src/com/android/car/media/BrowseViewController.java - platform/packages/apps/Car/Media - Git at Google

 /*
  * Copyright 2018 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.android.car.media;

 import static com.android.car.arch.common.LiveDataFunctions.ifThenElse;

 import android.car.content.pm.CarPackageManager;
 import android.content.Context;
 import android.os.Handler;
 import android.text.TextUtils;
 import android.util.Log;
 import android.view.ViewGroup;
 import android.view.inputmethod.InputMethodManager;
 import android.widget.ImageView;
 import android.widget.TextView;

 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.FragmentActivity;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 import androidx.lifecycle.ViewModelProviders;
 import androidx.recyclerview.widget.GridLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;

 import com.android.car.apps.common.util.ViewUtils;
 import com.android.car.arch.common.FutureData;
 import com.android.car.media.browse.BrowseAdapter;
 import com.android.car.media.browse.LimitedBrowseAdapter;
 import com.android.car.media.common.GridSpacingItemDecoration;
 import com.android.car.media.common.MediaItemMetadata;
 import com.android.car.media.common.browse.BrowsedMediaItems;
 import com.android.car.media.common.browse.MediaBrowserViewModel;
 import com.android.car.media.common.source.MediaSource;
 import com.android.car.media.widgets.AppBarController;
 import com.android.car.ui.FocusArea;
 import com.android.car.ui.baselayout.Insets;
 import com.android.car.ui.toolbar.Toolbar;
 import com.android.car.uxr.LifeCycleObserverUxrContentLimiter;
 import com.android.car.uxr.UxrContentLimiterImpl;

 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 import java.util.Stack;

 /**
  * A view controller that implements the content forward browsing experience.
  *
  * This can be used to display either search or browse results at the root level. Deeper levels will
  * be handled the same way between search and browse, using a back stack to return to the root.
  */
 public class BrowseViewController extends ViewControllerBase {
     private static final String TAG = "BrowseViewController";

     private static final String REGULAR_BROWSER_VIEW_MODEL_KEY
             = "com.android.car.media.regular_browser_view_model";
     private static final String SEARCH_BROWSER_VIEW_MODEL_KEY
             = "com.android.car.media.search_browser_view_model";

     private final Callbacks mCallbacks;
     private final FocusArea mFocusArea;
     private final LifeCycleObserverUxrContentLimiter mUxrContentLimiter;
     private final RecyclerView mBrowseList;
     private final ImageView mErrorIcon;
     private final TextView mMessage;
     private final LimitedBrowseAdapter mLimitedBrowseAdapter;
     private String mSearchQuery;
     private final int mFadeDuration;
     private final int mLoadingIndicatorDelay;
     private final boolean mIsSearchController;
     private final boolean mSetFocusAreaHighlightBottom;
     private final MutableLiveData<Boolean> mShowSearchResults = new MutableLiveData<>();
     private final Handler mHandler = new Handler();
     /**
      * Stores the reference to {@link MediaActivity.ViewModel#getSearchStack} or to
      * {@link MediaActivity.ViewModel#getBrowseStack}. Updated in {@link #onMediaSourceChanged}.
      */
     private Stack<MediaItemMetadata> mBrowseStack = new Stack<>();
     private final MediaActivity.ViewModel mViewModel;
     private final MediaBrowserViewModel mRootMediaBrowserViewModel;
     private final MediaBrowserViewModel.WithMutableBrowseId mMediaBrowserViewModel;
     private final BrowseAdapter.Observer mBrowseAdapterObserver = new BrowseAdapter.Observer() {

         @Override
         protected void onPlayableItemClicked(MediaItemMetadata item) {
             hideKeyboard();
             getParent().onPlayableItemClicked(item);
         }

         @Override
         protected void onBrowsableItemClicked(MediaItemMetadata item) {
             hideKeyboard();
             navigateInto(item);
         }
     };

     private boolean mBrowseTreeHasChildren;
     private boolean mAcceptTabSelection = true;

     /**
      * Media items to display as tabs. If null, it means we haven't finished loading them yet. If
      * empty, it means there are no tabs to show
      */
     @Nullable
     private List<MediaItemMetadata> mTopItems;

     /**
      * Callbacks (implemented by the hosting Activity)
      */
     public interface Callbacks {
         /**
          * Method invoked when the user clicks on a playable item
          *
          * @param item item to be played.
          */
         void onPlayableItemClicked(MediaItemMetadata item);

         /** Called once the list of the root node's children has been loaded. */
         void onRootLoaded();

         /** Change to a new UI mode. */
         void changeMode(MediaActivity.Mode mode);

         FragmentActivity getActivity();
     }

     /**
      * Moves the user one level up in the browse tree. Returns whether that was possible.
      */
     private boolean navigateBack() {
         boolean result = false;
         if (!isAtTopStack()) {
             mBrowseStack.pop();
             mMediaBrowserViewModel.search(mSearchQuery);
             mMediaBrowserViewModel.setCurrentBrowseId(getCurrentMediaItemId());
             updateAppBar();
             result = true;
         }
         if (isAtTopStack()) {
             mShowSearchResults.setValue(mIsSearchController);
         }
         return result;
     }

     private void reopenSearch() {
         if (mIsSearchController) {
             mBrowseStack.clear();
             updateAppBar();
             mShowSearchResults.setValue(true);
         } else {
             Log.e(TAG, "reopenSearch called on browse controller");
         }
     }

     @NonNull
     private Callbacks getParent() {
         return mCallbacks;
     }

     private FragmentActivity getActivity() {
         return mCallbacks.getActivity();
     }

