@hazae41/next-as-immutable
v1.0.1
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Create immutable Next.js webapps
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hazae41Readme
Next.js as Immutable
Create immutable Next.js webapps that are secure and resilient.
npm i -D @hazae41/next-as-immutableExamples
Here is a list of immutable Next.js webapps
- https://dstorage.hazae41.me/v0 / https://github.com/hazae41/dstorage
Setup
Install @hazae41/immutable
npm i @hazae41/immutableInstall @hazae41/next-as-immutable as devDependencies
npm i -D @hazae41/next-as-immutableModify your package.json to add node ./scripts/build.mjs in order to postprocess each production build
"scripts": {
"dev": "next dev",
"build": "next build && node ./scripts/build.mjs",
"start": "npx serve --config ../serve.json ./out",
"lint": "next lint"
},Modify your next.config.js to use exported build, immutable build ID, and immutable Cache-Control headers
const { withNextAsImmutable } = require("@hazae41/next-as-immutable")
module.exports = withNextAsImmutable({
/**
* Your Next.js config
*/
})Create a ./serve.json file with this content
{
"headers": [
{
"source": "**/*",
"headers": [
{
"key": "Cache-Control",
"value": "public, max-age=31536000, immutable"
}
]
}
]
}Create a ./public/start.html file with this content
<!DOCTYPE html>
<html>
<head>
<title>Loading...</title>
<script type="module">
try {
const latestScriptUrl = new URL(`/service_worker.latest.js`, location.href)
const latestScriptRes = await fetch(latestScriptUrl, { cache: "reload" })
if (!latestScriptRes.ok)
throw new Error(`Failed to fetch latest service-worker`)
if (latestScriptRes.headers.get("cache-control") !== "public, max-age=31536000, immutable")
throw new Error(`Wrong Cache-Control header for latest service-worker`)
const { pathname } = latestScriptUrl
const filename = pathname.split("/").at(-1)
const basename = filename.split(".").at(0)
const latestHashBytes = new Uint8Array(await crypto.subtle.digest("SHA-256", await latestScriptRes.arrayBuffer()))
const latestHashRawHex = Array.from(latestHashBytes).map(b => b.toString(16).padStart(2, "0")).join("")
const latestVersion = latestHashRawHex.slice(0, 6)
const latestVersionScriptPath = `${basename}.${latestVersion}.js`
const latestVersionScriptUrl = new URL(latestVersionScriptPath, latestScriptUrl)
localStorage.setItem("service_worker.current.version", JSON.stringify(latestVersion))
await navigator.serviceWorker.register(latestVersionScriptUrl, { updateViaCache: "all" })
await navigator.serviceWorker.ready
location.reload()
} catch (e) {
console.error(e)
alert(`Failed to load the latest version of the webapp.`)
return
}
</script>
</head>
</html>Create a ./scripts/build.mjs file with this content
import crypto from "crypto"
import fs from "fs"
import path from "path"
export function* walkSync(dir) {
const files = fs.readdirSync(dir, { withFileTypes: true })
for (const file of files) {
if (file.isDirectory()) {
yield* walkSync(path.join(dir, file.name))
} else {
yield path.join(dir, file.name)
}
}
}
/**
* Replace all .html files by start.html
*/
for (const pathname of walkSync(`./out`)) {
if (pathname === `./out/start.html`)
continue
const dirname = path.dirname(pathname)
const filename = path.basename(pathname)
if (!filename.endsWith(".html"))
continue
fs.copyFileSync(pathname, `./${dirname}/_${filename}`)
fs.copyFileSync(`./out/start.html`, pathname)
}
fs.rmSync(`./out/start.html`)
/**
* Find files to cache and compute their hash
*/
const files = new Array()
for (const pathname of walkSync(`./out`)) {
if (pathname === `./out/service_worker.latest.js`)
continue
const dirname = path.dirname(pathname)
const filename = path.basename(pathname)
if (fs.existsSync(`./${dirname}/_${filename}`))
continue
if (filename.endsWith(".html") && fs.existsSync(`./${dirname}/_${filename.slice(0, -5)}/index.html`))
continue
if (!filename.endsWith(".html") && fs.existsSync(`./${dirname}/_${filename}/index`))
continue
const text = fs.readFileSync(pathname)
const hash = crypto.createHash("sha256").update(text).digest("hex")
const relative = path.relative(`./out`, pathname)
files.push([`/${relative}`, hash])
}
/**
* Inject `files` into the service-worker and version it
*/
const original = fs.readFileSync(`./out/service_worker.latest.js`, "utf8")
const replaced = original.replaceAll("FILES", JSON.stringify(files))
const version = crypto.createHash("sha256").update(replaced).digest("hex").slice(0, 6)
fs.writeFileSync(`./out/service_worker.latest.js`, replaced, "utf8")
fs.writeFileSync(`./out/service_worker.${version}.js`, replaced, "utf8")Add this glue code to your service-worker
import { Immutable } from "@hazae41/immutable"
declare const self: ServiceWorkerGlobalScope
self.addEventListener("install", (event) => {
/**
* Auto-activate as the update was already accepted
*/
self.skipWaiting()
})
/**
* Declare global template
*/
declare const FILES: [string, string][]
/**
* Only cache on production
*/
if (process.env.NODE_ENV === "production") {
const cache = new Immutable.Cache(new Map(FILES))
self.addEventListener("activate", (event) => {
/**
* Uncache previous version
*/
event.waitUntil(cache.uncache())
/**
* Precache current version
*/
event.waitUntil(cache.precache())
})
/**
* Respond with cache
*/
self.addEventListener("fetch", (event) => cache.handle(event))
}Use Immutable.register(pathOrUrl) to register your service-worker in your code
e.g. If you were doing this
await navigator.serviceWorker.register("/service_worker.js")You now have to do this (always use .latest.js)
await Immutable.register("/service_worker.latest.js")You can use the returned async function to update your app
navigator.serviceWorker.addEventListener("controllerchange", () => location.reload())
const update = await Immutable.register("/service_worker.latest.js")
if (update != null) {
/**
* Update available
*/
button.onclick = async () => await update()
return
}
await navigator.serviceWorker.readyYou now have an immutable but updatable Next.js app!