From 2e425b52238cf7b13ec1689492cbffb0c5e5951a Mon Sep 17 00:00:00 2001
From: David Evans <davidje13@users.noreply.github.com>
Date: Mon, 25 Oct 2021 22:18:40 +0100
Subject: [PATCH] Add cache-control stale-while-revalidate config

---
 bin/server.js                | 20 +++++++++++-----
 bin/server/RequestHandler.js | 45 +++++++++++++++++++++++++-----------
 2 files changed, 45 insertions(+), 20 deletions(-)

diff --git a/bin/server.js b/bin/server.js
index 7bde87b..8445ed3 100755
--- a/bin/server.js
+++ b/bin/server.js
@@ -32,18 +32,26 @@ function devMapper(file, type, data) {
 	}
 }
 
+const MINUTE = 60;
+const HOUR = MINUTE * 60;
+const DAY = HOUR * 24;
+const YEAR = DAY * 365;
+
 const STATIC_CACHE = {
-	maxAgeSeconds: 10 * 60, // 10 minutes
-	staleSeconds: 60 * 60 * 24 * 365, // 1 year
+	maxAgeSeconds: 10 * MINUTE,
+	staleIfErrorSeconds: YEAR,
+	staleWhileRevalidateSeconds: YEAR,
 };
 const RENDER_CACHE = {
 	immutable: true,
-	maxAgeSeconds: 60 * 60 * 24 * 30, // 1 month
-	staleSeconds: 60 * 60 * 24 * 365, // 1 year
+	maxAgeSeconds: 30 * DAY,
+	staleIfErrorSeconds: YEAR,
+	staleWhileRevalidateSeconds: YEAR,
 };
 const PREVIEW_CACHE = {
-	maxAgeSeconds: 60 * 60, // 1 hour
-	staleSeconds: 60 * 60 * 24, // 1 day
+	maxAgeSeconds: HOUR,
+	staleIfErrorSeconds: DAY,
+	staleWhileRevalidateSeconds: DAY,
 };
 const SKETCH_CSS_SHA = 'sha256-s7UPtBgvov5WNF9C1DlTZDpqwLgEmfiWha5a5p/Zn7E=';
 
diff --git a/bin/server/RequestHandler.js b/bin/server/RequestHandler.js
index 82c5d34..a490862 100644
--- a/bin/server/RequestHandler.js
+++ b/bin/server/RequestHandler.js
@@ -1,20 +1,42 @@
+function makeCacheControlHeader({
+	mode = 'public',
+	maxAgeSeconds = -1,
+	staleIfErrorSeconds = -1,
+	staleWhileRevalidateSeconds = -1,
+	immutable = false,
+}) {
+	const parts = [];
+	if(mode) {
+		parts.push(mode);
+	}
+	if(maxAgeSeconds >= 0) {
+		parts.push(`max-age=${maxAgeSeconds}`);
+	}
+	if(staleIfErrorSeconds >= 0) {
+		parts.push(`stale-if-error=${staleIfErrorSeconds}`);
+	}
+	if(staleWhileRevalidateSeconds >= 0) {
+		parts.push(`stale-while-revalidate=${staleWhileRevalidateSeconds}`);
+	}
+	if(immutable) {
+		parts.push('immutable');
+	}
+	return parts.join(', ');
+}
+
 class RequestHandler {
 	constructor(method, matcher, handleFn) {
 		this.method = method;
 		this.matcher = matcher;
 		this.handleFn = handleFn;
-		this.cacheMaxAge = 0;
-		this.cacheStale = 0;
-		this.immutable = false;
+		this.cacheControl = '';
 		this.allowAllOrigins = false;
 		this.staticHeaders = [];
 		this.info = `Custom handler at ${this.method} ${this.matcher}`;
 	}
 
-	setCache({ maxAgeSeconds = 0, staleSeconds = 0, immutable = false }) {
-		this.cacheMaxAge = maxAgeSeconds;
-		this.cacheStale = staleSeconds;
-		this.immutable = immutable;
+	setCache(options) {
+		this.cacheControl = options ? makeCacheControlHeader(options) : '';
 		return this;
 	}
 
@@ -32,13 +54,8 @@ class RequestHandler {
 		if(this.allowAllOrigins) {
 			res.setHeader('Access-Control-Allow-Origin', '*');
 		}
-		if(this.cacheMaxAge > 0) {
-			res.setHeader(
-				'Cache-Control',
-				`public, max-age=${this.cacheMaxAge}` +
-				(this.cacheStale ? `, stale-if-error=${this.cacheStale}` : '') +
-				(this.immutable ? ', immutable' : '')
-			);
+		if(this.cacheControl) {
+			res.setHeader('Cache-Control', this.cacheControl);
 		}
 		for(const header of this.staticHeaders) {
 			res.setHeader(header.name, header.value);