implement channel discovery

refactor muc search to use http
cache channel search results

17 files changed, 635 insertions, 3 deletions

diff --git a/build.gradle b/build.gradle
index a27b439b0..53875273a 100644
--- a/build.gradle
+++ b/build.gradle
@@ -83,6 +83,9 @@ dependencies {
     implementation 'com.leinardi.android:speed-dial:2.0.1'
     implementation 'com.squareup.picasso:picasso:2.71828'
     implementation 'com.squareup.okhttp3:okhttp:3.12.2' // versions > 3.12.x don't support API level < 21 anymore
+    implementation 'com.squareup.retrofit2:retrofit:2.5.0'
+    implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
+    implementation 'com.google.guava:guava:27.1-android'
 }
 
 ext {
diff --git a/proguard-rules.pro b/proguard-rules.pro
index e60465e6c..336771bcd 100644
--- a/proguard-rules.pro
+++ b/proguard-rules.pro
@@ -19,6 +19,8 @@
 -dontwarn org.bouncycastle.cert.dane.**
 -dontwarn rocks.xmpp.addr.**
 -dontwarn com.google.firebase.analytics.connector.AnalyticsConnector
+-dontwarn java.lang.**
+-dontwarn javax.lang.**
 
 # JSR 305 annotations are for embedding nullability information.
 -dontwarn javax.annotation.**
diff --git a/src/main/AndroidManifest.xml b/src/main/AndroidManifest.xml
index 71b2e5909..217f90d1e 100644
--- a/src/main/AndroidManifest.xml
+++ b/src/main/AndroidManifest.xml
@@ -312,6 +312,9 @@
         <activity
             android:name=".ui.MucUsersActivity"
             android:label="@string/group_chat_members" />
+        <activity
+            android:name=".ui.ChannelDiscoveryActivity"
+            android:label="@string/discover_channels" />
 
         <service android:name=".services.ExportBackupService" />
         <service android:name=".services.ImportBackupService" />
diff --git a/src/main/java/de/pixart/messenger/Config.java b/src/main/java/de/pixart/messenger/Config.java
index a5d25786b..e61b1d28e 100644
--- a/src/main/java/de/pixart/messenger/Config.java
+++ b/src/main/java/de/pixart/messenger/Config.java
@@ -54,6 +54,7 @@ public final class Config {
     public static final String DOMAIN_LOCK = null; //BuildConfig.DOMAIN_LOCK; //only allow account creation for this domain
     public static final String MAGIC_CREATE_DOMAIN = "blabber.im";
     public static final String QUICKSY_DOMAIN = "quicksy.im";
+    public static final String CHANNEL_DISCOVERY = "https://search.jabbercat.org";
     public static final boolean DISALLOW_REGISTRATION_IN_UI = false; //hide the register checkbox
 
