/*
 * Copyright (C) 2016 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.systemui.qs;

import static com.android.systemui.qs.dagger.QSFragmentModule.QQS_FOOTER;
import static com.android.systemui.qs.dagger.QSFragmentModule.QS_FOOTER;

import android.animation.TimeInterpolator;
import android.animation.ValueAnimator;
import android.util.Log;
import android.view.View;
import android.view.View.OnAttachStateChangeListener;
import android.view.View.OnLayoutChangeListener;

import com.android.systemui.dagger.qualifiers.Main;
import com.android.systemui.plugins.qs.QS;
import com.android.systemui.plugins.qs.QSTile;
import com.android.systemui.plugins.qs.QSTileView;
import com.android.systemui.qs.PagedTileLayout.PageListener;
import com.android.systemui.qs.QSHost.Callback;
import com.android.systemui.qs.QSPanel.QSTileLayout;
import com.android.systemui.qs.TouchAnimator.Builder;
import com.android.systemui.qs.TouchAnimator.Listener;
import com.android.systemui.qs.dagger.QSScope;
import com.android.systemui.qs.tileimpl.HeightOverrideable;
import com.android.systemui.tuner.TunerService;
import com.android.systemui.tuner.TunerService.Tunable;
import com.android.wm.shell.animation.Interpolators;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.Executor;

import javax.inject.Inject;
import javax.inject.Named;

/** */
@QSScope
public class QSAnimator implements Callback, PageListener, Listener, OnLayoutChangeListener,
        OnAttachStateChangeListener, Tunable {

    private static final String TAG = "QSAnimator";

    private static final String ALLOW_FANCY_ANIMATION = "sysui_qs_fancy_anim";
    private static final String MOVE_FULL_ROWS = "sysui_qs_move_whole_rows";

    public static final float EXPANDED_TILE_DELAY = .86f;
    public static final float SHORT_PARALLAX_AMOUNT = 0.1f;
    private static final long QQS_FADE_IN_DURATION = 200L;
    // Fade out faster than fade in to finish before QQS hides.
    private static final long QQS_FADE_OUT_DURATION = 50L;

    /**
     * List of all views that will be reset when clearing animation state
     * see {@link #clearAnimationState()} }
     */
    private final ArrayList<View> mAllViews = new ArrayList<>();
    /**
     * List of {@link View}s representing Quick Settings that are being animated from the quick QS
     * position to the normal QS panel. These views will only show once the animation is complete,
     * to prevent overlapping of semi transparent views
     */
    private final ArrayList<View> mAnimatedQsViews = new ArrayList<>();
    private final QuickQSPanel mQuickQsPanel;
    private final QSPanelController mQsPanelController;
    private final QuickQSPanelController mQuickQSPanelController;
    private final QuickStatusBarHeader mQuickStatusBarHeader;
    private final QSSecurityFooter mSecurityFooter;
    private final QS mQs;
    private final View mQSFooterActions;
    private final View mQQSFooterActions;

    private PagedTileLayout mPagedLayout;

    private boolean mOnFirstPage = true;
    private QSExpansionPathInterpolator mQSExpansionPathInterpolator;
    private TouchAnimator mFirstPageAnimator;
    private TouchAnimator mFirstPageDelayedAnimator;
    private TouchAnimator mTranslationXAnimator;
    private TouchAnimator mTranslationYAnimator;
    private TouchAnimator mNonfirstPageAnimator;
    private TouchAnimator mNonfirstPageDelayedAnimator;
    // This animates fading of SecurityFooter and media divider
    private TouchAnimator mAllPagesDelayedAnimator;
    private TouchAnimator mBrightnessAnimator;
    private TouchAnimator mQQSFooterActionsAnimator;
    private HeightExpansionAnimator mQQSTileHeightAnimator;
    private HeightExpansionAnimator mOtherTilesExpandAnimator;

    private boolean mNeedsAnimatorUpdate = false;
    private boolean mToShowing;
    private boolean mOnKeyguard;

    private boolean mAllowFancy;
    private boolean mFullRows;
    private int mNumQuickTiles;
    private float mLastPosition;
    private final QSTileHost mHost;
    private final Executor mExecutor;
    private final TunerService mTunerService;
    private boolean mShowCollapsedOnKeyguard;
    private boolean mTranslateWhileExpanding;