     /**
      * @return whether the user is at the top of the browsing stack.
      */
     private boolean isAtTopStack() {
         if (mIsSearchController) {
             return mBrowseStack.isEmpty();
         } else {
             // The mBrowseStack stack includes the tab...
             return mBrowseStack.size() <= 1;
         }
     }

     /**
      * Creates a new instance of this controller meant to browse the root node.
      * @return a fully initialized {@link BrowseViewController}
      */
     public static BrowseViewController newInstance(Callbacks callbacks,
             CarPackageManager carPackageManager, ViewGroup container) {
         boolean isSearchController = false;
         return new BrowseViewController(callbacks, carPackageManager, container, isSearchController);
     }

     /**
      * Creates a new instance of this controller meant to display search results. The root browse
      * screen will be the search results for the provided query.
      *
      * @return a fully initialized {@link BrowseViewController}
      */
     static BrowseViewController newSearchInstance(Callbacks callbacks,
             CarPackageManager carPackageManager, ViewGroup container) {
         boolean isSearchController = true;
         return new BrowseViewController(callbacks, carPackageManager, container, isSearchController);
     }

     private void updateSearchQuery(@Nullable String query) {
         mSearchQuery = query;
         mMediaBrowserViewModel.search(query);
     }

     /**
      * Clears search state, removes any UI elements from previous results.
      */
     @Override
     void onMediaSourceChanged(@Nullable MediaSource mediaSource) {
         super.onMediaSourceChanged(mediaSource);

         mBrowseTreeHasChildren = false;

         if (mIsSearchController) {
             updateSearchQuery(mViewModel.getSearchQuery());
             mAppBarController.setSearchQuery(mSearchQuery);
             mBrowseStack = mViewModel.getSearchStack();
             mShowSearchResults.setValue(isAtTopStack());
         } else {
             mBrowseStack = mViewModel.getBrowseStack();
             mShowSearchResults.setValue(false);
             updateTabs((mediaSource != null) ? null : new ArrayList<>());
         }

         mLimitedBrowseAdapter.submitItems(null, null);
         stopLoadingIndicator();
         ViewUtils.hideViewAnimated(mErrorIcon, mFadeDuration);
         ViewUtils.hideViewAnimated(mMessage, mFadeDuration);

         mMediaBrowserViewModel.setCurrentBrowseId(getCurrentMediaItemId());

         updateAppBar();
     }

     private BrowseViewController(Callbacks callbacks, CarPackageManager carPackageManager,
             ViewGroup container, boolean isSearchController) {
         super(callbacks.getActivity(), carPackageManager, container, R.layout.fragment_browse);

         mCallbacks = callbacks;
         mIsSearchController = isSearchController;

         mLoadingIndicatorDelay = mContent.getContext().getResources()
                 .getInteger(R.integer.progress_indicator_delay);
         mSetFocusAreaHighlightBottom = mContent.getContext().getResources().getBoolean(
                 R.bool.set_browse_list_focus_area_highlight_above_minimized_control_bar);

         mAppBarController.setListener(mAppBarListener);
         mFocusArea = mContent.findViewById(R.id.focus_area);
         mBrowseList = mContent.findViewById(R.id.browse_list);
         mErrorIcon = mContent.findViewById(R.id.error_icon);
         mMessage = mContent.findViewById(R.id.error_message);
         mFadeDuration = mContent.getContext().getResources().getInteger(
                 R.integer.new_album_art_fade_in_duration);


         FragmentActivity activity = callbacks.getActivity();

         mViewModel = ViewModelProviders.of(activity).get(MediaActivity.ViewModel.class);

         // Browse logic for the root node
         mRootMediaBrowserViewModel = MediaBrowserViewModel.Factory.getInstanceForBrowseRoot(
                 mMediaSourceVM, ViewModelProviders.of(activity));
         mRootMediaBrowserViewModel.getBrowsedMediaItems()
                 .observe(activity, futureData -> onItemsUpdate(/* forRoot */ true, futureData));

         mRootMediaBrowserViewModel.supportsSearch().observe(activity,
                 mAppBarController::setSearchSupported);


         // Browse logic for current node
         mMediaBrowserViewModel = MediaBrowserViewModel.Factory.getInstanceWithMediaBrowser(
                 mIsSearchController ? SEARCH_BROWSER_VIEW_MODEL_KEY : REGULAR_BROWSER_VIEW_MODEL_KEY,
                 ViewModelProviders.of(activity),
                 mMediaSourceVM.getConnectedMediaBrowser());

         mBrowseList.addItemDecoration(new GridSpacingItemDecoration(
                 activity.getResources().getDimensionPixelSize(R.dimen.grid_item_spacing)));

         GridLayoutManager manager = (GridLayoutManager) mBrowseList.getLayoutManager();
         mLimitedBrowseAdapter = new LimitedBrowseAdapter(
                 new BrowseAdapter(mBrowseList.getContext()), manager, mBrowseAdapterObserver);
         mBrowseList.setAdapter(mLimitedBrowseAdapter);

         mUxrContentLimiter = new LifeCycleObserverUxrContentLimiter(
                 new UxrContentLimiterImpl(activity, R.xml.uxr_config));
         mUxrContentLimiter.setAdapter(mLimitedBrowseAdapter);
         activity.getLifecycle().addObserver(mUxrContentLimiter);

         mMediaBrowserViewModel.rootBrowsableHint().observe(activity,
                 hint -> mLimitedBrowseAdapter.getBrowseAdapter().setRootBrowsableViewType(hint));
         mMediaBrowserViewModel.rootPlayableHint().observe(activity,
                 hint -> mLimitedBrowseAdapter.getBrowseAdapter().setRootPlayableViewType(hint));
         LiveData<FutureData<List<MediaItemMetadata>>> mediaItems = ifThenElse(mShowSearchResults,
                 mMediaBrowserViewModel.getSearchedMediaItems(),
                 mMediaBrowserViewModel.getBrowsedMediaItems());

         mediaItems.observe(activity, futureData -> onItemsUpdate(/* forRoot */ false, futureData));

         updateAppBar();
     }

     private AppBarController.AppBarListener mAppBarListener = new BasicAppBarListener() {
         @Override
         public void onTabSelected(MediaItemMetadata item) {
             if (mAcceptTabSelection) {
                 showTopItem(item);
             }
         }

