Add support for add subreddit to multireddit api method

Author: mrboisvert

src/main/java/org/quantumbadger/redreader/reddit/RedditAPI.java

@@ -25,6 +25,7 @@
 import androidx.annotation.Nullable;
 import androidx.appcompat.app.AppCompatActivity;
 
+import org.json.JSONObject;
 import org.quantumbadger.redreader.account.RedditAccount;
 import org.quantumbadger.redreader.activities.BugReportActivity;
 import org.quantumbadger.redreader.cache.CacheManager;
@@ -65,6 +66,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -959,6 +961,35 @@ public void onFailure(@NonNull final RRError error) {
 		));
 	}
 
+	public static void addSubredditToMultireddit(
+			final CacheManager cm,
+			final APIResponseHandler.ActionResponseHandler handler,
+			final RedditAccount user,
+			final String multiredditName,
+			final String subredditName,
+			final Context context) {
+
+		final Uri.Builder builder = Constants.Reddit.getUriBuilder(
+				Constants.Reddit.PATH_MULTIREDDIT)
+				.appendPath("user")
+				.appendPath(user.username)
+				.appendPath("m")
+				.appendPath(multiredditName)
+				.appendPath("r")
+				.appendPath(subredditName);
+
+		final Map<String, String> jsonData = new HashMap<>();
+		jsonData.put("name", subredditName);
+
+		cm.makeRequest(createPutRequest(
+				UriString.from(builder.build()),
+				user,
+				new ArrayList<>(Collections.singleton(
+					new PostField("model", new JSONObject(jsonData).toString()))),
+				context,
+				new GenericResponseHandler(handler)));
+	}
+
 	@Nullable
 	private static APIResponseHandler.APIFailureType findFailureType(final JsonValue response) {