     public static final boolean USE_RANDOM_RESOURCE_ON_EVERY_BIND = false;
diff --git a/src/main/java/de/pixart/messenger/http/services/MuclumbusService.java b/src/main/java/de/pixart/messenger/http/services/MuclumbusService.java
new file mode 100644
index 000000000..7c8ca9e32
--- /dev/null
+++ b/src/main/java/de/pixart/messenger/http/services/MuclumbusService.java
@@ -0,0 +1,92 @@
+package de.pixart.messenger.http.services;
+
+import com.google.common.base.Objects;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+
+import de.pixart.messenger.services.AvatarService;
+import de.pixart.messenger.utils.UIHelper;
+import retrofit2.Call;
+import retrofit2.http.Body;
+import retrofit2.http.GET;
+import retrofit2.http.POST;
+import retrofit2.http.Query;
+import rocks.xmpp.addr.Jid;
+
+public interface MuclumbusService {
+
+    @GET("/api/1.0/rooms/unsafe")
+    Call<Rooms> getRooms(@Query("p") int page);
+
+    @POST("/api/1.0/search")
+    Call<SearchResult> search(@Body SearchRequest searchRequest);
+
+    class Rooms {
+        int page;
+        int total;
+        int pages;
+        public List<Room> items;
+    }
+
+    class Room implements AvatarService.Avatarable {
+
+        public String address;
+        public String name;
+        public String description;
+
+        public String getName() {
+            return name;
+        }
+
+        public String getDescription() {
+            return description;
+        }
+
+        public Jid getRoom() {
+            try {
+                return Jid.of(address);
+            } catch (IllegalArgumentException e) {
+                return null;
+            }
+        }
+
+        @Override
+        public int getAvatarBackgroundColor() {
+            Jid room = getRoom();
+            return UIHelper.getColorForName(room != null ? room.asBareJid().toEscapedString() : name);
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+            Room room = (Room) o;
+            return Objects.equal(address, room.address) &&
+                    Objects.equal(name, room.name) &&
+                    Objects.equal(description, room.description);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hashCode(address, name, description);
+        }
+    }
+
+    class SearchRequest {
+        public Set<String> keywords;
+
+        public SearchRequest(String keyword) {
+            this.keywords = Collections.singleton(keyword);
+        }
+    }
+
+    class SearchResult {
+        public Result result;
+    }
+
+    class Result {
+        public List<Room> items;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/de/pixart/messenger/services/AvatarService.java b/src/main/java/de/pixart/messenger/services/AvatarService.java
index b37811b7f..c38fdcc99 100644
--- a/src/main/java/de/pixart/messenger/services/AvatarService.java
+++ b/src/main/java/de/pixart/messenger/services/AvatarService.java
@@ -38,6 +38,7 @@ import de.pixart.messenger.entities.Conversational;
 import de.pixart.messenger.entities.ListItem;
 import de.pixart.messenger.entities.Message;
 import de.pixart.messenger.entities.MucOptions;
+import de.pixart.messenger.http.services.MuclumbusService;
 import de.pixart.messenger.utils.UIHelper;
 import de.pixart.messenger.xmpp.OnAdvancedStreamFeaturesLoaded;
 import de.pixart.messenger.xmpp.XmppConnection;
@@ -82,10 +83,21 @@ public class AvatarService implements OnAdvancedStreamFeaturesLoaded {
             return get((ListItem) avatarable, size, cachedOnly);
         } else if (avatarable instanceof MucOptions.User) {
             return get((MucOptions.User) avatarable, size, cachedOnly);
+        } else if (avatarable instanceof MuclumbusService.Room) {
+            return get((MuclumbusService.Room) avatarable, size, cachedOnly);
         }
         throw new AssertionError("AvatarService does not know how to generate avatar from "+avatarable.getClass().getName());
     }
 