    @Inject
    public QSAnimator(QS qs, QuickQSPanel quickPanel, QuickStatusBarHeader quickStatusBarHeader,
            QSPanelController qsPanelController,
            QuickQSPanelController quickQSPanelController, QSTileHost qsTileHost,
            QSSecurityFooter securityFooter, @Main Executor executor, TunerService tunerService,
            QSExpansionPathInterpolator qsExpansionPathInterpolator,
            @Named(QS_FOOTER) FooterActionsView qsFooterActionsView,
            @Named(QQS_FOOTER) FooterActionsView qqsFooterActionsView) {
        mQs = qs;
        mQuickQsPanel = quickPanel;
        mQsPanelController = qsPanelController;
        mQuickQSPanelController = quickQSPanelController;
        mQuickStatusBarHeader = quickStatusBarHeader;
        mQQSFooterActions = qqsFooterActionsView;
        mQSFooterActions = qsFooterActionsView;
        mSecurityFooter = securityFooter;
        mHost = qsTileHost;
        mExecutor = executor;
        mTunerService = tunerService;
        mQSExpansionPathInterpolator = qsExpansionPathInterpolator;
        mHost.addCallback(this);
        mQsPanelController.addOnAttachStateChangeListener(this);
        qs.getView().addOnLayoutChangeListener(this);
        if (mQsPanelController.isAttachedToWindow()) {
            onViewAttachedToWindow(null);
        }
        QSTileLayout tileLayout = mQsPanelController.getTileLayout();
        if (tileLayout instanceof PagedTileLayout) {
            mPagedLayout = ((PagedTileLayout) tileLayout);
        } else {
            Log.w(TAG, "QS Not using page layout");
        }
        mQsPanelController.setPageListener(this);
    }

    public void onRtlChanged() {
        updateAnimators();
    }

    /**
     * Request an update to the animators. This will update them lazily next time the position
     * is changed.
     */
    public void requestAnimatorUpdate() {
        mNeedsAnimatorUpdate = true;
    }

    public void setOnKeyguard(boolean onKeyguard) {
        mOnKeyguard = onKeyguard;
        updateQQSVisibility();
        if (mOnKeyguard) {
            clearAnimationState();
        }
    }

    /**
     * Sets whether or not the keyguard is currently being shown with a collapsed header.
     */
    void setShowCollapsedOnKeyguard(boolean showCollapsedOnKeyguard) {
        mShowCollapsedOnKeyguard = showCollapsedOnKeyguard;
        updateQQSVisibility();
        setCurrentPosition();
    }


    private void setCurrentPosition() {
        setPosition(mLastPosition);
    }

    private void updateQQSVisibility() {
        mQuickQsPanel.setVisibility(mOnKeyguard
                && !mShowCollapsedOnKeyguard ? View.INVISIBLE : View.VISIBLE);
    }

    @Override
    public void onViewAttachedToWindow(View v) {
        mTunerService.addTunable(this, ALLOW_FANCY_ANIMATION,
                MOVE_FULL_ROWS);
    }

    @Override
    public void onViewDetachedFromWindow(View v) {
        mHost.removeCallback(this);
        mTunerService.removeTunable(this);
    }

    @Override
    public void onTuningChanged(String key, String newValue) {
        if (ALLOW_FANCY_ANIMATION.equals(key)) {
            mAllowFancy = TunerService.parseIntegerSwitch(newValue, true);
            if (!mAllowFancy) {
                clearAnimationState();
            }
        } else if (MOVE_FULL_ROWS.equals(key)) {
            mFullRows = TunerService.parseIntegerSwitch(newValue, true);
        }
        updateAnimators();
    }

