Baseline for the new ConversationLayout

Introduced a new Layout for Conversation Notifications.
There are still various open issues that will be
fixed in follow up Cls

Bug: 150905003
Test: Add conversations, obverve visuals
Change-Id: I8ab2e2988d3205a4491006df68ec14235109466f
diff --git a/core/java/com/android/internal/widget/ConversationLayout.java b/core/java/com/android/internal/widget/ConversationLayout.java
new file mode 100644
index 0000000..128f544
--- /dev/null
+++ b/core/java/com/android/internal/widget/ConversationLayout.java
@@ -0,0 +1,728 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.internal.widget;
+
+import android.annotation.AttrRes;
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.annotation.StyleRes;
+import android.app.Notification;
+import android.app.Person;
+import android.app.RemoteInputHistoryItem;
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.graphics.Rect;
+import android.graphics.drawable.Icon;
+import android.os.Bundle;
+import android.os.Parcelable;
+import android.text.TextUtils;
+import android.util.ArrayMap;
+import android.util.AttributeSet;
+import android.util.DisplayMetrics;
+import android.view.Gravity;
+import android.view.RemotableViewMethod;
+import android.view.View;
+import android.view.ViewGroup;
+import android.view.ViewTreeObserver;
+import android.view.animation.Interpolator;
+import android.view.animation.PathInterpolator;
+import android.widget.FrameLayout;
+import android.widget.ImageView;
+import android.widget.RemoteViews;
+import android.widget.TextView;
+
+import com.android.internal.R;
+import com.android.internal.graphics.ColorUtils;
+import com.android.internal.util.ContrastColorUtil;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.regex.Pattern;
+
+/**
+ * A custom-built layout for the Notification.MessagingStyle allows dynamic addition and removal
+ * messages and adapts the layout accordingly.
+ */
+@RemoteViews.RemoteView
+public class ConversationLayout extends FrameLayout
+        implements ImageMessageConsumer, IMessagingLayout {
+
+    public static final boolean CONVERSATION_LAYOUT_ENABLED = true;
+    private static final float COLOR_SHIFT_AMOUNT = 60;
+    /**
+     *  Pattren for filter some ingonable characters.
+     *  p{Z} for any kind of whitespace or invisible separator.
+     *  p{C} for any kind of punctuation character.
+     */
+    private static final Pattern IGNORABLE_CHAR_PATTERN
+            = Pattern.compile("[\\p{C}\\p{Z}]");
+    private static final Pattern SPECIAL_CHAR_PATTERN
+            = Pattern.compile ("[!@#$%&*()_+=|<>?{}\\[\\]~-]");
+    private static final Consumer<MessagingMessage> REMOVE_MESSAGE
+            = MessagingMessage::removeMessage;
+    public static final Interpolator LINEAR_OUT_SLOW_IN = new PathInterpolator(0f, 0f, 0.2f, 1f);
+    public static final Interpolator FAST_OUT_LINEAR_IN = new PathInterpolator(0.4f, 0f, 1f, 1f);
+    public static final Interpolator FAST_OUT_SLOW_IN = new PathInterpolator(0.4f, 0f, 0.2f, 1f);
+    public static final OnLayoutChangeListener MESSAGING_PROPERTY_ANIMATOR
+            = new MessagingPropertyAnimator();
+    private List<MessagingMessage> mMessages = new ArrayList<>();
+    private List<MessagingMessage> mHistoricMessages = new ArrayList<>();
+    private MessagingLinearLayout mMessagingLinearLayout;
+    private boolean mShowHistoricMessages;
+    private ArrayList<MessagingGroup> mGroups = new ArrayList<>();
+    private TextView mTitleView;
+    private int mLayoutColor;
+    private int mSenderTextColor;
+    private int mMessageTextColor;
+    private int mAvatarSize;
+    private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
+    private Paint mTextPaint = new Paint();
+    private Icon mAvatarReplacement;
+    private boolean mIsOneToOne;
+    private ArrayList<MessagingGroup> mAddedGroups = new ArrayList<>();
+    private Person mUser;
+    private CharSequence mNameReplacement;
+    private boolean mIsCollapsed;
+    private ImageResolver mImageResolver;
+    private ImageView mConversationIcon;
+    private TextView mHeaderText;
+    private View mConversationIconBadge;
+    private Icon mLargeIcon;
+    private View mExpandButtonContainer;
+    private NotificationExpandButton mExpandButton;
+    private int mExpandButtonExpandedTopMargin;
+    private int mBadgedSideMargins;
+    private int mIconSizeBadged;
+    private int mIconSizeCentered;
+    private View mIcon;
+    private int mExpandedGroupTopMargin;
+
+    public ConversationLayout(@NonNull Context context) {
+        super(context);
+    }
+
+    public ConversationLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public ConversationLayout(@NonNull Context context, @Nullable AttributeSet attrs,
+            @AttrRes int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+    }
+
+    public ConversationLayout(@NonNull Context context, @Nullable AttributeSet attrs,
+            @AttrRes int defStyleAttr, @StyleRes int defStyleRes) {
+        super(context, attrs, defStyleAttr, defStyleRes);
+    }
+
+    @Override
+    protected void onFinishInflate() {
+        super.onFinishInflate();
+        mMessagingLinearLayout = findViewById(R.id.notification_messaging);
+        mMessagingLinearLayout.setMessagingLayout(this);
+        // We still want to clip, but only on the top, since views can temporarily out of bounds
+        // during transitions.
