[Downloads Home] Support items with the same creation time.

The DateOrderedListMutator kept OfflineItems in a Map keyed by their
creation time. Two entries with the same one (or within the same
millisecond) would therefore override each other. This replaces the map
with a sorted set and a custom comparator to keep the descending sort
order.

Bug: 962889
Change-Id: I1bef6b32a42dc34b49946512e31f440999cf7287
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1609901
Commit-Queue: Richard Knoll <knollr@chromium.org>
Reviewed-by: Xing Liu <xingliu@chromium.org>
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659446}

chrome/android/java/src/org/chromium/chrome/browser/download/home/list/DateOrderedListMutator.java

@@ -21,7 +21,9 @@ import java.util.Collection;
 import java.util.Date;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.TreeMap;
+import java.util.TreeSet;
 
 /**
  * A class responsible for turning a {@link Collection} of {@link OfflineItem}s into a list meant
@@ -186,13 +188,13 @@ class DateOrderedListMutator implements OfflineItemFilterObserver {
                     if (!mHideSectionHeaders) {
                         sectionHeaderItem.showTitle = !mHideTitleFromSectionHeaders;
                         sectionHeaderItem.showMenu = filter == OfflineItemFilter.IMAGE;
-                        sectionHeaderItem.items = new ArrayList<>(section.items.values());
+                        sectionHeaderItem.items = new ArrayList<>(section.items);
                     }
                     listItems.add(sectionHeaderItem);
                 }
 
                 // Add the items in the section.
-                for (OfflineItem offlineItem : section.items.values()) {
+                for (OfflineItem offlineItem : section.items) {
                     OfflineItemListItem item = new OfflineItemListItem(offlineItem);
                     if (mConfig.supportFullWidthImages && section.items.size() == 1
                             && offlineItem.filter == OfflineItemFilter.IMAGE) {
@@ -258,7 +260,7 @@ class DateOrderedListMutator implements OfflineItemFilterObserver {
 
         public boolean contains(ContentId id) {
             for (Section section : sections.values()) {
-                for (OfflineItem item : section.items.values()) {
+                for (OfflineItem item : section.items) {
                     if (item.id.equals(id)) return true;
                 }
             }
@@ -268,15 +270,25 @@ class DateOrderedListMutator implements OfflineItemFilterObserver {
 
     /** Represents a group of items having the same filter type. */
     private static class Section {
-        public Map<Date, OfflineItem> items =
-                new TreeMap<>((lhs, rhs) -> { return rhs.compareTo(lhs); });
+        /**
+         * The list of items in a section for a day. Ordered by descending creation time then
+         * namespace and finally by id.
+         */
+        public Set<OfflineItem> items = new TreeSet<>((lhs, rhs) -> {
+            int comparison = Long.compare(rhs.creationTimeMs, lhs.creationTimeMs);
+            if (comparison != 0) return comparison;
+            comparison = lhs.id.namespace.compareTo(rhs.id.namespace);
+            if (comparison != 0) return comparison;
+            return lhs.id.id.compareTo(rhs.id.id);
+        });
 
         public void addOrUpdateItem(OfflineItem item) {
-            items.put(new Date(item.creationTimeMs), item);
+            items.remove(item);
+            items.add(item);
         }
 
         public void removeItem(OfflineItem item) {
-            items.remove(new Date(item.creationTimeMs));
+            items.remove(item);
         }
     }
 }

chrome/android/junit/src/org/chromium/chrome/browser/download/home/list/DateOrderedListMutatorTest.java

@@ -735,6 +735,56 @@ public class DateOrderedListMutatorTest {
         assertOfflineItem(mModel.get(5), buildCalendar(2018, 1, 1, 4), item2);
     }
 
+    /**
+     * Action                               List
+     * 1. Set()                             [ ]
+     *
+     * 2. Add(item3 @ 4:00 1/1/2018)        [ DATE    @ 0:00 1/1/2018,
+     *                                        SECTION   @ Video,
+     *                                        item3  @ 4:00 1/1/2018 ]
+     *
+     * 3. Add(item1 @ 4:00 1/1/2018)        [ DATE    @ 0:00 1/1/2018,
+     *                                        SECTION   @ Video,
+     *                                        item1  @ 4:00 1/1/2018,
+     *                                        item3  @ 4:00 1/1/2018 ]
+     *
+     * 4. Add(item2 @ 4:00 1/1/2018)        [ DATE    @ 0:00 1/1/2018,
+     *                                        SECTION   @ Video,
+     *                                        item1  @ 4:00 1/1/2018,
+     *                                        item2  @ 4:00 1/1/2018,
+     *                                        item3  @ 4:00 1/1/2018 ]
+     */
+    @Test
+    public void testAddMultipleItemsSameTimestamp() {
+        when(mSource.getItems()).thenReturn(Collections.emptySet());
+        DateOrderedListMutator list = createMutatorWithoutJustNowProvider();
+        mModel.addObserver(mObserver);
+
+        OfflineItem item3 = buildItem("3", buildCalendar(2018, 1, 1, 4), OfflineItemFilter.VIDEO);
+        when(mSource.getItems()).thenReturn(CollectionUtil.newArrayList(item3));
+        list.onItemsAdded(CollectionUtil.newArrayList(item3));
+
+        Assert.assertEquals(2, mModel.size());
+        assertOfflineItem(mModel.get(1), buildCalendar(2018, 1, 1, 4), item3);
+
+        OfflineItem item1 = buildItem("1", buildCalendar(2018, 1, 1, 4), OfflineItemFilter.VIDEO);
+        when(mSource.getItems()).thenReturn(CollectionUtil.newArrayList(item3, item1));
+        list.onItemsAdded(CollectionUtil.newArrayList(item1));
+
+        Assert.assertEquals(3, mModel.size());
+        assertOfflineItem(mModel.get(1), buildCalendar(2018, 1, 1, 4), item1);
+        assertOfflineItem(mModel.get(2), buildCalendar(2018, 1, 1, 4), item3);
+
+        OfflineItem item2 = buildItem("2", buildCalendar(2018, 1, 1, 4), OfflineItemFilter.VIDEO);
+        when(mSource.getItems()).thenReturn(CollectionUtil.newArrayList(item3, item1, item2));
+        list.onItemsAdded(CollectionUtil.newArrayList(item2));
+
+        Assert.assertEquals(4, mModel.size());
+        assertOfflineItem(mModel.get(1), buildCalendar(2018, 1, 1, 4), item1);
+        assertOfflineItem(mModel.get(2), buildCalendar(2018, 1, 1, 4), item2);
+        assertOfflineItem(mModel.get(3), buildCalendar(2018, 1, 1, 4), item3);
+    }
+
     /**
      * Action                                          List
      * 1. Set(item1 @ 6:00 IN_PROGRESS 1/1/2018)       [ DATE    @ 0:00 1/1/2018,