Support domain redirects via `/.well-known/host-meta`

Closes #312

mastodon/src/main/java/org/joinmastodon/android/fragments/onboarding/InstanceCatalogFragment.java

@@ -1,5 +1,6 @@
 package org.joinmastodon.android.fragments.onboarding;
 
+import android.app.Activity;
 import android.app.ProgressDialog;
 import android.content.Context;
 import android.net.Uri;
@@ -9,6 +10,7 @@ import android.os.LocaleList;
 import android.text.Editable;
 import android.text.TextUtils;
 import android.text.TextWatcher;
+import android.util.Log;
 import android.view.KeyEvent;
 import android.view.View;
 import android.view.ViewGroup;
@@ -21,6 +23,7 @@ import android.widget.RadioButton;
 import android.widget.TextView;
 
 import org.joinmastodon.android.R;
+import org.joinmastodon.android.api.MastodonAPIController;
 import org.joinmastodon.android.api.MastodonAPIRequest;
 import org.joinmastodon.android.api.MastodonErrorResponse;
 import org.joinmastodon.android.api.requests.instance.GetInstance;
@@ -36,7 +39,13 @@ import org.joinmastodon.android.ui.M3AlertDialogBuilder;
 import org.joinmastodon.android.ui.tabs.TabLayout;
 import org.joinmastodon.android.ui.utils.UiUtils;
 import org.parceler.Parcels;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+import org.xml.sax.InputSource;
 
+import java.io.IOException;
 import java.net.IDN;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -46,6 +55,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
+import javax.xml.parsers.DocumentBuilderFactory;
+
 import androidx.annotation.NonNull;
 import androidx.recyclerview.widget.DiffUtil;
 import androidx.recyclerview.widget.RecyclerView;
@@ -58,6 +69,9 @@ import me.grishka.appkit.utils.MergeRecyclerAdapter;
 import me.grishka.appkit.utils.SingleViewRecyclerAdapter;
 import me.grishka.appkit.utils.V;
 import me.grishka.appkit.views.UsableRecyclerView;
+import okhttp3.Call;
+import okhttp3.Request;
+import okhttp3.Response;
 
 public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstance>{
 	private InstancesAdapter adapter;
@@ -75,9 +89,11 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 	private List<CatalogCategory> categories=new ArrayList<>();
 	private String loadingInstanceDomain;
 	private GetInstance loadingInstanceRequest;
+	private Call loadingInstanceRedirectRequest;
 	private HashMap<String, Instance> instancesCache=new HashMap<>();
 	private ProgressDialog instanceProgressDialog;
 	private View buttonBar;
+	private HashMap<String, String> redirects=new HashMap<>(), redirectsInverse=new HashMap<>();
 
 	private boolean isSignup;
 
@@ -271,7 +287,7 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 		}else{
 			showProgressDialog();
 			if(!domain.equals(loadingInstanceDomain)){
-				loadInstanceInfo(domain);
+				loadInstanceInfo(domain, false);
 			}
 		}
 	}
@@ -353,7 +369,7 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 		Instance instance=instancesCache.get(normalizeInstanceDomain(currentSearchQuery));
 		if(instance==null){
 			showProgressDialog();
-			loadInstanceInfo(currentSearchQuery);
+			loadInstanceInfo(currentSearchQuery, false);
 		}else{
 			proceedWithAuthOrSignup(instance);
 		}
@@ -363,7 +379,7 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 	private void onSearchChangedDebounced(){
 		currentSearchQuery=searchEdit.getText().toString().toLowerCase();
 		updateFilteredList();
-		loadInstanceInfo(currentSearchQuery);
+		loadInstanceInfo(currentSearchQuery, false);
 	}
 
 	private void updateFilteredList(){
@@ -403,13 +419,7 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 	private void showProgressDialog(){
 		instanceProgressDialog=new ProgressDialog(getActivity());
 		instanceProgressDialog.setMessage(getString(R.string.loading_instance));
-		instanceProgressDialog.setOnCancelListener(dialog->{
+		instanceProgressDialog.setOnCancelListener(dialog->cancelLoadingInstanceInfo());
-			if(loadingInstanceRequest!=null){
-				loadingInstanceRequest.cancel();
-				loadingInstanceRequest=null;
-				loadingInstanceDomain=null;
-			}
-		});
 		instanceProgressDialog.show();
 	}
 
@@ -429,10 +439,12 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 		}catch(IllegalArgumentException x){
 			return null;
 		}
+		if(redirects.containsKey(domain))
+			return redirects.get(domain);
 		return domain;
 	}
 
