Use JSON SPARQL query for fetching nearby places (#2398)

* Use JSON response for nearby places

* Move okhttp calls to a different class

* wip

* Fetch picture of the day using JSON API

* Search images using JSON APIs

* tests

* Fix injection based on code review comments

app/src/main/java/fr/free/nrw/commons/mwapi/ApacheHttpClientMediaWikiApi.java

@@ -5,7 +5,6 @@ import android.net.Uri;
 import android.os.Build;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
-import android.support.annotation.VisibleForTesting;
 import android.text.TextUtils;
 
 import com.google.gson.Gson;
@@ -21,7 +20,6 @@ import org.apache.http.impl.client.DefaultHttpClient;
 import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
 import org.apache.http.params.BasicHttpParams;
 import org.apache.http.params.CoreProtocolPNames;
-import org.apache.http.util.EntityUtils;
 import org.w3c.dom.Element;
 import org.w3c.dom.Node;
 import org.w3c.dom.NodeList;
@@ -41,12 +39,8 @@ import java.util.concurrent.Callable;
 
 import fr.free.nrw.commons.BuildConfig;
 import fr.free.nrw.commons.Media;
-import fr.free.nrw.commons.PageTitle;
 import fr.free.nrw.commons.R;
-import fr.free.nrw.commons.achievements.FeaturedImages;
-import fr.free.nrw.commons.achievements.FeedbackResponse;
 import fr.free.nrw.commons.auth.AccountUtil;
-import fr.free.nrw.commons.campaigns.CampaignResponseDTO;
 import fr.free.nrw.commons.category.CategoryImageUtils;
 import fr.free.nrw.commons.category.QueryContinue;
 import fr.free.nrw.commons.kvstore.BasicKvStore;
@@ -59,10 +53,6 @@ import fr.free.nrw.commons.utils.ViewUtil;
 import in.yuvi.http.fluent.Http;
 import io.reactivex.Observable;
 import io.reactivex.Single;
-import okhttp3.HttpUrl;
-import okhttp3.OkHttpClient;
-import okhttp3.Request;
-import okhttp3.Response;
 import timber.log.Timber;
 
 import static fr.free.nrw.commons.utils.ContinueUtils.getQueryContinue;
@@ -71,8 +61,6 @@ import static fr.free.nrw.commons.utils.ContinueUtils.getQueryContinue;
  * @author Addshore
  */
 public class ApacheHttpClientMediaWikiApi implements MediaWikiApi {
-    private String wikiMediaToolforgeUrl = "https://tools.wmflabs.org/";
-
     private static final String THUMB_SIZE = "640";
     private AbstractHttpClient httpClient;
     private CustomMwApi api;
@@ -81,9 +69,6 @@ public class ApacheHttpClientMediaWikiApi implements MediaWikiApi {
     private BasicKvStore defaultKvStore;
     private BasicKvStore categoryKvStore;
     private Gson gson;
-    private final OkHttpClient okHttpClient;
-    private final String WIKIMEDIA_CAMPAIGNS_BASE_URL =
-            "https://raw.githubusercontent.com/commons-app/campaigns/master/campaigns.json";
 
     private final String ERROR_CODE_BAD_TOKEN = "badtoken";
 
@@ -92,10 +77,8 @@ public class ApacheHttpClientMediaWikiApi implements MediaWikiApi {
                                         String wikidatApiURL,
                                         BasicKvStore defaultKvStore,
                                         BasicKvStore categoryKvStore,
-                                        Gson gson,
-                                        OkHttpClient okHttpClient) {
+                                        Gson gson) {
         this.context = context;
-        this.okHttpClient = okHttpClient;
         BasicHttpParams params = new BasicHttpParams();
         SchemeRegistry schemeRegistry = new SchemeRegistry();
         schemeRegistry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));
@@ -120,11 +103,6 @@ public class ApacheHttpClientMediaWikiApi implements MediaWikiApi {
         return "Commons/" + ConfigUtils.getVersionNameWithSha(context) + " (https://mediawiki.org/wiki/Apps/Commons) Android/" + Build.VERSION.RELEASE;
     }
 
