Implemented a warning before adding duplicate to playlist.

app/src/main/java/org/schabi/newpipe/database/playlist/dao/PlaylistStreamDAO.java

@@ -26,6 +26,7 @@ import static org.schabi.newpipe.database.playlist.model.PlaylistStreamEntity.PL
 import static org.schabi.newpipe.database.stream.model.StreamEntity.STREAM_ID;
 import static org.schabi.newpipe.database.stream.model.StreamEntity.STREAM_TABLE;
 import static org.schabi.newpipe.database.stream.model.StreamEntity.STREAM_THUMBNAIL_URL;
+import static org.schabi.newpipe.database.stream.model.StreamEntity.STREAM_URL;
 import static org.schabi.newpipe.database.stream.model.StreamStateEntity.JOIN_STREAM_ID_ALIAS;
 import static org.schabi.newpipe.database.stream.model.StreamStateEntity.STREAM_PROGRESS_MILLIS;
 import static org.schabi.newpipe.database.stream.model.StreamStateEntity.STREAM_STATE_TABLE;
@@ -49,6 +50,16 @@ public interface PlaylistStreamDAO extends BasicDAO<PlaylistStreamEntity> {
             + " WHERE " + JOIN_PLAYLIST_ID + " = :playlistId")
     void deleteBatch(long playlistId);
 
+    @Query("SELECT COALESCE(COUNT(*), 0)"
+            + " FROM " + STREAM_TABLE
+            + " LEFT JOIN " + PLAYLIST_STREAM_JOIN_TABLE
+            + " ON " + STREAM_ID + " = " + JOIN_STREAM_ID
+            + " WHERE " + JOIN_PLAYLIST_ID + " = :playlistId "
+            + " AND " + STREAM_URL + " = :streamURL"
+    )
+    Flowable<Integer> getDuplicates(long playlistId, String streamURL);
+
+
     @Query("SELECT COALESCE(MAX(" + JOIN_INDEX + "), -1)"
             + " FROM " + PLAYLIST_STREAM_JOIN_TABLE
             + " WHERE " + JOIN_PLAYLIST_ID + " = :playlistId")

app/src/main/java/org/schabi/newpipe/local/dialog/PlaylistAppendDialog.java

@@ -1,5 +1,6 @@
 package org.schabi.newpipe.local.dialog;
 
+import android.app.AlertDialog;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -128,6 +129,19 @@ public final class PlaylistAppendDialog extends PlaylistDialog {
     private void onPlaylistSelected(@NonNull final LocalPlaylistManager manager,
                                     @NonNull final PlaylistMetadataEntry playlist,
                                     @NonNull final List<StreamEntity> streams) {
+
+        final int numOfDuplicates = manager.getPlaylistDuplicates(playlist.uid,
+                        streams.get(0).getUrl()).blockingFirst();
+        if (numOfDuplicates > 0) {
+            createDuplicateDialog(numOfDuplicates, manager, playlist, streams);
+        } else {
+            addStreamToPlaylist(manager, playlist, streams);
+        }
+    }
+
+    private void addStreamToPlaylist(@NonNull final LocalPlaylistManager manager,
+                                     @NonNull final PlaylistMetadataEntry playlist,
+                                     @NonNull final List<StreamEntity> streams) {
         final Toast successToast = Toast.makeText(getContext(),
                 R.string.playlist_add_stream_success, Toast.LENGTH_SHORT);
 
@@ -142,7 +156,23 @@ public final class PlaylistAppendDialog extends PlaylistDialog {
         playlistDisposables.add(manager.appendToPlaylist(playlist.uid, streams)
                 .observeOn(AndroidSchedulers.mainThread())
                 .subscribe(ignored -> successToast.show()));
-
         requireDialog().dismiss();
     }
+
+    private void createDuplicateDialog(final int duplicates,
+                                       @NonNull final LocalPlaylistManager manager,
+                                       @NonNull final PlaylistMetadataEntry playlist,
+                                       @NonNull final List<StreamEntity> streams) {
+        //TODO: change color
+        final AlertDialog.Builder builder = new AlertDialog.Builder(this.getActivity());
+        builder.setTitle(R.string.duplicate_stream_in_playlist_title);
+        builder.setMessage(getString(R.string.duplicate_stream_in_playlist_description,
+                duplicates));
+
+        builder.setPositiveButton(android.R.string.yes, (dialog, i) -> {
+            addStreamToPlaylist(manager, playlist, streams);
+        });
+        builder.setNeutralButton(R.string.cancel, null);
+        builder.create().show();
+    }
 }

app/src/main/java/org/schabi/newpipe/local/playlist/LocalPlaylistManager.java

@@ -91,6 +91,10 @@ public class LocalPlaylistManager {
         return playlistStreamTable.getOrderedStreamsOf(playlistId).subscribeOn(Schedulers.io());
     }
 
+    public Flowable<Integer> getPlaylistDuplicates(final long playlistId, final String streamURL) {
+        return playlistStreamTable.getDuplicates(playlistId, streamURL);
+    }
+
     public Single<Integer> deletePlaylist(final long playlistId) {
         return Single.fromCallable(() -> playlistTable.deletePlaylist(playlistId))
                 .subscribeOn(Schedulers.io());

app/src/main/res/values/strings.xml

@@ -447,6 +447,9 @@
     <string name="playlist_add_stream_success">Playlisted</string>
     <string name="playlist_thumbnail_change_success">Playlist thumbnail changed.</string>
     <string name="playlist_no_uploader">Auto-generated (no uploader found)</string>
+    <string name="duplicate_stream_in_playlist_title">Duplicated Video Found</string>
+    <string name="duplicate_stream_in_playlist_description">The playlist contains this stream
+        already %d time(s).\nDo you want to add it one more time?</string>
     <!-- Players -->
     <string name="caption_none">No Captions</string>
     <string name="resize_fit">Fit</string>