Handle Etag and If-none-match headers and 304 responses

server.js

@@ -19,11 +19,21 @@ function getFox (req, res, version) {
   let width = parseInt(req.params.width) || 400
   if (width > 400) width = 400
   const seed = sanitize(req.params.seed) || uuid()
+  const etag = `W/${seed}`
+  const contentType = 'image/png'
+
+  res.set('Cache-Control', 'public; max-age=' + cacheTimeout)
+  res.set('Content-Type', contentType)
+  res.set('Etag', etag)
+
+  if (req.headers['if-none-match'] === etag) {
+      res.status(304).end('')
+      return
+  }
+
   const canvas = composeImage(width, width, seed, version)
-  const buffer = canvas.toBuffer('image/png')
-  res.set('Cache-Control', 'max-age=' + cacheTimeout)
-  res.set('Content-length', buffer.length)
-  res.type('png')
+  const buffer = canvas.toBuffer(contentType)
+  res.set('Content-Length', buffer.length)
   res.end(buffer, 'binary')
 }
 

test/test.js

@@ -50,6 +50,21 @@ describe('Foxy-moxy v1', () => {
 
 describe('Foxy-moxy v2', () => {
   describe('fox generation', () => {
+    it('should give 304 when presented with correct etag', (done) = async function () {
+      const uncachedResponse = await request(app)
+        .get(`/2/400/${testUID}`)
+        .expect('Content-Type', 'image/png')
+        .expect(200)
+
+      const cachedResponse = await request(app)
+        .get(`/2/400/${testUID}`)
+        .set('If-None-Match', uncachedResponse.headers.etag)
+        .expect('Content-Type', 'image/png')
+        .expect(304)
+
+      done()
+    })
+
     it('should respect widths < 400', (done) => {
       const width = 158
       request(app)