Upstream oodles of Chrome for Android code into Chromium.

chrome/android/java_staging/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkManager.java

Index: chrome/android/java_staging/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkManager.java
diff --git a/chrome/android/java_staging/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkManager.java b/chrome/android/java_staging/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkManager.java
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@@ -0,0 +1,648 @@
+// Copyright 2015 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.enhancedbookmarks;
+
+import android.annotation.TargetApi;
+import android.app.Activity;
+import android.app.ActivityOptions;
+import android.content.Intent;
+import android.os.Build;
+import android.preference.PreferenceManager;
+import android.support.v4.widget.DrawerLayout;
+import android.util.Log;
+import android.view.Gravity;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ViewSwitcher;
+
+import com.google.android.apps.chrome.R;
+
+import org.chromium.base.ObserverList;
+import org.chromium.base.metrics.RecordHistogram;
+import org.chromium.chrome.browser.BookmarksBridge.BookmarkItem;
+import org.chromium.chrome.browser.BookmarksBridge.BookmarkModelObserver;
+import org.chromium.chrome.browser.UrlConstants;
+import org.chromium.chrome.browser.enhanced_bookmarks.EnhancedBookmarksBridge.FiltersObserver;
+import org.chromium.chrome.browser.enhanced_bookmarks.EnhancedBookmarksModel;
+import org.chromium.chrome.browser.enhanced_bookmarks.LaunchLocation;
+import org.chromium.chrome.browser.ntp.NewTabPageUma;
+import org.chromium.chrome.browser.partnerbookmarks.PartnerBookmarksShim;
+import org.chromium.chrome.browser.snackbar.SnackbarManager.SnackbarManageable;
+import org.chromium.components.bookmarks.BookmarkId;
+import org.chromium.ui.base.DeviceFormFactor;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLDecoder;
+import java.net.URLEncoder;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.Stack;
+
+/**
+ * The new bookmark manager that is planned to replace the existing bookmark manager. It holds all
+ * views and shared logics between tablet and phone. For tablet/phone specific logics, see
+ * {@link EnhancedBookmarkActivity} (phone) and {@link EnhancedBookmarkPage} (tablet).
+ */
+public class EnhancedBookmarkManager implements EnhancedBookmarkDelegate {
+    private static final String PREF_LAST_USED_URL = "enhanced_bookmark_last_used_url";
+    static final String PREF_WAS_IN_LIST_MODE = "enhanced_bookmark_list_mode_choice";
+    // TODO(ianwen): upstream these metrics upstream.
+    // UI modes for bookmarks presentation. Default option is grid mode.
+    static final int DEFAULT_MODE = 0;
+    static final int LIST_MODE = 1;
+    static final int GRID_MODE = 2;
+
+    private Activity mActivity;
+    private ViewGroup mMainView;
+    private EnhancedBookmarksModel mEnhancedBookmarksModel;
+    private EnhancedBookmarkUndoController mUndoController;
+    private final ObserverList<EnhancedBookmarkUIObserver> mUIObservers =
+            new ObserverList<EnhancedBookmarkUIObserver>();
+    private Set<BookmarkId> mSelectedBookmarks = new HashSet<>();
+    private boolean mListModeEnabled;
+    private EnhancedBookmarkStateChangeListener mUrlChangeListener;
+    private EnhancedBookmarkContentView mContentView;
+    private EnhancedBookmarkSearchView mSearchView;
+    private ViewSwitcher mViewSwitcher;
+    private DrawerLayout mDrawer;
+    private EnhancedBookmarkDrawerListView mDrawerListView;
+    private final Stack<UIState> mStateStack = new Stack<>();
+
+    private final BookmarkModelObserver mBookmarkModelObserver = new BookmarkModelObserver() {
+        @Override
+        public void bookmarkNodeRemoved(BookmarkItem parent, int oldIndex, BookmarkItem node) {
+            // If the folder is removed in folder mode, show the parent folder or falls back to all
+            // bookmarks mode.