         @Override
         public void onSearchSelection() {
             if (mIsSearchController) {
                 reopenSearch();
             } else {
                 mCallbacks.changeMode(MediaActivity.Mode.SEARCHING);
             }
         }

         @Override
         public void onSearch(String query) {
             if (Log.isLoggable(TAG, Log.DEBUG)) {
                 Log.d(TAG, "onSearch: " + query);
             }
             mViewModel.setSearchQuery(query);
             updateSearchQuery(query);
         }
     };


     private Runnable mLoadingIndicatorRunnable = new Runnable() {
         @Override
         public void run() {
             mMessage.setText(R.string.browser_loading);
             ViewUtils.showViewAnimated(mMessage, mFadeDuration);
         }
     };

     boolean onBackPressed() {
         boolean success = navigateBack();
         if (!success && (mIsSearchController)) {
             mCallbacks.changeMode(MediaActivity.Mode.BROWSING);
             return true;
         }
         return success;
     }

     boolean browseTreeHasChildren() {
         return mBrowseTreeHasChildren;
     }

     private void startLoadingIndicator() {
         // Display the indicator after a certain time, to avoid flashing the indicator constantly,
         // even when performance is acceptable.
         mHandler.postDelayed(mLoadingIndicatorRunnable, mLoadingIndicatorDelay);
     }

     private void stopLoadingIndicator() {
         mHandler.removeCallbacks(mLoadingIndicatorRunnable);
         ViewUtils.hideViewAnimated(mMessage, mFadeDuration);
     }

     private void navigateInto(@Nullable MediaItemMetadata item) {
         if (item != null) {
             mBrowseStack.push(item);
             mMediaBrowserViewModel.setCurrentBrowseId(item.getId());
         } else {
             mMediaBrowserViewModel.setCurrentBrowseId(null);
         }

         mShowSearchResults.setValue(false);
         updateAppBar();
     }

     /**
      * @return the current item being displayed
      */
     @Nullable
     private MediaItemMetadata getCurrentMediaItem() {
         return mBrowseStack.isEmpty() ? null : mBrowseStack.lastElement();
     }

     @Nullable
     private String getCurrentMediaItemId() {
         MediaItemMetadata currentItem = getCurrentMediaItem();
         return currentItem != null ? currentItem.getId() : null;
     }

     @Override
     public void onCarUiInsetsChanged(@NonNull Insets insets) {
         int leftPadding = mBrowseList.getPaddingLeft();
         int rightPadding = mBrowseList.getPaddingRight();
         int bottomPadding = mBrowseList.getPaddingBottom();
         mBrowseList.setPadding(leftPadding, insets.getTop(), rightPadding, bottomPadding);
         mFocusArea.setHighlightPadding(leftPadding, insets.getTop(), rightPadding, bottomPadding);
     }

     void onPlaybackControlsChanged(boolean visible) {
         int leftPadding = mBrowseList.getPaddingLeft();
         int topPadding = mBrowseList.getPaddingTop();
         int rightPadding = mBrowseList.getPaddingRight();
         int bottomPadding = visible
                 ? getActivity().getResources().getDimensionPixelOffset(
                         R.dimen.browse_fragment_bottom_padding)
                 : 0;
         mBrowseList.setPadding(leftPadding, topPadding, rightPadding, bottomPadding);
         mFocusArea.setHighlightPadding(leftPadding, topPadding, rightPadding,
                 mSetFocusAreaHighlightBottom ? bottomPadding : 0);
         // Set the bottom offset to bottomPadding regardless of mSetFocusAreaHighlightBottom so that
         // RotaryService can find the correct target when the user nudges the rotary controller.
         mFocusArea.setBoundsOffset(leftPadding, topPadding, rightPadding, bottomPadding);

         ViewGroup.MarginLayoutParams messageLayout =
                 (ViewGroup.MarginLayoutParams) mMessage.getLayoutParams();
         messageLayout.bottomMargin = bottomPadding;
         mMessage.setLayoutParams(messageLayout);
     }

     private void hideKeyboard() {
         InputMethodManager in =
                 (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
         in.hideSoftInputFromWindow(mContent.getWindowToken(), 0);
     }

     private void showTopItem(@Nullable MediaItemMetadata item) {
         mViewModel.getBrowseStack().clear();
         navigateInto(item);
     }

     /**
      * Updates the tabs displayed on the app bar, based on the top level items on the browse tree.
      * If there is at least one browsable item, we show the browse content of that node. If there
      * are only playable items, then we show those items. If there are not items at all, we show the
      * empty message. If we receive null, we show the error message.
      *
      * @param items top level items, null if the items are still being loaded, or empty list if
      *              items couldn't be loaded.
      */
     private void updateTabs(@Nullable List<MediaItemMetadata> items) {
         if (Objects.equals(mTopItems, items)) {
             // When coming back to the app, the live data sends an update even if the list hasn't
             // changed. Updating the tabs then recreates the browse view, which produces jank
             // (b/131830876), and also resets the navigation to the top of the first tab...
             return;
         }
         mTopItems = items;

         if (mTopItems == null || mTopItems.isEmpty()) {
             mAppBarController.setItems(null);
             mAppBarController.setActiveItem(null);
             if (items != null) {
                 // Only do this when not loading the tabs or we loose the saved one.
                 showTopItem(null);
             }
             updateAppBar();
             return;
         }

