Added connectionDropped and connectionEstablished events + better response codes for API + updated api/README (#172)

Author: devgianlu

api/README.md

@@ -4,11 +4,13 @@
 This module depends on `librespot-core` and provides an API to interact with the Spotify client.
 
 ## Available endpoints
-
-All the endpoints will respond with `200` if successful or `204` if there isn't any active session.
+All the endpoints will respond with `200` if successful or:
+- `204`, if there isn't any active session (Zeroconf only)
+- `500`, if the session is invalid
+- `503`, if the session is reconnecting (`Retry-After` is always 10 seconds)
 
 ### Player
-- `POST \player\load` Load a track from a given uri. The request body should contain two parameters: `uri` and `play`.
+- `POST \player\load` Load a track from a given URI. The request body should contain two parameters: `uri` and `play`.
 - `POST \player\pause` Pause playback.
 - `POST \player\resume` Resume playback.
 - `POST \player\next` Skip to next track.
@@ -28,22 +30,22 @@ All the endpoints will respond with `200` if successful or `204` if there isn't
 - `POST \token\{scope}` Request an access token for a specific scope.
 
 ### Events
-
 You can subscribe for players events by creating a WebSocket connection to `/events`.
 The currently available events are:
-- `contextChanged`
-- `trackChanged`
-- `playbackPaused`
-- `playbackResumed`
-- `trackSeeked`
-- `metadataAvailable`
-- `playbackHaltStateChanged`
-- `sessionCleared`
-- `sessionChanged`
-- `inactiveSession`
+- `contextChanged`, the Spotify context URI changed
+- `trackChanged`, the Spotify track URI changed
+- `playbackPaused`, playback has been paused
+- `playbackResumed`, playback has been resumed
+- `trackSeeked`, track has been seeked
+- `metadataAvailable`, metadata for the current track is available
+- `playbackHaltStateChanged`, playback halted or resumed from halt
+- `sessionCleared`, (Zeroconf only) current session went away
+- `sessionChanged`, (Zeroconf only) current session changed
+- `inactiveSession`, current session is now inactive (no audio)
+- `connectionDropped`, a network error occurred and we're trying to reconnect
+- `connectionEstablished`, successfully reconnected
 
 ## Examples
-
 `curl -X POST -d "uri=spotify:track:xxxxxxxxxxxxxxxxxxxxxx&play=true" http://localhost:24879/player/load`
 
 `curl -X POST http://localhost:24879/metadata/track/spotify:track:xxxxxxxxxxxxxxxxxxxxxx`

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

@@ -2,6 +2,7 @@
 
 import io.undertow.server.HttpHandler;
 import io.undertow.server.HttpServerExchange;
+import io.undertow.util.Headers;
 import io.undertow.util.StatusCodes;
 import org.jetbrains.annotations.NotNull;
 import xyz.gianlu.librespot.api.SessionWrapper;
@@ -25,6 +26,17 @@ public final void handleRequest(HttpServerExchange exchange) throws Exception {
             return;
         }
 
+        if (s.reconnecting()) {
+            exchange.setStatusCode(StatusCodes.SERVICE_UNAVAILABLE);
+            exchange.getResponseHeaders().add(Headers.RETRY_AFTER, 10);
+            return;
+        }
+
+        if (!s.valid()) {
+            exchange.setStatusCode(StatusCodes.INTERNAL_SERVER_ERROR);
+            return;
+        }
+
         handleRequest(exchange, s);
     }
 

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

@@ -15,7 +15,7 @@
 import xyz.gianlu.librespot.mercury.model.PlayableId;
 import xyz.gianlu.librespot.player.Player;
 
-public final class EventsHandler extends WebSocketProtocolHandshakeHandler implements Player.EventsListener, SessionWrapper.Listener {
+public final class EventsHandler extends WebSocketProtocolHandshakeHandler implements Player.EventsListener, SessionWrapper.Listener, Session.ReconnectionListener {
     private static final Logger LOGGER = Logger.getLogger(EventsHandler.class);
 
     public EventsHandler() {
@@ -110,5 +110,20 @@ public void onNewSession(@NotNull Session session) {
         dispatch(obj);
 
         session.player().addEventsListener(this);
+        session.addReconnectionListener(this);
+    }
+
+    @Override
+    public void onConnectionDropped() {
+        JsonObject obj = new JsonObject();
+        obj.addProperty("event", "connectionDropped");
+        dispatch(obj);
+    }
+
+    @Override
+    public void onConnectionEstablished() {
+        JsonObject obj = new JsonObject();
+        obj.addProperty("event", "connectionEstablished");
+        dispatch(obj);
     }
 }

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

@@ -45,12 +45,6 @@ protected void appendToQueue(@NotNull Packet packet) {
 
     protected abstract void exception(@NotNull Exception ex);
 
-    private static final class LooperException extends Exception {
-        private LooperException(Throwable cause) {
-            super(cause);
-        }
-    }
-
     private final class Looper implements Runnable {
         private volatile boolean shouldStop = false;
 
@@ -66,8 +60,7 @@ public void run() {
                             exception(ex);
                         }
                     });
-                } catch (InterruptedException ex) {
-                    executorService.execute(() -> exception(new LooperException(ex)));
+                } catch (InterruptedException ignored) {
                 }
             }
         }

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

@@ -76,6 +76,7 @@ public final class Session implements Closeable {
     private final AtomicBoolean authLock = new AtomicBoolean(false);
     private final OkHttpClient client;
     private final List<CloseListener> closeListeners = Collections.synchronizedList(new ArrayList<>());
+    private final List<ReconnectionListener> reconnectionListeners = Collections.synchronizedList(new ArrayList<>());
     private ConnectionHolder conn;
     private CipherPair cipherPair;
     private Receiver receiver;
@@ -528,6 +529,10 @@ public boolean valid() {
         return apWelcome != null && conn != null && !conn.socket.isClosed();
     }
 
+    public boolean reconnecting() {
+        return !closed && conn == null;
+    }
+
     @NotNull
     public String deviceId() {
         return inner.deviceId;
@@ -554,6 +559,10 @@ public Random random() {
     }
 
     private void reconnect() {
+        synchronized (reconnectionListeners) {
+            reconnectionListeners.forEach(ReconnectionListener::onConnectionDropped);
+        }
+
         try {
             if (conn != null) {
                 conn.socket.close();
@@ -569,7 +578,12 @@ private void reconnect() {
                     .build(), true);
 
             LOGGER.info(String.format("Re-authenticated as %s!", apWelcome.getCanonicalUsername()));
+
+            synchronized (reconnectionListeners) {
+                reconnectionListeners.forEach(ReconnectionListener::onConnectionEstablished);
+            }
         } catch (IOException | GeneralSecurityException | SpotifyAuthenticationException ex) {
+            conn = null;
             LOGGER.error("Failed reconnecting, retrying in 10 seconds...", ex);
             scheduler.schedule(this::reconnect, 10, TimeUnit.SECONDS);
         }
@@ -589,6 +603,16 @@ public void addCloseListener(@NotNull CloseListener listener) {
         if (!closeListeners.contains(listener)) closeListeners.add(listener);
     }
 
+    public void addReconnectionListener(@NotNull ReconnectionListener listener) {
+        if (!reconnectionListeners.contains(listener)) reconnectionListeners.add(listener);
+    }
+
+    public interface ReconnectionListener {
+        void onConnectionDropped();
+
+        void onConnectionEstablished();
+    }
+
     public interface ProxyConfiguration {
         boolean proxyEnabled();