Categories related client API's migrated to retrofit (commons-app#3053)

* Commit 1

* searchCategories migrated to retrofit

* SearchCategoriesFragment migrated to new API

* Removed unused code

* Created tests

* implemented searching by prefix
fixed SearchCategoryFragment behaviour where the same categories would be added to the list instead of new ones.

* added tests

* Migrated searchTitles to searchCategories, function behaviour seems identical

app/src/main/java/fr/free/nrw/commons/category/CategoriesModel.java

@@ -23,6 +23,7 @@ public class CategoriesModel{
     private static final int SEARCH_CATS_LIMIT = 25;
 
     private final MediaWikiApi mwApi;
+    private final CategoryClient categoryClient;
     private final CategoryDao categoryDao;
     private final JsonKvStore directKvStore;
 
@@ -32,9 +33,11 @@ public class CategoriesModel{
     @Inject GpsCategoryModel gpsCategoryModel;
     @Inject
     public CategoriesModel(MediaWikiApi mwApi,
+                           CategoryClient categoryClient,
                            CategoryDao categoryDao,
                            @Named("default_preferences") JsonKvStore directKvStore) {
         this.mwApi = mwApi;
+        this.categoryClient = categoryClient;
         this.categoryDao = categoryDao;
         this.directKvStore = directKvStore;
         this.categoriesCache = new HashMap<>();
@@ -121,8 +124,8 @@ public Observable<CategoryItem> searchAll(String term, List<String> imageTitleLi
         }
 
         //otherwise, search API for matching categories
-        return mwApi
-                .allCategories(term, SEARCH_CATS_LIMIT)
+        return categoryClient
+                .searchCategoriesForPrefix(term, SEARCH_CATS_LIMIT)
                 .map(name -> new CategoryItem(name, false));
     }
 
@@ -185,7 +188,7 @@ private Observable<CategoryItem> titleCategories(List<String> titleList) {
      * @return
      */
     private Observable<CategoryItem> getTitleCategories(String title) {
-        return mwApi.searchTitles(title, SEARCH_CATS_LIMIT)
+        return categoryClient.searchCategories(title, SEARCH_CATS_LIMIT)
                 .map(name -> new CategoryItem(name, false));
     }
 

app/src/main/java/fr/free/nrw/commons/category/CategoryClient.java

@@ -0,0 +1,97 @@
+package fr.free.nrw.commons.category;
+
+
+import org.wikipedia.dataclient.mwapi.MwQueryPage;
+import org.wikipedia.dataclient.mwapi.MwQueryResponse;
+
+import java.util.List;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import io.reactivex.Observable;
+import timber.log.Timber;
+
+/**
+ * Category Client to handle custom calls to Commons MediaWiki APIs
+ */
+@Singleton
+public class CategoryClient {
+
+    private final CategoryInterface CategoryInterface;
+
+    @Inject
+    public CategoryClient(CategoryInterface CategoryInterface) {
+        this.CategoryInterface = CategoryInterface;
+    }
+
+    /**
+     * Searches for categories containing the specified string.
+     *
+     * @param filter    The string to be searched
+     * @param itemLimit How many results are returned
+     * @param offset    Starts returning items from the nth result. If offset is 9, the response starts with the 9th item of the search result
+     * @return
+     */
+    public Observable<String> searchCategories(String filter, int itemLimit, int offset) {
+        return responseToCategoryName(CategoryInterface.searchCategories(filter, itemLimit, offset));
+
+    }
+
+    /**
+     * Searches for categories containing the specified string.
+     *
+     * @param filter    The string to be searched
+     * @param itemLimit How many results are returned
+     * @return
+     */
+    public Observable<String> searchCategories(String filter, int itemLimit) {
+        return searchCategories(filter, itemLimit, 0);
+
+    }
+
+    /**
+     * Searches for categories starting with the specified string.
+     *
+     * @param prefix    The prefix to be searched
+     * @param itemLimit How many results are returned
+     * @param offset    Starts returning items from the nth result. If offset is 9, the response starts with the 9th item of the search result
+     * @return
+     */
+    public Observable<String> searchCategoriesForPrefix(String prefix, int itemLimit, int offset) {
+        return responseToCategoryName(CategoryInterface.searchCategoriesForPrefix(prefix, itemLimit, offset));
+    }
+
+    /**
+     * Searches for categories starting with the specified string.
+     *
+     * @param prefix    The prefix to be searched
+     * @param itemLimit How many results are returned
+     * @return
+     */
+    public Observable<String> searchCategoriesForPrefix(String prefix, int itemLimit) {
+        return searchCategoriesForPrefix(prefix, itemLimit, 0);
+    }
+
+
+    /**
+     * Internal function to reduce code reuse. Extracts the categories returned from MwQueryResponse.
+     *
+     * @param responseObservable The query response observable
+     * @return Observable emitting the categories returned. If our search yielded "Category:Test", "Test" is emitted.
+     */
+    private Observable<String> responseToCategoryName(Observable<MwQueryResponse> responseObservable) {
+        return responseObservable
+                .flatMap(mwQueryResponse -> {
+                    List<MwQueryPage> pages = mwQueryResponse.query().pages();
+                    if (pages != null)
+                        return Observable.fromIterable(pages);
+                    else
+                        Timber.d("No categories returned.");
+                    return Observable.empty();
+                })
+                .map(MwQueryPage::title)
+                .doOnEach(s -> Timber.d("Category returned: %s", s))
+                .map(cat -> cat.replace("Category:", ""));
+    }
+}