+            if (getCurrentState() == STATE_FOLDER
+                    && node.getId().equals(mStateStack.peek().mFolder)) {
+                if (mEnhancedBookmarksModel.getTopLevelFolderIDs(true, true).contains(
+                        node.getId())) {
+                    openAllBookmarks();
+                } else {
+                    openFolder(parent.getId());
+                }
+            }
+            clearSelection();
+        }
+
+        @Override
+        public void bookmarkNodeMoved(BookmarkItem oldParent, int oldIndex, BookmarkItem newParent,
+                int newIndex) {
+            clearSelection();
+        }
+
+        @Override
+        public void bookmarkModelLoaded() {
+            initializeIfBookmarkModelLoaded();
+        }
+
+        @Override
+        public void bookmarkModelChanged() {
+            // If the folder no longer exists in folder mode, we need to fall back. Relying on the
+            // default behavior by setting the folder mode again.
+            if (getCurrentState() == STATE_FOLDER) {
+                setState(mStateStack.peek());
+            }
+            clearSelection();
+        }
+    };
+
+    private final FiltersObserver mFiltersObserver = new FiltersObserver() {
+        @Override
+        public void onFiltersChanged() {
+            // if the current selected filter was removed, we need to fall back. Relying on the
+            // default behavior by setting the filter mode again.
+            if (getCurrentState() == STATE_FILTER) {
+                setState(mStateStack.peek());
+            }
+        }
+    };
+
+    /**
+     * Creates an instance of {@link EnhancedBookmarkManager}. It also initializes resources,
+     * bookmark models and jni bridges.
+     * @param activity The activity context to use.
+     */
+    public EnhancedBookmarkManager(Activity activity) {
+        mActivity = activity;
+        mEnhancedBookmarksModel = new EnhancedBookmarksModel();
+        mMainView = (ViewGroup) mActivity.getLayoutInflater().inflate(R.layout.eb_main, null);
+        mDrawer = (DrawerLayout) mMainView.findViewById(R.id.eb_drawer_layout);
+        mDrawerListView = (EnhancedBookmarkDrawerListView) mMainView.findViewById(
+                R.id.eb_drawer_list);
+        mContentView = (EnhancedBookmarkContentView) mMainView.findViewById(R.id.eb_content_view);
+        mViewSwitcher = (ViewSwitcher) mMainView.findViewById(R.id.eb_view_switcher);
+        mUndoController = new EnhancedBookmarkUndoController(activity, mEnhancedBookmarksModel,
+                ((SnackbarManageable) activity).getSnackbarManager());
+        mSearchView = (EnhancedBookmarkSearchView) getView().findViewById(R.id.eb_search_view);
+        mEnhancedBookmarksModel.addModelObserver(mBookmarkModelObserver);
+        initializeIfBookmarkModelLoaded();
+
+        // Load partner bookmarks explicitly. We load partner bookmarks in the deferred startup
+        // code, but that might be executed much later. Especially on L, showing loading
+        // progress bar blocks that so it won't be loaded. http://crbug.com/429383
+        PartnerBookmarksShim.kickOffReading(activity);
+    }
+
+    /**
+     * Destroys and cleans up itself. This must be called after done using this class.
+     */
+    public void destroy() {
+        for (EnhancedBookmarkUIObserver observer : mUIObservers) {
+            observer.onDestroy();
+        }
+        assert mUIObservers.size() == 0;
+
+        if (mUndoController != null) {
+            mUndoController.destroy();
+            mUndoController = null;
+        }
+        mEnhancedBookmarksModel.removeModelObserver(mBookmarkModelObserver);
+        mEnhancedBookmarksModel.removeFiltersObserver(mFiltersObserver);
+        mEnhancedBookmarksModel.destroy();
+        mEnhancedBookmarksModel = null;
+    }
+
+    /**
+     * Called when the user presses the back key. This is only going to be called on Phone.
+     * @return True if manager handles this event, false if it decides to ignore.
+     */
+    public boolean onBackPressed() {
+        if (doesDrawerExist()) {
+            if (mDrawer.isDrawerVisible(Gravity.START)) {
+                mDrawer.closeDrawer(Gravity.START);
+                return true;
+            }
+        }
+
+        if (mContentView.onBackPressed()) return true;
+
+        if (!mStateStack.empty()) {
+            mStateStack.pop();
+            if (!mStateStack.empty()) {
+                setState(mStateStack.pop());
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public View getView() {
+        return mMainView;
+    }
+
+    /**
+     * Sets the listener that reacts upon the change of the UI state of bookmark manager.
+     */
+    public void setUrlChangeListener(EnhancedBookmarkStateChangeListener urlListner) {
+        mUrlChangeListener = urlListner;
+    }
+
+    /**
+     * @return Current URL representing the UI state of bookmark manager. If no state has been shown
+     *         yet in this session, on phone return last used state stored in preference; on tablet
+     *         return the url previously set by {@link #updateForUrl(String)}.