-    @VisibleForTesting
-    public void setWikiMediaToolforgeUrl(String wikiMediaToolforgeUrl) {
-        this.wikiMediaToolforgeUrl = wikiMediaToolforgeUrl;
-    }
-
     /**
      * @param username String
      * @param password String
@@ -760,44 +738,6 @@ public class ApacheHttpClientMediaWikiApi implements MediaWikiApi {
         return CategoryImageUtils.getMediaList(childNodes);
     }
 
-    /**
-     * This method takes search keyword as input and returns a list of  Media objects filtered using search query
-     * It uses the generator query API to get the images searched using a query, 25 at a time.
-     * @param query keyword to search images on commons
-     * @return
-     */
-    @Override
-    @NonNull
-    public List<Media> searchImages(String query, int offset) {
-        CustomApiResult apiResult=null;
-        try {
-            apiResult= api.action("query")
-                    .param("format", "xml")
-                    .param("generator", "search")
-                    .param("gsrwhat", "text")
-                    .param("gsrnamespace", "6")
-                    .param("gsrlimit", "25")
-                    .param("gsroffset",offset)
-                    .param("gsrsearch", query)
-                    .param("prop", "imageinfo")
-                    .param("iiprop", "url|extmetadata")
-                    .get();
-        } catch (IOException e) {
-            Timber.e(e, "Failed to obtain searchImages");
-        }
-
-        CustomApiResult searchImagesNode = apiResult.getNode("/api/query/pages");
-        if (searchImagesNode == null
-                || searchImagesNode.getDocument() == null
-                || searchImagesNode.getDocument().getChildNodes() == null
-                || searchImagesNode.getDocument().getChildNodes().getLength() == 0) {
-            return new ArrayList<>();
-        }
-
-        NodeList childNodes = searchImagesNode.getDocument().getChildNodes();
-        return CategoryImageUtils.getMediaList(childNodes);
-    }
-
     /**
      * This method takes search keyword as input and returns a list of categories objects filtered using search query
      * It uses the generator query API to get the categories searched using a query, 25 at a time.
@@ -924,25 +864,6 @@ public class ApacheHttpClientMediaWikiApi implements MediaWikiApi {
         }
     }
 
-    @Override
-    @NonNull
-    public Single<Integer> getUploadCount(String userName) {
-        final String uploadCountUrlTemplate =
-                wikiMediaToolforgeUrl + "urbanecmbot/commonsmisc/uploadsbyuser.py";
-
-        return Single.fromCallable(() -> {
-            String url = String.format(
-                    Locale.ENGLISH,
-                    uploadCountUrlTemplate,
-                    new PageTitle(userName).getText());
-            HttpResponse response = Http.get(url).use(httpClient)
-                    .data("user", userName)
-                    .asResponse();
-            String uploadCount = EntityUtils.toString(response.getEntity()).trim();
-            return Integer.parseInt(uploadCount);
-        });
-    }
-
     /**
 
      * Checks to see if a user is currently blocked from Commons
@@ -976,86 +897,6 @@ public class ApacheHttpClientMediaWikiApi implements MediaWikiApi {
         return userBlocked;
     }
 
