📰 Tweak the suggestion ranks for UMA to handle fetchMore

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/SectionList.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SectionList.java
index a0190f41f7137b9deb110cbb95d81fa366ea2421..725bef361304c2611074060745898a75627609b8 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SectionList.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SectionList.java
@@ -4,6 +4,8 @@
 
 package org.chromium.chrome.browser.ntp.cards;
 
+import android.util.Pair;
+
 import org.chromium.base.Log;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
@@ -15,6 +17,7 @@
 import org.chromium.chrome.browser.ntp.snippets.SnippetsConfig;
 import org.chromium.chrome.browser.ntp.snippets.SuggestionsSource;
 import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
+import org.chromium.chrome.browser.suggestions.SuggestionsMetricsReporter;
 
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -24,8 +27,9 @@
  * 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 SectionList
-        extends InnerNode implements SuggestionsSource.Observer, SuggestionsSection.Delegate {
+public class SectionList extends InnerNode implements SuggestionsSource.Observer,
+                                                      SuggestionsSection.Delegate,
+                                                      SuggestionsMetricsReporter.SuggestionRanker {
     private static final String TAG = "Ntp";
 
     /** Maps suggestion categories to sections, with stable iteration ordering. */
@@ -35,6 +39,7 @@
 
     public SectionList(NewTabPageManager newTabPageManager, OfflinePageBridge offlinePageBridge) {
         mNewTabPageManager = newTabPageManager;
+        mNewTabPageManager.getSuggestionsMetricsReporter().setRanker(this);
         mNewTabPageManager.getSuggestionsSource().setObserver(this);
         mOfflinePageBridge = offlinePageBridge;
         resetSections(/* alwaysAllowEmptySections = */ false);
@@ -63,7 +68,8 @@ public void resetSections(boolean alwaysAllowEmptySections) {
                     resetSection(category, categoryStatus, alwaysAllowEmptySections);
         }
 
-        mNewTabPageManager.trackSnippetsPageImpression(categories, suggestionsPerCategory);
+        mNewTabPageManager.getSuggestionsMetricsReporter().onPageShown(
+                categories, suggestionsPerCategory);
     }
 
     /**
@@ -175,17 +181,6 @@ public void onFullRefreshRequired() {
 
     private void setSuggestions(@CategoryInt int category, List<SnippetArticle> suggestions,
             @CategoryStatusEnum int status) {
-        // Count the number of suggestions before this category.
-        int globalPositionOffset = 0;
-        for (Map.Entry<Integer, SuggestionsSection> entry : mSections.entrySet()) {
-            if (entry.getKey() == category) break;
-            globalPositionOffset += entry.getValue().getSuggestionsCount();
-        }
-        // Assign global indices to the new suggestions.
-        for (SnippetArticle suggestion : suggestions) {
-            suggestion.mGlobalPosition = globalPositionOffset + suggestion.mPosition;
-        }
-
         mSections.get(category).addSuggestions(suggestions, status);
     }
 
@@ -216,6 +211,29 @@ public void dismissSection(SuggestionsSection section) {
         removeSection(section);
     }
 
+    @Override
+    public Pair<Integer, Integer> getSuggestionRank(SnippetArticle suggestion) {
+        int globalRank = 0;
+        for (Map.Entry<Integer, SuggestionsSection> kvPair : mSections.entrySet()) {
+            if (kvPair.getKey() == suggestion.mCategory) {
+                int localRank = kvPair.getValue().getSuggestionRank(suggestion);
+                globalRank += localRank;
+
+                assert localRank != -1;
+                return new Pair<>(localRank, globalRank);
+            }
+            globalRank += kvPair.getValue().getSuggestionsCount();
+        }
+
+        throw new IndexOutOfBoundsException();
+    }
+
+    @Override
+    public int getActionItemRank(@CategoryInt int category) {
+        assert mSections.get(category).getActionItem().isVisible();
+        return mSections.get(category).getSuggestionsCount();
+    }
+
     @VisibleForTesting
     void removeSection(SuggestionsSection section) {
         mSections.remove(section.getCategory());