Amazfit Cor: implement basic music controls

Play/pause and skip to previous/next song work. The currently playing song
name is shown on the Cor. The track length and progress are now shown as
we don't know how to send these yet.

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/model/MusicSpec.java

@@ -75,4 +75,16 @@ public class MusicSpec {
         result = 31 * result + trackNr;
         return result;
     }
+
+    @Override
+    public String toString() {
+        return "MusicSpec{" +
+                "artist='" + artist + '\'' +
+                ", album='" + album + '\'' +
+                ", track='" + track + '\'' +
+                ", duration=" + duration +
+                ", trackCount=" + trackCount +
+                ", trackNr=" + trackNr +
+                '}';
+    }
 }

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/model/MusicStateSpec.java

@@ -71,4 +71,15 @@ public class MusicStateSpec {
         result = 31 * result + (int) repeat;
         return result;
     }
+
+    @Override
+    public String toString() {
+        return "MusicStateSpec{" +
+                "state=" + state +
+                ", position=" + position +
+                ", playRate=" + playRate +
+                ", shuffle=" + shuffle +
+                ", repeat=" + repeat +
+                '}';
+    }
 }

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/huami/HuamiSupport.java

@@ -34,6 +34,8 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 import java.util.ArrayList;
 import java.util.Calendar;
 import java.util.Date;
@@ -171,6 +173,10 @@ public class HuamiSupport extends AbstractBTLEDeviceSupport {
     private RealtimeSamplesSupport realtimeSamplesSupport;
     private boolean alarmClockRinging;
 
+    private boolean isMusicAppStarted = false;
+    private MusicSpec bufferMusicSpec = null;
+    private MusicStateSpec bufferMusicStateSpec = null;
+
     public HuamiSupport() {
         this(LOG);
     }
@@ -726,12 +732,102 @@ public class HuamiSupport extends AbstractBTLEDeviceSupport {
 
     @Override
     public void onSetMusicState(MusicStateSpec stateSpec) {
-        // not supported
+        if (bufferMusicStateSpec != stateSpec)
+            bufferMusicStateSpec = stateSpec;
+        sendMusicStateToDevice();
+
     }
 
     @Override
     public void onSetMusicInfo(MusicSpec musicSpec) {
-        // not supported
+        if (bufferMusicSpec != musicSpec)
+            bufferMusicSpec = musicSpec;
+
+        if (!isMusicAppStarted) {
+            return;
+        }
+        sendMusicStateToDevice();
+    }
+
+
+    private void sendMusicStateToDevice() {
+
+
+        if (characteristicChunked == null) {
+            return;
+        }
+        if (bufferMusicSpec == null && bufferMusicStateSpec == null) {
+            try {
+                TransactionBuilder builder = performInitialized("send dummy playback info to enable music controls");
+                writeToChunked(builder, 3, new byte[]{1, 0, 1, 0, 0, 0, 1, 0});
+                builder.queue(getQueue());
+            } catch (IOException e) {
+                LOG.error("Unable to send dummy music controls");
+            }
+            return;
+        }
+
+        byte flags = 0x00;
+        flags |= 0x01;
+        int length = 8;
+        if (bufferMusicSpec.track != null && bufferMusicSpec.track.getBytes().length > 0) {
+            length += bufferMusicSpec.track.getBytes().length + 1;
+            flags |= 0x02;
+        }
+        if (bufferMusicSpec.album != null && bufferMusicSpec.album.getBytes().length > 0) {
+            length += bufferMusicSpec.album.getBytes().length + 1;
+            flags |= 0x04;
+        }
+        if (bufferMusicSpec.artist != null && bufferMusicSpec.artist.getBytes().length > 0) {
+            length += bufferMusicSpec.artist.getBytes().length + 1;
+            flags |= 0x08;
+        }
+
+
+//        LOG.info("Music flags are: " + (flags & 0xff));
+        try {
+            ByteBuffer buf = ByteBuffer.allocate(length);
+            buf.order(ByteOrder.LITTLE_ENDIAN);
+            buf.put(flags);
+            byte state;
+            switch (bufferMusicStateSpec.state) {
+                case MusicStateSpec.STATE_PLAYING:
+                    state = 1;
+                    break;
+                default:
+                    state = 0;
+            }
+
+            buf.put(state);
+            buf.put(new byte[]{0x1, 0x0, 0x0, 0x0}); //unknown
+            buf.put(new byte[]{0x1,0x0}); //show track
+//            buf.put(new byte[]{0x1,0x1}); //show album
+
+
+            if (bufferMusicSpec.track != null && bufferMusicSpec.track.getBytes().length > 0) {
+                buf.put(bufferMusicSpec.track.getBytes());
+                buf.put((byte) 0);
+            }
+            if (bufferMusicSpec.album != null && bufferMusicSpec.album.getBytes().length > 0) {
+                buf.put(bufferMusicSpec.album.getBytes());
+                buf.put((byte) 0);
+            }
+            if (bufferMusicSpec.artist != null && bufferMusicSpec.artist.getBytes().length > 0) {
+                buf.put(bufferMusicSpec.artist.getBytes());
+                buf.put((byte) 0);
+            }
+
+
+            TransactionBuilder builder = performInitialized("send playback info");
+            writeToChunked(builder, 3, buf.array());
+
+            builder.queue(getQueue());
+        } catch (IOException e) {
+            LOG.error("Unable to send playback state");
+        }
+
+//        LOG.info("Sent music: " + bufferMusicSpec.toString() + " " + bufferMusicStateSpec.toString());
+
     }
 
     @Override
@@ -1012,6 +1108,15 @@ public class HuamiSupport extends AbstractBTLEDeviceSupport {
                     case 6:
                         deviceEventMusicControl.event = GBDeviceEventMusicControl.Event.VOLUMEDOWN;
                         break;
+                    case (byte) 224:
+                        LOG.info("Music app started");
+                        isMusicAppStarted = true;
+                        sendMusicStateToDevice();
+                        break;
+                    case (byte) 225:
+                        LOG.info("Music app terminated");
+                        isMusicAppStarted = false;
+                        break;
                     default:
                         LOG.info("unhandled music control event " + value[1]);
                         return;