Page Renderer Save
Write HTML-pages as Clojure maps, with all that meta. Bindings for garden and hiccup. Helps with PWA generation too. Offline-ready web apps with service workers, social meta and async stylesheets.
page-renderer
Create offline-ready web apps with service workers, social meta, async assets and cache-busting.
So it's like a layer of knowledge about the real world on top of Hiccup.
Features
Out of the box:
- Meta for SEO, Twitter, Facebook (Open Graph), link sharing
- Precaching Service Worker generation based on Workbox
- Clojure stylesheets with
garden - Clojure markup rendered with
hiccup - Built-in cache-busting for assets
- Async stylesheets loading
- And also: that responsive
viewport=somethingmeta tag and language tag
Requirements
Java 8 or later.
Usage
1. Define a page
(ns pages.home)
(defn page [req]
;; essentials
{:title "Lightpad"
:body [:body.page [:h1 "Ah, a Page!"]]
:head-tags [[:meta {:name "custom" :property "stuff"}]]
:stylesheet-async "large-stuff.css" ; injects an async renderer(s)
:script "/app.js" ; async by default
:garden-css [:h1 {:font-size :20px}] ; critical path css (or just inline the whole thing)
:garden-css-cache? true ; uses simple-dimple memoize cache, so only lives in the lifecycle
;; seo and meta
:description "Like a notepad but cyberpunk"
:twitter-site "@lightpad_ai"
;; images
:favicon "https://lightpad.ai/favicon.png"
:og-image "https://lightpad.ai/og-image.png"
;; PWA stuff
:manifest true
:lang "en"
:theme-color "hsl(0, 0%, 96%)"
:service-worker "/service-worker.js" ; will inject also a service worker lifecycle script
:sw-default-url "/app"
:sw-add-assets ["/icons/fonts/icomoon.woff", "/lightning-150.png"]})
2. Wire it up to your routes (e.g. Compojure)
(ns server
(:require [page-renderer.api :as pr]
[compojure.core :refer [defroutes GET]]
[pages.home :as p]))
(defroutes
(GET "/" req
{:status 200
:headers {"Content-Type" "text/html"}
:body (pr/render-page (p/page req)})
(GET "/service-worker.js" req
{:status 200
:headers {"Content-Type" "text/javascript"}
; will generate a simple Workbox-based service worker on the fly with cache-busting
:body (pr/generate-service-worker (p/page req))})
(GET "/quicker-way" req (pr/respond-page (p/page req))))
3. Celebrate
Page output
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<link href="/favicon.png" rel="icon" type="image/png">
<meta content="width=device-width, initial-scale=1, maximum-scale=1" name="viewport">
<title>Page</title>
<meta content="Some bird stuff" name="description">
<meta content="summary" name="twitter:card">
<meta content="birds.org" name="twitter:site">
<meta content="Some bird stuff" name="twitter:description">
<meta content="https://birds.org/great-tit.png?mtime=1560280129605" name="twitter:image">
<meta content="Page" property="og:title">
<meta content="Some bird stuff" property="og:description">
<meta content="https://birds.org/great-tit.png?mtime=1560280129605" property="og:image">
<style id="inline-css--garden">
h1 {
font-size: 20px;
}
</style>
<!-- Service Worker Lifecycle Snippet -->
<script>
import { Workbox } from 'https://storage.googleapis.com/workbox-cdn/releases/4.1.0/workbox-window.prod.mjs';
const promptStr = 'New version of the application is downloaded, do you want to update? May take two reloads.';
function createUIPrompt(opts) {
if (confirm(promptStr)) {
opts.onAccept()
}
}
if ('serviceWorker' in navigator) {
const wb = new Workbox('/service-worker.js');
wb.addEventListener('waiting', (event) => {
const prompt = createUIPrompt({
onAccept: async () => {
wb.addEventListener('activated', (event) => {
console.log('sw-init: activated')
window.location.reload();
})
wb.addEventListener('controlling', (event) => {
console.log('sw-init: controlling')
});
wb.messageSW({type: 'SKIP_WAITING'});
}
})
});
wb.register();
}
</script>
</head>
<body class="page">
<h1>Ah, a Page!</h1>
<script>
(function(){
var link = document.createElement('link');
link.rel='stylesheet';
link.href='large-stuff.css';
link.type='text/css';
document.head.appendChild(link);
})()
</script>
</body>
</html>
Service Worker
importScripts('https://storage.googleapis.com/workbox-cdn/releases/4.3.1/workbox-sw.js')
workbox.precaching.precacheAndRoute([
{ url: '/heavy-stuff.css', revision: 'file-hash' },
{ url: '/fonts/icomoon.woff', revision: 'file-hash' },
{ url: '/lightpad/compiled/app.js', revision: 'file-hash' },
{ url: '/favicon.png', revision: 'file-hash' },
{ url: '/app', revision: 'file-hash' }
], { ignoreURLParametersMatching: [/hash/] })
workbox.routing.registerNavigationRoute(
workbox.precaching.getCacheKeyForURL('/app'), {
whitelist: [ /^\/app/ ],
blacklist: [ /^\/app\/service-worker.js/ ]
}
)
workbox.routing.setCatchHandler(({event}) => {
console.log('swm: event ', event)
})
addEventListener('message', (event) => {
if (event.data && event.data.type === 'SKIP_WAITING') {
console.log('swm: skipping waiting')
skipWaiting()
}
})
self.addEventListener('activate', () => {
console.log('swm: activated')
})
self.addEventListener('install', () => {
console.log('swm: installed')
})
API
Use page-renderer.api namespace.