+    private Bitmap get(final MuclumbusService.Room result, final int size, boolean cacheOnly) {
+        final Jid room = result.getRoom();
+        Conversation conversation = room != null ? mXmppConnectionService.findFirstMuc(room) : null;
+        if (conversation != null) {
+            return get(conversation, size, cacheOnly);
+        }
+        return get(result.getName(), room != null ? room.asBareJid().toEscapedString() : result.getName(), size, cacheOnly);
+    }
+
     private Bitmap get(final Contact contact, final int size, boolean cachedOnly) {
         if (contact.isSelf()) {
             return get(contact.getAccount(), size, cachedOnly);
diff --git a/src/main/java/de/pixart/messenger/services/ChannelDiscoveryService.java b/src/main/java/de/pixart/messenger/services/ChannelDiscoveryService.java
new file mode 100644
index 000000000..21711c647
--- /dev/null
+++ b/src/main/java/de/pixart/messenger/services/ChannelDiscoveryService.java
@@ -0,0 +1,103 @@
+package de.pixart.messenger.services;
+
+import android.util.Log;
+
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+
+import java.util.List;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import de.pixart.messenger.Config;
+import de.pixart.messenger.http.services.MuclumbusService;
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+import retrofit2.Retrofit;
+import retrofit2.converter.gson.GsonConverterFactory;
+
+public class ChannelDiscoveryService {
+
+    private final XmppConnectionService service;
+
+    private final MuclumbusService muclumbusService;
+
+    private final Cache<String, List<MuclumbusService.Room>> cache;
+
+    public ChannelDiscoveryService(XmppConnectionService service) {
+        this.service = service;
+        Retrofit retrofit = new Retrofit.Builder()
+                .baseUrl(Config.CHANNEL_DISCOVERY)
+                .addConverterFactory(GsonConverterFactory.create())
+                .callbackExecutor(Executors.newSingleThreadExecutor())
+                .build();
+        this.muclumbusService = retrofit.create(MuclumbusService.class);
+        this.cache = CacheBuilder.newBuilder().expireAfterWrite(5, TimeUnit.MINUTES).build();
+    }
+
+    public void discover(String query, OnChannelSearchResultsFound onChannelSearchResultsFound) {
+        final boolean all = query == null || query.trim().isEmpty();
+        Log.d(Config.LOGTAG, "discover channels. query=" + query);
+        List<MuclumbusService.Room> result = cache.getIfPresent(all ? "" : query);
+        if (result != null) {
+            onChannelSearchResultsFound.onChannelSearchResultsFound(result);
+            return;
+        }
+        if (all) {
+            discoverChannels(onChannelSearchResultsFound);
+        } else {
+            discoverChannels(query, onChannelSearchResultsFound);
+        }
+    }
+
+    private void discoverChannels(OnChannelSearchResultsFound listener) {
+        Call<MuclumbusService.Rooms> call = muclumbusService.getRooms(1);
+        try {
+            call.enqueue(new Callback<MuclumbusService.Rooms>() {
+                @Override
+                public void onResponse(Call<MuclumbusService.Rooms> call, Response<MuclumbusService.Rooms> response) {
+                    final MuclumbusService.Rooms body = response.body();
+                    if (body == null) {
+                        return;
+                    }
+                    cache.put("", body.items);
+                    listener.onChannelSearchResultsFound(body.items);
+                }
+
+                @Override
+                public void onFailure(Call<MuclumbusService.Rooms> call, Throwable throwable) {
+
+                }
+            });
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    private void discoverChannels(final String query, OnChannelSearchResultsFound listener) {
