[Android NTP] Move suggestion sections into a separate node.

chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SectionList.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SectionList.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SectionList.java
similarity index 34%
copy from chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
copy to chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SectionList.java
index aa2fab2040a2760bd113edb1fdf1afa7f78708a6..2143c590c1b5ea768d29bf718f04b28ba84f0b89 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SectionList.java
@@ -4,28 +4,12 @@
 
 package org.chromium.chrome.browser.ntp.cards;
 
-import android.annotation.SuppressLint;
-import android.graphics.Canvas;
-import android.support.annotation.StringRes;
-import android.support.v7.widget.RecyclerView;
-import android.support.v7.widget.RecyclerView.Adapter;
-import android.support.v7.widget.RecyclerView.ViewHolder;
-import android.support.v7.widget.helper.ItemTouchHelper;
-import android.view.View;
-import android.view.ViewGroup;
-
 import org.chromium.base.Log;
-import org.chromium.base.VisibleForTesting;
-import org.chromium.chrome.R;
-import org.chromium.chrome.browser.ntp.NewTabPage.DestructionObserver;
 import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
-import org.chromium.chrome.browser.ntp.UiConfig;
 import org.chromium.chrome.browser.ntp.snippets.CategoryInt;
 import org.chromium.chrome.browser.ntp.snippets.CategoryStatus;
 import org.chromium.chrome.browser.ntp.snippets.CategoryStatus.CategoryStatusEnum;
-import org.chromium.chrome.browser.ntp.snippets.SectionHeaderViewHolder;
 import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
-import org.chromium.chrome.browser.ntp.snippets.SnippetArticleViewHolder;
 import org.chromium.chrome.browser.ntp.snippets.SnippetsBridge;
 import org.chromium.chrome.browser.ntp.snippets.SnippetsConfig;
 import org.chromium.chrome.browser.ntp.snippets.SuggestionsSource;
@@ -37,146 +21,35 @@ import java.util.List;
 import java.util.Map;
 
 /**
- * A class that handles merging above the fold elements and below the fold cards into an adapter
- * that will be used to back the NTP RecyclerView. The first element in the adapter should always be
- * the above-the-fold view (containing the logo, search box, and most visited tiles) and subsequent
- * elements will be the cards shown to the user
+ * A node in the tree containing a list of all suggestions sections. It listens to changes in the
+ * suggestions source and updates the corresponding sections.
  */
-public class NewTabPageAdapter
-        extends Adapter<NewTabPageViewHolder> implements SuggestionsSource.Observer, NodeParent {
+public class SectionList extends InnerNode implements SuggestionsSource.Observer {
     private static final String TAG = "Ntp";
 
-    private final NewTabPageManager mNewTabPageManager;
-    private final View mAboveTheFoldView;
-    private final UiConfig mUiConfig;
-    private final ItemTouchCallbacks mItemTouchCallbacks = new ItemTouchCallbacks();
-    private final OfflinePageBridge mOfflinePageBridge;
-    private NewTabPageRecyclerView mRecyclerView;
-
-    /**
-     * List of all child nodes (which can themselves contain multiple child nodes).
-     */
-    private final List<TreeNode> mChildren = new ArrayList<>();
-    private final AboveTheFoldItem mAboveTheFold = new AboveTheFoldItem();
-    private final SignInPromo mSigninPromo;
-    private final AllDismissedItem mAllDismissed;
-    private final Footer mFooter;
-    private final SpacingItem mBottomSpacer = new SpacingItem();
-    private final InnerNode mRoot;
-
     /** Maps suggestion categories to sections, with stable iteration ordering. */
     private final Map<Integer, SuggestionsSection> mSections = new LinkedHashMap<>();
+    private final List<TreeNode> mChildren = new ArrayList<>();
+    private final NewTabPageManager mNewTabPageManager;
+    private final OfflinePageBridge mOfflinePageBridge;
 