(defn ^String render-page [renderable])
Produces an html string.
(defn ^String generate-service-worker [renderable])
Produces a JavaScript ServiceWorker script text. Service worker will additionally load Workbox script.
(defn ^Map respond-page [renderable])
Produces Ring compatible response map with status 200.
(defn ^Map respond-service-worker [^Map renderable])
Produces Ring compatible response map with status 200.
renderable – is a map that may have the following fields
Mains
-
^Vector :body- a vector for Hiccup to render into HTML of the document's body -
^String :title- content for title tag -
^String :favicon- favicon's url -
^String :og-image- Open Graph image URL -
^String :script- script name, will be loaded asynchronously -
^String :stylesheet- stylesheet filename, will be plugged into the head, will cause browser waiting for download.
Assets
-
^String :stylesheet-async- stylesheet filename, will be loaded asynchronously by script. -
^String :garden-css- data structure for Garden CSS -
^String :garden-css-caching?- enable memoize Garden CSS (default: false) -
^String :script-sync- script name, will be loaded synchronously -
^String :js-module- entry point for JS modules. If you prefer your scripts to be served as modules -
^Boolean :skip-cachebusting?- will skip automatic cachebusting if set. Defaults to false. -
^String :on-dom-interactive-js- a js snippet to run once DOM is interactive or ready. -
^String/Collection<String> :stylesheet-inline- stylesheet filename, will be inlined into the head.
PWA related
-
^String :link-image-src- url to image-src -
^String :link-apple-icon- url to image used for apple-touch-icon link -
^String :link-apple-startup-image- url to image used for apple-touch-startup-image link -
^String :theme-color- theme color for PWA (defaults to white) -
^String/Boolean :manifest- truthy value will add a manifest link If a string is passed – it'll be treated as a manifest url. Otherwise '/manifest.json' will be specified. -
^String/Boolean :service-worker- service worker url, defaults to /service-worker.js -
^String :sw-default-url– application default url. Must be an absolute path like '/app'. Defaults to '/'. Will be used in a regexp. -
^List<String> :sw-add-assets- a collection of additional assets you want to precache, like ["/fonts/icon-font.woff" "/logo.png"]
More meta
-
^String :lang- when provided will render a meta tag and a document attribute for page language. -
^String :meta-title- content for the title tag (preferred) -
^String :meta-keywords- content for the keywords tag -
^String :meta-description- meta description -
^Map :meta-props– meta which must be rendered as props {'fb:app_id' 123} -
^String :head-tags- data structure to render into HTML of the document's head
Open Graph meta (@link https://ogp.me)
-
^String :og-title- OpenGraph title -
^String :og-description- OpenGraph description -
^String :og-image- absolute url to image for OpenGraph -
^String :og-type- OpenGraph object type -
^String :og-url- OpenGraph page permalink
Twitter meta (@link https://developer.twitter.com/en/docs/tweets/optimize-with-cards/guides/getting-started)
-
^String :twitter-site- Twitter @username. Required for all Twitter meta to render -
^String :twitter-creator- Twitter @username. -
^Keyword :twitter-card-type- Twitter card type one of #{:summary :summary_large_image :app :player} -
^String :twitter-description- Twitter card description -
^String :twitter-image- Twitter image link. Twitter images are useu -
^String :twitter-image-alt- Twitter image alt
Service Worker generation
page-renderer allows you to produce a full-blown offline-ready
PWA fast.
Your users will be able to "install" it as a PWA app on mobile platforms or as Chrome
app on desktop platforms. All you need to do is just add another route to your scheme.
How it works
If you use service-worker field then page-renderer will generate
a precaching service worker. The worker utilizes
Workbox (by Google)
and will precache all the assets that you've defined in renderable, and will be able
to serve them offline. It also does proper cache-busting with hashes.
page-renderer will also inject a service worker lifecycle management script into
your page so that your users will be prompted to download a newer version of your
website when it's ready.
How cache-busting works here
page-renderer provides very basic, but bulletproof cache-busting by providing
a url param with content-hash (or last modification timestamp), like /file?hash=abec112221122.
For every stylesheet, script and image on resource paths – it will generate
a content hash. If the file can't be found on the classpath
or inside a local resources/public directory it will receive the library load time,
roughly equaling the application start time.
Where to see in action:
- Liverm0r/PWA-clojure – PWA example by Artur Dumchev
- Plus Minus game by Artur Dumchev. Repo
Personally I use it for all my website projects including:
- Lightpad.ai – includes generated service worker, installable PWA
- Spacegangster.io – my website
Troubleshooting
If you are using a frontend proxy server like Nginx – don't forget to prevent it from serving service-worker as a static asset. My js assets block looks like this
location ~ ^(?!/service-worker).*\.(?:js|css|svg)$ {
etag off;
expires 1y;
gzip_vary on;
add_header Cache-Control "public";
access_log off;
}
Also note the switched off etag. If you use page-renderer you can turn off etag and use expires header only for more aggressive caching and preventing avoidable requests. See details in this thread on StackOverflow.
License
Copyright © 2019 Ivan Fedorov
Distributed under the MIT License.
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