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chrome/android/java/src/org/chromium/chrome/browser/widget/DateDividedAdapter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/widget/DateDividedAdapter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/widget/DateDividedAdapter.java b/chrome/android/java/src/org/chromium/chrome/browser/widget/DateDividedAdapter.java
index 3c10048252ca4e2cc54549019eac13f6913cc7a2..b2ec1635a0396cad302c201b9d7986a1ffdfc24b 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/widget/DateDividedAdapter.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/widget/DateDividedAdapter.java
@@ -16,7 +16,6 @@ import android.view.ViewGroup;
 import android.widget.TextView;
 
 import org.chromium.chrome.R;
-import org.chromium.chrome.browser.widget.DateDividedAdapter.ItemGroup;
 
 import java.util.ArrayList;
 import java.util.Calendar;
@@ -53,7 +52,7 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
         private boolean mIsLastInGroup;
 
         /** See {@link #mPosition}. */
-        private final void setPosition(int position) {
+        public final void setPosition(int position) {
             mPosition = position;
         }
 
@@ -152,9 +151,9 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
     /**
      * A bucket of items with the same date.
      */
-    protected static class ItemGroup {
-        private final Date mDate;
-        private final List<TimedItem> mItems = new ArrayList<>();
+    public static class ItemGroup {
+        protected final Date mDate;
+        protected final List<TimedItem> mItems = new ArrayList<>();
 
         /** Index of the header, relative to the full list.  Must be set only once.*/
         private int mIndex;
@@ -183,15 +182,26 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
             mIndex = index;
 
             sortIfNeeded();
+            setPositionForItems(index + 1);
+            markFirstAndLastItem();
+        }
+
+        protected void setPositionForItems(int startIndex) {
+            int index = startIndex;
             for (int i = 0; i < mItems.size(); i++) {
-                index += 1;
                 TimedItem item = mItems.get(i);
                 item.setPosition(index);
-                item.setIsFirstInGroup(i == 0);
-                item.setIsLastInGroup(i == mItems.size() - 1);
+                index += 1;
             }
         }
 
+        protected void markFirstAndLastItem() {
+            TimedItem first = mItems.get(0);
+            TimedItem last = mItems.get(mItems.size() - 1);
+            first.setIsFirstInGroup(true);
+            last.setIsLastInGroup(true);
+        }
+
         /** Unsets the position of all TimedItems in this group. */
         public void resetPosition() {
             mIndex = TimedItem.INVALID_POSITION;
@@ -212,7 +222,7 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
             if (mIsListHeader || mIsListFooter) return 1;
 
             // Plus 1 to account for the date header.
-            return mItems.size() + 1;
+            return mItems.isEmpty() ? 0 : mItems.size() + 1;
         }
 
         public TimedItem getItemAt(int index) {
@@ -220,6 +230,10 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
             if (index == 0 || mIsListHeader || mIsListFooter) return null;
 
             sortIfNeeded();
+            return getItemAtInternal(index);
+        }
+
+        protected TimedItem getItemAtInternal(int index) {
             return mItems.get(index - 1);
         }
 
@@ -227,26 +241,44 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
          * Rather than sorting the list each time a new item is added, the list is sorted when
          * something requires a correct ordering of the items.
          */
-        private void sortIfNeeded() {
+        protected void sortIfNeeded() {
             if (mIsSorted) return;
             mIsSorted = true;
 
             Collections.sort(mItems, new Comparator<TimedItem>() {
                 @Override
                 public int compare(TimedItem lhs, TimedItem rhs) {
-                    // More recent items are listed first.  Ideally we'd use Long.compare, but that
-                    // is an API level 19 call for some inexplicable reason.
-                    long timeDelta = lhs.getTimestamp() - rhs.getTimestamp();
-                    if (timeDelta > 0) {
-                        return -1;
-                    } else if (timeDelta == 0) {
-                        return 0;
-                    } else {
-                        return 1;
-                    }
+                    return compareItem(lhs, rhs);
                 }
             });
         }
+
+        protected int compareItem(TimedItem lhs, TimedItem rhs) {
+            // More recent items are listed first.  Ideally we'd use Long.compare, but that
+            // is an API level 19 call for some inexplicable reason.
+            long timeDelta = lhs.getTimestamp() - rhs.getTimestamp();
+            if (timeDelta > 0) {
+                return -1;
+            } else if (timeDelta == 0) {
+                return 0;
+            } else {
+                return 1;
+            }
+        }
+
+        public int getItemViewType(int position) {
+            return position == 0 ? TYPE_DATE : TYPE_NORMAL;
+        }
+
+        /**
+         * Returns the number of rows that should be removed when the given item is deleted.
+         * e.g. When the last item is deleted, the date header should also be removed.
+         * @param item The item to be removed.
+         * @return The number of rows to be removed.
+         */
+        public int getNumberOfRowsToBeRemovedForItem(TimedItem item) {

[Theresa, 2017/02/13 19:15:00]

Instead of introducing this method, can ItemGroup#removeItem() return the number
of items that were removed?