+        DisplayMetrics displayMetrics = getResources().getDisplayMetrics();
+        int size = Math.max(displayMetrics.widthPixels, displayMetrics.heightPixels);
+        Rect rect = new Rect(0, 0, size, size);
+        mMessagingLinearLayout.setClipBounds(rect);
+        mTitleView = findViewById(R.id.title);
+        mAvatarSize = getResources().getDimensionPixelSize(R.dimen.messaging_avatar_size);
+        mTextPaint.setTextAlign(Paint.Align.CENTER);
+        mTextPaint.setAntiAlias(true);
+        mConversationIcon = findViewById(R.id.conversation_icon);
+        mIcon = findViewById(R.id.icon);
+        mConversationIconBadge = findViewById(R.id.conversation_icon_badge);
+        mHeaderText = findViewById(R.id.header_text);
+        mExpandButtonContainer = findViewById(R.id.expand_button_container);
+        mExpandButton = findViewById(R.id.expand_button);
+        mExpandButtonExpandedTopMargin = getResources().getDimensionPixelSize(
+                R.dimen.conversation_expand_button_top_margin_expanded);
+        mBadgedSideMargins = getResources().getDimensionPixelSize(
+                R.dimen.conversation_badge_side_margin);
+        mIconSizeBadged = getResources().getDimensionPixelSize(
+                R.dimen.conversation_icon_size_badged);
+        mIconSizeCentered = getResources().getDimensionPixelSize(
+                R.dimen.conversation_icon_size_centered);
+        mExpandedGroupTopMargin = getResources().getDimensionPixelSize(
+                R.dimen.conversation_icon_margin_top_centered);
+    }
+
+    @RemotableViewMethod
+    public void setAvatarReplacement(Icon icon) {
+        mAvatarReplacement = icon;
+    }
+
+    @RemotableViewMethod
+    public void setNameReplacement(CharSequence nameReplacement) {
+        mNameReplacement = nameReplacement;
+    }
+
+    /**
+     * Set this layout to show the collapsed representation.