    @Override
    public void onPageChanged(boolean isFirst) {
        if (mOnFirstPage == isFirst) return;
        if (!isFirst) {
            clearAnimationState();
        }
        mOnFirstPage = isFirst;
    }

    private void translateContent(
            View qqsView,
            View qsView,
            View commonParent,
            int xOffset,
            int yOffset,
            int[] temp,
            TouchAnimator.Builder animatorBuilderX,
            TouchAnimator.Builder animatorBuilderY
    ) {
        getRelativePosition(temp, qqsView, commonParent);
        int qqsPosX = temp[0];
        int qqsPosY = temp[1];
        getRelativePosition(temp, qsView, commonParent);
        int qsPosX = temp[0];
        int qsPosY = temp[1];

        int xDiff = qsPosX - qqsPosX - xOffset;
        animatorBuilderX.addFloat(qqsView, "translationX", 0, xDiff);
        animatorBuilderX.addFloat(qsView, "translationX", -xDiff, 0);
        int yDiff = qsPosY - qqsPosY - yOffset;
        animatorBuilderY.addFloat(qqsView, "translationY", 0, yDiff);
        animatorBuilderY.addFloat(qsView, "translationY", -yDiff, 0);
        mAllViews.add(qqsView);
        mAllViews.add(qsView);
    }

    private void updateAnimators() {
        mNeedsAnimatorUpdate = false;
        TouchAnimator.Builder firstPageBuilder = new Builder();
        TouchAnimator.Builder translationYBuilder = new Builder();
        TouchAnimator.Builder translationXBuilder = new Builder();

        Collection<QSTile> tiles = mHost.getTiles();
        int count = 0;
        int[] loc1 = new int[2];
        int[] loc2 = new int[2];

        clearAnimationState();
        mAllViews.clear();
        mAnimatedQsViews.clear();
        mQQSTileHeightAnimator = null;
        mOtherTilesExpandAnimator = null;

        mNumQuickTiles = mQuickQsPanel.getNumQuickTiles();

        QSTileLayout tileLayout = mQsPanelController.getTileLayout();
        mAllViews.add((View) tileLayout);
        int height = mQs.getView() != null ? mQs.getView().getMeasuredHeight() : 0;
        int heightDiff = height - mQs.getHeader().getBottom()
                + mQs.getHeader().getPaddingBottom();
        if (!mTranslateWhileExpanding) {
            heightDiff *= SHORT_PARALLAX_AMOUNT;
        }
        firstPageBuilder.addFloat(tileLayout, "translationY", heightDiff, 0);

        int qqsTileHeight = 0;

        if (mQsPanelController.areThereTiles()) {
            for (QSTile tile : tiles) {
                QSTileView tileView = mQsPanelController.getTileView(tile);
                if (tileView == null) {
                    Log.e(TAG, "tileView is null " + tile.getTileSpec());
                    continue;
                }
                final View tileIcon = tileView.getIcon().getIconView();
                View view = mQs.getView();

                // This case: less tiles to animate in small displays.
                if (count < mQuickQSPanelController.getTileLayout().getNumVisibleTiles()
                        && mAllowFancy) {
                    // Quick tiles.
                    QSTileView quickTileView = mQuickQSPanelController.getTileView(tile);
                    if (quickTileView == null) continue;

                    getRelativePosition(loc1, quickTileView, view);
                    getRelativePosition(loc2, tileView, view);
                    int yOffset = loc2[1] - loc1[1];
                    int xOffset = loc2[0] - loc1[0];