+     */
+    public String getCurrentUrl() {
+        if (mStateStack.isEmpty()) return null;
+        return mStateStack.peek().mUrl;
+    }
+
+    /**
+     * Updates UI based on the new URL on tablet. If the bookmark model is not loaded yet, creates a
+     * temporary loading state carrying this url. This method is supposed to align with
+     * {@link EnhancedBookmarkPage#updateForUrl(String)}
+     * <p>
+     * @param url The url to navigate to.
+     */
+    public void updateForUrl(String url) {
+        if (mEnhancedBookmarksModel != null && mEnhancedBookmarksModel.isBookmarkModelLoaded()) {
+            setState(UIState.createStateFromUrl(url, mEnhancedBookmarksModel));
+        } else {
+            // Note this does not guarantee to update the UI, as at this time the onCreateView()
+            // might not has even been called yet.
+            setState(UIState.createLoadingState(url));
+        }
+    }
+
+    /**
+     * Initialization method that has 3 different behaviors based on whether bookmark model is
+     * loaded. If the bookmark model is not loaded yet, it pushes a loading state to backstack which
+     * contains the url from preference. If the model is loaded and the backstack is empty, it
+     * creates a state by fetching the last visited bookmark url stored in preference. If the
+     * bookmark model is loaded but backstack contains a pending loading state, it creates a new
+     * state by getting the url of the loading state and replace the previous loading state with the
+     * new normal state.
+     */
+    private void initializeIfBookmarkModelLoaded() {
+        if (mEnhancedBookmarksModel.isBookmarkModelLoaded()) {
+            mEnhancedBookmarksModel.addFiltersObserver(mFiltersObserver);
+            mSearchView.onEnhancedBookmarkDelegateInitialized(this);
+            mDrawerListView.onEnhancedBookmarkDelegateInitialized(this);
+            mContentView.onEnhancedBookmarkDelegateInitialized(this);
+            if (mStateStack.isEmpty()) {
+                setState(UIState.createStateFromUrl(getUrlFromPreference(),
+                        mEnhancedBookmarksModel));
+            } else if (mStateStack.peek().mState == STATE_LOADING) {
+                String url = mStateStack.pop().mUrl;
+                setState(UIState.createStateFromUrl(url, mEnhancedBookmarksModel));
+            }
+            // Restore the previous view mode selection saved in preference.
+            initListModeOptionTo(getListModePreference());
+        } else {
+            mContentView.showLoadingUi();
+            mDrawerListView.showLoadingUi();
+            mContentView.showLoadingUi();
+            if (mStateStack.isEmpty() || mStateStack.peek().mState != STATE_LOADING) {
+                setState(UIState.createLoadingState(getUrlFromPreference()));
+            } else if (!mStateStack.isEmpty()) {
+                // Refresh the UI. This is needed because on tablet, updateForUrl might set up
+                // loading state too early and at that time all UI components are not created yet.
+                // Therefore we need to set the previous loading state once again to trigger all UI
+                // updates.
+                setState(mStateStack.pop());
+            }
+        }
+    }
+
+    /**
+     * Saves url to preference. Note this method should be used after the main view is attached to
+     * an activity.
+     */
+    private void saveUrlToPreference(String url) {
+        PreferenceManager.getDefaultSharedPreferences(mActivity).edit()
+                .putString(PREF_LAST_USED_URL, url).apply();
+    }
+
+    /**
+     * Fetches url to preference. Note this method should be used after the main view is attached to
+     * an activity.
+     */
+    private String getUrlFromPreference() {
+        return PreferenceManager.getDefaultSharedPreferences(mActivity).getString(
+                PREF_LAST_USED_URL, UrlConstants.BOOKMARKS_URL);
+    }
+
+    private void saveListModePreference() {
+        PreferenceManager.getDefaultSharedPreferences(mActivity).edit()
+                .putInt(PREF_WAS_IN_LIST_MODE, mListModeEnabled ? LIST_MODE : GRID_MODE).apply();
+    }
+
+    private boolean getListModePreference() {
+        int mode = PreferenceManager.getDefaultSharedPreferences(mActivity).getInt(
+                PREF_WAS_IN_LIST_MODE, DEFAULT_MODE);
+        return mode == LIST_MODE ? true : false;
+    }
+
+    private void initListModeOptionTo(boolean isListModeEnabled) {
+        mListModeEnabled = isListModeEnabled;
+        for (EnhancedBookmarkUIObserver observer: mUIObservers) {
+            observer.onListModeChange(isListModeEnabled);
+        }
+        // Every time the enhanced bookmark manager launches or the user clicks the list-mode
+        // toggle, we record the list view state.