+     *
+     * @param isCollapsed is it collapsed
+     */
+    @RemotableViewMethod
+    public void setIsCollapsed(boolean isCollapsed) {
+        mIsCollapsed = isCollapsed;
+        mMessagingLinearLayout.setMaxDisplayedLines(isCollapsed ? 1 : Integer.MAX_VALUE);
+        updateExpandButton();
+    }
+
+    @RemotableViewMethod
+    public void setData(Bundle extras) {
+        Parcelable[] messages = extras.getParcelableArray(Notification.EXTRA_MESSAGES);
+        List<Notification.MessagingStyle.Message> newMessages
+                = Notification.MessagingStyle.Message.getMessagesFromBundleArray(messages);
+        Parcelable[] histMessages = extras.getParcelableArray(Notification.EXTRA_HISTORIC_MESSAGES);
+        List<Notification.MessagingStyle.Message> newHistoricMessages
+                = Notification.MessagingStyle.Message.getMessagesFromBundleArray(histMessages);
+
+        // mUser now set (would be nice to avoid the side effect but WHATEVER)
+        setUser(extras.getParcelable(Notification.EXTRA_MESSAGING_PERSON));
+
+
+        // Append remote input history to newMessages (again, side effect is lame but WHATEVS)
+        RemoteInputHistoryItem[] history = (RemoteInputHistoryItem[])
+                extras.getParcelableArray(Notification.EXTRA_REMOTE_INPUT_HISTORY_ITEMS);
+        addRemoteInputHistoryToMessages(newMessages, history);
+
+        boolean showSpinner =
+                extras.getBoolean(Notification.EXTRA_SHOW_REMOTE_INPUT_SPINNER, false);
+
+        // bind it, baby
+        bind(newMessages, newHistoricMessages, showSpinner);
+    }
+
+    @Override
+    public void setImageResolver(ImageResolver resolver) {
+        mImageResolver = resolver;
+    }
+
+    private void addRemoteInputHistoryToMessages(
+            List<Notification.MessagingStyle.Message> newMessages,
+            RemoteInputHistoryItem[] remoteInputHistory) {
+        if (remoteInputHistory == null || remoteInputHistory.length == 0) {
+            return;
+        }
+        for (int i = remoteInputHistory.length - 1; i >= 0; i--) {
+            RemoteInputHistoryItem historyMessage = remoteInputHistory[i];
+            Notification.MessagingStyle.Message message = new Notification.MessagingStyle.Message(
+                    historyMessage.getText(), 0, (Person) null, true /* remoteHistory */);
+            if (historyMessage.getUri() != null) {
+                message.setData(historyMessage.getMimeType(), historyMessage.getUri());
+            }
+            newMessages.add(message);
+        }
+    }
+
+    private void bind(List<Notification.MessagingStyle.Message> newMessages,
+            List<Notification.MessagingStyle.Message> newHistoricMessages,
+            boolean showSpinner) {
+        // convert MessagingStyle.Message to MessagingMessage, re-using ones from a previous binding
+        // if they exist
+        List<MessagingMessage> historicMessages = createMessages(newHistoricMessages,
+                true /* isHistoric */);
+        List<MessagingMessage> messages = createMessages(newMessages, false /* isHistoric */);
+
+        // Copy our groups, before they get clobbered
+        ArrayList<MessagingGroup> oldGroups = new ArrayList<>(mGroups);
+
+        // Add our new MessagingMessages to groups
+        List<List<MessagingMessage>> groups = new ArrayList<>();
+        List<Person> senders = new ArrayList<>();
+
+        // Lets first find the groups (populate `groups` and `senders`)
+        findGroups(historicMessages, messages, groups, senders);
+
+        // Let's now create the views and reorder them accordingly
+        //   side-effect: updates mGroups, mAddedGroups
+        createGroupViews(groups, senders, showSpinner);
+
+        // Let's first check which groups were removed altogether and remove them in one animation
+        removeGroups(oldGroups);
+
+        // Let's remove the remaining messages
+        mMessages.forEach(REMOVE_MESSAGE);
+        mHistoricMessages.forEach(REMOVE_MESSAGE);
+
+        mMessages = messages;
+        mHistoricMessages = historicMessages;
+
+        updateHistoricMessageVisibility();
+        updateTitleAndNamesDisplay();
+
+        updateConversationIconAndHeaderText();
+
+    }
+
+    private void updateConversationIconAndHeaderText() {
+        // TODO: resolve this from shortcuts
+        // Set avatar and name
+        if (mIsOneToOne) {
+            // Let's resolve the icon / text from the last sender
+            mConversationIcon.setVisibility(VISIBLE);
+            mHeaderText.setVisibility(VISIBLE);