app/src/main/java/fr/free/nrw/commons/category/CategoryInterface.java

@@ -0,0 +1,31 @@
+package fr.free.nrw.commons.category;
+
+import org.wikipedia.dataclient.mwapi.MwQueryResponse;
+
+import io.reactivex.Observable;
+import retrofit2.http.GET;
+import retrofit2.http.Query;
+
+/**
+ * Interface for interacting with Commons category related APIs
+ */
+public interface CategoryInterface {
+
+    /**
+     * Searches for categories with the specified name.
+     * Replaces ApacheHttpClientMediaWikiApi#allCategories
+     *
+     * @param filter    The string to be searched
+     * @param itemLimit How many results are returned
+     * @return
+     */
+    @GET("w/api.php?action=query&format=json&formatversion=2"
+            + "&generator=search&gsrnamespace=14")
+    Observable<MwQueryResponse> searchCategories(@Query("gsrsearch") String filter,
+                                                 @Query("gsrlimit") int itemLimit, @Query("gsroffset") int offset);
+
+    @GET("w/api.php?action=query&format=json&formatversion=2"
+            + "&generator=allcategories")
+    Observable<MwQueryResponse> searchCategoriesForPrefix(@Query("gacprefix") String prefix,
+                                                          @Query("gaclimit") int itemLimit, @Query("gacoffset") int offset);
+}

app/src/main/java/fr/free/nrw/commons/di/NetworkingModule.java

@@ -18,6 +18,7 @@
 import dagger.Module;
 import dagger.Provides;
 import fr.free.nrw.commons.BuildConfig;
+import fr.free.nrw.commons.category.CategoryInterface;
 import fr.free.nrw.commons.kvstore.JsonKvStore;
 import fr.free.nrw.commons.media.MediaInterface;
 import fr.free.nrw.commons.mwapi.ApacheHttpClientMediaWikiApi;
@@ -132,4 +133,10 @@ public ReviewInterface provideReviewInterface(@Named(NAMED_COMMONS_WIKI_SITE) Wi
     public MediaInterface provideMediaInterface(@Named(NAMED_COMMONS_WIKI_SITE) WikiSite commonsWikiSite) {
         return ServiceFactory.get(commonsWikiSite, BuildConfig.COMMONS_URL, MediaInterface.class);
     }
+
+    @Provides
+    @Singleton
+    public CategoryInterface provideCategoryInterface(@Named(NAMED_COMMONS_WIKI_SITE) WikiSite commonsWikiSite) {
+        return ServiceFactory.get(commonsWikiSite, BuildConfig.COMMONS_URL, CategoryInterface.class);
+    }
 }

app/src/main/java/fr/free/nrw/commons/explore/categories/SearchCategoryFragment.java