+            return mItems.size() == 1 ? 2 : 1;
+        }
     }
 
     // Cached async tasks to get the two Calendar objects, which are used when comparing dates.
@@ -257,6 +289,7 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
     public static final int TYPE_HEADER = -1;
     public static final int TYPE_DATE = 0;
     public static final int TYPE_NORMAL = 1;
+    public static final int TYPE_SUBSECTION_HEADER = 2;
 
     private int mSize;
     private boolean mHasListHeader;
@@ -282,6 +315,14 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
     protected abstract ViewHolder createViewHolder(ViewGroup parent);
 
     /**
+     * Creates a {@link ViewHolder} for a subsection in the given view parent.
+     * @see #onCreateViewHolder(ViewGroup, int)
+     */
+    protected ViewHolder createSubsectionHeader(ViewGroup parent) {
+        return null;
+    }
+
+    /**
      * Creates a {@link BasicViewHolder} in the given view parent for the header.
      * @see #onCreateViewHolder(ViewGroup, int)
      */
@@ -330,28 +371,31 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
                 if (group.isSameDay(date)) {
                     found = true;
                     group.addItem(timedItem);
-                    mSize++;
                     break;
                 }
             }
             if (!found) {
                 // Create a new ItemGroup with the date for the new item. This increases the
                 // size by two because we add new views for the date and the item itself.
-                ItemGroup newGroup = new ItemGroup(timedItem.getTimestamp());
+                ItemGroup newGroup = createGroup(timedItem.getTimestamp());
                 newGroup.addItem(timedItem);
                 mGroups.add(newGroup);
-                mSize += 2;
             }
         }
 
+        computeItemCount();
         setGroupPositions();
         notifyDataSetChanged();
     }
 
+    protected ItemGroup createGroup(long timestamp) {
+        return new ItemGroup(timestamp);
+    }
+
     /**
      * Tells each group where they start in the list.
      */
-    private void setGroupPositions() {
+    protected void setGroupPositions() {
         int startIndex = 0;
         for (ItemGroup group : mGroups) {
             group.resetPosition();
@@ -461,15 +505,14 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
             return TYPE_HEADER;
         } else if (pair.second == TYPE_FOOTER) {
             return TYPE_FOOTER;
-        } else if (pair.second == 0) {
-            return TYPE_DATE;
         } else {
-            return TYPE_NORMAL;
+            ItemGroup group = pair.first;
+            return group.getItemViewType(pair.second);
         }
     }
 
     @Override
-    public final RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
         if (viewType == TYPE_DATE) {
             return createDateViewHolder(parent);
         } else if (viewType == TYPE_NORMAL) {
@@ -478,13 +521,15 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
             return createHeader(parent);
         } else if (viewType == TYPE_FOOTER) {
             return createFooter(parent);
+        } else if (viewType == TYPE_SUBSECTION_HEADER) {
+            return createSubsectionHeader(parent);
         }
         assert false;
         return null;
     }
 
     @Override
-    public final void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
+    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
         Pair<Date, TimedItem> pair = getItemAt(position);
         if (holder instanceof DateViewHolder) {
             ((DateViewHolder) holder).setDate(pair.first);
@@ -530,19 +575,26 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
      */
     protected void removeItem(TimedItem item) {
         ItemGroup group = getGroupAt(item.getPosition()).first;
+        int numRowsToRemove = group.getNumberOfRowsToBeRemovedForItem(item);
         group.removeItem(item);
-        mSize--;
 
-        // Remove the group if only the date header is left.
-        if (group.size() == 1) {
+        // Remove the group if it is empty.
+        if (group.size() == 0) {
             mGroups.remove(group);
-            mSize--;
         }
 
+        mSize -= numRowsToRemove;
         setGroupPositions();
         notifyDataSetChanged();
     }
 
+    protected void computeItemCount() {
+        mSize = 0;
+        for (ItemGroup group : mGroups) {
+            mSize += group.size();
+        }
+    }
+
     /**
      * Creates a long ID that identifies a particular day in history.
      * @param date Date to process.
@@ -563,7 +615,7 @@ public abstract class DateDividedAdapter extends Adapter<RecyclerView.ViewHolder
      * {@link #compareCalendar(Calendar, Calendar)} instead.
      * @return 0 if date1 and date2 are in the same day; 1 if date1 is before date2; -1 otherwise.
      */
-    private static int compareDate(Date date1, Date date2) {
+    protected static int compareDate(Date date1, Date date2) {
         Pair<Calendar, Calendar> pair = getCachedCalendars();
         Calendar cal1 = pair.first, cal2 = pair.second;
         cal1.setTime(date1);