+            boolean found = false;
+            for (int i = mGroups.size() - 1; i >= 0; i--) {
+                MessagingGroup messagingGroup = mGroups.get(i);
+                Person messageSender = messagingGroup.getSender();
+                if (!mUser.equals(messageSender)) {
+                    // Make sure the header is actually visible
+                    // TODO: figure out what to do if there's a converationtitle + a Sender
+                    mHeaderText.setText(messagingGroup.getSenderName());
+                    mConversationIcon.setImageIcon(messagingGroup.getAvatarIcon());
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                mHeaderText.setText(mUser.getName());
+                mConversationIcon.setImageIcon(mUser.getIcon());
+            }
+        } else {
+            mHeaderText.setVisibility(GONE);
+            if (mIsCollapsed) {
+                mConversationIcon.setVisibility(VISIBLE);
+                if (mLargeIcon != null) {
+                    mConversationIcon.setImageIcon(mLargeIcon);
+                } else {
+                    // TODO: generate LargeIcon from Conversation
+                }
+            } else {
+                mConversationIcon.setVisibility(GONE);
+            }
+        }
+        // update the icon position and sizing
+        int gravity;
+        int marginStart;
+        int marginTop;
+        int iconSize;
+        if (mIsOneToOne || mIsCollapsed) {
+            // Baded format
+            gravity = Gravity.LEFT;
+            marginStart = mBadgedSideMargins;
+            marginTop = mBadgedSideMargins;
+            iconSize = mIconSizeBadged;
+        } else {
+            gravity = Gravity.CENTER_HORIZONTAL;
+            marginStart = 0;
+            marginTop = mExpandedGroupTopMargin;
+            iconSize = mIconSizeCentered;
+        }
+        FrameLayout.LayoutParams layoutParams =
+                (LayoutParams) mConversationIconBadge.getLayoutParams();
+        layoutParams.gravity = gravity;
+        layoutParams.topMargin = marginTop;
+        layoutParams.setMarginStart(marginStart);
+        mConversationIconBadge.setLayoutParams(layoutParams);
+        ViewGroup.LayoutParams iconParams = mIcon.getLayoutParams();
+        iconParams.width = iconSize;
+        iconParams.height = iconSize;
+        mIcon.setLayoutParams(iconParams);
+    }
+
+    @RemotableViewMethod
+    public void setLargeIcon(Icon largeIcon) {
+        mLargeIcon = largeIcon;
+    }
+
+    private void removeGroups(ArrayList<MessagingGroup> oldGroups) {
+        int size = oldGroups.size();
+        for (int i = 0; i < size; i++) {
+            MessagingGroup group = oldGroups.get(i);
+            if (!mGroups.contains(group)) {
+                List<MessagingMessage> messages = group.getMessages();
+                Runnable endRunnable = () -> {
+                    mMessagingLinearLayout.removeTransientView(group);
+                    group.recycle();
+                };
+
+                boolean wasShown = group.isShown();
+                mMessagingLinearLayout.removeView(group);
+                if (wasShown && !MessagingLinearLayout.isGone(group)) {
+                    mMessagingLinearLayout.addTransientView(group, 0);
+                    group.removeGroupAnimated(endRunnable);
+                } else {
+                    endRunnable.run();
+                }
+                mMessages.removeAll(messages);
+                mHistoricMessages.removeAll(messages);
+            }
+        }
+    }
+
+    private void updateTitleAndNamesDisplay() {
+        ArrayMap<CharSequence, String> uniqueNames = new ArrayMap<>();
+        ArrayMap<Character, CharSequence> uniqueCharacters = new ArrayMap<>();
+        for (int i = 0; i < mGroups.size(); i++) {
+            MessagingGroup group = mGroups.get(i);
+            CharSequence senderName = group.getSenderName();
+            if (!group.needsGeneratedAvatar() || TextUtils.isEmpty(senderName)) {
+                continue;
+            }
+            if (!uniqueNames.containsKey(senderName)) {
+                // Only use visible characters to get uniqueNames
+                String pureSenderName = IGNORABLE_CHAR_PATTERN
+                        .matcher(senderName).replaceAll("" /* replacement */);
+                char c = pureSenderName.charAt(0);
+                if (uniqueCharacters.containsKey(c)) {
+                    // this character was already used, lets make it more unique. We first need to
+                    // resolve the existing character if it exists