-    /**
-     * This takes userName as input, which is then used to fetch the feedback/achievements
-     * statistics using OkHttp and JavaRx. This function return JSONObject
-     * @param userName MediaWiki user name
-     * @return
-     */
-    @Override
-    public Single<FeedbackResponse> getAchievements(String userName) {
-        final String fetchAchievementUrlTemplate =
-                wikiMediaToolforgeUrl + "urbanecmbot/commonsmisc/feedback.py";
-        return Single.fromCallable(() -> {
-            String url = String.format(
-                    Locale.ENGLISH,
-                    fetchAchievementUrlTemplate,
-                    new PageTitle(userName).getText());
-            HttpUrl.Builder urlBuilder = HttpUrl.parse(url).newBuilder();
-            urlBuilder.addQueryParameter("user", userName);
-            Timber.i("Url %s", urlBuilder.toString());
-            Request request = new Request.Builder()
-                    .url(urlBuilder.toString())
-                    .build();
-            Response response = okHttpClient.newCall(request).execute();
-            if (response != null && response.body() != null && response.isSuccessful()) {
-                String json = response.body().string();
-                if (json == null) {
-                    return null;
-                }
-                Timber.d("Response for achievements is %s", json);
-                try {
-                    return gson.fromJson(json, FeedbackResponse.class);
-                }
-                catch (Exception e){
-                    return new FeedbackResponse("",0,0,0,new FeaturedImages(0,0),0,"",0);
-                }
-
-
-            }
-            return null;
-        });
-
-    }
-
-    /**
-     * The method returns the picture of the day
-     *
-     * @return Media object corresponding to the picture of the day
-     */
-    @Override
-    @Nullable
-    public Single<Media> getPictureOfTheDay() {
-        return Single.fromCallable(() -> {
-            CustomApiResult apiResult = null;
-            try {
-                String template = "Template:Potd/" + DateUtils.getCurrentDate();
-                CustomMwApi.RequestBuilder requestBuilder = api.action("query")
-                        .param("generator", "images")
-                        .param("format", "xml")
-                        .param("titles", template)
-                        .param("prop", "imageinfo")
-                        .param("iiprop", "url|extmetadata");
-
-                apiResult = requestBuilder.get();
-            } catch (IOException e) {
-                Timber.e(e, "Failed to obtain searchCategories");
-            }
-
-            if (apiResult == null) {
-                return null;
-            }
-
-            CustomApiResult imageNode = apiResult.getNode("/api/query/pages/page");
-            if (imageNode == null
-                    || imageNode.getDocument() == null) {
-                return null;
-            }
-
-            return CategoryImageUtils.getMediaFromPage(imageNode.getDocument());
-        });
-    }
-
     private Date parseMWDate(String mwDate) {
         SimpleDateFormat isoFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ENGLISH); // Assuming MW always gives me UTC
         isoFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
@@ -1076,19 +917,4 @@ public class ApacheHttpClientMediaWikiApi implements MediaWikiApi {
             Timber.e(e, "Error occurred while logging out");
         }
     }
-
-    @Override public Single<CampaignResponseDTO> getCampaigns() {
-        return Single.fromCallable(() -> {
-            Request request = new Request.Builder().url(WIKIMEDIA_CAMPAIGNS_BASE_URL).build();
-            Response response = okHttpClient.newCall(request).execute();
-            if (response != null && response.body() != null && response.isSuccessful()) {
-                String json = response.body().string();
-                if (json == null) {
-                    return null;
-                }
-                return gson.fromJson(json, CampaignResponseDTO.class);
-            }
-            return null;
-        });
-    }
 }

app/src/main/java/fr/free/nrw/commons/mwapi/MediaWikiApi.java

@@ -11,6 +11,8 @@ import java.util.List;
 
 import fr.free.nrw.commons.Media;
 import fr.free.nrw.commons.achievements.FeedbackResponse;
+import fr.free.nrw.commons.location.LatLng;
+import fr.free.nrw.commons.nearby.Place;
 import fr.free.nrw.commons.notification.Notification;
 import io.reactivex.Observable;
 import io.reactivex.Single;
@@ -48,9 +50,6 @@ public interface MediaWikiApi {
 
     List<String> getParentCategoryList(String categoryName);
 
-    @NonNull
-    List<Media> searchImages(String title, int offset);
-
     @NonNull
     List<String> searchCategory(String title, int offset);
 
@@ -98,19 +97,11 @@ public interface MediaWikiApi {
     @NonNull
     LogEventResult logEvents(String user, String lastModified, String queryContinue, int limit) throws IOException;
 
-    @NonNull
-    Single<Integer> getUploadCount(String userName);
 
     boolean isUserBlockedFromCommons();
 
-    Single<FeedbackResponse> getAchievements(String userName);
-
-    Single<Media> getPictureOfTheDay();
-
     void logout();
 