@@ -25,6 +25,7 @@
 import butterknife.BindView;
 import butterknife.ButterKnife;
 import fr.free.nrw.commons.R;
+import fr.free.nrw.commons.category.CategoryClient;
 import fr.free.nrw.commons.category.CategoryDetailsActivity;
 import fr.free.nrw.commons.di.CommonsDaggerSupportFragment;
 import fr.free.nrw.commons.explore.recentsearches.RecentSearch;
@@ -58,9 +59,12 @@ public class SearchCategoryFragment extends CommonsDaggerSupportFragment {
     String query;
     @BindView(R.id.bottomProgressBar)
     ProgressBar bottomProgressBar;
+    boolean isLoadingCategories;
 
     @Inject RecentSearchesDao recentSearchesDao;
     @Inject MediaWikiApi mwApi;
+    @Inject CategoryClient categoryClient;
+
     @Inject
     @Named("default_preferences")
     JsonKvStore basicKvStore;
@@ -135,48 +139,51 @@ public void updateCategoryList(String query) {
         progressBar.setVisibility(GONE);
         queryList.clear();
         categoriesAdapter.clear();
-        compositeDisposable.add(Observable.fromCallable(() -> mwApi.searchCategory(query,queryList.size()))
+        compositeDisposable.add(categoryClient.searchCategories(query,25)
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .timeout(TIMEOUT_SECONDS, TimeUnit.SECONDS)
                 .doOnSubscribe(disposable -> saveQuery(query))
+                .collect(ArrayList<String>::new, ArrayList::add)
                 .subscribe(this::handleSuccess, this::handleError));
     }
 
 
     /**
-     * Adds more results to existing search results
+     * Adds 25 more results to existing search results
      */
     public void addCategoriesToList(String query) {
+        if(isLoadingCategories) return;
+        isLoadingCategories=true;
         this.query = query;
         bottomProgressBar.setVisibility(View.VISIBLE);
         progressBar.setVisibility(GONE);
-        compositeDisposable.add(Observable.fromCallable(() -> mwApi.searchCategory(query,queryList.size()))
+        compositeDisposable.add(categoryClient.searchCategories(query,25, queryList.size())
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .timeout(TIMEOUT_SECONDS, TimeUnit.SECONDS)
+                .collect(ArrayList<String>::new, ArrayList::add)
                 .subscribe(this::handlePaginationSuccess, this::handleError));
     }
 
     /**
      * Handles the success scenario
      * it initializes the recycler view by adding items to the adapter
-     * @param mediaList
      */
     private void handlePaginationSuccess(List<String> mediaList) {
         queryList.addAll(mediaList);
         progressBar.setVisibility(View.GONE);
         bottomProgressBar.setVisibility(GONE);
         categoriesAdapter.addAll(mediaList);
         categoriesAdapter.notifyDataSetChanged();
+        isLoadingCategories=false;
     }
 
 
 
     /**
      * Handles the success scenario
      * it initializes the recycler view by adding items to the adapter
-     * @param mediaList
      */
     private void handleSuccess(List<String> mediaList) {
         queryList = mediaList;
@@ -194,7 +201,6 @@ private void handleSuccess(List<String> mediaList) {
 
     /**
      * Logs and handles API error scenario
-     * @param throwable
      */
     private void handleError(Throwable throwable) {
         Timber.e(throwable, "Error occurred while loading queried categories");
@@ -213,7 +219,7 @@ private void handleError(Throwable throwable) {
     private void initErrorView() {
         progressBar.setVisibility(GONE);
         categoriesNotFoundView.setVisibility(VISIBLE);
-        categoriesNotFoundView.setText(getString(R.string.categories_not_found, query));
+        categoriesNotFoundView.setText(getString(R.string.categories_not_found));
     }
 
     /**