+        Call<MuclumbusService.SearchResult> searchResultCall = muclumbusService.search(new MuclumbusService.SearchRequest(query));
+
+        searchResultCall.enqueue(new Callback<MuclumbusService.SearchResult>() {
+            @Override
+            public void onResponse(Call<MuclumbusService.SearchResult> call, Response<MuclumbusService.SearchResult> response) {
+                System.out.println(response.message());
+                MuclumbusService.SearchResult body = response.body();
+                if (body == null) {
+                    return;
+                }
+                cache.put(query, body.result.items);
+                listener.onChannelSearchResultsFound(body.result.items);
+            }
+
+            @Override
+            public void onFailure(Call<MuclumbusService.SearchResult> call, Throwable throwable) {
+                throwable.printStackTrace();
+            }
+        });
+    }
+
+    public interface OnChannelSearchResultsFound {
+        void onChannelSearchResultsFound(List<MuclumbusService.Room> results);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/de/pixart/messenger/services/XmppConnectionService.java b/src/main/java/de/pixart/messenger/services/XmppConnectionService.java
index 5de9a7501..1456d5a8e 100644
--- a/src/main/java/de/pixart/messenger/services/XmppConnectionService.java
+++ b/src/main/java/de/pixart/messenger/services/XmppConnectionService.java
@@ -78,6 +78,7 @@ import java.util.Set;
 import java.util.WeakHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Executors;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 
@@ -110,6 +111,7 @@ import de.pixart.messenger.generator.MessageGenerator;
 import de.pixart.messenger.generator.PresenceGenerator;
 import de.pixart.messenger.http.CustomURLStreamHandlerFactory;
 import de.pixart.messenger.http.HttpConnectionManager;
+import de.pixart.messenger.http.services.MuclumbusService;
 import de.pixart.messenger.parser.AbstractParser;
 import de.pixart.messenger.parser.IqParser;
 import de.pixart.messenger.parser.MessageParser;
@@ -162,13 +164,14 @@ import de.pixart.messenger.xmpp.stanzas.IqPacket;
 import de.pixart.messenger.xmpp.stanzas.MessagePacket;
 import de.pixart.messenger.xmpp.stanzas.PresencePacket;
 import me.leolin.shortcutbadger.ShortcutBadger;
+import retrofit2.Retrofit;
+import retrofit2.converter.gson.GsonConverterFactory;
 import rocks.xmpp.addr.Jid;
 
 import static de.pixart.messenger.ui.SettingsActivity.CHAT_STATES;
 import static de.pixart.messenger.ui.SettingsActivity.CONFIRM_MESSAGES;
 import static de.pixart.messenger.ui.SettingsActivity.ENABLE_MULTI_ACCOUNTS;
 import static de.pixart.messenger.ui.SettingsActivity.INDICATE_RECEIVED;
-import static de.pixart.messenger.ui.SettingsActivity.ENABLE_MULTI_ACCOUNTS;
 
 public class XmppConnectionService extends Service {
 
@@ -255,9 +258,11 @@ public class XmppConnectionService extends Service {
     private long mLastActivity = 0;
     private MemorizingTrustManager mMemorizingTrustManager;
     private NotificationService mNotificationService = new NotificationService(this);
+    private ChannelDiscoveryService mChannelDiscoveryService = new ChannelDiscoveryService(this);
     private ShortcutService mShortcutService = new ShortcutService(this);
     private AtomicBoolean mInitialAddressbookSyncCompleted = new AtomicBoolean(false);
     protected AtomicBoolean mForceForegroundService = new AtomicBoolean(false);
+    private AtomicBoolean mForceDuringOnCreate = new AtomicBoolean(false);
     private OnMessagePacketReceived mMessageParser = new MessageParser(this);
     private OnPresencePacketReceived mPresenceParser = new PresenceParser(this);
     private IqParser mIqParser = new IqParser(this);
@@ -834,6 +839,10 @@ public class XmppConnectionService extends Service {
         editor.commit();
     }
 