+                    CharSequence existingName = uniqueCharacters.get(c);
+                    if (existingName != null) {
+                        uniqueNames.put(existingName, findNameSplit((String) existingName));
+                        uniqueCharacters.put(c, null);
+                    }
+                    uniqueNames.put(senderName, findNameSplit((String) senderName));
+                } else {
+                    uniqueNames.put(senderName, Character.toString(c));
+                    uniqueCharacters.put(c, pureSenderName);
+                }
+            }
+        }
+
+        // Now that we have the correct symbols, let's look what we have cached
+        ArrayMap<CharSequence, Icon> cachedAvatars = new ArrayMap<>();
+        for (int i = 0; i < mGroups.size(); i++) {
+            // Let's now set the avatars
+            MessagingGroup group = mGroups.get(i);
+            boolean isOwnMessage = group.getSender() == mUser;
+            CharSequence senderName = group.getSenderName();
+            if (!group.needsGeneratedAvatar() || TextUtils.isEmpty(senderName)
+                    || (mIsOneToOne && mAvatarReplacement != null && !isOwnMessage)) {
+                continue;
+            }
+            String symbol = uniqueNames.get(senderName);
+            Icon cachedIcon = group.getAvatarSymbolIfMatching(senderName,
+                    symbol, mLayoutColor);
+            if (cachedIcon != null) {
+                cachedAvatars.put(senderName, cachedIcon);
+            }
+        }
+
+        for (int i = 0; i < mGroups.size(); i++) {
+            // Let's now set the avatars
+            MessagingGroup group = mGroups.get(i);
+            CharSequence senderName = group.getSenderName();
+            if (!group.needsGeneratedAvatar() || TextUtils.isEmpty(senderName)) {
+                continue;
+            }
+            if (mIsOneToOne && mAvatarReplacement != null && group.getSender() != mUser) {
+                group.setAvatar(mAvatarReplacement);
+            } else {
+                Icon cachedIcon = cachedAvatars.get(senderName);
+                if (cachedIcon == null) {
+                    cachedIcon = createAvatarSymbol(senderName, uniqueNames.get(senderName),
+                            mLayoutColor);
+                    cachedAvatars.put(senderName, cachedIcon);
+                }
+                group.setCreatedAvatar(cachedIcon, senderName, uniqueNames.get(senderName),
+                        mLayoutColor);
+            }
+        }
+    }
+
+    private Icon createAvatarSymbol(CharSequence senderName, String symbol, int layoutColor) {
+        if (symbol.isEmpty() || TextUtils.isDigitsOnly(symbol) ||
+                SPECIAL_CHAR_PATTERN.matcher(symbol).find()) {
+            Icon avatarIcon = Icon.createWithResource(getContext(),
+                    R.drawable.messaging_user);
+            avatarIcon.setTint(findColor(senderName, layoutColor));
+            return avatarIcon;
+        } else {
+            Bitmap bitmap = Bitmap.createBitmap(mAvatarSize, mAvatarSize, Bitmap.Config.ARGB_8888);
+            Canvas canvas = new Canvas(bitmap);
+            float radius = mAvatarSize / 2.0f;
+            int color = findColor(senderName, layoutColor);
+            mPaint.setColor(color);
+            canvas.drawCircle(radius, radius, radius, mPaint);
+            boolean needDarkText = ColorUtils.calculateLuminance(color) > 0.5f;
+            mTextPaint.setColor(needDarkText ? Color.BLACK : Color.WHITE);
+            mTextPaint.setTextSize(symbol.length() == 1 ? mAvatarSize * 0.5f : mAvatarSize * 0.3f);
+            int yPos = (int) (radius - ((mTextPaint.descent() + mTextPaint.ascent()) / 2));
+            canvas.drawText(symbol, radius, yPos, mTextPaint);
+            return Icon.createWithBitmap(bitmap);
+        }
+    }
+
+    private int findColor(CharSequence senderName, int layoutColor) {
+        double luminance = ContrastColorUtil.calculateLuminance(layoutColor);
+        float shift = Math.abs(senderName.hashCode()) % 5 / 4.0f - 0.5f;
+
+        // we need to offset the range if the luminance is too close to the borders
+        shift += Math.max(COLOR_SHIFT_AMOUNT / 2.0f / 100 - luminance, 0);
+        shift -= Math.max(COLOR_SHIFT_AMOUNT / 2.0f / 100 - (1.0f - luminance), 0);
+        return ContrastColorUtil.getShiftedColor(layoutColor,
+                (int) (shift * COLOR_SHIFT_AMOUNT));
+    }
+
+    private String findNameSplit(String existingName) {
+        String[] split = existingName.split(" ");
+        if (split.length > 1) {