                    // Offset the translation animation on the views
                    // (that goes from 0 to getOffsetTranslation)
                    int offsetWithQSBHTranslation =
                            yOffset - mQuickStatusBarHeader.getOffsetTranslation();
                    translationYBuilder.addFloat(quickTileView, "translationY", 0,
                            offsetWithQSBHTranslation);
                    translationYBuilder.addFloat(tileView, "translationY",
                            -offsetWithQSBHTranslation, 0);

                    translationXBuilder.addFloat(quickTileView, "translationX", 0, xOffset);
                    translationXBuilder.addFloat(tileView, "translationX", -xOffset, 0);

                    if (mQQSTileHeightAnimator == null) {
                        mQQSTileHeightAnimator = new HeightExpansionAnimator(this,
                                quickTileView.getMeasuredHeight(), tileView.getMeasuredHeight());
                        qqsTileHeight = quickTileView.getMeasuredHeight();
                    }

                    mQQSTileHeightAnimator.addView(quickTileView);

                    // Icons
                    translateContent(
                            quickTileView.getIcon(),
                            tileView.getIcon(),
                            view,
                            xOffset,
                            yOffset,
                            loc1,
                            translationXBuilder,
                            translationYBuilder
                    );

                    // Label containers
                    translateContent(
                            quickTileView.getLabelContainer(),
                            tileView.getLabelContainer(),
                            view,
                            xOffset,
                            yOffset,
                            loc1,
                            translationXBuilder,
                            translationYBuilder
                    );

                    // Secondary icon
                    translateContent(
                            quickTileView.getSecondaryIcon(),
                            tileView.getSecondaryIcon(),
                            view,
                            xOffset,
                            yOffset,
                            loc1,
                            translationXBuilder,
                            translationYBuilder
                    );

                    firstPageBuilder.addFloat(quickTileView.getSecondaryLabel(), "alpha", 0, 1);

                    mAnimatedQsViews.add(tileView);
                    mAllViews.add(quickTileView);
                    mAllViews.add(quickTileView.getSecondaryLabel());
                } else if (mFullRows && isIconInAnimatedRow(count)) {

                    firstPageBuilder.addFloat(tileView, "translationY", -heightDiff, 0);

                    mAllViews.add(tileIcon);
                } else {
                    // Pretend there's a corresponding QQS tile (for the position) that we are
                    // expanding from.
                    SideLabelTileLayout qqsLayout =
                            (SideLabelTileLayout) mQuickQsPanel.getTileLayout();
                    getRelativePosition(loc1, qqsLayout, view);
                    getRelativePosition(loc2, tileView, view);
                    int diff = loc2[1] - (loc1[1] + qqsLayout.getPhantomTopPosition(count));
                    translationYBuilder.addFloat(tileView, "translationY", -diff, 0);
                    if (mOtherTilesExpandAnimator == null) {
                        mOtherTilesExpandAnimator =
                                new HeightExpansionAnimator(
                                        this, qqsTileHeight, tileView.getMeasuredHeight());
                    }
                    mOtherTilesExpandAnimator.addView(tileView);
                    tileView.setClipChildren(true);
                    tileView.setClipToPadding(true);
                    firstPageBuilder.addFloat(tileView.getSecondaryLabel(), "alpha", 0, 1);
                    mAllViews.add(tileView.getSecondaryLabel());
                }

                mAllViews.add(tileView);
                count++;
            }
        }

        if (mAllowFancy) {
            animateBrightnessSlider(firstPageBuilder);

            mFirstPageAnimator = firstPageBuilder
                    .setListener(this)
                    .build();
            // Fade in the tiles/labels as we reach the final position.
            Builder builder = new Builder()
                    .addFloat(tileLayout, "alpha", 0, 1);
            mFirstPageDelayedAnimator = builder.build();

            if (mQQSFooterActions.getVisibility() != View.GONE) {
                // only when qqs footer is present (which means split shade mode) it needs to
                // be animated
                updateQQSFooterAnimation();
            }


