Add support for opaque shared URLs, fixes #1122 (#1123)

src/main/java/org/quantumbadger/redreader/common/LinkHandler.java

@@ -47,6 +47,7 @@
 import org.quantumbadger.redreader.cache.CacheRequest;
 import org.quantumbadger.redreader.fragments.ShareOrderDialog;
 import org.quantumbadger.redreader.fragments.UserProfileDialog;
+import org.quantumbadger.redreader.http.HTTPBackend;
 import org.quantumbadger.redreader.image.AlbumInfo;
 import org.quantumbadger.redreader.image.DeviantArtAPI;
 import org.quantumbadger.redreader.image.GetAlbumInfoListener;
@@ -63,6 +64,7 @@
 import org.quantumbadger.redreader.reddit.kthings.RedditPost;
 import org.quantumbadger.redreader.reddit.url.ComposeMessageURL;
 import org.quantumbadger.redreader.reddit.url.PostCommentListingURL;
+import org.quantumbadger.redreader.reddit.url.OpaqueSharedURL;
 import org.quantumbadger.redreader.reddit.url.RedditURLParser;
 
 import java.util.ArrayList;
@@ -227,7 +229,26 @@ public static void onLinkClicked(
 		if(redditURL != null) {
 
 			switch(redditURL.pathType()) {
-
+				case RedditURLParser.OPAQUE_SHARED_URL:
+					// kick off a thread to get the real url
+					new Thread(() -> {
+						final String toFetchUrl = OpaqueSharedURL.getUrlToFetch(
+								(OpaqueSharedURL) redditURL
+						).toString();
+						final String realUrl = HTTPBackend.getBackend()
+								.resolveRedirectUri(toFetchUrl);
+						if(realUrl != null) {
+							activity.runOnUiThread(() -> onLinkClicked(
+									activity,
+									realUrl,
+									forceNoImage,
+									post,
+									albumInfo,
+									albumImageIndex,
+									fromExternalIntent));
+						}
+					}).start();
+					return;
 				case RedditURLParser.SUBREDDIT_POST_LISTING_URL:
 				case RedditURLParser.MULTIREDDIT_POST_LISTING_URL:
 				case RedditURLParser.USER_POST_LISTING_URL:

src/main/java/org/quantumbadger/redreader/fragments/PostListingFragment.java

@@ -376,6 +376,7 @@ public void onRequestSuccess(
 			case RedditURLParser.USER_COMMENT_LISTING_URL:
 			case RedditURLParser.USER_PROFILE_URL:
 			case RedditURLParser.COMPOSE_MESSAGE_URL:
+			case RedditURLParser.OPAQUE_SHARED_URL:
 				BugReportActivity.handleGlobalError(getActivity(), new RuntimeException(
 						"Unknown url type "
 								+ mPostListingURL.pathType()

src/main/java/org/quantumbadger/redreader/http/HTTPBackend.java

@@ -18,8 +18,10 @@
 package org.quantumbadger.redreader.http;
 
 import android.content.Context;
+
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+
 import org.quantumbadger.redreader.cache.CacheRequest;
 import org.quantumbadger.redreader.common.Optional;
 import org.quantumbadger.redreader.http.body.HTTPRequestBody;
@@ -87,6 +89,8 @@ void onError(
 		void onSuccess(String mimetype, Long bodyBytes, InputStream body);
 	}
 
+	public abstract @Nullable String resolveRedirectUri(String url);
+
 	public abstract Request prepareRequest(Context context, RequestDetails details);
 
 	public abstract void recreateHttpBackend();

src/main/java/org/quantumbadger/redreader/http/okhttp/OKHTTPBackend.java

@@ -31,6 +31,7 @@
 import okhttp3.MediaType;
 import okhttp3.MultipartBody;
 import okhttp3.OkHttpClient;
+import okhttp3.Request.Builder;
 import okhttp3.RequestBody;
 import okhttp3.Response;
 import okhttp3.ResponseBody;
@@ -173,10 +174,29 @@ public synchronized void recreateHttpBackend() {
 		httpBackend = new OKHTTPBackend();
 	}
 