+        int listViewstate = PreferenceManager.getDefaultSharedPreferences(getView().getContext())
+                .getInt(EnhancedBookmarkManager.PREF_WAS_IN_LIST_MODE,
+                        EnhancedBookmarkManager.DEFAULT_MODE);
+        RecordHistogram.recordEnumeratedHistogram("EnhancedBookmarks.ViewMode", listViewstate, 3);
+    }
+
+    /**
+     * This is the ultimate internal method that updates UI and controls backstack. And it is the
+     * only method that pushes states to {@link #mStateStack}.
+     * <p>
+     * If the given state is not valid, all_bookmark state will be shown. Afterwards, this method
+     * checks the current state: if currently in loading state, it pops it out and adds the new
+     * state to the back stack. It also notifies the {@link #mUrlChangeListener} (if any) that the
+     * url has changed.
+     * <p>
+     * Also note that even if we store states to {@link #mStateStack}, on tablet the back navigation
+     * and back button are not controlled by the manager: the tab handles back key and backstack
+     * navigation.
+     */
+    private void setState(UIState state) {
+        if (!state.isValid(mEnhancedBookmarksModel)) {
+            state = UIState.createAllBookmarksState(mEnhancedBookmarksModel);
+        }
+        if (!mStateStack.isEmpty()) {
+            if (mStateStack.peek().equals(state)) return;
+            if (mStateStack.peek().mState == STATE_LOADING) {
+                mStateStack.pop();
+            }
+        }
+        mStateStack.push(state);
+        if (state.mState != STATE_LOADING) {
+            // Loading state may be pushed to the stack but should never be stored in preferences.
+            saveUrlToPreference(state.mUrl);
+            // If a loading state is replaced by another loading state, do not notify this change.
+            if (mUrlChangeListener != null) mUrlChangeListener.onBookmarkUIStateChange(state.mUrl);
+        }
+
+        clearSelection();
+
+        for (EnhancedBookmarkUIObserver observer : mUIObservers) {
+            notifyStateChange(observer);
+        }
+    }
+
+    // EnhancedBookmarkDelegate implementations.
+
+    @Override
+    public void openFolder(BookmarkId folder) {
+        closeSearchUI();
+        setState(UIState.createFolderState(folder, mEnhancedBookmarksModel));
+    }
+
+    @Override
+    public void openFilter(String filter) {
+        closeSearchUI();
+        setState(UIState.createFilterState(filter, mEnhancedBookmarksModel));
+    }
+
+    @Override
+    public void openAllBookmarks() {
+        closeSearchUI();
+        setState(UIState.createAllBookmarksState(mEnhancedBookmarksModel));
+    }
+
+    @Override
+    public void clearSelection() {
+        mSelectedBookmarks.clear();
+        for (EnhancedBookmarkUIObserver observer : mUIObservers) {
+            observer.onSelectionStateChange(new ArrayList<BookmarkId>(mSelectedBookmarks));
+        }
+    }
+
+    @Override
+    public boolean toggleSelectionForBookmark(BookmarkId bookmark) {
+        if (!mEnhancedBookmarksModel.getBookmarkById(bookmark).isEditable()) return false;
+
+        if (mSelectedBookmarks.contains(bookmark)) mSelectedBookmarks.remove(bookmark);
+        else mSelectedBookmarks.add(bookmark);
+        for (EnhancedBookmarkUIObserver observer : mUIObservers) {
+            observer.onSelectionStateChange(new ArrayList<BookmarkId>(mSelectedBookmarks));
+        }
+
+        return isBookmarkSelected(bookmark);
+    }
+
+    @Override
+    public boolean isBookmarkSelected(BookmarkId bookmark) {
+        return mSelectedBookmarks.contains(bookmark);
+    }
+
+    @Override
+    public boolean isSelectionEnabled() {
+        return !mSelectedBookmarks.isEmpty();
+    }
+
+    @Override
+    public List<BookmarkId> getSelectedBookmarks() {
+        return new ArrayList<BookmarkId>(mSelectedBookmarks);
+    }
+
+    @Override
+    public void setListModeEnabled(boolean isListModeEnabled) {
+        initListModeOptionTo(isListModeEnabled);
+        saveListModePreference();
+    }
+
+    @Override
+    public boolean isListModeEnabled() {
+        return mListModeEnabled;
+    }
+
+    @Override
+    public void notifyStateChange(EnhancedBookmarkUIObserver observer) {
+        int state = getCurrentState();
+        switch (state) {
+            case STATE_ALL_BOOKMARKS:
+                observer.onAllBookmarksStateSet();
+                break;
+            case STATE_FOLDER:
+                observer.onFolderStateSet(mStateStack.peek().mFolder);
+                break;
+            case STATE_FILTER:
+                observer.onFilterStateSet(mStateStack.peek().mFilter);
+                break;
+            case STATE_LOADING:
+                // In loading state, onEnhancedBookmarkDelegateInitialized() is not called for all
+                // UIObservers, which means that there will be no observers at the time. Do nothing.