         MediaItemMetadata oldTab = mViewModel.getSelectedTab();
         try {
             mAcceptTabSelection = false;
             mAppBarController.setItems(mTopItems.size() == 1 ? null : mTopItems);
             updateAppBar();

             if (items.contains(oldTab)) {
                 mAppBarController.setActiveItem(oldTab);
             } else {
                 showTopItem(items.get(0));
             }
         }  finally {
             mAcceptTabSelection = true;
         }
     }

     private void updateAppBarTitle() {
         boolean isStacked = !isAtTopStack();

         final CharSequence title;
         if (isStacked) {
             // If not at top level, show the current item as title
             title = getCurrentMediaItem().getTitle();
         } else if (mTopItems == null) {
             // If still loading the tabs, force to show an empty bar.
             title = "";
         } else if (mTopItems.size() == 1) {
             // If we finished loading tabs and there is only one, use that as title.
             title = mTopItems.get(0).getTitle();
         } else {
             // Otherwise (no tabs or more than 1 tabs), show the current media source title.
             MediaSource mediaSource = mMediaSourceVM.getPrimaryMediaSource().getValue();
             title = getAppBarDefaultTitle(mediaSource);
         }

         mAppBarController.setTitle(title);
     }

     /**
      * Update elements of the appbar that change depending on where we are in the browse.
      */
     private void updateAppBar() {
         boolean isStacked = !isAtTopStack();
         if (Log.isLoggable(TAG, Log.DEBUG)) {
             Log.d(TAG, "App bar is in stacked state: " + isStacked);
         }
         Toolbar.State unstackedState =
                 mIsSearchController ? Toolbar.State.SEARCH : Toolbar.State.HOME;
         updateAppBarTitle();
         mAppBarController.setState(isStacked ? Toolbar.State.SUBPAGE : unstackedState);
         mAppBarController.showSearchIfSupported(!mIsSearchController || isStacked);
     }

     private String getErrorMessage(boolean forRoot) {
         if (forRoot) {
             MediaSource mediaSource = mMediaSourceVM.getPrimaryMediaSource().getValue();
             return getActivity().getString(
                     R.string.cannot_connect_to_app,
                     mediaSource != null
                             ? mediaSource.getDisplayName()
                             : getActivity().getString(
                                     R.string.unknown_media_provider_name));
         } else {
             return getActivity().getString(R.string.unknown_error);
         }
     }


     private void onItemsUpdate(boolean forRoot, FutureData<List<MediaItemMetadata>> futureData) {

         // Prevent showing loading spinner or any error messages if search is uninitialized
         if (mIsSearchController && TextUtils.isEmpty(mSearchQuery)) {
             return;
         }

         if (!forRoot && !mBrowseTreeHasChildren && !mIsSearchController) {
             // Ignore live data ghost values
             return;
         }

         if (futureData.isLoading()) {
             startLoadingIndicator();
             ViewUtils.hideViewAnimated(mErrorIcon, 0);
             ViewUtils.hideViewAnimated(mMessage, 0);
             // TODO(b/139759881) build a jank-free animation of the transition.
             mBrowseList.setAlpha(0f);
             mLimitedBrowseAdapter.submitItems(null, null);

             if (forRoot) {
                 if (Log.isLoggable(TAG, Log.INFO)) {
                     Log.i(TAG, "Loading browse tree...");
                 }
                 mBrowseTreeHasChildren = false;
                 updateTabs(null);
             }
             return;
         }

         stopLoadingIndicator();

         List<MediaItemMetadata> items =
                 BrowsedMediaItems.filterItems(forRoot, futureData.getData());
         if (forRoot) {
             boolean browseTreeHasChildren = items != null && !items.isEmpty();
             if (Log.isLoggable(TAG, Log.INFO)) {
                 Log.i(TAG, "Browse tree loaded, status (has children or not) changed: "
                         + mBrowseTreeHasChildren + " -> " + browseTreeHasChildren);
             }
             mBrowseTreeHasChildren = browseTreeHasChildren;
             mCallbacks.onRootLoaded();
             updateTabs(items != null ? items : new ArrayList<>());
         } else {
             mLimitedBrowseAdapter.submitItems(getCurrentMediaItem(), items);
         }

         int duration = forRoot ? 0 : mFadeDuration;
         if (items == null) {
             mMessage.setText(getErrorMessage(forRoot));
             ViewUtils.hideViewAnimated(mBrowseList, duration);
             ViewUtils.showViewAnimated(mMessage, duration);
             ViewUtils.showViewAnimated(mErrorIcon, duration);
         } else if (items.isEmpty()) {
             mMessage.setText(R.string.nothing_to_play);
             ViewUtils.hideViewAnimated(mBrowseList, duration);
             ViewUtils.hideViewAnimated(mErrorIcon, duration);
             ViewUtils.showViewAnimated(mMessage, duration);
         } else if (!forRoot) {
             ViewUtils.showViewAnimated(mBrowseList, duration);
             ViewUtils.hideViewAnimated(mErrorIcon, duration);
             ViewUtils.hideViewAnimated(mMessage, duration);
         }
     }
 }
	/*
	* Copyright 2018 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.android.car.media;