            // Fade in the security footer and the divider as we reach the final position
            builder = new Builder().setStartDelay(EXPANDED_TILE_DELAY);
            builder.addFloat(mSecurityFooter.getView(), "alpha", 0, 1);
            if (mQsPanelController.shouldUseHorizontalLayout()
                    && mQsPanelController.mMediaHost.hostView != null) {
                builder.addFloat(mQsPanelController.mMediaHost.hostView, "alpha", 0, 1);
            } else {
                // In portrait, media view should always be visible
                mQsPanelController.mMediaHost.hostView.setAlpha(1.0f);
            }
            mAllPagesDelayedAnimator = builder.build();
            mAllViews.add(mSecurityFooter.getView());
            translationYBuilder.setInterpolator(mQSExpansionPathInterpolator.getYInterpolator());
            translationXBuilder.setInterpolator(mQSExpansionPathInterpolator.getXInterpolator());
            mTranslationYAnimator = translationYBuilder.build();
            mTranslationXAnimator = translationXBuilder.build();
            if (mQQSTileHeightAnimator != null) {
                mQQSTileHeightAnimator.setInterpolator(
                        mQSExpansionPathInterpolator.getYInterpolator());
            }
            if (mOtherTilesExpandAnimator != null) {
                mOtherTilesExpandAnimator.setInterpolator(
                        mQSExpansionPathInterpolator.getYInterpolator());
            }
        }
        mNonfirstPageAnimator = new TouchAnimator.Builder()
                .addFloat(mQuickQsPanel, "alpha", 1, 0)
                .setListener(mNonFirstPageListener)
                .setEndDelay(.5f)
                .build();
        mNonfirstPageDelayedAnimator = new TouchAnimator.Builder()
                .setStartDelay(.14f)
                .addFloat(tileLayout, "alpha", 0, 1).build();
    }

    private void animateBrightnessSlider(Builder firstPageBuilder) {
        View qsBrightness = mQsPanelController.getBrightnessView();
        View qqsBrightness = mQuickQSPanelController.getBrightnessView();
        if (qqsBrightness != null && qqsBrightness.getVisibility() == View.VISIBLE) {
            // animating in split shade mode
            mAnimatedQsViews.add(qsBrightness);
            mAllViews.add(qqsBrightness);
            int translationY = getRelativeTranslationY(qsBrightness, qqsBrightness);
            mBrightnessAnimator = new Builder()
                    // we need to animate qs brightness even if animation will not be visible,
                    // as we might start from sliderScaleY set to 0.3 if device was in collapsed QS
                    // portrait orientation before
                    .addFloat(qsBrightness, "sliderScaleY", 0.3f, 1)
                    .addFloat(qqsBrightness, "translationY", 0, translationY)
                    .build();
        } else if (qsBrightness != null) {
            firstPageBuilder.addFloat(qsBrightness, "translationY",
                    qsBrightness.getMeasuredHeight() * 0.5f, 0);
            mBrightnessAnimator = new Builder()
                    .addFloat(qsBrightness, "alpha", 0, 1)
                    .addFloat(qsBrightness, "sliderScaleY", 0.3f, 1)
                    .setInterpolator(Interpolators.ALPHA_IN)
                    .setStartDelay(0.3f)
                    .build();
            mAllViews.add(qsBrightness);
        } else {
            mBrightnessAnimator = null;
        }
    }

    private void updateQQSFooterAnimation() {
        int translationY = getRelativeTranslationY(mQSFooterActions, mQQSFooterActions);
        mQQSFooterActionsAnimator = new TouchAnimator.Builder()
                .addFloat(mQQSFooterActions, "translationY", 0, translationY)
                .build();
        mAnimatedQsViews.add(mQSFooterActions);
    }

    private int getRelativeTranslationY(View view1, View view2) {
        int[] qsPosition = new int[2];
        int[] qqsPosition = new int[2];
        View commonView = mQs.getView();
        getRelativePositionInt(qsPosition, view1, commonView);
        getRelativePositionInt(qqsPosition, view2, commonView);
        return (qsPosition[1] - qqsPosition[1]) - mQuickStatusBarHeader.getOffsetTranslation();
    }