+    public void discoverChannels(String query, ChannelDiscoveryService.OnChannelSearchResultsFound onChannelSearchResultsFound) {
+        mChannelDiscoveryService.discover(query, onChannelSearchResultsFound);
+    }
+
     public boolean isDataSaverDisabled() {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
             ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
@@ -1144,6 +1153,7 @@ public class XmppConnectionService extends Service {
         if (Compatibility.runsTwentySix()) {
             mNotificationService.initializeChannels();
         }
+        mForceDuringOnCreate.set(Compatibility.runsAndTargetsTwentySix(this));
         final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
         final int cacheSize = maxMemory / 8;
         this.mBitmapCache = new LruCache<String, Bitmap>(cacheSize) {
@@ -1213,6 +1223,8 @@ public class XmppConnectionService extends Service {
             intentFilter.addAction(NotificationManager.ACTION_INTERRUPTION_FILTER_CHANGED);
             registerReceiver(this.mInternalEventReceiver, intentFilter);
         }
+        mForceDuringOnCreate.set(false);
+        toggleForegroundService();
         //start export log service every day at given time
         ScheduleAutomaticExport();
         // cancel scheduled exporter
@@ -1307,7 +1319,7 @@ public class XmppConnectionService extends Service {
 
     private void toggleForegroundService(boolean force) {
         final boolean status;
-        if (force || mForceForegroundService.get() || (Compatibility.keepForegroundService(this)/* && hasEnabledAccounts()*/)) {
+        if (force || mForceDuringOnCreate.get() || mForceForegroundService.get() || (Compatibility.keepForegroundService(this) && hasEnabledAccounts())) {
             final Notification notification = this.mNotificationService.createForegroundNotification();
             startForeground(NotificationService.FOREGROUND_NOTIFICATION_ID, notification);
             if (!mForceForegroundService.get()) {
diff --git a/src/main/java/de/pixart/messenger/ui/ChannelDiscoveryActivity.java b/src/main/java/de/pixart/messenger/ui/ChannelDiscoveryActivity.java
new file mode 100644
index 000000000..e0b70b6ac
--- /dev/null
+++ b/src/main/java/de/pixart/messenger/ui/ChannelDiscoveryActivity.java
@@ -0,0 +1,196 @@
+package de.pixart.messenger.ui;
+
+import android.app.AlertDialog;
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.databinding.DataBindingUtil;
+import android.os.Bundle;
+import android.support.v7.widget.Toolbar;
+import android.text.Html;
+import android.view.KeyEvent;
+import android.view.Menu;
+import android.view.MenuItem;
+import android.view.View;
+import android.view.inputmethod.InputMethodManager;
+import android.widget.EditText;
+import android.widget.TextView;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
+
+import de.pixart.messenger.R;
+import de.pixart.messenger.databinding.ActivityChannelDiscoveryBinding;
+import de.pixart.messenger.entities.Account;
+import de.pixart.messenger.entities.Conversation;
+import de.pixart.messenger.http.services.MuclumbusService;
+import de.pixart.messenger.services.ChannelDiscoveryService;
+import de.pixart.messenger.ui.adapter.ChannelSearchResultAdapter;
+import de.pixart.messenger.ui.util.PendingItem;
+import de.pixart.messenger.ui.util.SoftKeyboardUtils;
+import de.pixart.messenger.utils.AccountUtils;
+import rocks.xmpp.addr.Jid;
+
+public class ChannelDiscoveryActivity extends XmppActivity implements MenuItem.OnActionExpandListener, TextView.OnEditorActionListener, ChannelDiscoveryService.OnChannelSearchResultsFound, ChannelSearchResultAdapter.OnChannelSearchResultSelected {
+    private static final String CHANNEL_DISCOVERY_OPT_IN = "channel_discovery_opt_in";
+    private final ChannelSearchResultAdapter adapter = new ChannelSearchResultAdapter();
+    private ActivityChannelDiscoveryBinding binding;
+    private final PendingItem<String> mInitialSearchValue = new PendingItem<>();
+    private MenuItem mMenuSearchView;
+    private EditText mSearchEditText;
+    private boolean optedIn = false;
+
+    @Override
+    protected void refreshUiReal() {
+
+    }
+
+    @Override
+    void onBackendConnected() {
+        if (optedIn) {
+            String query;
+            if (mMenuSearchView != null && mMenuSearchView.isActionViewExpanded()) {
+                query = mSearchEditText.getText().toString();
+            } else {
+                query = mInitialSearchValue.peek();
+            }
+            xmppConnectionService.discoverChannels(query, this);
+        }
+    }
+
+    @Override
+    protected void onCreate(final Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        binding = DataBindingUtil.setContentView(this, R.layout.activity_channel_discovery);
+        setSupportActionBar((Toolbar) binding.toolbar);
+        configureActionBar(getSupportActionBar(), true);
+        binding.list.setAdapter(this.adapter);
+        this.adapter.setOnChannelSearchResultSelectedListener(this);
+        optedIn = getPreferences().getBoolean(CHANNEL_DISCOVERY_OPT_IN, false);
+
+        final String search = savedInstanceState == null ? null : savedInstanceState.getString("search");
+        if (search != null) {
+            mInitialSearchValue.push(search);
+        }
+    }
+
+    @Override
+    public boolean onCreateOptionsMenu(final Menu menu) {