+            return Character.toString(split[0].charAt(0))
+                    + Character.toString(split[1].charAt(0));
+        }
+        return existingName.substring(0, 1);
+    }
+
+    @RemotableViewMethod
+    public void setLayoutColor(int color) {
+        mLayoutColor = color;
+    }
+
+    @RemotableViewMethod
+    public void setIsOneToOne(boolean oneToOne) {
+        mIsOneToOne = oneToOne;
+    }
+
+    @RemotableViewMethod
+    public void setSenderTextColor(int color) {
+        mSenderTextColor = color;
+    }
+
+    @RemotableViewMethod
+    public void setMessageTextColor(int color) {
+        mMessageTextColor = color;
+    }
+
+    private void setUser(Person user) {
+        mUser = user;
+        if (mUser.getIcon() == null) {
+            Icon userIcon = Icon.createWithResource(getContext(),
+                    R.drawable.messaging_user);
+            userIcon.setTint(mLayoutColor);
+            mUser = mUser.toBuilder().setIcon(userIcon).build();
+        }
+    }
+
+    private void createGroupViews(List<List<MessagingMessage>> groups,
+            List<Person> senders, boolean showSpinner) {
+        mGroups.clear();
+        for (int groupIndex = 0; groupIndex < groups.size(); groupIndex++) {
+            List<MessagingMessage> group = groups.get(groupIndex);
+            MessagingGroup newGroup = null;
+            // we'll just take the first group that exists or create one there is none
+            for (int messageIndex = group.size() - 1; messageIndex >= 0; messageIndex--) {
+                MessagingMessage message = group.get(messageIndex);
+                newGroup = message.getGroup();
+                if (newGroup != null) {
+                    break;
+                }
+            }
+            // Create a new group, adding it to the linear layout as well
+            if (newGroup == null) {
+                newGroup = MessagingGroup.createGroup(mMessagingLinearLayout);
+                mAddedGroups.add(newGroup);
+            }
+            newGroup.setDisplayImagesAtEnd(mIsCollapsed);
+            newGroup.setLayoutColor(mLayoutColor);
+            newGroup.setTextColors(mSenderTextColor, mMessageTextColor);
+            Person sender = senders.get(groupIndex);
+            CharSequence nameOverride = null;
+            if (sender != mUser && mNameReplacement != null) {
+                nameOverride = mNameReplacement;
+            }
+            newGroup.setShowingAvatar(!mIsOneToOne && !mIsCollapsed);
+            newGroup.setSingleLine(mIsCollapsed);
+            newGroup.setSender(sender, nameOverride);
+            newGroup.setSending(groupIndex == (groups.size() - 1) && showSpinner);
+            mGroups.add(newGroup);
+
+            // Reposition to the correct place (if we're re-using a group)
+            if (mMessagingLinearLayout.indexOfChild(newGroup) != groupIndex) {
+                mMessagingLinearLayout.removeView(newGroup);
+                mMessagingLinearLayout.addView(newGroup, groupIndex);
+            }
+            newGroup.setMessages(group);
+        }
+    }
+
+    private void findGroups(List<MessagingMessage> historicMessages,
+            List<MessagingMessage> messages, List<List<MessagingMessage>> groups,
+            List<Person> senders) {
+        CharSequence currentSenderKey = null;
+        List<MessagingMessage> currentGroup = null;
+        int histSize = historicMessages.size();
+        for (int i = 0; i < histSize + messages.size(); i++) {
+            MessagingMessage message;
+            if (i < histSize) {
+                message = historicMessages.get(i);
+            } else {
+                message = messages.get(i - histSize);
+            }
+            boolean isNewGroup = currentGroup == null;
+            Person sender = message.getMessage().getSenderPerson();
+            CharSequence key = sender == null ? null
+                    : sender.getKey() == null ? sender.getName() : sender.getKey();
+            isNewGroup |= !TextUtils.equals(key, currentSenderKey);
+            if (isNewGroup) {
+                currentGroup = new ArrayList<>();
+                groups.add(currentGroup);
+                if (sender == null) {
+                    sender = mUser;
+                }
+                senders.add(sender);
+                currentSenderKey = key;
+            }
+            currentGroup.add(message);
+        }
+    }
+
+    /**
+     * Creates new messages, reusing existing ones if they are available.
+     *
+     * @param newMessages the messages to parse.
