feature(proxy): support brotli compression

components/proxy/pom.xml

@@ -57,6 +57,31 @@
       <classifier>linux-aarch_64</classifier>
     </dependency>
 
+    <dependency>
+      <groupId>com.aayushatharva.brotli4j</groupId>
+      <artifactId>brotli4j</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>com.aayushatharva.brotli4j</groupId>
+      <artifactId>native-linux-x86_64</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>com.aayushatharva.brotli4j</groupId>
+      <artifactId>native-linux-aarch64</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>com.aayushatharva.brotli4j</groupId>
+      <artifactId>native-osx-x86_64</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>com.aayushatharva.brotli4j</groupId>
+      <artifactId>native-osx-aarch64</artifactId>
+    </dependency>
+
     <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>

components/proxy/src/main/java/com/hotels/styx/proxy/HttpCompressor.java

@@ -15,6 +15,7 @@
  */
 package com.hotels.styx.proxy;
 
+import io.netty.handler.codec.compression.CompressionOptions;
 import io.netty.handler.codec.http.HttpContentCompressor;
 import io.netty.handler.codec.http.HttpHeaderNames;
 import io.netty.handler.codec.http.HttpResponse;
@@ -53,6 +54,14 @@ public class HttpCompressor extends HttpContentCompressor {
             "application/json");
 
 
+    public HttpCompressor() {
+        this(0);
+    }
+
+    public HttpCompressor(int contentSizeThreshold) {
+        super(contentSizeThreshold, (CompressionOptions[]) null);
+    }
+
     private boolean shouldCompress(String contentType) {
         return ENCODING_TYPES.contains(contentType != null ? contentType.toLowerCase() : "");
     }

components/proxy/src/test/java/com/hotels/styx/proxy/BrotliTest.java

@@ -0,0 +1,18 @@
+package com.hotels.styx.proxy;
+
+import io.netty.handler.codec.compression.Brotli;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+
+public class BrotliTest {
+    @Test
+    @EnabledOnOs(value = { OS.LINUX, OS.MAC })
+    public void brotliCompressionIsAvailable() throws Throwable {
+        Brotli.ensureAvailability();
+        assertTrue(Brotli.isAvailable());
+    }
+}

components/proxy/src/test/java/com/hotels/styx/proxy/HttpCompressorTest.java

@@ -0,0 +1,82 @@
+/*
+  Copyright (C) 2013-2024 Expedia Inc.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+ */
+package com.hotels.styx.proxy;
+
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.http.DefaultFullHttpResponse;
+import io.netty.handler.codec.http.HttpContentEncoder;
+import io.netty.handler.codec.http.HttpResponse;
+import io.netty.handler.codec.http.HttpResponseStatus;
+import io.netty.handler.codec.http.HttpVersion;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.mockito.Answers.RETURNS_DEEP_STUBS;
+import static org.mockito.Mockito.mock;
+
+
+public class HttpCompressorTest {
+    private HttpCompressor compressor;
+    private ChannelHandlerContext ctx;
+
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        compressor = new HttpCompressor();
+        ctx = mock(ChannelHandlerContext.class, RETURNS_DEEP_STUBS);
+        compressor.handlerAdded(ctx);
+    }
+
+
+    @ParameterizedTest
+    @MethodSource("responseEncodingParameters")
+    public void validateResponseEncoding(final String acceptEncoding, final String contentType, final String expectedEncoding) throws Exception {
+        HttpResponse httpResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
+        httpResponse.headers().add("Content-Type", contentType);
+        HttpContentEncoder.Result result = compressor.beginEncode(httpResponse, acceptEncoding);
+        if (expectedEncoding == null) {
+            assertNull(result);
+        } else {
+            assertEquals(result.targetContentEncoding(), expectedEncoding);
+            assertNotNull(result.contentEncoder());
+        }
+    }
+
+    private static Stream<Arguments> responseEncodingParameters() {
+        // Note:  "br" is brotli compression
+        return Stream.of(
+            Arguments.of("br", "application/json", "br"),
+            Arguments.of("br", "image/jpeg", null),
+            Arguments.of("gzip", "application/json", "gzip"),
+            Arguments.of("gzip", "image/jpeg", null),
+            Arguments.of("br, gzip", "application/json", "br"),
+            Arguments.of("gzip, br", "application/json", "br"),
+            Arguments.of("", "application/json", null),
+            Arguments.of("", "image/jpeg", null),
+            Arguments.of("br, garbage", "application/json", "br"),
+            Arguments.of("gzip, garbage", "application/json", "gzip"),
+            Arguments.of("garbage", "application/json", null),
+            Arguments.of("?", "application/json", null),
+            Arguments.of(",", "application/json", null)
+        );
+    }
+}

pom.xml

@@ -110,6 +110,7 @@
     <janino.version>3.1.12</janino.version>
     <micrometer.version>1.12.3</micrometer.version>
     <netty.version>4.1.107.Final</netty.version>
+    <brotli4j.version>1.16.0</brotli4j.version>
     <okhttp.version>4.12.0</okhttp.version>
     <pcollections.version>3.0.5</pcollections.version>
     <reactive-streams.version>1.0.4</reactive-streams.version>
@@ -291,6 +292,36 @@
         <version>${guava.version}</version>
       </dependency>
 
+      <dependency>
+        <groupId>com.aayushatharva.brotli4j</groupId>
+        <artifactId>brotli4j</artifactId>
+        <version>${brotli4j.version}</version>
+      </dependency>
+
+      <dependency>
+        <groupId>com.aayushatharva.brotli4j</groupId>
+        <artifactId>native-linux-x86_64</artifactId>
+        <version>${brotli4j.version}</version>
+      </dependency>
+
+      <dependency>
+        <groupId>com.aayushatharva.brotli4j</groupId>
+        <artifactId>native-linux-aarch64</artifactId>
+        <version>${brotli4j.version}</version>
+      </dependency>
+
+      <dependency>
+        <groupId>com.aayushatharva.brotli4j</groupId>
+        <artifactId>native-osx-x86_64</artifactId>
+        <version>${brotli4j.version}</version>
+      </dependency>
+
+      <dependency>
+        <groupId>com.aayushatharva.brotli4j</groupId>
+        <artifactId>native-osx-aarch64</artifactId>
+        <version>${brotli4j.version}</version>
+      </dependency>
+
       <dependency>
         <groupId>net.bytebuddy</groupId>
         <artifactId>byte-buddy</artifactId>