-    private class ItemTouchCallbacks extends ItemTouchHelper.Callback {
-        @Override
-        public void onSwiped(ViewHolder viewHolder, int direction) {
-            mRecyclerView.onItemDismissStarted(viewHolder);
-            NewTabPageAdapter.this.dismissItem(viewHolder.getAdapterPosition());
-        }
-
-        @Override
-        public void clearView(RecyclerView recyclerView, ViewHolder viewHolder) {
-            // clearView() is called when an interaction with the item is finished, which does
-            // not mean that the user went all the way and dismissed the item before releasing it.
-            // We need to check that the item has been removed.
-            if (viewHolder.getAdapterPosition() == RecyclerView.NO_POSITION) {
-                mRecyclerView.onItemDismissFinished(viewHolder);
-            }
-
-            super.clearView(recyclerView, viewHolder);
-        }
-
-        @Override
-        public boolean onMove(RecyclerView recyclerView, ViewHolder viewHolder, ViewHolder target) {
-            assert false; // Drag and drop not supported, the method will never be called.
-            return false;
-        }
-
-        @Override
-        public int getMovementFlags(RecyclerView recyclerView, ViewHolder viewHolder) {
-            assert viewHolder instanceof NewTabPageViewHolder;
-
-            int swipeFlags = 0;
-            if (((NewTabPageViewHolder) viewHolder).isDismissable()) {
-                swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;
-            }
-
-            return makeMovementFlags(0 /* dragFlags */, swipeFlags);
-        }
+    public SectionList(NodeParent parent, NewTabPageManager newTabPageManager,
+            OfflinePageBridge offlinePageBridge) {
+        super(parent);
+        mNewTabPageManager = newTabPageManager;
+        mNewTabPageManager.getSuggestionsSource().setObserver(this);

[dgn, 2016/12/13 14:54:47]

setObserver will hook into the native code and might end up with
onNewSuggestions being called. I think it should move at the end of init() to
make sure everything is properly setup before we start receiving events.

+        mOfflinePageBridge = offlinePageBridge;
+    }
 
-        @Override
-        public void onChildDraw(Canvas c, RecyclerView recyclerView, ViewHolder viewHolder,
-                float dX, float dY, int actionState, boolean isCurrentlyActive) {
-            assert viewHolder instanceof NewTabPageViewHolder;
-
-            // The item has already been removed. We have nothing more to do.
-            // In some cases a removed children may call this method when unrelated items are
-            // interacted with, but this check also covers the case.
-            // See https://crbug.com/664466, b/32900699
-            if (viewHolder.getAdapterPosition() == RecyclerView.NO_POSITION) return;
-
-            // We use our own implementation of the dismissal animation, so we don't call the
-            // parent implementation. (by default it changes the translation-X and elevation)
-            mRecyclerView.updateViewStateForDismiss(dX, (NewTabPageViewHolder) viewHolder);
-
-            // If there is another item that should be animated at the same time, do the same to it.
-            NewTabPageViewHolder siblingViewHolder = getDismissSibling(viewHolder);
-            if (siblingViewHolder != null) {
-                mRecyclerView.updateViewStateForDismiss(dX, siblingViewHolder);
-            }
-        }
+    @Override
+    public void init() {
+        super.init();
+        resetSections(/* alwaysAllowEmptySections = */ false);
     }
 