-	private void loadInstanceInfo(String _domain){
+	private void loadInstanceInfo(String _domain, boolean isFromRedirect){
 		String domain=normalizeInstanceDomain(_domain);
 		Instance cachedInstance=instancesCache.get(domain);
 		if(cachedInstance!=null){
@@ -446,10 +458,11 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 			return;
 		}
 		if(loadingInstanceDomain!=null){
-			if(loadingInstanceDomain.equals(domain))
+			if(loadingInstanceDomain.equals(domain)){
 				return;
-			else
+			}else{
-				loadingInstanceRequest.cancel();
+				cancelLoadingInstanceInfo();
+			}
 		}
 		loadingInstanceDomain=domain;
 		loadingInstanceRequest=new GetInstance();
@@ -465,7 +478,7 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 							instanceProgressDialog=null;
 							proceedWithAuthOrSignup(result);
 						}
-						if(domain.equals(currentSearchQuery)){
+						if(domain.equals(currentSearchQuery) || currentSearchQuery.equals(redirects.get(domain)) || currentSearchQuery.equals(redirectsInverse.get(domain))){
 							boolean found=false;
 							for(CatalogInstance ci:filteredData){
 								if(ci.domain.equals(domain)){
@@ -484,20 +497,105 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 					@Override
 					public void onError(ErrorResponse error){
 						loadingInstanceRequest=null;
-						loadingInstanceDomain=null;
+						if(!isFromRedirect && error instanceof MastodonErrorResponse me && me.httpStatus==404){
-						if(instanceProgressDialog!=null){
+							fetchDomainFromHostMetaAndMaybeRetry(domain, error);
-							instanceProgressDialog.dismiss();
+							return;
-							instanceProgressDialog=null;
-							new M3AlertDialogBuilder(getActivity())
-									.setTitle(R.string.error)
-									.setMessage(getString(R.string.not_a_mastodon_instance, domain)+"\n\n"+((MastodonErrorResponse)error).error)
-									.setPositiveButton(R.string.ok, null)
-									.show();
 						}
+						loadingInstanceDomain=null;
+						showInstanceInfoLoadError(domain, error);
 					}
 				}).execNoAuth(domain);
 	}
 
+	private void cancelLoadingInstanceInfo(){
+		if(loadingInstanceRequest!=null){
+			loadingInstanceRequest.cancel();
+			loadingInstanceRequest=null;
+		}
+		if(loadingInstanceRedirectRequest!=null){
+			loadingInstanceRedirectRequest.cancel();
+			loadingInstanceRedirectRequest=null;
+		}
+		loadingInstanceDomain=null;
+		if(instanceProgressDialog!=null){
+			instanceProgressDialog.dismiss();
+			instanceProgressDialog=null;
+		}
+	}
+
+	private void showInstanceInfoLoadError(String domain, Object error){
+		if(instanceProgressDialog!=null){
+			instanceProgressDialog.dismiss();
+			instanceProgressDialog=null;
+			String additionalInfo;
+			if(error instanceof MastodonErrorResponse me){
+				additionalInfo="\n\n"+me.error;
+			}else if(error instanceof Throwable t){
+				additionalInfo="\n\n"+t.getLocalizedMessage();
+			}else{
+				additionalInfo="";
+			}
+			new M3AlertDialogBuilder(getActivity())
+					.setTitle(R.string.error)
+					.setMessage(getString(R.string.not_a_mastodon_instance, domain)+additionalInfo)
+					.setPositiveButton(R.string.ok, null)
+					.show();
+		}
+	}
+
+	private void fetchDomainFromHostMetaAndMaybeRetry(String domain, Object origError){
+		String url="https://"+domain+"/.well-known/host-meta";
+		Request req=new Request.Builder()
+				.url(url)
+				.build();
+		loadingInstanceRedirectRequest=MastodonAPIController.getHttpClient().newCall(req);
+		loadingInstanceRedirectRequest.enqueue(new okhttp3.Callback(){
+			@Override
+			public void onFailure(@NonNull Call call, @NonNull IOException e){
+				loadingInstanceRedirectRequest=null;
+				loadingInstanceDomain=null;
+				Activity a=getActivity();
+				if(a==null)
+					return;
+				a.runOnUiThread(()->showInstanceInfoLoadError(domain, e));
+			}
+
+			@Override
+			public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException{
+				loadingInstanceRedirectRequest=null;
+				loadingInstanceDomain=null;
+				Activity a=getActivity();
+				if(a==null)
+					return;
+				try(response){
+					if(!response.isSuccessful()){
+						a.runOnUiThread(()->showInstanceInfoLoadError(domain, response.code()+" "+response.message()));
+						return;
+					}
+					InputSource source=new InputSource(response.body().charStream());
+					Document doc=DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(source);
+					NodeList list=doc.getElementsByTagName("Link");
+					for(int i=0;i<list.getLength();i++){
+						if(list.item(i) instanceof Element el){
+							String template=el.getAttribute("template");
+							if("lrdd".equals(el.getAttribute("rel")) && !TextUtils.isEmpty(template) && template.contains("{uri}")){
+								Uri uri=Uri.parse(template.replace("{uri}", "qwe"));
+								String redirectDomain=normalizeInstanceDomain(uri.getHost());
+								redirects.put(domain, redirectDomain);
+								redirectsInverse.put(redirectDomain, domain);
+								a.runOnUiThread(()->loadInstanceInfo(redirectDomain, true));
+								return;
+							}
+						}
+					}
+					a.runOnUiThread(()->showInstanceInfoLoadError(domain, origError));
+				}catch(Exception x){
+					a.runOnUiThread(()->showInstanceInfoLoadError(domain, x));
+				}
+			}
+		});
+	}
+
 	@Override
 	public void onApplyWindowInsets(WindowInsets insets){
 		if(Build.VERSION.SDK_INT>=27){
@@ -580,7 +678,7 @@ public class InstanceCatalogFragment extends BaseRecyclerFragment<CatalogInstanc
 			if(chosenInstance==null)
 				nextButton.setEnabled(true);
 			chosenInstance=item;
-			loadInstanceInfo(chosenInstance.domain);
+			loadInstanceInfo(chosenInstance.domain, false);
 		}
 	}
 }