Added /discovery/list API endpoint (#352)

Author: devgianlu

api/README.md

@@ -45,6 +45,10 @@ All the endpoints will respond with `200` if successful or:
 - `POST /instance/terminate` Terminates the API server.
 - `POST /instance/close` Closes the current session (and player).
 
+### Discovery (Spotify Connect)
+- `POST /discovery/list` List all Spotify Connect devices on the network.
+
+
 ### Events
 You can subscribe for players events by creating a WebSocket connection to `/events`.
 The currently available events are:

api/src/main/java/xyz/gianlu/librespot/api/ApiServer.java

@@ -46,6 +46,7 @@ public ApiServer(int port, @NotNull String host, @NotNull SessionWrapper wrapper
                 .post("/profile/{user_id}/{action}", new ProfileHandler(wrapper))
                 .post("/web-api/{endpoint}", new WebApiHandler(wrapper))
                 .post("/instance/{action}", InstanceHandler.forSession(this, wrapper))
+                .post("/discovery/{action}", new DiscoveryHandler())
                 .get("/events", events)
                 .setFallbackHandler(new PathHandler(ResponseCodeHandler.HANDLE_404)
                         .addPrefixPath("/web-api", new WebApiHandler(wrapper)));

api/src/main/java/xyz/gianlu/librespot/api/handlers/DiscoveryHandler.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2021 devgianlu
+ *
+ * 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 xyz.gianlu.librespot.api.handlers;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonObject;
+import io.undertow.server.HttpHandler;
+import io.undertow.server.HttpServerExchange;
+import io.undertow.util.Headers;
+import xyz.gianlu.librespot.ZeroconfServer;
+import xyz.gianlu.librespot.api.Utils;
+import xyz.gianlu.zeroconf.DiscoveredService;
+import xyz.gianlu.zeroconf.Zeroconf;
+
+import java.util.Deque;
+import java.util.Map;
+
+/**
+ * @author devgianlu
+ */
+public final class DiscoveryHandler implements HttpHandler {
+    private final Zeroconf zeroconf;
+
+    public DiscoveryHandler() {
+        zeroconf = new Zeroconf();
+    }
+
+    @Override
+    public void handleRequest(HttpServerExchange exchange) throws Exception {
+        exchange.startBlocking();
+        if (exchange.isInIoThread()) {
+            exchange.dispatch(this);
+            return;
+        }
+
+        Map<String, Deque<String>> params = Utils.readParameters(exchange);
+        String action = Utils.getFirstString(params, "action");
+        if (action == null) {
+            Utils.invalidParameter(exchange, "action");
+            return;
+        }
+
+        switch (action) {
+            case "list":
+                JsonArray array = new JsonArray();
+                for (DiscoveredService service : zeroconf.discover(ZeroconfServer.SERVICE, "tcp", ".local")) {
+                    JsonObject obj = new JsonObject();
+                    obj.addProperty("name", service.name);
+                    obj.addProperty("target", service.target);
+                    obj.addProperty("port", service.port);
+                    array.add(obj);
+                }
+
+                exchange.getResponseHeaders().put(Headers.CONTENT_TYPE, "application/json");
+                exchange.getResponseSender().send(array.toString());
+                break;
+            default:
+                Utils.invalidParameter(exchange, "action");
+                break;
+        }
+    }
+}

lib/pom.xml

@@ -116,7 +116,7 @@
         <dependency>
             <groupId>xyz.gianlu.zeroconf</groupId>
             <artifactId>zeroconf</artifactId>
-            <version>1.1.3</version>
+            <version>1.2.1</version>
         </dependency>
 
         <!-- HTTP -->

lib/src/main/java/xyz/gianlu/librespot/ZeroconfServer.java

@@ -54,6 +54,7 @@
  * @author Gianlu
  */
 public class ZeroconfServer implements Closeable {
+    public static final String SERVICE = "spotify-connect";
     private final static int MAX_PORT = 65536;
     private final static int MIN_PORT = 1024;
     private static final Logger LOGGER = LoggerFactory.getLogger(ZeroconfServer.class);
@@ -154,7 +155,7 @@ private ZeroconfServer(@NotNull Inner inner, int listenPort, boolean listenAllIn
         txt.put("CPath", "/");
         txt.put("VERSION", "1.0");
         txt.put("Stack", "SP");
-        Service service = new Service(inner.deviceName, "spotify-connect", listenPort);
+        Service service = new Service(inner.deviceName, SERVICE, listenPort);
         service.setText(txt);
 
         zeroconf.announce(service);

pom.xml

@@ -49,6 +49,13 @@
         <url>https://github.com/librespot-org/librespot-java/</url>
     </scm>
 
+    <repositories>
+        <repository>
+            <id>github</id>
+            <url>https://maven.pkg.github.com/devgianlu/*</url>
+        </repository>
+    </repositories>
+
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven.compiler.source>1.8</maven.compiler.source>