-    Single<CampaignResponseDTO> getCampaigns();
-
     interface ProgressListener {
         void onProgress(long transferred, long total);
     }

app/src/main/java/fr/free/nrw/commons/mwapi/OkHttpJsonApiClient.java

@@ -0,0 +1,253 @@
+package fr.free.nrw.commons.mwapi;
+
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+
+import com.google.gson.Gson;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import fr.free.nrw.commons.Media;
+import fr.free.nrw.commons.PageTitle;
+import fr.free.nrw.commons.achievements.FeaturedImages;
+import fr.free.nrw.commons.achievements.FeedbackResponse;
+import fr.free.nrw.commons.campaigns.CampaignResponseDTO;
+import fr.free.nrw.commons.location.LatLng;
+import fr.free.nrw.commons.media.model.MwQueryPage;
+import fr.free.nrw.commons.mwapi.model.MwQueryResponse;
+import fr.free.nrw.commons.nearby.Place;
+import fr.free.nrw.commons.nearby.model.NearbyResponse;
+import fr.free.nrw.commons.nearby.model.NearbyResultItem;
+import fr.free.nrw.commons.upload.FileUtils;
+import fr.free.nrw.commons.utils.DateUtils;
+import io.reactivex.Observable;
+import io.reactivex.Single;
+import okhttp3.HttpUrl;
+import okhttp3.OkHttpClient;
+import okhttp3.Request;
+import okhttp3.Response;
+import timber.log.Timber;
+
+@Singleton
+public class OkHttpJsonApiClient {
+    private final OkHttpClient okHttpClient;
+    private final HttpUrl wikiMediaToolforgeUrl;
+    private final String sparqlQueryUrl;
+    private final String campaignsUrl;
+    private final String commonsBaseUrl;
+    private Gson gson;
+
+
+    @Inject
+    public OkHttpJsonApiClient(OkHttpClient okHttpClient,
+                               HttpUrl wikiMediaToolforgeUrl,
+                               String sparqlQueryUrl,
+                               String campaignsUrl,
+                               String commonsBaseUrl,
+                               Gson gson) {
+        this.okHttpClient = okHttpClient;
+        this.wikiMediaToolforgeUrl = wikiMediaToolforgeUrl;
+        this.sparqlQueryUrl = sparqlQueryUrl;
+        this.campaignsUrl = campaignsUrl;
+        this.commonsBaseUrl = commonsBaseUrl;
+        this.gson = gson;
+    }
+
+    @NonNull
+    public Single<Integer> getUploadCount(String userName) {
+        HttpUrl.Builder urlBuilder = wikiMediaToolforgeUrl.newBuilder();
+        urlBuilder
+                .addPathSegments("urbanecmbot/commonsmisc/uploadsbyuser.py")
+                .addQueryParameter("user", userName);
+        Request request = new Request.Builder()
+                .url(urlBuilder.build())
+                .build();
+
+        return Single.fromCallable(() -> {
+            Response response = okHttpClient.newCall(request).execute();
+            if (response != null && response.isSuccessful()) {
+                return Integer.parseInt(response.body().string().trim());
+            }
+            return 0;
+        });
+    }
+
+    /**
+     * This takes userName as input, which is then used to fetch the feedback/achievements
+     * statistics using OkHttp and JavaRx. This function return JSONObject
+     *
+     * @param userName MediaWiki user name
+     * @return
+     */
+    public Single<FeedbackResponse> getAchievements(String userName) {
+        final String fetchAchievementUrlTemplate =
+                wikiMediaToolforgeUrl + "urbanecmbot/commonsmisc/feedback.py";
+        return Single.fromCallable(() -> {
+            String url = String.format(
+                    Locale.ENGLISH,
+                    fetchAchievementUrlTemplate,
+                    new PageTitle(userName).getText());
+            HttpUrl.Builder urlBuilder = HttpUrl.parse(url).newBuilder();
+            urlBuilder.addQueryParameter("user", userName);
+            Timber.i("Url %s", urlBuilder.toString());
+            Request request = new Request.Builder()
+                    .url(urlBuilder.toString())
+                    .build();
+            Response response = okHttpClient.newCall(request).execute();
+            if (response != null && response.body() != null && response.isSuccessful()) {
+                String json = response.body().string();
+                if (json == null) {
+                    return null;
+                }
+                Timber.d("Response for achievements is %s", json);
+                try {
+                    return gson.fromJson(json, FeedbackResponse.class);
+                } catch (Exception e) {
+                    return new FeedbackResponse("", 0, 0, 0, new FeaturedImages(0, 0), 0, "", 0);
+                }
+
+
+            }
+            return null;
+        });
+    }
+
+    public Observable<List<Place>> getNearbyPlaces(LatLng cur, String lang, double radius) throws IOException {
+        String wikidataQuery = FileUtils.readFromResource("/queries/nearby_query.rq");
+        String query = wikidataQuery
+                .replace("${RAD}", String.format(Locale.ROOT, "%.2f", radius))
+                .replace("${LAT}", String.format(Locale.ROOT, "%.4f", cur.getLatitude()))
+                .replace("${LONG}", String.format(Locale.ROOT, "%.4f", cur.getLongitude()))
+                .replace("${LANG}", lang);
+
+        HttpUrl.Builder urlBuilder = HttpUrl