+	@Override
+	public String resolveRedirectUri(final String url) {
+		try {
+			final Builder builder = new Builder();
+			final okhttp3.Request headRequest = builder.url(url).head().build();
+			final OkHttpClient noRedirectsClient =
+					mClient.newBuilder().followRedirects(false).build();
+			try (Response response = noRedirectsClient.newCall(headRequest).execute()) {
+				if (response.isRedirect()) {
+					return response.header("Location");
+				}
+			}
+		} catch (final IOException e) {
+			Log.e(TAG, "Failed to resolve redirect URL", e);
+			return null;
+		}
+		return null;
+	}
+
 	@Override
 	public Request prepareRequest(final Context context, final RequestDetails details) {
 
-		final okhttp3.Request.Builder builder = new okhttp3.Request.Builder();
+		final Builder builder = new Builder();
 
 		builder.header("User-Agent", Constants.ua(context));
 

src/main/java/org/quantumbadger/redreader/reddit/url/OpaqueSharedURL.java

@@ -0,0 +1,76 @@
+/*******************************************************************************
+ * This file is part of RedReader.
+ *
+ * RedReader is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * RedReader is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with RedReader.  If not, see <http://www.gnu.org/licenses/>.
+ ******************************************************************************/
+
+package org.quantumbadger.redreader.reddit.url;
+
+import android.net.Uri;
+
+import androidx.annotation.Nullable;
+
+import java.util.List;
+
+public class OpaqueSharedURL extends RedditURLParser.RedditURL {
+
+	@Nullable
+	public final String subreddit;
+	@Nullable public final String shareKey;
+
+	public OpaqueSharedURL(@Nullable final String subreddit, @Nullable final String shareKey) {
+		this.subreddit = subreddit;
+		this.shareKey = shareKey;
+	}
+
+	@Override
+	public Uri generateJsonUri() {
+		return null;
+	}
+
+	@Override
+	public int pathType() {
+		return RedditURLParser.OPAQUE_SHARED_URL;
+	}
+
+	public static OpaqueSharedURL parse(final Uri uri) {
+		// URLs look like https://reddit.com/r/RedReader/s/<alphanumeric>
+		// first pull out the path segments and ensure they match the example (should be 4)
+		final List<String> pathSegments = uri.getPathSegments();
+		if (pathSegments.size() != 4) {
+			return null;
+		}
+
+		// ensure the first segment is "r" and the third is "s"
+		if (!pathSegments.get(0).equals("r") || !pathSegments.get(2).equals("s")) {
+			return null;
+		}
+
+		return new OpaqueSharedURL(pathSegments.get(1), pathSegments.get(3));
+	}
+
+	public static Uri getUrlToFetch(final OpaqueSharedURL url) {
+		return Uri.parse(String.format("https://www.reddit.com/r/%s/s/%s", url.subreddit, url.shareKey));
+	}
+
+	@Nullable
+	public String getSubreddit() {
+		return subreddit;
+	}
+
+	@Nullable
+	public String getShareKey() {
+		return shareKey;
+	}
+}

src/main/java/org/quantumbadger/redreader/reddit/url/RedditURLParser.java

@@ -41,6 +41,7 @@ public class RedditURLParser {
 	public static final int POST_COMMENT_LISTING_URL = 7;
 	public static final int MULTIREDDIT_POST_LISTING_URL = 8;
 	public static final int COMPOSE_MESSAGE_URL = 9;
+	public static final int OPAQUE_SHARED_URL = 10;
 
 	@IntDef({
 			SUBREDDIT_POST_LISTING_URL,
@@ -52,7 +53,9 @@ public class RedditURLParser {
 			UNKNOWN_COMMENT_LISTING_URL,
 			POST_COMMENT_LISTING_URL,
 			MULTIREDDIT_POST_LISTING_URL,
-			COMPOSE_MESSAGE_URL})
+			COMPOSE_MESSAGE_URL,
+			OPAQUE_SHARED_URL
+	})
 	@Retention(RetentionPolicy.SOURCE)
 	public @interface PathType {
 	}
@@ -122,6 +125,13 @@ public static RedditURL parse(final Uri rawUri) {
 
 		final Uri uri = optionalUri.get();
 
+		{
+			final OpaqueSharedURL opaqueSharedURL = OpaqueSharedURL.parse(uri);
+			if(opaqueSharedURL != null) {
+				return opaqueSharedURL;
+			}
+		}
+
 		{
 			final SubredditPostListURL subredditPostListURL = SubredditPostListURL.parse(uri);
 			if(subredditPostListURL != null) {