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

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

+// 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;

[Michael van Ouwerkerk, 2016/12/12 16:09:57]

Fwiw, I'm not convinced having packages 'cards' and 'snippets' is a useful
split. I can't quite decide which package makes more sense for this class.

[Bernhard Bauer, 2016/12/12 17:39:19]

Yeah, I agree, the current split feels kind of arbitrary. I'm just not sure what
a better split would be. We could do model (SnippetArticle, CategoryInt, etc.) /
view (all the ViewHolder classes) / controller (all the TreeNode subclasses)?

[Michael van Ouwerkerk, 2016/12/13 11:08:21]

Yes I considered that split, but we have things like nested ViewHolder classes.
And I'm not sure we would gain much with a split of any sort, these packages are
not that large.

+
+import org.chromium.base.Log;
+import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
+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.SnippetArticle;
+import org.chromium.chrome.browser.ntp.snippets.SnippetsBridge;
+import org.chromium.chrome.browser.ntp.snippets.SnippetsConfig;
+import org.chromium.chrome.browser.ntp.snippets.SuggestionsSource;
+import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
+
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 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 {

[Michael van Ouwerkerk, 2016/12/12 16:09:57]

It seems it would be nice to see a diff between this file and
NewTabPageAdapter.java. A lot of this is just a move. Could you hint things to
show that?

[Bernhard Bauer, 2016/12/12 17:39:19]

Done!

