Refactor project structure

app/src/main/java/com/cappielloantonio/play/interfaces/Playback.java

@@ -0,0 +1,41 @@
+package com.cappielloantonio.play.interfaces;
+
+import com.cappielloantonio.play.model.Song;
+
+public interface Playback {
+    void setDataSource(Song song);
+
+    void queueDataSource(Song song);
+
+    void setCallbacks(PlaybackCallbacks callbacks);
+
+    boolean isReady();
+
+    boolean isPlaying();
+
+    boolean isLoading();
+
+    void start();
+
+    void pause();
+
+    void stop();
+
+    int getProgress();
+
+    int getDuration();
+
+    void setProgress(int progress);
+
+    void setVolume(int volume);
+
+    int getVolume();
+
+    interface PlaybackCallbacks {
+        void onStateChanged(int state);
+
+        void onReadyChanged(boolean ready, int reason);
+
+        void onTrackChanged(int reason);
+    }
+}