	import static com.android.car.arch.common.LiveDataFunctions.ifThenElse;

	import android.car.content.pm.CarPackageManager;
	import android.content.Context;
	import android.os.Handler;
	import android.text.TextUtils;
	import android.util.Log;
	import android.view.ViewGroup;
	import android.view.inputmethod.InputMethodManager;
	import android.widget.ImageView;
	import android.widget.TextView;

	import androidx.annotation.NonNull;
	import androidx.annotation.Nullable;
	import androidx.fragment.app.FragmentActivity;
	import androidx.lifecycle.LiveData;
	import androidx.lifecycle.MutableLiveData;
	import androidx.lifecycle.ViewModelProviders;
	import androidx.recyclerview.widget.GridLayoutManager;
	import androidx.recyclerview.widget.RecyclerView;

	import com.android.car.apps.common.util.ViewUtils;
	import com.android.car.arch.common.FutureData;
	import com.android.car.media.browse.BrowseAdapter;
	import com.android.car.media.browse.LimitedBrowseAdapter;
	import com.android.car.media.common.GridSpacingItemDecoration;
	import com.android.car.media.common.MediaItemMetadata;
	import com.android.car.media.common.browse.BrowsedMediaItems;
	import com.android.car.media.common.browse.MediaBrowserViewModel;
	import com.android.car.media.common.source.MediaSource;
	import com.android.car.media.widgets.AppBarController;
	import com.android.car.ui.FocusArea;
	import com.android.car.ui.baselayout.Insets;
	import com.android.car.ui.toolbar.Toolbar;
	import com.android.car.uxr.LifeCycleObserverUxrContentLimiter;
	import com.android.car.uxr.UxrContentLimiterImpl;

	import java.util.ArrayList;
	import java.util.List;
	import java.util.Objects;
	import java.util.Stack;

	/**
	* A view controller that implements the content forward browsing experience.
	*
	* This can be used to display either search or browse results at the root level. Deeper levels will
	* be handled the same way between search and browse, using a back stack to return to the root.
	*/
	public class BrowseViewController extends ViewControllerBase {
	private static final String TAG = "BrowseViewController";

	private static final String REGULAR_BROWSER_VIEW_MODEL_KEY
	= "com.android.car.media.regular_browser_view_model";
	private static final String SEARCH_BROWSER_VIEW_MODEL_KEY
	= "com.android.car.media.search_browser_view_model";

	private final Callbacks mCallbacks;
	private final FocusArea mFocusArea;
	private final LifeCycleObserverUxrContentLimiter mUxrContentLimiter;
	private final RecyclerView mBrowseList;
	private final ImageView mErrorIcon;
	private final TextView mMessage;
	private final LimitedBrowseAdapter mLimitedBrowseAdapter;
	private String mSearchQuery;
	private final int mFadeDuration;
	private final int mLoadingIndicatorDelay;
	private final boolean mIsSearchController;
	private final boolean mSetFocusAreaHighlightBottom;
	private final MutableLiveData<Boolean> mShowSearchResults = new MutableLiveData<>();
	private final Handler mHandler = new Handler();
	/**
	* Stores the reference to {@link MediaActivity.ViewModel#getSearchStack} or to
	* {@link MediaActivity.ViewModel#getBrowseStack}. Updated in {@link #onMediaSourceChanged}.
	*/
	private Stack<MediaItemMetadata> mBrowseStack = new Stack<>();
	private final MediaActivity.ViewModel mViewModel;
	private final MediaBrowserViewModel mRootMediaBrowserViewModel;
	private final MediaBrowserViewModel.WithMutableBrowseId mMediaBrowserViewModel;
	private final BrowseAdapter.Observer mBrowseAdapterObserver = new BrowseAdapter.Observer() {

	@Override
	protected void onPlayableItemClicked(MediaItemMetadata item) {
	hideKeyboard();
	getParent().onPlayableItemClicked(item);
	}

	@Override
	protected void onBrowsableItemClicked(MediaItemMetadata item) {
	hideKeyboard();
	navigateInto(item);
	}
	};

	private boolean mBrowseTreeHasChildren;
	private boolean mAcceptTabSelection = true;

	/**
	* Media items to display as tabs. If null, it means we haven't finished loading them yet. If
	* empty, it means there are no tabs to show
	*/
	@Nullable
	private List<MediaItemMetadata> mTopItems;

	/**
	* Callbacks (implemented by the hosting Activity)
	*/
	public interface Callbacks {
	/**
	* Method invoked when the user clicks on a playable item
	*
	* @param item item to be played.
	*/
	void onPlayableItemClicked(MediaItemMetadata item);

	/** Called once the list of the root node's children has been loaded. */
	void onRootLoaded();

	/** Change to a new UI mode. */
	void changeMode(MediaActivity.Mode mode);

	FragmentActivity getActivity();
	}

	/**
	* Moves the user one level up in the browse tree. Returns whether that was possible.
	*/
	private boolean navigateBack() {
	boolean result = false;
	if (!isAtTopStack()) {
	mBrowseStack.pop();
	mMediaBrowserViewModel.search(mSearchQuery);
	mMediaBrowserViewModel.setCurrentBrowseId(getCurrentMediaItemId());
	updateAppBar();
	result = true;
	}
	if (isAtTopStack()) {
	mShowSearchResults.setValue(mIsSearchController);
	}
	return result;
	}

	private void reopenSearch() {
	if (mIsSearchController) {
	mBrowseStack.clear();
	updateAppBar();
	mShowSearchResults.setValue(true);
	} else {
	Log.e(TAG, "reopenSearch called on browse controller");
	}
	}