+                .parse(sparqlQueryUrl)
+                .newBuilder()
+                .addQueryParameter("query", query)
+                .addQueryParameter("format", "json");
+
+        Request request = new Request.Builder()
+                .url(urlBuilder.build())
+                .build();
+
+        return Observable.fromCallable(() -> {
+            Response response = okHttpClient.newCall(request).execute();
+            if (response != null && response.body() != null && response.isSuccessful()) {
+                String json = response.body().string();
+                if (json == null) {
+                    return new ArrayList<>();
+                }
+                NearbyResponse nearbyResponse = gson.fromJson(json, NearbyResponse.class);
+                List<NearbyResultItem> bindings = nearbyResponse.getResults().getBindings();
+                List<Place> places = new ArrayList<>();
+                for (NearbyResultItem item : bindings) {
+                    places.add(Place.from(item));
+                }
+                return places;
+            }
+            return new ArrayList<>();
+        });
+    }
+
+    public Single<CampaignResponseDTO> getCampaigns() {
+        return Single.fromCallable(() -> {
+            Request request = new Request.Builder().url(campaignsUrl)
+                    .build();
+            Response response = okHttpClient.newCall(request).execute();
+            if (response != null && response.body() != null && response.isSuccessful()) {
+                String json = response.body().string();
+                if (json == null) {
+                    return null;
+                }
+                return gson.fromJson(json, CampaignResponseDTO.class);
+            }
+            return null;
+        });
+    }
+
+    /**
+     * The method returns the picture of the day
+     *
+     * @return Media object corresponding to the picture of the day
+     */
+    @Nullable
+    public Single<Media> getPictureOfTheDay() {
+        String template = "Template:Potd/" + DateUtils.getCurrentDate();
+        HttpUrl.Builder urlBuilder = HttpUrl
+                .parse(commonsBaseUrl)
+                .newBuilder()
+                .addQueryParameter("action", "query")
+                .addQueryParameter("generator", "images")
+                .addQueryParameter("format", "json")
+                .addQueryParameter("titles", template)
+                .addQueryParameter("prop", "imageinfo")
+                .addQueryParameter("iiprop", "url|extmetadata");
+
+        Request request = new Request.Builder()
+                .url(urlBuilder.build())
+                .build();
+
+        return Single.fromCallable(() -> {
+            Response response = okHttpClient.newCall(request).execute();
+            if (response != null && response.body() != null && response.isSuccessful()) {
+                String json = response.body().string();
+                if (json == null) {
+                    return null;
+                }
+                MwQueryResponse mwQueryPage = gson.fromJson(json, MwQueryResponse.class);
+                return Media.from(mwQueryPage.query().firstPage());
+            }
+            return null;
+        });
+    }
+
+    /**
+     * This method takes search keyword as input and returns a list of  Media objects filtered using search query
+     * It uses the generator query API to get the images searched using a query, 25 at a time.
+     * @param query keyword to search images on commons
+     * @return
+     */
+    @Nullable
+    public Single<List<Media>> searchImages(String query, int offset) {
+        HttpUrl.Builder urlBuilder = HttpUrl
+                .parse(commonsBaseUrl)
+                .newBuilder()
+                .addQueryParameter("action", "query")
+                .addQueryParameter("generator", "search")
+                .addQueryParameter("format", "json")
+                .addQueryParameter("gsrwhat", "text")
+                .addQueryParameter("gsrnamespace", "6")
+                .addQueryParameter("gsrlimit", "25")
+                .addQueryParameter("gsroffset", String.valueOf(offset))
+                .addQueryParameter("gsrsearch", query)
+                .addQueryParameter("prop", "imageinfo")
+                .addQueryParameter("iiprop", "url|extmetadata");
+
+        Request request = new Request.Builder()
+                .url(urlBuilder.build())
+                .build();
+
+        return Single.fromCallable(() -> {
+            Response response = okHttpClient.newCall(request).execute();
+            List<Media> mediaList = new ArrayList<>();
+            if (response != null && response.body() != null && response.isSuccessful()) {
+                String json = response.body().string();
+                if (json == null) {
+                    return mediaList;
+                }
+                MwQueryResponse mwQueryResponse = gson.fromJson(json, MwQueryResponse.class);
+                List<MwQueryPage> pages = mwQueryResponse.query().pages();
+                for (MwQueryPage page : pages) {
+                    mediaList.add(Media.from(page));
+                }
+            }
+            return mediaList;
+        });
+    }
+}

