Zeroconf ApiServer (#128)

* Add Zeroconf Apiserver functionality
xyz.gianlu.librespot.core.ZeroconfServer now extends java.util.Observable, notifies observers when a new Session is created
add method xyz.gianlu.librespot.api.server.ApiServer.clearHandlers(), clears the ApiHandlers Map
add class ZeroconfApiServer, extends xyz.gianlu.librespot.api.server.ApiServer, observes the ZeroconfServer, updates when a new Session is created in ZeroconfServer

* fix Observer not getting updated
Session had to be authenticated before registering request handlers

* Moved from Observable to Listener pattern
Observer and Observable is deprecated in java 11+

* removed unused imports

* Minor refactoring

Author: fiechtor

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

@@ -1,8 +1,12 @@
 package xyz.gianlu.librespot.api;
 
+import xyz.gianlu.librespot.AbsConfiguration;
 import xyz.gianlu.librespot.FileConfiguration;
 import xyz.gianlu.librespot.api.server.ApiServer;
+import xyz.gianlu.librespot.api.server.ZeroconfApiServer;
+import xyz.gianlu.librespot.core.AuthConfiguration;
 import xyz.gianlu.librespot.core.Session;
+import xyz.gianlu.librespot.core.ZeroconfServer;
 import xyz.gianlu.librespot.spirc.SpotifyIrc;
 
 import java.io.IOException;
@@ -14,11 +18,16 @@
 public class Main {
 
     public static void main(String[] args) throws IOException, GeneralSecurityException, SpotifyIrc.IrcException, Session.SpotifyAuthenticationException {
-        Session session = new Session.Builder(new FileConfiguration(args)).create();
+        AbsConfiguration conf = new FileConfiguration(args);
+        if (conf.authStrategy() == AuthConfiguration.Strategy.ZEROCONF) {
+            ZeroconfServer.create(conf).addSessionListener(new ZeroconfApiServer(24879));
+        } else {
+            Session session = new Session.Builder(conf).create();
 
-        ApiServer server = new ApiServer(24879);
-        server.registerHandler(new PlayerHandler(session));
-        server.registerHandler(new MetadataHandler(session));
-        server.registerHandler(new MercuryHandler(session));
+            ApiServer server = new ApiServer(24879);
+            server.registerHandler(new PlayerHandler(session));
+            server.registerHandler(new MetadataHandler(session));
+            server.registerHandler(new MercuryHandler(session));
+        }
     }
 }

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

@@ -64,6 +64,10 @@ public void registerHandler(@NotNull AbsApiHandler handler) {
         handlers.put(handler.prefix, handler);
     }
 
+    public void clearHandlers() {
+        handlers.clear();
+    }
+
     private void handleRequest(@NotNull Request request) throws PredefinedJsonRpcException {
         int index = request.method.indexOf('.');
         if (index == -1)

api/src/main/java/xyz/gianlu/librespot/api/server/ZeroconfApiServer.java

@@ -0,0 +1,29 @@
+package xyz.gianlu.librespot.api.server;
+
+import org.apache.log4j.Logger;
+import org.jetbrains.annotations.NotNull;
+import xyz.gianlu.librespot.api.MercuryHandler;
+import xyz.gianlu.librespot.api.MetadataHandler;
+import xyz.gianlu.librespot.api.PlayerHandler;
+import xyz.gianlu.librespot.core.Session;
+import xyz.gianlu.librespot.core.ZeroconfServer;
+
+import java.io.IOException;
+
+public class ZeroconfApiServer extends ApiServer implements ZeroconfServer.SessionListener {
+    private static final Logger LOGGER = Logger.getLogger(ZeroconfApiServer.class);
+
+    public ZeroconfApiServer(int port) throws IOException {
+        super(port);
+    }
+
+    @Override
+    public void sessionChanged(@NotNull Session session) {
+        clearHandlers();
+
+        registerHandler(new PlayerHandler(session));
+        registerHandler(new MetadataHandler(session));
+        registerHandler(new MercuryHandler(session));
+        LOGGER.info("Refreshed handlers for new session.");
+    }
+}

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

@@ -22,6 +22,7 @@
 import java.io.IOException;
 import java.io.OutputStream;
 import java.net.*;
+import java.nio.charset.StandardCharsets;
 import java.security.GeneralSecurityException;
 import java.security.MessageDigest;
 import java.util.*;
@@ -81,10 +82,12 @@ public class ZeroconfServer implements Closeable {
     private final DiffieHellman keys;
     private final JmDNS[] instances;
     private volatile Session session;
+    private final List<SessionListener> sessionListeners;
 
     private ZeroconfServer(Session.Inner inner, Configuration conf) throws IOException {
         this.inner = inner;
         this.keys = new DiffieHellman(inner.random);
+        this.sessionListeners = new ArrayList<>();
 
         int port = conf.zeroconfListenPort();
         if (port == -1)
@@ -312,12 +315,22 @@ private void handleAddUser(OutputStream out, Map<String, String> params, String
 
             session.connect();
             session.authenticate(credentials);
+
+            sessionListeners.forEach(l -> l.sessionChanged(session));
         } catch (Session.SpotifyAuthenticationException | SpotifyIrc.IrcException ex) {
             LOGGER.fatal("Failed handling connection! Going away.", ex);
             close();
         }
     }
 
+    public void addSessionListener(@NotNull SessionListener listener) {
+        sessionListeners.add(listener);
+    }
+
+    public void removeSessionListener(@NotNull SessionListener listener) {
+        sessionListeners.remove(listener);
+    }
+
     public interface Configuration {
         boolean zeroconfListenAll();
 
@@ -327,6 +340,10 @@ public interface Configuration {
         String[] zeroconfInterfaces();
     }
 
+    public interface SessionListener {
+        void sessionChanged(@NotNull Session session);
+    }
+
     private class HttpRunner implements Runnable, Closeable {
         private final ServerSocket serverSocket;
         private final ExecutorService executorService = Executors.newCachedThreadPool();
@@ -402,7 +419,7 @@ private void handle(@NotNull Socket socket) throws IOException {
                 Map<String, String> params = new HashMap<>(pairs.length);
                 for (String pair : pairs) {
                     String[] split = Utils.split(pair, '=');
-                    params.put(URLDecoder.decode(split[0], "UTF-8"), URLDecoder.decode(split[1], "UTF-8"));
+                    params.put(URLDecoder.decode(split[0], StandardCharsets.UTF_8), URLDecoder.decode(split[1], StandardCharsets.UTF_8));
                 }
 
                 String action = params.get("action");
@@ -436,5 +453,7 @@ public void close() throws IOException {
             shouldStop = true;
             serverSocket.close();
         }
+
     }
+
 }