fix: content encoding priorities (#258)

* fix: content encoding priorities

* test: add corresponding tests

---------

Co-authored-by: Shishir Karanth <shishira.k@cimpress.com>

index.js

@@ -142,7 +142,7 @@ function processCompressParams (opts) {
   params.encodings = Array.isArray(opts.encodings)
     ? supportedEncodings
       .filter(encoding => opts.encodings.includes(encoding))
-      .sort((a, b) => opts.encodings.indexOf(a) - supportedEncodings.indexOf(b))
+      .sort((a, b) => opts.encodings.indexOf(a) - opts.encodings.indexOf(b))
     : supportedEncodings
 
   return params
@@ -174,7 +174,7 @@ function processDecompressParams (opts) {
   params.encodings = Array.isArray(opts.requestEncodings)
     ? supportedEncodings
       .filter(encoding => opts.requestEncodings.includes(encoding))
-      .sort((a, b) => opts.requestEncodings.indexOf(a) - supportedEncodings.indexOf(b))
+      .sort((a, b) => opts.requestEncodings.indexOf(a) - opts.requestEncodings.indexOf(b))
     : supportedEncodings
 
   if (opts.forceRequestEncoding) {

test/global-compress.test.js

@@ -2703,7 +2703,7 @@ test('It should sort and follow custom `encodings` options', async (t) => {
   const fastify = Fastify()
   await fastify.register(compressPlugin, {
     global: true,
-    encodings: ['gzip', 'br']
+    encodings: ['br', 'gzip']
   })
 
   fastify.get('/', (request, reply) => {
@@ -2725,6 +2725,35 @@ test('It should sort and follow custom `encodings` options', async (t) => {
   t.equal(payload.toString('utf-8'), file)
 })
 
+test('It should sort and prefer the order of custom `encodings` options', async (t) => {
+  t.plan(2)
+
+  const fastify = Fastify()
+  await fastify.register(compressPlugin, {
+    global: true,
+    encodings: ['gzip', 'deflate', 'br']
+  })
+
+  fastify.get('/', (request, reply) => {
+    reply
+      .type('text/plain')
+      .compress(createReadStream('./package.json'))
+  })
+
+  const response = await fastify.inject({
+    url: '/',
+    method: 'GET',
+    headers: {
+      'accept-encoding': 'hello,gzip,br'
+    }
+  })
+
+  const file = readFileSync('./package.json', 'utf8')
+  const payload = zlib.gunzipSync(response.rawPayload)
+  t.equal(response.headers['content-encoding'], 'gzip')
+  t.equal(payload.toString('utf-8'), file)
+})
+
 test('It should sort and follow custom `requestEncodings` options', async (t) => {
   t.plan(2)