	@NonNull
	private Callbacks getParent() {
	return mCallbacks;
	}

	private FragmentActivity getActivity() {
	return mCallbacks.getActivity();
	}

	/**
	* @return whether the user is at the top of the browsing stack.
	*/
	private boolean isAtTopStack() {
	if (mIsSearchController) {
	return mBrowseStack.isEmpty();
	} else {
	// The mBrowseStack stack includes the tab...
	return mBrowseStack.size() <= 1;
	}
	}

	/**
	* Creates a new instance of this controller meant to browse the root node.
	* @return a fully initialized {@link BrowseViewController}
	*/
	public static BrowseViewController newInstance(Callbacks callbacks,
	CarPackageManager carPackageManager, ViewGroup container) {
	boolean isSearchController = false;
	return new BrowseViewController(callbacks, carPackageManager, container, isSearchController);
	}

	/**
	* Creates a new instance of this controller meant to display search results. The root browse
	* screen will be the search results for the provided query.
	*
	* @return a fully initialized {@link BrowseViewController}
	*/
	static BrowseViewController newSearchInstance(Callbacks callbacks,
	CarPackageManager carPackageManager, ViewGroup container) {
	boolean isSearchController = true;
	return new BrowseViewController(callbacks, carPackageManager, container, isSearchController);
	}

	private void updateSearchQuery(@Nullable String query) {
	mSearchQuery = query;
	mMediaBrowserViewModel.search(query);
	}

	/**
	* Clears search state, removes any UI elements from previous results.
	*/
	@Override
	void onMediaSourceChanged(@Nullable MediaSource mediaSource) {
	super.onMediaSourceChanged(mediaSource);

	mBrowseTreeHasChildren = false;

	if (mIsSearchController) {
	updateSearchQuery(mViewModel.getSearchQuery());
	mAppBarController.setSearchQuery(mSearchQuery);
	mBrowseStack = mViewModel.getSearchStack();
	mShowSearchResults.setValue(isAtTopStack());
	} else {
	mBrowseStack = mViewModel.getBrowseStack();
	mShowSearchResults.setValue(false);
	updateTabs((mediaSource != null) ? null : new ArrayList<>());
	}

	mLimitedBrowseAdapter.submitItems(null, null);
	stopLoadingIndicator();
	ViewUtils.hideViewAnimated(mErrorIcon, mFadeDuration);
	ViewUtils.hideViewAnimated(mMessage, mFadeDuration);

	mMediaBrowserViewModel.setCurrentBrowseId(getCurrentMediaItemId());

	updateAppBar();
	}

	private BrowseViewController(Callbacks callbacks, CarPackageManager carPackageManager,
	ViewGroup container, boolean isSearchController) {
	super(callbacks.getActivity(), carPackageManager, container, R.layout.fragment_browse);

	mCallbacks = callbacks;
	mIsSearchController = isSearchController;

	mLoadingIndicatorDelay = mContent.getContext().getResources()
	.getInteger(R.integer.progress_indicator_delay);
	mSetFocusAreaHighlightBottom = mContent.getContext().getResources().getBoolean(
	R.bool.set_browse_list_focus_area_highlight_above_minimized_control_bar);

	mAppBarController.setListener(mAppBarListener);
	mFocusArea = mContent.findViewById(R.id.focus_area);
	mBrowseList = mContent.findViewById(R.id.browse_list);
	mErrorIcon = mContent.findViewById(R.id.error_icon);
	mMessage = mContent.findViewById(R.id.error_message);
	mFadeDuration = mContent.getContext().getResources().getInteger(
	R.integer.new_album_art_fade_in_duration);


	FragmentActivity activity = callbacks.getActivity();

	mViewModel = ViewModelProviders.of(activity).get(MediaActivity.ViewModel.class);

	// Browse logic for the root node
	mRootMediaBrowserViewModel = MediaBrowserViewModel.Factory.getInstanceForBrowseRoot(
	mMediaSourceVM, ViewModelProviders.of(activity));
	mRootMediaBrowserViewModel.getBrowsedMediaItems()
	.observe(activity, futureData -> onItemsUpdate(/* forRoot */ true, futureData));

	mRootMediaBrowserViewModel.supportsSearch().observe(activity,
	mAppBarController::setSearchSupported);


	// Browse logic for current node
	mMediaBrowserViewModel = MediaBrowserViewModel.Factory.getInstanceWithMediaBrowser(
	mIsSearchController ? SEARCH_BROWSER_VIEW_MODEL_KEY : REGULAR_BROWSER_VIEW_MODEL_KEY,
	ViewModelProviders.of(activity),
	mMediaSourceVM.getConnectedMediaBrowser());

	mBrowseList.addItemDecoration(new GridSpacingItemDecoration(
	activity.getResources().getDimensionPixelSize(R.dimen.grid_item_spacing)));