-    /**
-     * Creates the adapter that will manage all the cards to display on the NTP.
-     *
-     * @param manager the NewTabPageManager to use to interact with the rest of the system.
-     * @param aboveTheFoldView the layout encapsulating all the above-the-fold elements
-     *                         (logo, search box, most visited tiles)
-     * @param uiConfig the NTP UI configuration, to be passed to created views.
-     * @param offlinePageBridge the OfflinePageBridge used to determine if articles are available
-     *                              offline.
-     *
-     */
-    public NewTabPageAdapter(NewTabPageManager manager, View aboveTheFoldView, UiConfig uiConfig,
-            OfflinePageBridge offlinePageBridge) {
-        mNewTabPageManager = manager;
-        mAboveTheFoldView = aboveTheFoldView;
-        mUiConfig = uiConfig;
-        mOfflinePageBridge = offlinePageBridge;
-        mRoot = new InnerNode(this) {
-            @Override
-            protected List<TreeNode> getChildren() {
-                return mChildren;
-            }
-
-            @Override
-            public void onItemRangeChanged(TreeNode child, int index, int count) {
-                if (mChildren.isEmpty()) return; // The sections have not been initialised yet.
-                super.onItemRangeChanged(child, index, count);
-            }
-
-            @Override
-            public void onItemRangeInserted(TreeNode child, int index, int count) {
-                if (mChildren.isEmpty()) return; // The sections have not been initialised yet.
-                super.onItemRangeInserted(child, index, count);
-            }
-
-            @Override
-            public void onItemRangeRemoved(TreeNode child, int index, int count) {
-                if (mChildren.isEmpty()) return; // The sections have not been initialised yet.
-                super.onItemRangeRemoved(child, index, count);
-            }
-        };
-
-        mSigninPromo = new SignInPromo(mRoot);
-        mAllDismissed = new AllDismissedItem(mRoot);
-        mFooter = new Footer(mRoot);
-        DestructionObserver signInObserver = mSigninPromo.getObserver();
-        if (signInObserver != null) mNewTabPageManager.addDestructionObserver(signInObserver);
-
-        resetSections(/*alwaysAllowEmptySections=*/false);
-        mNewTabPageManager.getSuggestionsSource().setObserver(this);
+    @Override
+    protected List<TreeNode> getChildren() {
+        return mChildren;
     }
 
     /**
@@ -204,8 +77,6 @@ public class NewTabPageAdapter
         }
 
         mNewTabPageManager.trackSnippetsPageImpression(categories, suggestionsPerCategory);
-
-        updateChildren();
     }
 
     /**
@@ -224,17 +95,20 @@ public class NewTabPageAdapter
         List<SnippetArticle> suggestions = suggestionsSource.getSuggestionsForCategory(category);
         SuggestionsCategoryInfo info = suggestionsSource.getCategoryInfo(category);
 
+        SuggestionsSection section = mSections.get(category);
+
         // Do not show an empty section if not allowed.
         if (suggestions.isEmpty() && !info.showIfEmpty() && !alwaysAllowEmptySections) {
-            mSections.remove(category);
+            if (section != null) removeSection(section);
             return 0;
         }
 
         // Create the section if needed.
-        SuggestionsSection section = mSections.get(category);
         if (section == null) {
-            section = new SuggestionsSection(mRoot, info, mNewTabPageManager, mOfflinePageBridge);
+            section = new SuggestionsSection(this, mNewTabPageManager, mOfflinePageBridge, info);
             mSections.put(category, section);
+            mChildren.add(section);
+            didAddChild(section);
         }
 
         // Add the new suggestions.
@@ -243,11 +117,6 @@ public class NewTabPageAdapter
         return suggestions.size();
     }
 
-    /** Returns callbacks to configure the interactions with the RecyclerView's items. */
-    public ItemTouchHelper.Callback getItemTouchCallbacks() {
-        return mItemTouchCallbacks;
-    }
-
     @Override
     public void onNewSuggestions(@CategoryInt int category) {
         @CategoryStatusEnum
@@ -298,7 +167,9 @@ public class NewTabPageAdapter
                 return;
 
             case CategoryStatus.SIGNED_OUT:
-                // TODO(dgn): We currently can only reach this through an old variation parameter.
+                resetSection(category, status, /* alwaysAllowEmptySections = */ false);
+                return;
+
             default:
                 mSections.get(category).setStatus(status);
                 return;
@@ -313,86 +184,7 @@ public class NewTabPageAdapter
 