+                assert mUIObservers.isEmpty();
+                break;
+            default:
+                assert false : "State not valid";
+                break;
+        }
+    }
+
+    @Override
+    public boolean doesDrawerExist() {
+        return mDrawer != null;
+    }
+
+    @Override
+    public void closeDrawer() {
+        if (!doesDrawerExist()) return;
+
+        mDrawer.closeDrawer(Gravity.START);
+    }
+
+    @Override
+    public DrawerLayout getDrawerLayout() {
+        return mDrawer;
+    }
+
+    @Override
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    public void startDetailActivity(BookmarkId bookmarkId, View view) {
+        Intent intent = new Intent(mActivity, EnhancedBookmarkDetailActivity.class);
+        intent.putExtra(EnhancedBookmarkDetailActivity.INTENT_BOOKMARK_ID, bookmarkId.toString());
+        // Shared element animation is disabled on tablet because of bad quality.
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP || view == null
+                || DeviceFormFactor.isTablet(mActivity)) {
+            mActivity.startActivity(intent);
+        } else {
+            ActivityOptions options = ActivityOptions.makeSceneTransitionAnimation(mActivity, view,
+                    mActivity.getString(R.string.enhanced_bookmark_detail_transition_name));
+            mActivity.startActivity(intent, options.toBundle());
+        }
+    }
+
+    @Override
+    public void openBookmark(BookmarkId bookmark, int launchLocation) {
+        clearSelection();
+        NewTabPageUma.recordAction(NewTabPageUma.ACTION_OPENED_BOOKMARK);
+        RecordHistogram.recordEnumeratedHistogram("Stars.LaunchLocation", launchLocation,
+                LaunchLocation.COUNT);
+        EnhancedBookmarkUtils.openBookmark(mActivity,
+                mEnhancedBookmarksModel.getBookmarkById(bookmark).getUrl());
+        finishActivityOnPhone();
+    }
+
+    @Override
+    public void openSearchUI() {
+        // Give search view focus, because it needs to handle back key event.
+        mViewSwitcher.showNext();
+    }
+
+    @Override
+    public void closeSearchUI() {
+        if (mSearchView.getVisibility() != View.VISIBLE) return;
+        mViewSwitcher.showPrevious();
+    }
+
+    @Override
+    public void finishActivityOnPhone() {
+        Activity activity = mActivity;
+        if (activity instanceof EnhancedBookmarkActivity) {
+            activity.finish();
+        }
+    }
+
+    @Override
+    public void addUIObserver(EnhancedBookmarkUIObserver observer) {
+        mUIObservers.addObserver(observer);
+    }
+
+    @Override
+    public void removeUIObserver(EnhancedBookmarkUIObserver observer) {
+        mUIObservers.removeObserver(observer);
+    }
+
+    @Override
+    public EnhancedBookmarksModel getModel() {
+        return mEnhancedBookmarksModel;
+    }
+
+    @Override
+    public int getCurrentState() {
+        if (mStateStack.isEmpty()) return STATE_LOADING;
+        return mStateStack.peek().mState;
+    }
+
+    /**
+     * Internal state that represents a url. Note every state needs to have a _valid_ url. For
+     * loading state, {@link #mUrl} indicates the target to open after the bookmark model is loaded.
