Load CommunalSource.Connector from config.

This changelist moves CommunalSource.Connector dependencies
behind a multi-binding provider. The selected connector is
based on a configuration, which specifies the fully qualified
class.

Test: manual
Bug: 205600269
Change-Id: I289800da19839897c57ae5205d76115fa3367468

packages/SystemUI/res/values/config.xml

@@ -742,4 +742,8 @@
 
     <!-- Flag to enable dream overlay service and its registration -->
     <bool name="config_dreamOverlayServiceEnabled">false</bool>
+
+    <!-- Class for the communal source connector to be used -->
+    <string name="config_communalSourceConnector" translatable="false"></string>
+
 </resources>

packages/SystemUI/src/com/android/systemui/communal/dagger/CommunalModule.java

@@ -23,6 +23,8 @@ import android.text.TextUtils;
 import android.view.View;
 import android.widget.FrameLayout;
 
+import androidx.annotation.Nullable;
+
 import com.android.systemui.R;
 import com.android.systemui.communal.CommunalSource;
 import com.android.systemui.communal.PackageObserver;
@@ -35,15 +37,19 @@ import com.android.systemui.idle.dagger.IdleViewComponent;
 
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 
 import javax.inject.Named;
+import javax.inject.Provider;
 
 import dagger.Binds;
 import dagger.Module;
 import dagger.Provides;
 import dagger.multibindings.ElementsIntoSet;
+import dagger.multibindings.IntoMap;
+import dagger.multibindings.StringKey;
 
 /**
  * Dagger Module providing Communal-related functionality.
@@ -97,4 +103,36 @@ public interface CommunalModule {
             CommunalSettingCondition communalSettingCondition) {
         return new HashSet<>(Collections.singletonList(communalSettingCondition));
     }
+
+    /**
+     * TODO(b/205638389): Remove when there is a base implementation of
+     * {@link CommunalSource.Connector}. Currently a place holder to allow a map to be present.
+     */
+    @Provides
+    @IntoMap
+    @Nullable
+    @StringKey("empty")
+    static CommunalSource.Connector provideEmptyCommunalSourceConnector() {
+        return null;
+    }
+
+    /** */
+    @Provides
+    static Optional<CommunalSource.Connector> provideCommunalSourceConnector(
+            @Main Resources resources,
+            Map<Class<?>, Provider<CommunalSource.Connector>> connectorCreators) {
+        final String className = resources.getString(R.string.config_communalSourceConnector);
+
+        if (TextUtils.isEmpty(className)) {
+            return Optional.empty();
+        }
+
+        try {
+            Class<?> clazz = Class.forName(className);
+            Provider<CommunalSource.Connector> provider = connectorCreators.get(clazz);
+            return provider != null ? Optional.of(provider.get()) : Optional.empty();
+        } catch (ClassNotFoundException e) {
+            return Optional.empty();
+        }
+    }
 }