add 60 second cache (projectwallace#15)

* add 60 second cache

* add log to verify that item is taken from cache

* fix cache age

* rm log line

Author: bartveneman

index.js

@@ -2,6 +2,12 @@ const got = require('got')
 const chromium = require('chrome-aws-lambda')
 const normalizeUrl = require('normalize-url')
 const isUrl = require('is-url')
+const LRU = require('lru-cache')
+
+const cssCache = new LRU({
+	max: 500,
+	maxAge: 60 * 1000
+})
 
 const extractCss = async url => {
 	const browser = await chromium.puppeteer.launch({
@@ -76,13 +82,20 @@ module.exports = async (req, res) => {
 		)
 	}
 
+	if (cssCache.has(url)) {
+		res.setHeader('Content-Type', 'text/css')
+		res.statusCode = 200
+		return res.end(cssCache.get(url))
+	}
+
 	try {
 		const css = url.endsWith('.css')
 			? (await got(url)).body
 			: await extractCss(url)
 
 		res.setHeader('Content-Type', 'text/css')
 		res.statusCode = 200
+		cssCache.set(url, css)
 		return res.end(css)
 	} catch (error) {
 		res.statusCode = 500

package-lock.json

@@ -15,6 +15,7 @@
 		"chrome-aws-lambda": "^1.19.0",
 		"got": "^9.6.0",
 		"is-url": "^1.2.4",
+		"lru-cache": "^5.1.1",
 		"normalize-url": "^4.3.0",
 		"puppeteer": "^1.19.0",
 		"puppeteer-core": "^1.18.1"

package.json

@@ -65,6 +65,8 @@ <h2>Example request urls:</h2>
 			</li>
 		</ul>
 
+		<p>Please note that there is a 1 minute cache for each (normalized) url.</p>
+
 		<p>
 			Source code
 			<a href="https://github.com/bartveneman/extract-css" rel="noopener"