     @Override
     public void onFullRefreshRequired() {
-        resetSections(/*alwaysAllowEmptySections=*/false);
-    }
-
-    @Override
-    @ItemViewType
-    public int getItemViewType(int position) {
-        return mRoot.getItemViewType(position);
-    }
-
-    @Override
-    public NewTabPageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
-        assert parent == mRecyclerView;
-
-        switch (viewType) {
-            case ItemViewType.ABOVE_THE_FOLD:
-                return new NewTabPageViewHolder(mAboveTheFoldView);
-
-            case ItemViewType.HEADER:
-                return new SectionHeaderViewHolder(mRecyclerView, mUiConfig);
-
-            case ItemViewType.SNIPPET:
-                return new SnippetArticleViewHolder(mRecyclerView, mNewTabPageManager, mUiConfig);
-
-            case ItemViewType.SPACING:
-                return new NewTabPageViewHolder(SpacingItem.createView(parent));
-
-            case ItemViewType.STATUS:
-                return new StatusCardViewHolder(mRecyclerView, mNewTabPageManager, mUiConfig);
-
-            case ItemViewType.PROGRESS:
-                return new ProgressViewHolder(mRecyclerView);
-
-            case ItemViewType.ACTION:
-                return new ActionItem.ViewHolder(mRecyclerView, mNewTabPageManager, mUiConfig);
-
-            case ItemViewType.PROMO:
-                return new SignInPromo.ViewHolder(mRecyclerView, mNewTabPageManager, mUiConfig);
-
-            case ItemViewType.FOOTER:
-                return new Footer.ViewHolder(mRecyclerView, mNewTabPageManager);
-
-            case ItemViewType.ALL_DISMISSED:
-                return new AllDismissedItem.ViewHolder(mRecyclerView, mNewTabPageManager, this);
-        }
-
-        assert false : viewType;
-        return null;
-    }
-
-    @Override
-    public void onBindViewHolder(NewTabPageViewHolder holder, final int position) {
-        mRoot.onBindViewHolder(holder, position);
-    }
-
-    @Override
-    public int getItemCount() {
-        return mRoot.getItemCount();
-    }
-
-    public int getAboveTheFoldPosition() {
-        return getChildPositionOffset(mAboveTheFold);
-    }
-
-    public int getFirstHeaderPosition() {
-        return getFirstPositionForType(ItemViewType.HEADER);
-    }
-
-    public int getFirstCardPosition() {
-        for (int i = 0; i < getItemCount(); ++i) {
-            if (CardViewHolder.isCard(getItemViewType(i))) return i;
-        }
-        return RecyclerView.NO_POSITION;
-    }
-
-    int getBottomSpacerPosition() {
-        return getChildPositionOffset(mBottomSpacer);
-    }
-
-    int getLastContentItemPosition() {
-        return getChildPositionOffset(hasAllBeenDismissed() ? mAllDismissed : mFooter);
+        resetSections(/* alwaysAllowEmptySections = */false);
     }
 
     private void setSuggestions(@CategoryInt int category, List<SnippetArticle> suggestions,
@@ -411,155 +203,6 @@ public class NewTabPageAdapter
         mSections.get(category).addSuggestions(suggestions, status);
     }
 