app/src/main/java/fr/free/nrw/commons/mwapi/model/MwException.java

@@ -0,0 +1,30 @@
+package fr.free.nrw.commons.mwapi.model;
+
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+
+public class MwException extends RuntimeException {
+    @SuppressWarnings("unused")
+    @NonNull
+    private final MwServiceError error;
+
+    public MwException(@NonNull MwServiceError error) {
+        this.error = error;
+    }
+
+    @NonNull
+    public MwServiceError getError() {
+        return error;
+    }
+
+    @Nullable
+    public String getTitle() {
+        return error.getTitle();
+    }
+
+    @Override
+    @Nullable
+    public String getMessage() {
+        return error.getDetails();
+    }
+}

app/src/main/java/fr/free/nrw/commons/mwapi/model/MwQueryResponse.java

@@ -0,0 +1,39 @@
+package fr.free.nrw.commons.mwapi.model;
+
+import android.support.annotation.Nullable;
+import android.support.annotation.VisibleForTesting;
+
+import com.google.gson.annotations.SerializedName;
+
+import java.util.Map;
+
+public class MwQueryResponse extends MwResponse {
+
+    @SuppressWarnings("unused") @SerializedName("batchcomplete") private boolean batchComplete;
+
+    @SuppressWarnings("unused") @SerializedName("continue") @Nullable
+    private Map<String, String> continuation;
+
+    @Nullable private MwQueryResult query;
+
+    public boolean batchComplete() {
+        return batchComplete;
+    }
+
+    @Nullable public Map<String, String> continuation() {
+        return continuation;
+    }
+
+    @Nullable public MwQueryResult query() {
+        return query;
+    }
+
+    public boolean success() {
+        return query != null;
+    }
+
+    @VisibleForTesting
+    protected void setQuery(@Nullable MwQueryResult query) {
+        this.query = query;
+    }
+}