+     */
+    private static class UIState {
+        private static final String TAG = "UIState";
+        private static final String URL_CHARSET = "UTF-8";
+        /**
+         * One of the four states:
+         * {@link EnhancedBookmarkDelegate#STATE_ALL_BOOKMARKS},
+         * {@link EnhancedBookmarkDelegate#STATE_FILTER},
+         * {@link EnhancedBookmarkDelegate#STATE_FOLDER},
+         * {@link EnhancedBookmarkDelegate#STATE_LOADING},
+         */
+        int mState;
+        String mUrl;
+        BookmarkId mFolder;
+        String mFilter;
+
+        static UIState createLoadingState(String url) {
+            UIState state = new UIState();
+            state.mUrl = url;
+            state.mState = STATE_LOADING;
+            return state;
+        }
+
+        static UIState createAllBookmarksState(EnhancedBookmarksModel bookmarkModel) {
+            return createStateFromUrl(UrlConstants.BOOKMARKS_URL, bookmarkModel);
+        }
+
+        static UIState createFolderState(BookmarkId folder, EnhancedBookmarksModel bookmarkModel) {
+            return createStateFromUrl(UrlConstants.BOOKMARKS_FOLDER_URL + folder.toString(),
+                    bookmarkModel);
+        }
+
+        static UIState createFilterState(String filter, EnhancedBookmarksModel bookmarkModel) {
+            return createStateFromUrl(encodeUrl(UrlConstants.BOOKMARKS_FILTER_URL, filter),
+                    bookmarkModel);
+        }
+
+        /**
+         * @return A state corresponding to the url. If the url is not valid, return all_bookmarks.
+         */
+        static UIState createStateFromUrl(String url, EnhancedBookmarksModel bookmarkModel) {
+            UIState state = new UIState();
+            state.mUrl = url;
+            if (url.equals(UrlConstants.BOOKMARKS_URL)) {
+                state.mState = STATE_ALL_BOOKMARKS;
+            } else if (url.startsWith(UrlConstants.BOOKMARKS_FILTER_URL)) {
+                String suffix = decodeSuffix(url, UrlConstants.BOOKMARKS_FILTER_URL);
+                if (!suffix.isEmpty()) {
+                    state.mState = STATE_FILTER;
+                    state.mFilter = suffix;
+                }
+            } else if (url.startsWith(UrlConstants.BOOKMARKS_FOLDER_URL)) {
+                String suffix = decodeSuffix(url, UrlConstants.BOOKMARKS_FOLDER_URL);
+                if (!suffix.isEmpty()) {
+                    state.mFolder = BookmarkId.getBookmarkIdFromString(suffix);
+                    state.mState = STATE_FOLDER;
+                }
+            }
+
+            if (!state.isValid(bookmarkModel)) {
+                state.mState = STATE_ALL_BOOKMARKS;
+                state.mUrl = UrlConstants.BOOKMARKS_URL;
+            }
+
+            return state;
+        }
+
+        /**
+         * @return Whether this state is valid.
+         */
+        boolean isValid(EnhancedBookmarksModel bookmarkModel) {
+            if (mUrl == null) return false;
+            if (mState == STATE_FOLDER) {
+                if (mFolder == null) return false;
+
+                return bookmarkModel.doesBookmarkExist(mFolder)
+                        && !mFolder.equals(bookmarkModel.getRootFolderId());
+            }
+            if (mState == STATE_FILTER) {
+                if (mFilter == null) return false;
+                else return bookmarkModel.getFilters().contains(mFilter);
+            }
+
+            return true;
+        }
+
+        static String decodeSuffix(String url, String prefix) {
+            String suffix = url.substring(prefix.length());
+            try {
+                suffix = URLDecoder.decode(suffix, URL_CHARSET);
+            } catch (UnsupportedEncodingException e) {
+                Log.w(TAG, "Bookmark URL parsing failed. " + URL_CHARSET + " not supported.");
+            }
+            return suffix;
+        }
+
+        static String encodeUrl(String prefix, String suffix) {
+            try {
+                suffix = URLEncoder.encode(suffix, URL_CHARSET);
+            } catch (UnsupportedEncodingException e) {
+                Log.w(TAG, "Bookmark URL parsing failed. " + URL_CHARSET + " not supported.");
+            }
+            return prefix + suffix;
+        }
+
+        @Override
+        public int hashCode() {
+            return 31 * mUrl.hashCode() + mState;
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (!(obj instanceof UIState)) return false;
+            UIState other = (UIState) obj;
+            return mState == other.mState && mUrl.equals(other.mUrl);
+        }
+    }
+}