-    private void updateChildren() {
-        mChildren.clear();
-        mChildren.add(mAboveTheFold);
-        mChildren.addAll(mSections.values());
-        mChildren.add(mSigninPromo);
-        mChildren.add(mAllDismissed);
-        mChildren.add(mFooter);
-        mChildren.add(mBottomSpacer);
-
-        updateAllDismissedVisibility();
-
-        // TODO(mvanouwerkerk): Notify about the subset of changed items. At least |mAboveTheFold|
-        // has not changed when refreshing from the all dismissed state.
-        notifyDataSetChanged();
-    }
-
-    private void updateAllDismissedVisibility() {
-        boolean showAllDismissed = hasAllBeenDismissed();
-        mAllDismissed.setVisible(showAllDismissed);
-        mFooter.setVisible(!showAllDismissed);
-    }
-
-    private void removeSection(SuggestionsSection section) {
-        mSections.remove(section.getCategory());
-        int startPos = getChildPositionOffset(section);
-        mChildren.remove(section);
-        notifyItemRangeRemoved(startPos, section.getItemCount());
-
-        updateAllDismissedVisibility();
-
-        notifyItemChanged(getBottomSpacerPosition());
-    }
-
-    @Override
-    public void onItemRangeChanged(TreeNode child, int itemPosition, int itemCount) {
-        assert child == mRoot;
-        notifyItemRangeChanged(itemPosition, itemCount);
-    }
-
-    @Override
-    public void onItemRangeInserted(TreeNode child, int itemPosition, int itemCount) {
-        assert child == mRoot;
-        notifyItemRangeInserted(itemPosition, itemCount);
-        notifyItemChanged(getItemCount() - 1); // Refresh the spacer too.
-
-        updateAllDismissedVisibility();
-    }
-
-    @Override
-    public void onItemRangeRemoved(TreeNode child, int itemPosition, int itemCount) {
-        assert child == mRoot;
-        notifyItemRangeRemoved(itemPosition, itemCount);
-        notifyItemChanged(getItemCount() - 1); // Refresh the spacer too.
-
-        updateAllDismissedVisibility();
-    }
-
-    @Override
-    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
-        super.onAttachedToRecyclerView(recyclerView);
-
-        // We are assuming for now that the adapter is used with a single RecyclerView.
-        // Getting the reference as we are doing here is going to be broken if that changes.
-        assert mRecyclerView == null;
-
-        // FindBugs chokes on the cast below when not checked, raising BC_UNCONFIRMED_CAST
-        assert recyclerView instanceof NewTabPageRecyclerView;
-
-        mRecyclerView = (NewTabPageRecyclerView) recyclerView;
-    }
-
-    /**
-     * Dismisses the item at the provided adapter position. Can also cause the dismissal of other
-     * items or even entire sections.
-     */
-    // TODO(crbug.com/635567): Fix this properly.
-    @SuppressLint("SwitchIntDef")
-    public void dismissItem(int position) {
-        int itemViewType = getItemViewType(position);
-
-        // TODO(dgn): Polymorphism is supposed to allow to avoid that kind of stuff.
-        switch (itemViewType) {
-            case ItemViewType.STATUS:
-            case ItemViewType.ACTION:
-                dismissSection(getSuggestionsSection(position));
-                return;
-
-            case ItemViewType.SNIPPET:
-                dismissSuggestion(position);
-                return;
-
-            case ItemViewType.PROMO:
-                dismissPromo();
-                return;
-
-            default:
-                Log.wtf(TAG, "Unsupported dismissal of item of type %d", itemViewType);
-                return;
-        }
-    }
-
-    private void dismissSection(SuggestionsSection section) {
-        assert SnippetsConfig.isSectionDismissalEnabled();
-
-        announceItemRemoved(section.getHeaderText());
-
-        mNewTabPageManager.getSuggestionsSource().dismissCategory(section.getCategory());
-        removeSection(section);
-    }
-
-    private void dismissSuggestion(int position) {
-        SnippetArticle suggestion = mRoot.getSuggestionAt(position);
-        SuggestionsSource suggestionsSource = mNewTabPageManager.getSuggestionsSource();
-        if (suggestionsSource == null) {
-            // It is possible for this method to be called after the NewTabPage has had destroy()
-            // called. This can happen when NewTabPageRecyclerView.dismissWithAnimation() is called
-            // and the animation ends after the user has navigated away. In this case we cannot
-            // inform the native side that the snippet has been dismissed (http://crbug.com/649299).
-            return;
-        }
-
-        announceItemRemoved(suggestion.mTitle);
-
-        suggestionsSource.dismissSuggestion(suggestion);
-        SuggestionsSection section = getSuggestionsSection(position);
-        section.removeSuggestion(suggestion);
-    }
-
-    private void dismissPromo() {
-        announceItemRemoved(mSigninPromo.getHeader());
-        mSigninPromo.dismiss();
-    }
-
-    /**
-     * Returns another view holder that should be dismissed at the same time as the provided one.
-     */
-    public NewTabPageViewHolder getDismissSibling(ViewHolder viewHolder) {
-        int swipePos = viewHolder.getAdapterPosition();
-        int siblingPosDelta = mRoot.getDismissSiblingPosDelta(swipePos);
-        if (siblingPosDelta == 0) return null;
-
-        return (NewTabPageViewHolder) mRecyclerView.findViewHolderForAdapterPosition(
-                siblingPosDelta + swipePos);
-    }
-
-    private boolean hasAllBeenDismissed() {
-        return mSections.isEmpty() && !mSigninPromo.isVisible();
-    }
-
     private boolean canLoadSuggestions(@CategoryInt int category, @CategoryStatusEnum int status) {
         // We never want to add suggestions from unknown categories.
         if (!mSections.containsKey(category)) return false;
@@ -576,54 +219,39 @@ public class NewTabPageAdapter
     }
 