+        getMenuInflater().inflate(R.menu.muc_users_activity, menu);
+        mMenuSearchView = menu.findItem(R.id.action_search);
+        final View mSearchView = mMenuSearchView.getActionView();
+        mSearchEditText = mSearchView.findViewById(R.id.search_field);
+        mSearchEditText.setHint(R.string.search_channels);
+        String initialSearchValue = mInitialSearchValue.pop();
+        if (initialSearchValue != null) {
+            mMenuSearchView.expandActionView();
+            mSearchEditText.append(initialSearchValue);
+            mSearchEditText.requestFocus();
+            if (optedIn) {
+                xmppConnectionService.discoverChannels(initialSearchValue, this);
+            }
+        }
+        mSearchEditText.setOnEditorActionListener(this);
+        mMenuSearchView.setOnActionExpandListener(this);
+        return true;
+    }
+
+    @Override
+    public boolean onMenuItemActionExpand(MenuItem item) {
+        mSearchEditText.post(() -> {
+            mSearchEditText.requestFocus();
+            final InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
+            imm.showSoftInput(mSearchEditText, InputMethodManager.SHOW_IMPLICIT);
+        });
+        return true;
+    }
+
+    @Override
+    public boolean onMenuItemActionCollapse(MenuItem item) {
+        final InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
+        imm.hideSoftInputFromWindow(mSearchEditText.getWindowToken(), InputMethodManager.HIDE_IMPLICIT_ONLY);
+        mSearchEditText.setText("");
+        toggleLoadingScreen();
+        if (optedIn) {
+            xmppConnectionService.discoverChannels(null, this);
+        }
+        return true;
+    }
+
+    private void toggleLoadingScreen() {
+        adapter.submitList(Collections.emptyList());
+        binding.progressBar.setVisibility(View.VISIBLE);
+    }
+
+    @Override
+    public void onStart() {
+        super.onStart();
+        if (!optedIn) {
+            final AlertDialog.Builder builder = new AlertDialog.Builder(this);
+            builder.setTitle(R.string.channel_discovery_opt_in_title);
+            builder.setMessage(Html.fromHtml(getString(R.string.channel_discover_opt_in_message)));
+            builder.setNegativeButton(R.string.cancel, (dialog, which) -> finish());
+            builder.setPositiveButton(R.string.confirm, (dialog, which) -> optIn());
+            builder.setOnCancelListener(dialog -> finish());
+            final AlertDialog dialog = builder.create();
+            dialog.setCanceledOnTouchOutside(false);
+            dialog.show();
+        }
+    }
+
+    @Override
+    public void onSaveInstanceState(Bundle savedInstanceState) {
+        if (mMenuSearchView != null && mMenuSearchView.isActionViewExpanded()) {
+            savedInstanceState.putString("search", mSearchEditText != null ? mSearchEditText.getText().toString() : null);
+        }
+        super.onSaveInstanceState(savedInstanceState);
+    }
+
+    private void optIn() {
+        SharedPreferences preferences = getPreferences();
+        preferences.edit().putBoolean(CHANNEL_DISCOVERY_OPT_IN, true).apply();
+        optedIn = true;
+        xmppConnectionService.discoverChannels(null, this);
+    }
+
+    @Override
+    public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
+        if (optedIn) {
+            xmppConnectionService.discoverChannels(v.getText().toString(), this);
+        }
+        toggleLoadingScreen();
+        SoftKeyboardUtils.hideSoftKeyboard(this);
+        return true;
+    }
+
+    @Override
+    public void onChannelSearchResultsFound(List<MuclumbusService.Room> results) {
+        runOnUiThread(() -> {
+            adapter.submitList(results);
+            binding.list.setVisibility(View.VISIBLE);
+            binding.progressBar.setVisibility(View.GONE);
+        });
+    }
+
+    @Override
+    public void onChannelSearchResult(final MuclumbusService.Room result) {
+        List<String> accounts = AccountUtils.getEnabledAccounts(xmppConnectionService);
+        if (accounts.size() == 1) {
+            joinChannelSearchResult(accounts.get(0), result);
+        } else if (accounts.size() > 0) {
+            final AtomicReference<String> account = new AtomicReference<>(accounts.get(0));
+            AlertDialog.Builder builder = new AlertDialog.Builder(this);
+            builder.setTitle(R.string.choose_account);
+            builder.setSingleChoiceItems(accounts.toArray(new CharSequence[0]), 0, (dialog, which) -> account.set(accounts.get(which)));
+            builder.setPositiveButton(R.string.join, (dialog, which) -> joinChannelSearchResult(account.get(), result));
+            builder.setNegativeButton(R.string.cancel, null);
+            builder.create().show();
+        }
+    }
+
+    public void joinChannelSearchResult(String accountJid, MuclumbusService.Room result) {
+        Account account = xmppConnectionService.findAccountByJid(Jid.of(accountJid));
+        final Conversation conversation = xmppConnectionService.findOrCreateConversation(account, result.getRoom(), true, true, true);
+        switchToConversation(conversation);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/de/pixart/messenger/ui/StartConversationActivity.java b/src/main/java/de/pixart/messenger/ui/StartConversationActivity.java
index 6706d004c..75e7c2f52 100644
--- a/src/main/java/de/pixart/messenger/ui/StartConversationActivity.java