	GridLayoutManager manager = (GridLayoutManager) mBrowseList.getLayoutManager();
	mLimitedBrowseAdapter = new LimitedBrowseAdapter(
	new BrowseAdapter(mBrowseList.getContext()), manager, mBrowseAdapterObserver);
	mBrowseList.setAdapter(mLimitedBrowseAdapter);

	mUxrContentLimiter = new LifeCycleObserverUxrContentLimiter(
	new UxrContentLimiterImpl(activity, R.xml.uxr_config));
	mUxrContentLimiter.setAdapter(mLimitedBrowseAdapter);
	activity.getLifecycle().addObserver(mUxrContentLimiter);

	mMediaBrowserViewModel.rootBrowsableHint().observe(activity,
	hint -> mLimitedBrowseAdapter.getBrowseAdapter().setRootBrowsableViewType(hint));
	mMediaBrowserViewModel.rootPlayableHint().observe(activity,
	hint -> mLimitedBrowseAdapter.getBrowseAdapter().setRootPlayableViewType(hint));
	LiveData<FutureData<List<MediaItemMetadata>>> mediaItems = ifThenElse(mShowSearchResults,
	mMediaBrowserViewModel.getSearchedMediaItems(),
	mMediaBrowserViewModel.getBrowsedMediaItems());

	mediaItems.observe(activity, futureData -> onItemsUpdate(/* forRoot */ false, futureData));

	updateAppBar();
	}

	private AppBarController.AppBarListener mAppBarListener = new BasicAppBarListener() {
	@Override
	public void onTabSelected(MediaItemMetadata item) {
	if (mAcceptTabSelection) {
	showTopItem(item);
	}
	}

	@Override
	public void onSearchSelection() {
	if (mIsSearchController) {
	reopenSearch();
	} else {
	mCallbacks.changeMode(MediaActivity.Mode.SEARCHING);
	}
	}

	@Override
	public void onSearch(String query) {
	if (Log.isLoggable(TAG, Log.DEBUG)) {
	Log.d(TAG, "onSearch: " + query);
	}
	mViewModel.setSearchQuery(query);
	updateSearchQuery(query);
	}
	};


	private Runnable mLoadingIndicatorRunnable = new Runnable() {
	@Override
	public void run() {
	mMessage.setText(R.string.browser_loading);
	ViewUtils.showViewAnimated(mMessage, mFadeDuration);
	}
	};

	boolean onBackPressed() {
	boolean success = navigateBack();
	if (!success && (mIsSearchController)) {
	mCallbacks.changeMode(MediaActivity.Mode.BROWSING);
	return true;
	}
	return success;
	}

	boolean browseTreeHasChildren() {
	return mBrowseTreeHasChildren;
	}

	private void startLoadingIndicator() {
	// Display the indicator after a certain time, to avoid flashing the indicator constantly,
	// even when performance is acceptable.
	mHandler.postDelayed(mLoadingIndicatorRunnable, mLoadingIndicatorDelay);
	}

	private void stopLoadingIndicator() {
	mHandler.removeCallbacks(mLoadingIndicatorRunnable);
	ViewUtils.hideViewAnimated(mMessage, mFadeDuration);
	}

	private void navigateInto(@Nullable MediaItemMetadata item) {
	if (item != null) {
	mBrowseStack.push(item);
	mMediaBrowserViewModel.setCurrentBrowseId(item.getId());
	} else {
	mMediaBrowserViewModel.setCurrentBrowseId(null);
	}

	mShowSearchResults.setValue(false);
	updateAppBar();
	}

	/**
	* @return the current item being displayed
	*/
	@Nullable
	private MediaItemMetadata getCurrentMediaItem() {
	return mBrowseStack.isEmpty() ? null : mBrowseStack.lastElement();
	}

	@Nullable
	private String getCurrentMediaItemId() {
	MediaItemMetadata currentItem = getCurrentMediaItem();
	return currentItem != null ? currentItem.getId() : null;
	}

	@Override
	public void onCarUiInsetsChanged(@NonNull Insets insets) {
	int leftPadding = mBrowseList.getPaddingLeft();
	int rightPadding = mBrowseList.getPaddingRight();
	int bottomPadding = mBrowseList.getPaddingBottom();
	mBrowseList.setPadding(leftPadding, insets.getTop(), rightPadding, bottomPadding);
	mFocusArea.setHighlightPadding(leftPadding, insets.getTop(), rightPadding, bottomPadding);
	}

	void onPlaybackControlsChanged(boolean visible) {
	int leftPadding = mBrowseList.getPaddingLeft();
	int topPadding = mBrowseList.getPaddingTop();
	int rightPadding = mBrowseList.getPaddingRight();
	int bottomPadding = visible
	? getActivity().getResources().getDimensionPixelOffset(
	R.dimen.browse_fragment_bottom_padding)
	: 0;
	mBrowseList.setPadding(leftPadding, topPadding, rightPadding, bottomPadding);
	mFocusArea.setHighlightPadding(leftPadding, topPadding, rightPadding,
	mSetFocusAreaHighlightBottom ? bottomPadding : 0);
	// Set the bottom offset to bottomPadding regardless of mSetFocusAreaHighlightBottom so that
	// RotaryService can find the correct target when the user nudges the rotary controller.
	mFocusArea.setBoundsOffset(leftPadding, topPadding, rightPadding, bottomPadding);

	ViewGroup.MarginLayoutParams messageLayout =
	(ViewGroup.MarginLayoutParams) mMessage.getLayoutParams();
	messageLayout.bottomMargin = bottomPadding;
	mMessage.setLayoutParams(messageLayout);
	}

	private void hideKeyboard() {
	InputMethodManager in =
	(InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
	in.hideSoftInputFromWindow(mContent.getWindowToken(), 0);
	}

	private void showTopItem(@Nullable MediaItemMetadata item) {
	mViewModel.getBrowseStack().clear();
	navigateInto(item);
	}