app/src/main/java/fr/free/nrw/commons/mwapi/model/MwQueryResult.java

@@ -0,0 +1,44 @@
+package fr.free.nrw.commons.mwapi.model;
+
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import fr.free.nrw.commons.media.model.ImageInfo;
+import fr.free.nrw.commons.media.model.MwQueryPage;
+
+public class MwQueryResult {
+    @SuppressWarnings("unused")
+    @Nullable
+    private HashMap<String, MwQueryPage> pages;
+
+    @NonNull
+    public List<MwQueryPage> pages() {
+        if (pages == null) {
+            return new ArrayList<>();
+        }
+        return new ArrayList<>(pages.values());
+    }
+
+    @Nullable
+    public MwQueryPage firstPage() {
+        return pages().get(0);
+    }
+
+    @NonNull
+    public Map<String, ImageInfo> images() {
+        Map<String, ImageInfo> result = new HashMap<>();
+        if (pages != null) {
+            for (MwQueryPage page : pages()) {
+                if (page.imageInfo() != null) {
+                    result.put(page.title(), page.imageInfo());
+                }
+            }
+        }
+        return result;
+    }
+}

app/src/main/java/fr/free/nrw/commons/mwapi/model/MwResponse.java

@@ -0,0 +1,38 @@
+package fr.free.nrw.commons.mwapi.model;
+
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+
+import com.google.gson.annotations.SerializedName;
+
+import java.util.Map;
+
+import fr.free.nrw.commons.json.PostProcessingTypeAdapter;
+
+public abstract class MwResponse implements PostProcessingTypeAdapter.PostProcessable {
+    @SuppressWarnings("unused")
+    @Nullable
+    private MwServiceError error;
+
+    @SuppressWarnings("unused")
+    @Nullable
+    private Map<String, Warning> warnings;
+
+    @SuppressWarnings("unused,NullableProblems")
+    @SerializedName("servedby")
+    @NonNull
+    private String servedBy;
+
+    @Override
+    public void postProcess() {
+        if (error != null) {
+            throw new MwException(error);
+        }
+    }
+
+    private class Warning {
+        @SuppressWarnings("unused,NullableProblems")
+        @NonNull
+        private String warnings;
+    }
+}

app/src/main/java/fr/free/nrw/commons/mwapi/model/MwServiceError.java

@@ -0,0 +1,85 @@
+package fr.free.nrw.commons.mwapi.model;
+
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+
+import java.util.Collections;
+import java.util.List;
+
+import fr.free.nrw.commons.utils.StringUtils;
+
+/**
+ * Gson POJO for a MediaWiki API error.
+ */
+public class MwServiceError implements ServiceError {
+    @SuppressWarnings("unused")
+    @Nullable
+    private String code;
+    @SuppressWarnings("unused")
+    @Nullable
+    private String info;
+    @SuppressWarnings("unused")
+    @Nullable
+    private String docref;
+    @SuppressWarnings("unused")
+    @NonNull
+    private List<Message> messages = Collections.emptyList();
+
+    @Override
+    @NonNull
+    public String getTitle() {
+        return StringUtils.defaultString(code);
+    }
+
+    @Override
+    @NonNull
+    public String getDetails() {
+        return StringUtils.defaultString(info);
+    }
+
+    @Nullable
+    public String getDocRef() {
+        return docref;
+    }
+
+    public boolean badToken() {
+        return "badtoken".equals(code);
+    }
+
+    public boolean badLoginState() {
+        return "assertuserfailed".equals(code);
+    }
+
+    public boolean hasMessageName(@NonNull String messageName) {
+        for (Message msg : messages) {
+            if (messageName.equals(msg.name)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Nullable
+    public String getMessageHtml(@NonNull String messageName) {
+        for (Message msg : messages) {
+            if (messageName.equals(msg.name)) {
+                return msg.html();
+            }
+        }
+        return null;
+    }
+
+    private static final class Message {
+        @SuppressWarnings("unused")
+        @Nullable
+        private String name;
+        @SuppressWarnings("unused")
+        @Nullable
+        private String html;
+
+        @NonNull
+        private String html() {
+            return StringUtils.defaultString(html);
+        }
+    }
+}

app/src/main/java/fr/free/nrw/commons/mwapi/model/ServiceError.java

@@ -0,0 +1,13 @@
+package fr.free.nrw.commons.mwapi.model;
+
+import android.support.annotation.NonNull;
+
+/**
+ * The API reported an error in the payload.
+ */
+public interface ServiceError {
+    @NonNull
+    String getTitle();
+
+    @NonNull String getDetails();
+}