+++ b/src/main/java/de/pixart/messenger/ui/StartConversationActivity.java
@@ -70,6 +70,7 @@ import de.pixart.messenger.ui.interfaces.OnBackendConnected;
 import de.pixart.messenger.ui.util.JidDialog;
 import de.pixart.messenger.ui.util.PendingItem;
 import de.pixart.messenger.ui.util.SoftKeyboardUtils;
+import de.pixart.messenger.utils.AccountUtils;
 import de.pixart.messenger.utils.MenuDoubleTabUtil;
 import de.pixart.messenger.utils.XmppUri;
 import de.pixart.messenger.xmpp.OnUpdateBlocklist;
@@ -307,6 +308,9 @@ public class StartConversationActivity extends XmppActivity implements XmppConne
                 prefilled = null;
             }
             switch (actionItem.getId()) {
+                case R.id.discover_public_channels:
+                    startActivity(new Intent(this, ChannelDiscoveryActivity.class));
+                    break;
                 case R.id.join_public_channel:
                     showJoinConferenceDialog(prefilled);
                     break;
@@ -763,7 +767,7 @@ public class StartConversationActivity extends XmppActivity implements XmppConne
             onActivityResult(mPostponedActivityResult.first, RESULT_OK, mPostponedActivityResult.second);
             this.mPostponedActivityResult = null;
         }
-        this.mActivatedAccounts.clear();
+        this.mActivatedAccounts.addAll(AccountUtils.getEnabledAccounts(xmppConnectionService));
         for (Account account : xmppConnectionService.getAccounts()) {
             if (account.getStatus() != Account.State.DISABLED) {
                 if (Config.DOMAIN_LOCK != null) {
diff --git a/src/main/java/de/pixart/messenger/ui/adapter/ChannelSearchResultAdapter.java b/src/main/java/de/pixart/messenger/ui/adapter/ChannelSearchResultAdapter.java
new file mode 100644
index 000000000..d137e3a6f
--- /dev/null
+++ b/src/main/java/de/pixart/messenger/ui/adapter/ChannelSearchResultAdapter.java
@@ -0,0 +1,78 @@
+package de.pixart.messenger.ui.adapter;
+
+import android.databinding.DataBindingUtil;
+import android.support.annotation.NonNull;
+import android.support.v7.recyclerview.extensions.ListAdapter;
+import android.support.v7.util.DiffUtil;
+import android.support.v7.widget.RecyclerView;
+import android.text.TextUtils;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import de.pixart.messenger.R;
+import de.pixart.messenger.databinding.SearchResultItemBinding;
+import de.pixart.messenger.http.services.MuclumbusService;
+import de.pixart.messenger.ui.util.AvatarWorkerTask;
+
+
+public class ChannelSearchResultAdapter extends ListAdapter<MuclumbusService.Room, ChannelSearchResultAdapter.ViewHolder> {
+
+    private OnChannelSearchResultSelected listener;
+
+    private static final DiffUtil.ItemCallback<MuclumbusService.Room> DIFF = new DiffUtil.ItemCallback<MuclumbusService.Room>() {
+        @Override
+        public boolean areItemsTheSame(@NonNull MuclumbusService.Room a, @NonNull MuclumbusService.Room b) {
+            return a.address != null && a.address.equals(b.address);
+        }
+
+        @Override
+        public boolean areContentsTheSame(@NonNull MuclumbusService.Room a, @NonNull MuclumbusService.Room b) {
+            return a.equals(b);
+        }
+    };
+
+    public ChannelSearchResultAdapter() {
+        super(DIFF);
+    }
+
+    @NonNull
+    @Override
+    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
+        return new ViewHolder(DataBindingUtil.inflate(LayoutInflater.from(viewGroup.getContext()), R.layout.search_result_item, viewGroup, false));
+    }
+
+    @Override
+    public void onBindViewHolder(@NonNull ViewHolder viewHolder, int position) {
+        final MuclumbusService.Room searchResult = getItem(position);
+        viewHolder.binding.name.setText(searchResult.getName());
+        final String description = searchResult.getDescription();
+        if (TextUtils.isEmpty(description)) {
+            viewHolder.binding.description.setVisibility(View.GONE);
+        } else {
+            viewHolder.binding.description.setText(description);
+            viewHolder.binding.description.setVisibility(View.VISIBLE);
+        }
+        viewHolder.binding.room.setText(searchResult.getRoom().asBareJid().toString());
+        AvatarWorkerTask.loadAvatar(searchResult, viewHolder.binding.avatar, R.dimen.avatar);
+        viewHolder.binding.getRoot().setOnClickListener(v -> listener.onChannelSearchResult(searchResult));
+    }
+
+    public void setOnChannelSearchResultSelectedListener(OnChannelSearchResultSelected listener) {
+        this.listener = listener;
+    }
+
+    public static class ViewHolder extends RecyclerView.ViewHolder {
+
+        private final SearchResultItemBinding binding;
+
+        private ViewHolder(SearchResultItemBinding binding) {
+            super(binding.getRoot());
+            this.binding = binding;
+        }
+    }
+
+    public interface OnChannelSearchResultSelected {
+        void onChannelSearchResult(MuclumbusService.Room result);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/de/pixart/messenger/utils/AccountUtils.java b/src/main/java/de/pixart/messenger/utils/AccountUtils.java
index d675ed680..593d3a089 100644
--- a/src/main/java/de/pixart/messenger/utils/AccountUtils.java
+++ b/src/main/java/de/pixart/messenger/utils/AccountUtils.java
@@ -4,8 +4,10 @@ import android.app.Activity;
 import android.content.Intent;
 import android.widget.Toast;
 