+    private static final String TAG = "Ntp";
+
+    /** 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;
+
+    public SectionList(NodeParent parent, NewTabPageManager newTabPageManager,
+            OfflinePageBridge offlinePageBridge) {
+        super(parent);
+        mNewTabPageManager = newTabPageManager;
+        mNewTabPageManager.getSuggestionsSource().setObserver(this);
+        mOfflinePageBridge = offlinePageBridge;
+    }
+
+    @Override
+    public void init() {
+        super.init();
+        resetSections(/* alwaysAllowEmptySections = */ false);
+    }
+
+    @Override
+    protected List<TreeNode> getChildren() {
+        return mChildren;
+    }
+
+    /**
+     * Resets the sections, reloading the whole new tab page content.
+     * @param alwaysAllowEmptySections Whether sections are always allowed to be displayed when
+     *     they are empty, even when they are normally not.
+     */
+    public void resetSections(boolean alwaysAllowEmptySections) {
+        mSections.clear();
+        mChildren.clear();
+
+        SuggestionsSource suggestionsSource = mNewTabPageManager.getSuggestionsSource();
+        int[] categories = suggestionsSource.getCategories();
+        int[] suggestionsPerCategory = new int[categories.length];
+        int i = 0;
+        for (int category : categories) {
+            int categoryStatus = suggestionsSource.getCategoryStatus(category);
+            if (categoryStatus == CategoryStatus.LOADING_ERROR
+                    || categoryStatus == CategoryStatus.NOT_PROVIDED
+                    || categoryStatus == CategoryStatus.CATEGORY_EXPLICITLY_DISABLED)
+                continue;
+
+            suggestionsPerCategory[i++] =
+                    resetSection(category, categoryStatus, alwaysAllowEmptySections);
+        }
+
+        mNewTabPageManager.trackSnippetsPageImpression(categories, suggestionsPerCategory);
+    }
+
+    /**
+     * Resets the section for {@code category}. Removes the section if there are no suggestions for
+     * it and it is not allowed to be empty. Otherwise, creates the section if it is not present
+     * yet. Sets the available suggestions on the section.
+     * @param category The category for which the section must be reset.
+     * @param categoryStatus The category status.
+     * @param alwaysAllowEmptySections Whether sections are always allowed to be displayed when
+     *     they are empty, even when they are normally not.
+     * @return The number of suggestions for the section.
+     */
+    private int resetSection(@CategoryInt int category, @CategoryStatusEnum int categoryStatus,
+            boolean alwaysAllowEmptySections) {
+        SuggestionsSource suggestionsSource = mNewTabPageManager.getSuggestionsSource();
+        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) {
+            if (section != null) removeSection(section);
+            return 0;
+        }
+
+        // Create the section if needed.
+        if (section == null) {
+            section = new SuggestionsSection(this, mNewTabPageManager, mOfflinePageBridge, info);
+            mSections.put(category, section);
+            mChildren.add(section);
+            didAddChild(section);
+        }
+
+        // Add the new suggestions.
+        setSuggestions(category, suggestions, categoryStatus);
+
+        return suggestions.size();
+    }
+
+    @Override
+    public void onNewSuggestions(@CategoryInt int category) {
+        @CategoryStatusEnum
+        int status = mNewTabPageManager.getSuggestionsSource().getCategoryStatus(category);
+
+        if (!canLoadSuggestions(category, status)) return;
+
+        // We never want to refresh the suggestions if we already have some content.
+        if (mSections.get(category).hasSuggestions()) return;
+
+        List<SnippetArticle> suggestions =
+                mNewTabPageManager.getSuggestionsSource().getSuggestionsForCategory(category);
+
+        Log.d(TAG, "Received %d new suggestions for category %d.", suggestions.size(), category);
+
+        // At first, there might be no suggestions available, we wait until they have been fetched.
+        if (suggestions.isEmpty()) return;
+
+        setSuggestions(category, suggestions, status);
+    }
+
+    @Override
+    public void onMoreSuggestions(@CategoryInt int category, List<SnippetArticle> suggestions) {
+        @CategoryStatusEnum
+        int status = mNewTabPageManager.getSuggestionsSource().getCategoryStatus(category);
+        if (!canLoadSuggestions(category, status)) return;
+
+        setSuggestions(category, suggestions, status);
+    }
+
+    @Override
+    public void onCategoryStatusChanged(@CategoryInt int category, @CategoryStatusEnum int status) {
+        // Observers should not be registered for this state.
+        assert status != CategoryStatus.ALL_SUGGESTIONS_EXPLICITLY_DISABLED;
+
+        // If there is no section for this category there is nothing to do.
+        if (!mSections.containsKey(category)) return;
+
+        switch (status) {
+            case CategoryStatus.NOT_PROVIDED:
+                // The section provider has gone away. Keep open UIs as they are.
+                return;
+
+            case CategoryStatus.CATEGORY_EXPLICITLY_DISABLED:
+            case CategoryStatus.LOADING_ERROR:
+                // Need to remove the entire section from the UI immediately.
+                removeSection(mSections.get(category));
+                return;
+
+            case CategoryStatus.SIGNED_OUT:
+                resetSection(category, status, /* alwaysAllowEmptySections = */ false);
+                return;
+
+            default:
+                mSections.get(category).setStatus(status);
+                return;
+        }
+    }
+
+    @Override
+    public void onSuggestionInvalidated(@CategoryInt int category, String idWithinCategory) {
+        if (!mSections.containsKey(category)) return;
+        mSections.get(category).removeSuggestionById(idWithinCategory);
+    }
+
+    @Override
+    public void onFullRefreshRequired() {
+        resetSections(/* alwaysAllowEmptySections = */false);
+    }
+
+    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);
+    }
+
+    private boolean canLoadSuggestions(@CategoryInt int category, @CategoryStatusEnum int status) {
+        // We never want to add suggestions from unknown categories.
+        if (!mSections.containsKey(category)) return false;
+
+        // The status may have changed while the suggestions were loading, perhaps they should not
+        // be displayed any more.
+        if (!SnippetsBridge.isCategoryEnabled(status)) {
+            Log.w(TAG, "Received suggestions for a disabled category (id=%d, status=%d)", category,
+                    status);
+            return false;
+        }
+
+        return true;
+    }
+
+    /**
+     * Dismisses a section.
+     * @param section The section to be dismissed.
+     */
+    public void dismissSection(SuggestionsSection section) {
+        assert SnippetsConfig.isSectionDismissalEnabled();
+
+        mNewTabPageManager.getSuggestionsSource().dismissCategory(section.getCategory());
+        removeSection(section);
+    }
+
+    private void removeSection(SuggestionsSection section) {
+        mSections.remove(section.getCategory());
+        willRemoveChild(section);
+        mChildren.remove(section);
+    }
+
+    /**
+     * Restores any sections that have been dismissed and triggers a new fetch.
+     */
+    public void restoreDismissedSections() {
+        mNewTabPageManager.getSuggestionsSource().restoreDismissedCategories();
+        resetSections(/* allowEmptySections = */ true);
+        mNewTabPageManager.getSuggestionsSource().fetchRemoteSuggestions();
+    }
+
+    /**
+     * @return Whether the list of sections is empty.
+     */
+    public boolean isEmpty() {
+        return mSections.isEmpty();
+    }
+
+    SuggestionsSection getSectionForTesting(@CategoryInt int categoryId) {
+        return mSections.get(categoryId);
+    }
+}