Optimise API calls and fix tests

Author: maskaravivek

app/src/main/java/fr/free/nrw/commons/review/ReviewActivity.java

@@ -13,6 +13,9 @@
 import android.widget.ProgressBar;
 import android.widget.TextView;
 
+import androidx.appcompat.widget.Toolbar;
+import androidx.drawerlayout.widget.DrawerLayout;
+
 import com.facebook.drawee.view.SimpleDraweeView;
 import com.google.android.material.navigation.NavigationView;
 import com.viewpagerindicator.CirclePageIndicator;
@@ -21,8 +24,6 @@
 
 import javax.inject.Inject;
 
-import androidx.appcompat.widget.Toolbar;
-import androidx.drawerlayout.widget.DrawerLayout;
 import butterknife.BindView;
 import butterknife.ButterKnife;
 import fr.free.nrw.commons.Media;
@@ -143,7 +144,11 @@ public boolean runRandomizer() {
         compositeDisposable.add(reviewHelper.getRandomMedia()
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
-                .subscribe(this::updateImage));
+                .subscribe(media -> {
+                    if (media != null) {
+                        updateImage(media);
+                    }
+                }));
         return true;
     }
 

app/src/main/java/fr/free/nrw/commons/review/ReviewHelper.java

@@ -1,6 +1,7 @@
 package fr.free.nrw.commons.review;
 
 
+import org.apache.commons.lang3.StringUtils;
 import org.wikipedia.dataclient.mwapi.MwQueryPage;
 import org.wikipedia.dataclient.mwapi.RecentChange;
 import org.wikipedia.util.DateUtil;
@@ -16,11 +17,9 @@
 import fr.free.nrw.commons.mwapi.OkHttpJsonApiClient;
 import io.reactivex.Observable;
 import io.reactivex.Single;
-import io.reactivex.functions.Predicate;
 
 @Singleton
 public class ReviewHelper {
-    private static final int MAX_RANDOM_TRIES = 5;
 
     private static final String[] imageExtensions = new String[]{".jpg", ".jpeg", ".png"};
 
@@ -73,21 +72,23 @@ private Observable<RecentChange> getRecentChanges() {
     public Single<Media> getRandomMedia() {
         return getRecentChanges()
                 .flatMapSingle(change -> getRandomMediaFromRecentChange(change))
-                .retry(MAX_RANDOM_TRIES, new Predicate<Throwable>() {
-                    @Override
-                    public boolean test(Throwable throwable) throws Exception {
-                        return throwable instanceof RuntimeException;
-                    }
-                })
+                .onExceptionResumeNext(Observable.just(new Media("")))
+                .filter(media -> !StringUtils.isBlank(media.getFilename()))
                 .firstOrError();
     }
 
+    /**
+     * Returns a proper Media object if the file is not already nominated for deletion
+     * Else it returns an empty Media object
+     * @param recentChange
+     * @return
+     */
     private Single<Media> getRandomMediaFromRecentChange(RecentChange recentChange) {
         return Single.just(recentChange)
                 .flatMap(change -> mediaWikiApi.pageExists("Commons:Deletion_requests/" + change.getTitle()))
                 .flatMap(isDeleted -> {
                     if (isDeleted) {
-                        throw new RuntimeException("Nominated for deletion");
+                        return Single.just(new Media(""));
                     }
                     return okHttpJsonApiClient.getMedia(recentChange.getTitle(), false);
                 });

app/src/test/kotlin/fr/free/nrw/commons/review/ReviewHelperTest.kt

@@ -63,8 +63,10 @@ class ReviewHelperTest {
         `when`(reviewInterface?.getFirstRevisionOfFile(ArgumentMatchers.anyString()))
                 .thenReturn(Observable.just(mockResponse))
 
+        val media = mock(Media::class.java)
+        `when`(media.filename).thenReturn("File:Test.jpg")
         `when`(okHttpJsonApiClient?.getMedia(ArgumentMatchers.anyString(), ArgumentMatchers.anyBoolean()))
-                .thenReturn(Single.just(mock(Media::class.java)))
+                .thenReturn(Single.just(media))
     }
 
     /**