+import java.util.ArrayList;
 import java.util.List;
 
+import de.pixart.messenger.Config;
 import de.pixart.messenger.R;
 import de.pixart.messenger.entities.Account;
 import de.pixart.messenger.services.XmppConnectionService;
@@ -18,6 +20,19 @@ public class AccountUtils {
         MANAGE_ACCOUNT_ACTIVITY = getManageAccountActivityClass();
     }
 
+    public static List<String> getEnabledAccounts(final XmppConnectionService service) {
+        ArrayList<String> accounts = new ArrayList<>();
+        for (Account account : service.getAccounts()) {
+            if (account.getStatus() != Account.State.DISABLED) {
+                if (Config.DOMAIN_LOCK != null) {
+                    accounts.add(account.getJid().getLocal());
+                } else {
+                    accounts.add(account.getJid().asBareJid().toString());
+                }
+            }
+        }
+        return accounts;
+    }
 
     public static Account getFirstEnabled(XmppConnectionService service) {
         final List<Account> accounts = service.getAccounts();
diff --git a/src/main/res/layout/activity_channel_discovery.xml b/src/main/res/layout/activity_channel_discovery.xml
new file mode 100644
index 000000000..ee253f3dd
--- /dev/null
+++ b/src/main/res/layout/activity_channel_discovery.xml
@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <LinearLayout
+        android:layout_width="fill_parent"
+        android:layout_height="fill_parent"
+        android:background="?attr/color_background_secondary"
+        android:orientation="vertical">
+
+        <include
+            android:id="@+id/toolbar"
+            layout="@layout/toolbar" />
+
+        <ProgressBar
+            android:id="@+id/progressBar"
+            style="?android:attr/progressBarStyle"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="center_horizontal"
+            app:layout_anchor="@+id/list" />
+
+        <android.support.design.widget.CoordinatorLayout
+            android:id="@+id/coordinator"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:background="?attr/color_background_secondary">
+
+            <android.support.v7.widget.RecyclerView
+                android:id="@+id/list"
+                android:layout_width="match_parent"
+                android:layout_height="match_parent"
+                android:background="?attr/color_background_secondary"
+                android:orientation="vertical"
+                android:visibility="gone"
+                app:layoutManager="android.support.v7.widget.LinearLayoutManager" />
+        </android.support.design.widget.CoordinatorLayout>
+
+    </LinearLayout>
+</layout>
\ No newline at end of file
diff --git a/src/main/res/layout/search_result_item.xml b/src/main/res/layout/search_result_item.xml
new file mode 100644
index 000000000..856aa7ab6
--- /dev/null
+++ b/src/main/res/layout/search_result_item.xml
@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <RelativeLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:background="?selectableItemBackground"
+        android:padding="@dimen/list_padding">
+
+        <com.makeramen.roundedimageview.RoundedImageView
+            android:id="@+id/avatar"
+            android:layout_width="48dp"
+            android:layout_height="48dp"
+            android:layout_alignParentStart="true"
+            android:layout_alignParentLeft="true"
+            android:scaleType="centerCrop"
+            app:riv_corner_radius="2dp" />
+
+        <LinearLayout
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="@dimen/avatar_item_distance"
+            android:layout_marginLeft="@dimen/avatar_item_distance"
+            android:layout_toEndOf="@+id/avatar"
+            android:layout_toRightOf="@+id/avatar"
+            android:orientation="vertical">
+
+            <TextView
+                android:id="@+id/name"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:singleLine="true"
+                android:textAppearance="@style/TextAppearance.Conversations.Subhead" />
+
+            <TextView
+                android:id="@+id/description"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:maxLines="2"
+                android:textAppearance="@style/TextAppearance.Conversations.Body1" />
+
+            <TextView
+                android:id="@+id/room"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:maxLines="2"
+                android:textAppearance="@style/TextAppearance.Conversations.Body1.Secondary" />
+        </LinearLayout>
+
+    </RelativeLayout>
+</layout>
\ No newline at end of file
diff --git a/src/main/res/menu/channel_discovery_activity.xml b/src/main/res/menu/channel_discovery_activity.xml
new file mode 100644
index 000000000..93e044f27
--- /dev/null
+++ b/src/main/res/menu/channel_discovery_activity.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/action_search"
+        android:icon="?attr/icon_search"
+        android:title="@string/search"
+        app:actionLayout="@layout/actionview_search"
+        app:showAsAction="collapseActionView|always" />
+</menu>
\ No newline at end of file
diff --git a/src/main/res/menu/start_conversation_fab_submenu.xml b/src/main/res/menu/start_conversation_fab_submenu.xml
index 212a94a7e..2cf545d68 100644
--- a/src/main/res/menu/start_conversation_fab_submenu.xml
+++ b/src/main/res/menu/start_conversation_fab_submenu.xml
@@ -1,6 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <menu xmlns:android="http://schemas.android.com/apk/res/android">
     <item
+        android:id="@+id/discover_public_channels"
+        android:icon="@drawable/ic_search_white_24dp"
+        android:title="@string/discover_channels" />
+    <item
         android:id="@+id/join_public_channel"
         android:icon="@drawable/ic_input_white_24dp"
         android:title="@string/join_public_channel" />
diff --git a/src/main/res/values/strings.xml b/src/main/res/values/strings.xml
index 90bcb50b7..4abc42743 100644
--- a/src/main/res/values/strings.xml
+++ b/src/main/res/values/strings.xml
@@ -904,4 +904,8 @@
     <string name="delete_locally">Delete locally</string>
     <string name="delete_from_server">Delete from server</string>
     <string name="go_online_to_delete">You have to activate and/or go online with the account you want to delete from server.</string>
+    <string name="discover_channels">Discover channels</string>
+    <string name="search_channels">Search channels</string>
+    <string name="channel_discovery_opt_in_title">Privacy notice</string>
+    <string name="channel_discover_opt_in_message"><![CDATA[Channel discovery uses a third party service called <a href="https://search.jabbercat.org">search.jabbercat.org</a>.<br><br>Using this feature will transmit your IP address and search terms to that service. See their <a href="https://search.jabbercat.org/privacy">Privacy Policy</a> for more information.]]></string>
 </resources>