextPage } from 'next'
+import Link from 'next/link'
+import Layout from '../components/Layout'
+
+const AboutPage: NextPage = () => (
+  <Layout title="About | Next.js + Temporal Example">
+    <h1>About</h1>
+    <p>This is the about page</p>
+    <p>
+      <Link href="/">
+        <a>Go home</a>
+      </Link>
+    </p>
+  </Layout>
+)
+
+export default AboutPage

examples/with-temporal/pages/api/orders/index.ts

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+import { NextApiRequest, NextApiResponse } from 'next'
+import { Connection, WorkflowClient } from '@temporalio/client'
+import { Order } from '../../../temporal/src/interfaces/workflows'
+
+export type Data = {
+  result: string
+}
+
+export default async function handler(
+  req: NextApiRequest,
+  res: NextApiResponse<Data>
+) {
+  if (req.method !== 'POST') {
+    res.send({ result: 'Error code 405: use POST' })
+    return
+  }
+
+  const userId: string = req.headers.authorization // FIXME insecure 😄
+  const { itemId, quantity } = JSON.parse(req.body)
+
+  // Connect to our Temporal Server running locally in Docker
+  const connection = new Connection()
+  const client = new WorkflowClient(connection.service)
+  const example = client.stub<Order>('order', { taskQueue: 'orders' })
+
+  // Execute the Order workflow and wait for it to finish
+  const result = await example.execute(userId, itemId, quantity)
+  res.status(200).json({ result })
+}

examples/with-temporal/pages/index.tsx

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+import Link from 'next/link'
+import Layout from '../components/Layout'
+import { Data } from './api/orders'
+
+const IndexPage = () => (
+  <Layout title="Home | Next.js + Temporal Example">
+    <h1>Hello Next.js 👋</h1>
+
+    <button
+      onClick={async () => {
+        const newOrder = { itemId: 'B102', quantity: 2 }
+        const response = await fetch('/api/orders', {
+          method: 'POST',
+          headers: { Authorization: '123' },
+          body: JSON.stringify(newOrder),
+        })
+        const data: Data = await response.json()
+        console.log(data)
+        alert(data.result)
+      }}
+    >
+      Create order
+    </button>
+
+    <p>
+      <Link href="/about">
+        <a>About</a>
+      </Link>
+    </p>
+  </Layout>
+)
+
+export default IndexPage

examples/with-temporal/temporal/src/activities/inventory.ts

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+export async function checkAndDecrementInventory(
+  itemId: string,
+  quantity: number
+): Promise<boolean> {
+  // TODO a database request that—in a single operation or transaction—checks
+  // whether there are `quantity` items remaining, and if so, decreases the
+  // total. Something like:
+  // const result = await db.collection('items').updateOne(
+  //   { _id: itemId, numAvailable: { $gte: quantity } },
+  //   { $inc: { numAvailable: -quantity } }
+  // )
+  // return result.modifiedCount === 1
+  console.log(`Reserving ${quantity} of item ${itemId}`)
+  return true
+}
+
+export async function incrementInventory(
+  itemId: string,
+  quantity: number
+): Promise<boolean> {
+  // TODO increment inventory:
+  // const result = await db.collection('items').updateOne(
+  //   { _id: itemId },
+  //   { $inc: { numAvailable: quantity } }
+  // )
+  // return result.modifiedCount === 1
+  return true
+}