+     */
+    private List<MessagingMessage> createMessages(
+            List<Notification.MessagingStyle.Message> newMessages, boolean historic) {
+        List<MessagingMessage> result = new ArrayList<>();
+        for (int i = 0; i < newMessages.size(); i++) {
+            Notification.MessagingStyle.Message m = newMessages.get(i);
+            MessagingMessage message = findAndRemoveMatchingMessage(m);
+            if (message == null) {
+                message = MessagingMessage.createMessage(this, m, mImageResolver);
+            }
+            message.setIsHistoric(historic);
+            result.add(message);
+        }
+        return result;
+    }
+
+    private MessagingMessage findAndRemoveMatchingMessage(Notification.MessagingStyle.Message m) {
+        for (int i = 0; i < mMessages.size(); i++) {
+            MessagingMessage existing = mMessages.get(i);
+            if (existing.sameAs(m)) {
+                mMessages.remove(i);
+                return existing;
+            }
+        }
+        for (int i = 0; i < mHistoricMessages.size(); i++) {
+            MessagingMessage existing = mHistoricMessages.get(i);
+            if (existing.sameAs(m)) {
+                mHistoricMessages.remove(i);
+                return existing;
+            }
+        }
+        return null;
+    }
+
+    public void showHistoricMessages(boolean show) {
+        mShowHistoricMessages = show;
+        updateHistoricMessageVisibility();
+    }
+
+    private void updateHistoricMessageVisibility() {
+        int numHistoric = mHistoricMessages.size();
+        for (int i = 0; i < numHistoric; i++) {
+            MessagingMessage existing = mHistoricMessages.get(i);
+            existing.setVisibility(mShowHistoricMessages ? VISIBLE : GONE);
+        }
+        int numGroups = mGroups.size();
+        for (int i = 0; i < numGroups; i++) {
+            MessagingGroup group = mGroups.get(i);
+            int visibleChildren = 0;
+            List<MessagingMessage> messages = group.getMessages();
+            int numGroupMessages = messages.size();
+            for (int j = 0; j < numGroupMessages; j++) {
+                MessagingMessage message = messages.get(j);
+                if (message.getVisibility() != GONE) {
+                    visibleChildren++;
+                }
+            }
+            if (visibleChildren > 0 && group.getVisibility() == GONE) {
+                group.setVisibility(VISIBLE);
+            } else if (visibleChildren == 0 && group.getVisibility() != GONE)   {
+                group.setVisibility(GONE);
+            }
+        }
+    }
+
+    @Override
+    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
+        super.onLayout(changed, left, top, right, bottom);
+        if (!mAddedGroups.isEmpty()) {
+            getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
+                @Override
+                public boolean onPreDraw() {
+                    for (MessagingGroup group : mAddedGroups) {
+                        if (!group.isShown()) {
+                            continue;
+                        }
+                        MessagingPropertyAnimator.fadeIn(group.getAvatar());
+                        MessagingPropertyAnimator.fadeIn(group.getSenderView());
+                        MessagingPropertyAnimator.startLocalTranslationFrom(group,
+                                group.getHeight(), LINEAR_OUT_SLOW_IN);
+                    }
+                    mAddedGroups.clear();
+                    getViewTreeObserver().removeOnPreDrawListener(this);
+                    return true;
+                }
+            });
+        }
+    }
+
+    public MessagingLinearLayout getMessagingLinearLayout() {
+        return mMessagingLinearLayout;
+    }
+
+    public ArrayList<MessagingGroup> getMessagingGroups() {
+        return mGroups;
+    }
+
+    private void updateExpandButton() {
+        int drawableId;
+        int contentDescriptionId;
+        int gravity;
+        int topMargin = 0;
+        if (mIsCollapsed) {
+            drawableId = R.drawable.ic_expand_notification;
+            contentDescriptionId = R.string.expand_button_content_description_collapsed;
+            gravity = Gravity.CENTER;
+        } else {
+            drawableId = R.drawable.ic_collapse_notification;
+            contentDescriptionId = R.string.expand_button_content_description_expanded;
+            gravity = Gravity.CENTER_HORIZONTAL | Gravity.TOP;
+            topMargin = mExpandButtonExpandedTopMargin;
+        }
+        mExpandButton.setImageDrawable(getContext().getDrawable(drawableId));
+        mExpandButton.setColorFilter(mExpandButton.getOriginalNotificationColor());
+
+        // update if the expand button is centered
+        FrameLayout.LayoutParams layoutParams = (LayoutParams) mExpandButton.getLayoutParams();
+        layoutParams.gravity = gravity;
+        layoutParams.topMargin = topMargin;
+        mExpandButton.setLayoutParams(layoutParams);
+
+        mExpandButtonContainer.setContentDescription(mContext.getText(contentDescriptionId));
+    }
+
+    public void updateExpandability(boolean expandable, @Nullable OnClickListener onClickListener) {
+        if (expandable) {
+            mExpandButtonContainer.setVisibility(VISIBLE);
+            mExpandButtonContainer.setOnClickListener(onClickListener);
+        } else {
+            // TODO: handle content paddings to end of layout
+            mExpandButtonContainer.setVisibility(GONE);
+        }
+    }
+}