     /**
-     * @param itemPosition The position of an item in the adapter.
-     * @return Returns the {@link SuggestionsSection} that contains the item at
-     *     {@code itemPosition}, or null if the item is not part of one.
+     * Dismisses a section.
+     * @param section The section to be dismissed.
      */
-    private SuggestionsSection getSuggestionsSection(int itemPosition) {
-        TreeNode child = mRoot.getChildForPosition(itemPosition);
-        if (!(child instanceof SuggestionsSection)) return null;
-        return (SuggestionsSection) child;
-    }
-
-    private int getChildPositionOffset(TreeNode child) {
-        return mRoot.getStartingOffsetForChild(child);
-    }
-
-    @VisibleForTesting
-    SnippetArticle getSuggestionAt(int position) {
-        return mRoot.getSuggestionAt(position);
-    }
+    public void dismissSection(SuggestionsSection section) {
+        assert SnippetsConfig.isSectionDismissalEnabled();
 
-    @VisibleForTesting
-    int getFirstPositionForType(@ItemViewType int viewType) {
-        int count = getItemCount();
-        for (int i = 0; i < count; i++) {
-            if (getItemViewType(i) == viewType) return i;
-        }
-        return RecyclerView.NO_POSITION;
+        mNewTabPageManager.getSuggestionsSource().dismissCategory(section.getCategory());
+        removeSection(section);
     }
 
-    SuggestionsSection getSectionForTesting(@CategoryInt int category) {
-        return mSections.get(category);
+    private void removeSection(SuggestionsSection section) {
+        mSections.remove(section.getCategory());
+        willRemoveChild(section);
+        mChildren.remove(section);
     }
 
-    InnerNode getRootForTesting() {
-        return mRoot;
+    /**
+     * Restores any sections that have been dismissed and triggers a new fetch.
+     */
+    public void restoreDismissedSections() {
+        mNewTabPageManager.getSuggestionsSource().restoreDismissedCategories();
+        resetSections(/* allowEmptySections = */ true);
+        mNewTabPageManager.getSuggestionsSource().fetchRemoteSuggestions();
     }
 
-    private void announceItemRemoved(String itemTitle) {
-        // In tests the RecyclerView can be null.
-        if (mRecyclerView == null) return;
-
-        mRecyclerView.announceForAccessibility(mRecyclerView.getResources().getString(
-                R.string.ntp_accessibility_item_removed, itemTitle));
+    /**
+     * @return Whether the list of sections is empty.
+     */
+    public boolean isEmpty() {
+        return mSections.isEmpty();
     }
 
-    private void announceItemRemoved(@StringRes int stringToAnnounce) {
-        // In tests the RecyclerView can be null.
-        if (mRecyclerView == null) return;
-
-        announceItemRemoved(mRecyclerView.getResources().getString(stringToAnnounce));
+    SuggestionsSection getSectionForTesting(@CategoryInt int categoryId) {
+        return mSections.get(categoryId);
     }
 }