    private boolean isIconInAnimatedRow(int count) {
        if (mPagedLayout == null) {
            return false;
        }
        final int columnCount = mPagedLayout.getColumnCount();
        return count < ((mNumQuickTiles + columnCount - 1) / columnCount) * columnCount;
    }

    private void getRelativePosition(int[] loc1, View view, View parent) {
        loc1[0] = 0 + view.getWidth() / 2;
        loc1[1] = 0;
        getRelativePositionInt(loc1, view, parent);
    }

    private void getRelativePositionInt(int[] loc1, View view, View parent) {
        if(view == parent || view == null) return;
        // Ignore tile pages as they can have some offset we don't want to take into account in
        // RTL.
        if (!isAPage(view)) {
            loc1[0] += view.getLeft();
            loc1[1] += view.getTop();
        }
        if (!(view instanceof PagedTileLayout)) {
            // Remove the scrolling position of all scroll views other than the viewpager
            loc1[0] -= view.getScrollX();
            loc1[1] -= view.getScrollY();
        }
        getRelativePositionInt(loc1, (View) view.getParent(), parent);
    }

    // Returns true if the view is a possible page in PagedTileLayout
    private boolean isAPage(View view) {
        return view.getClass().equals(SideLabelTileLayout.class);
    }

    public void setPosition(float position) {
        if (mNeedsAnimatorUpdate) {
            updateAnimators();
        }
        if (mFirstPageAnimator == null) return;
        if (mOnKeyguard) {
            if (mShowCollapsedOnKeyguard) {
                position = 0;
            } else {
                position = 1;
            }
        }
        mLastPosition = position;
        if (mOnFirstPage && mAllowFancy) {
            mQuickQsPanel.setAlpha(1);
            mFirstPageAnimator.setPosition(position);
            mFirstPageDelayedAnimator.setPosition(position);
            mTranslationYAnimator.setPosition(position);
            mTranslationXAnimator.setPosition(position);
            if (mQQSTileHeightAnimator != null) {
                mQQSTileHeightAnimator.setPosition(position);
            }
            if (mOtherTilesExpandAnimator != null) {
                mOtherTilesExpandAnimator.setPosition(position);
            }
        } else {
            mNonfirstPageAnimator.setPosition(position);
            mNonfirstPageDelayedAnimator.setPosition(position);
        }
        if (mAllowFancy) {
            mAllPagesDelayedAnimator.setPosition(position);
            if (mBrightnessAnimator != null) {
                mBrightnessAnimator.setPosition(position);
            }
            if (mQQSFooterActionsAnimator != null) {
                mQQSFooterActionsAnimator.setPosition(position);
            }
        }
    }

    @Override
    public void onAnimationAtStart() {
        mQuickQsPanel.setVisibility(View.VISIBLE);
    }

    @Override
    public void onAnimationAtEnd() {
        mQuickQsPanel.setVisibility(View.INVISIBLE);
        final int N = mAnimatedQsViews.size();
        for (int i = 0; i < N; i++) {
            mAnimatedQsViews.get(i).setVisibility(View.VISIBLE);
        }
    }

    @Override
    public void onAnimationStarted() {
        updateQQSVisibility();
        if (mOnFirstPage) {
            final int N = mAnimatedQsViews.size();
            for (int i = 0; i < N; i++) {
                mAnimatedQsViews.get(i).setVisibility(View.INVISIBLE);
            }
        }
    }

    private void clearAnimationState() {
        final int N = mAllViews.size();
        mQuickQsPanel.setAlpha(0);
        for (int i = 0; i < N; i++) {
            View v = mAllViews.get(i);
            v.setAlpha(1);
            v.setTranslationX(0);
            v.setTranslationY(0);
            v.setScaleY(1f);
            if (v instanceof SideLabelTileLayout) {
                ((SideLabelTileLayout) v).setClipChildren(false);
                ((SideLabelTileLayout) v).setClipToPadding(false);
            }
        }
        if (mQQSTileHeightAnimator != null) {
            mQQSTileHeightAnimator.resetViewsHeights();
        }
        if (mOtherTilesExpandAnimator != null) {
            mOtherTilesExpandAnimator.resetViewsHeights();
        }
        final int N2 = mAnimatedQsViews.size();
        for (int i = 0; i < N2; i++) {
            mAnimatedQsViews.get(i).setVisibility(View.VISIBLE);
        }
    }

