Zine: support multiple sections in the ui

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java
new file mode 100644
index 0000000000000000000000000000000000000000..f6ab60b750cff5b81ecee491b9921d3f06664335
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java
@@ -0,0 +1,68 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.ntp.cards;
+
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticleListItem;
+import org.chromium.chrome.browser.ntp.snippets.SnippetHeaderListItem;
+import org.chromium.chrome.browser.ntp.snippets.SuggestionsCategoryStatus;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A group of suggestions, with a header and a status card.
+ */
+public class SuggestionsSection implements NewTabPageItemGroup {
+    private final List<NewTabPageListItem> mItems;
+    private final SnippetHeaderListItem mHeader;
+    private StatusListItem mStatus;
+
+    SuggestionsSection(List<SnippetArticleListItem> suggestions,
+            @SuggestionsCategoryStatus int status, NewTabPageAdapter adapter) {
+        mItems = new ArrayList<>();

[PEConn, 2016/08/01 16:26:51]

Why ArrayList? The list is going to be kept fairly small (about 10 items) but
we're going to be doing random removals.

Mindyou, the data locality will probably make moving all the items up one
position in an ArrayList faster than following the links of a linked list.

[Bernhard Bauer, 2016/08/02 13:03:27]

Plus, purely algorithmically, traversing a linked list is also going to take
O(n). There isn't really a good data structure in the standard Java libraries
that allows insertion/deletion at random indices :-/

[PEConn, 2016/08/02 15:45:14]

Acknowledged.

+
+        // TODO(mvanouwerkerk): Pass in the header text.
+        mHeader = new SnippetHeaderListItem();
+
+        setSuggestions(suggestions, status, adapter);
+    }
+
+    @Override
+    public List<NewTabPageListItem> getItems() {
+        return mItems;
+    }
+
+    public void dismissSuggestion(SnippetArticleListItem suggestion) {
+        mItems.remove(suggestion);
+
+        if (!hasSuggestions() && !mItems.contains(mStatus)) {
+            mItems.add(mStatus);
+            mHeader.setVisible(false);
+        }
+    }
+
+    public boolean hasSuggestions() {
+        for (NewTabPageListItem item : mItems) {

[PEConn, 2016/08/01 16:26:51]

Why do we need to search for the first SnippetArticleListItem? Can't we just
check whether the first item is a SnippetHeaderListItem or a StatusListItem?

[Bernhard Bauer, 2016/08/02 13:03:27]

I slightly prefer this, as it reflects the intent of the method more clearly (we
have suggestions if we have at least one SnippetArticleListItem). And
performance-wise it shouldn't make a big difference, because we should get a
result by the second item anyway.

[PEConn, 2016/08/02 15:45:14]

Acknowledged.

+            if (item instanceof SnippetArticleListItem) return true;
+        }
+        return false;
+    }
+
+    public void setSuggestions(List<SnippetArticleListItem> suggestions,
+            @SuggestionsCategoryStatus int status, NewTabPageAdapter adapter) {
+        mItems.clear();
+
+        mItems.add(mHeader);
+        mHeader.setVisible(!suggestions.isEmpty());
+
+        mStatus = StatusListItem.create(status, adapter);
+
+        if (suggestions.isEmpty()) {
+            mItems.add(mStatus);
+        } else {
+            mItems.addAll(suggestions);
+        }
+    }
+}