	/**
	* Updates the tabs displayed on the app bar, based on the top level items on the browse tree.
	* If there is at least one browsable item, we show the browse content of that node. If there
	* are only playable items, then we show those items. If there are not items at all, we show the
	* empty message. If we receive null, we show the error message.
	*
	* @param items top level items, null if the items are still being loaded, or empty list if
	* items couldn't be loaded.
	*/
	private void updateTabs(@Nullable List<MediaItemMetadata> items) {
	if (Objects.equals(mTopItems, items)) {
	// When coming back to the app, the live data sends an update even if the list hasn't
	// changed. Updating the tabs then recreates the browse view, which produces jank
	// (b/131830876), and also resets the navigation to the top of the first tab...
	return;
	}
	mTopItems = items;

	if (mTopItems == null \|\| mTopItems.isEmpty()) {
	mAppBarController.setItems(null);
	mAppBarController.setActiveItem(null);
	if (items != null) {
	// Only do this when not loading the tabs or we loose the saved one.
	showTopItem(null);
	}
	updateAppBar();
	return;
	}

	MediaItemMetadata oldTab = mViewModel.getSelectedTab();
	try {
	mAcceptTabSelection = false;
	mAppBarController.setItems(mTopItems.size() == 1 ? null : mTopItems);
	updateAppBar();

	if (items.contains(oldTab)) {
	mAppBarController.setActiveItem(oldTab);
	} else {
	showTopItem(items.get(0));
	}
	} finally {
	mAcceptTabSelection = true;
	}
	}

	private void updateAppBarTitle() {
	boolean isStacked = !isAtTopStack();

	final CharSequence title;
	if (isStacked) {
	// If not at top level, show the current item as title
	title = getCurrentMediaItem().getTitle();
	} else if (mTopItems == null) {
	// If still loading the tabs, force to show an empty bar.
	title = "";
	} else if (mTopItems.size() == 1) {
	// If we finished loading tabs and there is only one, use that as title.
	title = mTopItems.get(0).getTitle();
	} else {
	// Otherwise (no tabs or more than 1 tabs), show the current media source title.
	MediaSource mediaSource = mMediaSourceVM.getPrimaryMediaSource().getValue();
	title = getAppBarDefaultTitle(mediaSource);
	}

	mAppBarController.setTitle(title);
	}

	/**
	* Update elements of the appbar that change depending on where we are in the browse.
	*/
	private void updateAppBar() {
	boolean isStacked = !isAtTopStack();
	if (Log.isLoggable(TAG, Log.DEBUG)) {
	Log.d(TAG, "App bar is in stacked state: " + isStacked);
	}
	Toolbar.State unstackedState =
	mIsSearchController ? Toolbar.State.SEARCH : Toolbar.State.HOME;
	updateAppBarTitle();
	mAppBarController.setState(isStacked ? Toolbar.State.SUBPAGE : unstackedState);
	mAppBarController.showSearchIfSupported(!mIsSearchController \|\| isStacked);
	}

	private String getErrorMessage(boolean forRoot) {
	if (forRoot) {
	MediaSource mediaSource = mMediaSourceVM.getPrimaryMediaSource().getValue();
	return getActivity().getString(
	R.string.cannot_connect_to_app,
	mediaSource != null
	? mediaSource.getDisplayName()
	: getActivity().getString(
	R.string.unknown_media_provider_name));
	} else {
	return getActivity().getString(R.string.unknown_error);
	}
	}



	private void onItemsUpdate(boolean forRoot, FutureData<List<MediaItemMetadata>> futureData) {

	// Prevent showing loading spinner or any error messages if search is uninitialized
	if (mIsSearchController && TextUtils.isEmpty(mSearchQuery)) {
	return;
	}

	if (!forRoot && !mBrowseTreeHasChildren && !mIsSearchController) {
	// Ignore live data ghost values
	return;
	}

	if (futureData.isLoading()) {
	startLoadingIndicator();
	ViewUtils.hideViewAnimated(mErrorIcon, 0);
	ViewUtils.hideViewAnimated(mMessage, 0);
	// TODO(b/139759881) build a jank-free animation of the transition.
	mBrowseList.setAlpha(0f);
	mLimitedBrowseAdapter.submitItems(null, null);

	if (forRoot) {
	if (Log.isLoggable(TAG, Log.INFO)) {
	Log.i(TAG, "Loading browse tree...");
	}
	mBrowseTreeHasChildren = false;
	updateTabs(null);
	}
	return;
	}

	stopLoadingIndicator();

	List<MediaItemMetadata> items =
	BrowsedMediaItems.filterItems(forRoot, futureData.getData());
	if (forRoot) {
	boolean browseTreeHasChildren = items != null && !items.isEmpty();
	if (Log.isLoggable(TAG, Log.INFO)) {
	Log.i(TAG, "Browse tree loaded, status (has children or not) changed: "
	+ mBrowseTreeHasChildren + " -> " + browseTreeHasChildren);
	}
	mBrowseTreeHasChildren = browseTreeHasChildren;
	mCallbacks.onRootLoaded();
	updateTabs(items != null ? items : new ArrayList<>());
	} else {
	mLimitedBrowseAdapter.submitItems(getCurrentMediaItem(), items);
	}

	int duration = forRoot ? 0 : mFadeDuration;
	if (items == null) {
	mMessage.setText(getErrorMessage(forRoot));
	ViewUtils.hideViewAnimated(mBrowseList, duration);
	ViewUtils.showViewAnimated(mMessage, duration);
	ViewUtils.showViewAnimated(mErrorIcon, duration);
	} else if (items.isEmpty()) {
	mMessage.setText(R.string.nothing_to_play);
	ViewUtils.hideViewAnimated(mBrowseList, duration);
	ViewUtils.hideViewAnimated(mErrorIcon, duration);
	ViewUtils.showViewAnimated(mMessage, duration);
	} else if (!forRoot) {
	ViewUtils.showViewAnimated(mBrowseList, duration);
	ViewUtils.hideViewAnimated(mErrorIcon, duration);
	ViewUtils.hideViewAnimated(mMessage, duration);
	}
	}
	}