    @Override
    public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft,
            int oldTop, int oldRight, int oldBottom) {
        mExecutor.execute(mUpdateAnimators);
    }

    @Override
    public void onTilesChanged() {
        // Give the QS panels a moment to generate their new tiles, then create all new animators
        // hooked up to the new views.
        mExecutor.execute(mUpdateAnimators);
    }

    private final TouchAnimator.Listener mNonFirstPageListener =
            new TouchAnimator.ListenerAdapter() {
                @Override
                public void onAnimationAtEnd() {
                    mQuickQsPanel.setVisibility(View.INVISIBLE);
                }

                @Override
                public void onAnimationStarted() {
                    mQuickQsPanel.setVisibility(View.VISIBLE);
                }
            };

    private final Runnable mUpdateAnimators = () -> {
        updateAnimators();
        setCurrentPosition();
    };

    /**
     * True whe QS will be pulled from the top, false when it will be clipped.
     */
    public void setTranslateWhileExpanding(boolean shouldTranslate) {
        mTranslateWhileExpanding = shouldTranslate;
    }

    private static class HeightExpansionAnimator {
        private final List<View> mViews = new ArrayList<>();
        private final ValueAnimator mAnimator;
        private final TouchAnimator.Listener mListener;

        private final ValueAnimator.AnimatorUpdateListener mUpdateListener =
                new ValueAnimator.AnimatorUpdateListener() {
            float mLastT = -1;
            @Override
            public void onAnimationUpdate(ValueAnimator valueAnimator) {
                float t = valueAnimator.getAnimatedFraction();
                final int viewCount = mViews.size();
                int height = (Integer) valueAnimator.getAnimatedValue();
                for (int i = 0; i < viewCount; i++) {
                    View v = mViews.get(i);
                    if (v instanceof HeightOverrideable) {
                        ((HeightOverrideable) v).setHeightOverride(height);
                    } else {
                        v.setBottom(v.getTop() + height);
                    }
                }
                if (t == 0f) {
                    mListener.onAnimationAtStart();
                } else if (t == 1f) {
                    mListener.onAnimationAtEnd();
                } else if (mLastT <= 0 || mLastT == 1) {
                    mListener.onAnimationStarted();
                }
                mLastT = t;
            }
        };

        HeightExpansionAnimator(TouchAnimator.Listener listener, int startHeight, int endHeight) {
            mListener = listener;
            mAnimator = ValueAnimator.ofInt(startHeight, endHeight);
            mAnimator.setRepeatCount(ValueAnimator.INFINITE);
            mAnimator.setRepeatMode(ValueAnimator.REVERSE);
            mAnimator.addUpdateListener(mUpdateListener);
        }

        void addView(View v) {
            mViews.add(v);
        }

        void setInterpolator(TimeInterpolator interpolator) {
            mAnimator.setInterpolator(interpolator);
        }

        void setPosition(float position) {
            mAnimator.setCurrentFraction(position);
        }

        void resetViewsHeights() {
            final int viewsCount = mViews.size();
            for (int i = 0; i < viewsCount; i++) {
                View v = mViews.get(i);
                if (v instanceof HeightOverrideable) {
                    ((HeightOverrideable) v).resetOverride();
                } else {
                    v.setBottom(v.getTop() + v.getMeasuredHeight());
                }
            }
        }
    }
}